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Passive homesGUIDELINES FORTHEDESIGNANDCONSTRUCTION OF PASSIVEHOUSE DWELLINGS IN IRELAND


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Sustainable Energy Ireland (SEI)

Sustainable Energy Ireland was established as Irelands national energy agency under the Sustainable Energy Act 2002. SEIsmission is to promote and assist the development o sustainable energy. This encompasses environmentally andeconomically sustainable production, supply and use o energy, in support o Government policy, across all sectors o theeconomy including public bodies, the business sector, local communities and individual consumers. Its remit relates mainlyto improving energy eiciency, advancing the development and competitive deployment o renewable sources o energyand combined heat and power, and reducing the environmental impact o energy production and use, particularly inrespect o greenhouse gas emissions.

SEI is charged with implementing signiicant aspects o government policy on sustainable energy and the climate changeabatement, including:

Assisting deployment o superior energy technologies in each sector as required;

Raising awareness and providing inormation, advice and publicity on best practice;

Stimulating research, development and demonstration;

Stimulating preparation o necessary standards and codes;

Publishing statistics and projections on sustainable energy and achievement o targets.

It is unded by the Government through the National Development Plan with programmes part inanced by the EuropeanUnion.

Sustainable Energy Ireland, 2007. All rights reserved.

No part o this material may be reproduced, in whole or in part, in any orm or by any means, without permission. The material contained in this

publication is presented in good aith, but its application must be considered in the light o individual projects. Sustainable Energy Ireland can not be heldresponsible or any eect, loss or expense resulting rom the use o material presented in this publication.

Prepared by MosArt Architecture and UCD Energy Research Groupwith contribution rom Sharon McManus as part o MEngSc thesis.


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Table o Contents

Preace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

SECTION ONE

ThePassive House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Passive House and the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Deinition o the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.2 Technical Deinition o the Passivhaus Standard or Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Application o the Passivhaus Standard in the EU and Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.1 Evolution o the Passivhaus Standard in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2.2 Application o the Passivhaus Standard in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

SECTION TWO

How to Design and Speciy a Passive House in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1 Building Design Process or a Passive House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 General Principles: Heat Energy Losses & Heat Energy Gains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.1 Passive House Building Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.2 Passive House Building Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.3 Energy Balance Calculations and Passive House Speciication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3.1 PHPP Sotware and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.3.2 Passive House Certiications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

SECTION THREE

Passive House Prototype or Application in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.1 Design and Speciication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.1 Combining Aesthetic and Energy Perormance in House Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.2 Decision Support using Passive House Planning Package (PHPP) Sotware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.1.3 Prototype Passive House External Wall Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.1.4 Prototype Passive House Design including Mechanical and Electrical Services . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.2 Cost Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

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PreaceBy Dr Wolfgang Feist, Founder of the Passive House Institute, Germany

Energy Eicient Passive Houses Reducing the Impact o Global Warming

The February 2007 report o the Inter-Governmental Panel on Climate Change(IPCC) has shown that climate change is already a very serious global issue. Thenegative eects it will have on the ecosystem, the world economy and on livingconditions are anticipated to be on a massive scale.

Climate change is caused largely by human behaviour due mainly to the use oossil uels as our main source o energy generation. The magnitude o utureclimate changes is closely linked to worldwide CO2 emissions into the earthsatmosphere. The worst eects o global warming, such as a thawing o the entireland-borne ice in Greenland and Antarctica, can still be prevented. However, thisrequires a substantial reduction in worldwide CO2 emissions ar below thecurrent level.

There is hardly any doubt that an energy system ready or the uture will have tobe sustainable. Sustainable development is economic development that can becontinued in the uture without causing signiicant problems or other people,the environment and uture generations.

Passive Housing can play a major role in reducing the impact o global warming.The energy requirement o a passive house is so low that a amily will never againneed to worry about energy price hikes. Passive Houses are virtually independento ossil sources o energy and can be ully supplied with renewable energy i acompact heat pump unit is used in combination with an ecological electricitysupplier. Due to the low energy requirement o passive houses the regionally

available renewable energy sources are suicient to provide a constant supply oenergy or everyone.

Irelands mild climate puts it in a avourable position to introduce Passive Housesto mainstream construction compared to the more severe climates prevalent incentral Europe.

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Foreword

Sustainable Energy Ireland is Irelands national energy agency, set up to support Irish government energy

policy objectives. Following the introduction o new legislation, most notably the European Community

Directive on the Energy Perormance o Buildings and the recent announcement o the intent to regulate

and require the use o renewable energy systems in new buildings, we are seeing the emergence o

extraordinary standards o energy perormance or building construction in Ireland, as well as a rapid

increase in the uptake o renewable energy technologies or building services.

Ireland is acing a number o serious challenges includingrising energy costs and meeting our emissions obligationsunder the Kyoto protocol. These and other actors havegiven rise to a undamental rethink in the way we design,construct and operate buildings. As we move orward, it isbecoming clear that building greenhas evolved and is astbecoming the preerred choice, providing high quality, higheiciency, dynamic and cost eective solutions orconsumers and businesses. The passive house is theultimate low energy building. The passive house standard isrecognised in Europe as the most advanced in terms oenergy perormance o buildings and going orward theEuropean Commission is set on implementing the passivehouse standard and also on setting more stringentrequirements or the reurbishment o existing buildings.

Today, the passive house oers one o the most desirabletechnological and economical solutions or comortableliving and working. It can be applied to new and existingbuildings in the commercial, industrial, public andresidential sectors. With close to 10,000 passive houses builtin Europe, this well proven and tested innovative standard isnow attracting signiicant interest in Ireland with pioneerslike MosArt and Scandinavian Homes leading an emergingmovement in the construction industry.

In response to the need to educate proessionals and theirclients on how to design, speciy and construct passive

houses and acilitate the urther development o thisstandard here in Ireland SEI commissioned Guidelines orthe Design and Construction o Passive House Dwellings inIreland. These detailed guidelines or sel-builders andarchitects ocus on new build houses and cover bothconventional block construction and timber rameconstruction methods. They will ultimately become part oa suite o guidelines to cover, or example, multipledwellings, non-residential buildings, extensions,renovations etc.

The guidelines cover the rationale and deinition o thepassive house standard, how to design and speciy a passivehouse along with, construction options, associated services,cost considerations and liestyle issues. SEI hopes they willbe useul in increasing awareness and understanding o thekey principles and techniques in designing, constructingand operating the ultimate low energy building thepassive house.

David Taylor

CEO Sustainable Energy Ireland

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SECTION ONE

The Passive House


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1.1 Passive House and thePassivhaus Standard

A passive house1 is an energy-eicient

building with year-round comort andgood indoor environmental conditionswithout the use o active space heating

or cooling systems. The space heatrequirement is reduced by means opassive measures to the point at which

there is no longer any need or aconventional heating system; the airsupply system essentially suices todistribute the remaining heatrequirement. A passive house providesvery high level o thermal comort and

provision o whole-house eventemperature. The concept is based onminimising heat losses and maximisingheat gains, thus enabling the use osimple building services. The

appearance o a passive house does notneed to dier rom a conventional houseand living in it does not require anyliestyle changes. Passive houses arelight and bright due to large glazedareas designed to optimise solar gains,

as well as healthy buildings in which tolive and work due to resh air supplythrough the ventilation system.

The Passivhaus Standard is a

construction standard developed by thePassivhaus Institut in Germany(http://www.passiv.de). The Standard canbe met using a variety o designstrategies, construction methods andtechnologies and is applicable to any

building type.

This publication outlines therequirements in applying that standardin Ireland and in all cases when reerring

to a passive house is describing a housebuilt to the requirements o thePassivhaus Standard.

1.1.1 Deinition o the Passivhaus

Standard

The Passivhaus Standard is a speciicconstruction standard or buildings withgood comort conditions during winterand summer, without traditional space

heating systems and without activecooling. Typically this includesoptimised insulation levels with minimalthermal bridges, very low air-leakagethrough the building, utilisation opassive solar and internal gains and

good indoor air quality maintained by amechanical ventilation system withhighly eicient heat recovery.Renewable energy sources are used asmuch as possible to meet the resulting

energy demand (PEP, 2006), includingthat required or the provision odomestic hot water (DHW). It should benoted that the primary ocus in buildingto the Passivhaus Standard is directedtowards creating a thermally eicient

envelope which makes the optimum useo ree heat gains in order to minimisespace heating requirement. While thereare also limitations on the amount oprimary energy that can be used by a

dwelling or such uses as DHW, lightingand household appliances, this will notbe the primary ocus o these guidelines.That is not intended to imply that suchenergy uses are insigniicant, however.

In act, a passive house will have thesame DHW requirements as any typicalhouse in Ireland and given the lowenergy required or space heating theenergy demand or DHW will represent arelatively high proportion o the overallconsumption. In order to address this,

some guidance is provided on strategiesto ensure that renewable energies areemployed as much as possible orproduction o DHW.

1

The Passive House

Passive house in Ghent, Belgium (2004).

Source: Passiefhuis Platform vzw.

Passive house in Oberosterreich, Austria (2000).

Source: IG Passivhaus Osterreich Innovative Passivhaus

projekte.

Interior of passive house in Oberosterreich, Austria

(2000). Source: IG Passivhaus Osterreich Innovative

Passivhaus projekte.


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Structural air-tightness (reduction o airiniltration) and minimal thermalbridging are essential. A whole-housemechanical heat recovery ventilationsystem (MHRV) is used to supplycontrolled amounts o resh air to the

house. The incoming resh air is pre-heated via a heat exchanger, by the

outgoing warm stale air. I additionalheat is required, a small eicient back-upsystem (using a renewable energysource, or example) can be used to

boost the temperature o the resh airsupplied to the house.

The energy requirement o a house builtto the Passivhaus Standard is:

Space heating requirement (deliver-ed energy) o 15kWh/(m2year)

treated loor area (TFA), and

The upper limit or total primaryenergy demand or space and waterheating, ventilation, electricity orans and pumps, household

appliances, and lighting notexceeding 120kWh/(m2year), regard-less o energy source.

Additionally, the air-leakage test results

must not exceed 0.6 air changes perhour using 50Pa overpressurisation andunder-pressurisation testing.

In order to maintain high comort levels

in any building, heat losses must bereplaced by heat gains. Heat losses occurthrough the building abric due totransmission through poorly insulatedwalls, loor, ceiling and glazing as well as

2

Air-leakage (or iniltration) is the

uncontrolled penetration o outside

air into a building. It takes place

through openings, primarily through

inadequate and imperect sealing

between window rames and walls,between the opening sections o the

window and along the joints o the

building envelope.

Thermal bridging reers to a material,

or assembly o materials, in a

building envelope through which

heat is transerred at a substantially

higher rate (due to higher thermal

conductivity) than through the

surrounding materials. Junctions

between window or door and wall,

wall and loor, and wall and rooshould be designed careully to avoid

thermal bridging. A thermal bridge

increases heat loss through the

structure, and in some extreme cases

may cause surace condensation or

interstitial condensation into the

construction. Surace mould growth

or wood rot may be the consequences

o a thermal bridge.

Measure/Solution Passivhaus Standard or the Prototype House

in the Irish Climate

1. Super Insulation

Insulation Walls U < 0.175 W/m2KInsulation Roo U < 0.15 W/m2KInsulation Floor U < 0.15 W/m2KWindow Frames, Doors U < 0.8 W/m2KWindow Glazing U < 0.8 W/m2KThermal Bridges Linear heat Coefcient < 0.01 W/mK

Structural Air Tightness n50 < 0.6/ air changes per hour

2. Heat Recovery/ Air Quality

Ventilation counter owair to air heat exchanger

Heat Recovery Efciency > 75%

Minimal Space Heating Post heating ventilation air/ Low temperatureheating

Efcient small capacity heating system Biomass, compact unit, gas etc.Air quality through ventilation rate Min 0.4 ac/hr or 30m3/pers/hrVentilation Supply Ducts Insulated Applicable

3. Domestic Hot Water Biomass, compact unit, gas, heat pump, etc.DHW cylinder and pipes well insulated ApplicableSolar thermal system Recommended

4. Passive Solar Gain

Window Glazing Solar energy transmittance g > 50%DHW solar heating Area to be dictated by house size andoccupancy

Solar Orientation Minimal glazing to northThermal Mass within Envelope Recommended

5. Electric Efciency

Energy labelled Household appliances A rated appliancesHot water connection to washingmachines/ dishwashers

Recommended

Compact Fluorescent Lighting RecommendedRegular maintenance ventilation lters RecommendedEnergy Efcient ans Recommended

6. On-site Renewables

Solar thermal system Recommended

Biomass system RecommendedPhotovoltaics Application in a case by case basisWind Turbine Application in a case by case basisOther including geothermal Application in a case by case basis

Table 1. Technical Definition of the Passivhaus Standard for Ireland.

Passive house in Hannover, Germany (2004).

Source: IG Passivhaus Deutschland Innovative

Passivhaus projekte.


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rom uncontrolled cold air iniltrationthrough leaky construction and poorlyitted windows and doors. In a typicaldwelling, such heat losses have to be

balanced by heat gains mostlycontributed by a space heating system.The internal heat gains rom occupantsand other sources such as householdappliances as well as passive solar gains

contribute a relatively small proportiono the total overall need in aconventional dwelling. In a passivehouse, the heat losses are reduced sodramatically (through better insulationand airtight detailing) such that thesame internal gains and passive solar

gain now contribute a relatively highproportion o the total need. As a resulto this, a smaller space heating system isthereore required compared to that

needed in a conventional dwelling.

A new built semi-detached, two-storeyIrish house built to comply with the

requirements o Building RegulationsTechnical Guidance Document (TGD)Part L 2005, Conservation o Fuel andEnergy), uses approx. 75kWh/m2

delivered energy or space heating and

159kWh/m2

primary energy. ThePassivhaus Standard requirement orspace heating is 15kWh/(m2year)delivered energy. When compared, thereduction in space heating demandrepresents 80%.

1.1.2 Technical Deinition o the

Passivhaus Standard or Ireland

In Table 1, a range o U-values arespeciied in order to meet the Passivhaus

Standard o space heating requirement(delivered energy) o 15kWh/(m2year) orthe Irish climate. Speciying U-values isdependent upon many variables andcan only be veriied through testing the

perormance o the dwelling design inthe PHPP sotware. The U-valuesincluded in Table 1 have been tested or

the prototype passive house presentedlater in Section 3. This prototype house isa semi-detached two storey house o

very compact orm. A detachedbungalow house o sprawling ormwould require much lower U-values tomeet the Passivhaus Standard. Due tothe mild Irish climate, it is possible to use

U-values or walls in the prototypehouse that are higher than thosetypically recommended by thePassivhaus Institute or colder centralEuropean climates.

A sensitivity analysis was undertakenusing dierent U-values or theprototype house in order to see, orexample, whether it would be possibleto relax the building abric requirementse.g. double glazing, in Ireland and stillachieve the Passivhaus Standard. The

results o this analysis are included inSection 2.

1.2 Applications o thePassivhaus Standard inthe EU and Ireland

1.2.1 Evolution o the PassivhausStandard in Europe

The Passivhaus Standard originated in1988 by Proessor Bo Adamson o the

University o Lund, Sweden and Dr.Wolgang Feist o the Institute orHousing and the Environment. Theconcept was developed through anumber o research projects and irst

tested on a row o terraced houses by Dr.Wolgang Feist in 1991 in Darmstadt,Germany. The Passivhaus Institut(http://www.passiv.de) was ounded in

Darmstadt, Germany in 1996 by Dr.Wolgang Feist as an independent

research institution. Since then, it hasbeen at the oreront o the PassiveHouse movement in Germany and hasbeen instrumental in disseminating thestandard throughout Europe and

overseas (more details in Section 2).

3

Comparison of delivered energy in conventional house and in house built to Passivhaus Standard.

Source: Passivhaus Institut. http://ww w.passiv.de.

0

10

20

30

40

50

60

70

80

21

kWh/my

Building Regulations 2005(TGD) Part L

Passive House

80% Reduction2

Delivered space heating energy comparison, Building Regulations (TGD) Part L and Passivhaus Standard.

Source: UCD Energy Research Group.


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Dwellings built to the PassivhausStandard have been constructed all overEurope in recent years but mostespecially in Germany and Austria wherethe Passivhaus Standard was irst

applied.2 Over 10,000 dwellings havebeen built to the standard throughoutEurope, including 4,000 in Germany and

Austria, Norway, Sweden, Denmark andBelgium and this number is continuingto grow. CEPHEUS3 (Cost Eicient Passive

Houses as European Standards) was aresearch project (19982001) thatassessed and validated the PassivhausStandard on a wider European scale. Theproject was sponsored by the European

Union as part o the THERMIEProgramme o the EuropeanCommission, Directorate-General oTransport and Energy. Under CEPHEUS,14 housing developments were built,resulting in a total o 221 homes

constructed to the Passivhaus Standardin ive European countries. Anotherproject supported by the EuropeanCommission, Dictorate General orEnergy and Transport is PEP, which

stands or Promotion o EuropeanPassive Houses (http://www.europeanpassivehouses.org). PEP is a consortiumo European partners aiming to spreadthe knowledge and experience on thepassive house concept throughout the

proessional building community,beyond the select group o specialists.

1.2.2 Application o Passivhaus

Standard in Ireland

The Kyoto Protocol came into orce in2005 and the proposed targets oreducing CO2 emissions by 8%compared to 1990 levels by the period

20082012 became legally binding orEU Member States (UNFCCC, 1997).Irelands target under the Kyoto Protocolto limit green house gas emissions to13% above 1990 levels by that periodwas reached in 1997, and it is likely that

the target will be overshot by up to 37%(74Mt CO2) by 2010 (OLeary et al, 2006).The EC Green Paper on Energy Eiciency(EC, 2005), states that it is possible orthe EU-25 Member States to achieveenergy savings o 20% by 2010, and sees

the greatest proportion o these savings(32%) coming rom the built environ-ment.

In Ireland the residential sector accounts

or 26% o primary energy consumption

and 27% o energy related CO2

emissions (11,376 kt CO2), the secondlargest sector ater transport at 32%. Theaverage dwelling emits approximately8.2 tonnes o CO2 emissions, 5 tonnes

rom direct uel use and 3.2 tonnes romelectricity use (OLeary et al, 2006) andIrish dwellings have a higher

consumption o energy, electricity andenergy related CO2 emissions perdwelling compared to the average o the

EU-15 (EC, 2005).

The Government White Paper Deliveringa Sustainable Energy Future or Ireland(DCMNR, 2007) highlighted that

amendment to the Building Regulationsin 2008 would bring a urther 40%energy reduction and related CO2emissions in new build construction. Therecent Programme or Government hasbrought orward that amendment to

2007 and committed to a urtheramendment in 2010 to 60% belowcurrent standards.

It is clear that the perormance o both

new build and existing housing stockmust be addressed i we are to achievethe objectives set out both at Europeanand national level. The energyrequirement o a house built to

Passivhaus Standard goes beyond theproposed 40% energy reduction andrelated CO2 emissions in new buildconstruction.

A study completed by UCD Energy

Research Group quantiied the potentialreduction or space heating energy andCO2 emissions when the PassivhausStandard or space heating o15kWh/m2year is applied to the Irish new

build residential construction market(Brophy et al. 2006). Five scenarios ovarying levels o application wereinvestigated. The tool used in this studywas a computer based model,developed as part o the Homes or the

21st Century study (Brophy et al. 1999),

which proiled the existing nationaldwelling stock by dwelling orm,insulation characteristics and heatingsystem types. The model was used to

predict the energy consumption andCO2 emissions o dwellings with a typicalloor area o 100m2, constructed to 2002building regulation standard. Thisprovided national common practiceenergy consumption and CO2 emissions

igures. It was ound that a typical Irish

4

Passive house in Guenzburg, Germany (2006).


Passivhaus Eusenstadt, Austria.

Source: Construct Ireland Issue 2, Vol 3.

Multy family dwelling, Hohe Strasse, Hannover,

Germany. Source: UCD Energy Research Group.

Kronsberg Passivhaus Complex Hannover, Germany.



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dwelling consumes 9,722 kWh/year odelivered energy on space heating andas a result releases 2,855 kgCO2/yearinto the atmosphere. The space heatingrequirements or the same size o

dwelling built to Passivhaus Standardswas ound to be only 1,500 kWh/year odelivered energy which equates to 176

kgCO2/year. (It was assumed 50:50 splitbetween the use o gas and woodpellets or space heating energy source

as typically used in passive houses). Thedierence in delivered energyconsumption and carbon dioxideemissions between the two constructiontypes or a single building over one year

was thereore 8,222 kWh/year and 2,680kgCO2 /year. Applying potential energyand CO2 emissions saving rates to the 20year average new build dwellingconstruction rate o 40,000 homes peryear the ollowing results were

calculated. The results showed thatsubstantial savings are achievablethrough the application o thePassivhaus Standard in Ireland (Table 2).

The Passivhaus Standard was irstintroduced in Ireland by the Swedisharchitect Hans Eek at the See the Lightconerence organised by SustainableEnergy Ireland (SEI) in June 2002. TomsOLeary o MosArt Architects, a delegate

at the conerence, was so enthused byMr Eeks presentation that he decided onthe spot to sell his townhouse, buy a sitein the countryside in Co. Wicklow andbuild a passive house. The OLeary amily

has been living in the Out o the Bluehouse since Spring 2005. This house isthe irst Irish passive house to becertiied by the Passivhaus Institute inGermany, and has been the ocus o aresearch, demonstration and energy

monitoring project unded bySustainable Energy Ireland. MosArtArchitects, the Passivhaus Institute o DrWolgang Feist and the UCD EnergyResearch Group are partners in the

project. The project is instrumental inestablishing the basis or thedeployment o the Passivhaus Standardin Ireland in dierent ways:

it has provided a learning experience

or proessionals involved in thedesign, speciication, constructionand servicing stages

it will provide a scientiic basis or

perormance assessment through

5

Percentage (and number) o newdwellings built to Passivhaus

Standard

Potential energy and CO2emissions savings per

year

Potential energy and CO2emissions savings in

3.29 GWh 0.691 TWh1% (400)

1.07 ktCO2 5.02 MtCO2

16.44 GWh 3.453 TWh5% (2,000)

5.36 ktCO2 25.10 MtCO2

65.78 GWh 13.813 TWh20% (8,000)

21.44 ktCO2 100.41 MtCO2

164.44 GWh 34.533 TWh50% (20,000)

53.59 ktCO2 251.03 MtCO2

20 years

Table 2: Potential for space heating energy and carbon dioxide savings.

Building Energy Rating Label. Source: Sustainable Energy Ir eland.

The EU Energy Perormance o Buildings Directive (EPBD) was transposed into Irish

law on 4th January 2006. This states that when a building is constructed, rented or

sold a Building Energy Rating (BER) certiicate and label must be made available to

prospective buyers or tenants. The BER is expressed in terms o kWh o primary

energy/m2/year. A passive house would achieve an A2 rating (UCD Energy Research

Group).


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monitoring and evaluation

it is an excellent demonstration tooland has been the ocus o manyvisits, presentations and journal

articles.

6

Reerences

Brophy, V., Clinch, J.P., Convery, F.J.,

Healy, J.D., King, C. and Lewis, J.O., 1999

Homes for the 21st Century - The Costs

& Benefits of Comfortable Housing for

Ireland. Dublin. Report prepared for

Energy Action Ltd.

Brophy, V., Kondratenko, I., Hernandez,

P., Burke, K., 2006 Potential for Energy

and CO2 Emission Savings through

application of the Passive house

Standard in Ireland. Published in the

Passive House Conference 2006 pp. 119-

124. Hanover, Germany.

European Commission (EC), 2005.

Green Paper on Energy Efficiency.

[Internet] EC. Available at:

http://ec.europa.eu/energy/efficiency/

index_en.html

European Commission (EC), 2006.

Promotion of European Passive Houses

(PEP)". [Internet] PEP. Available at:

http://www.europeanpassivehouses.or

g/html

Government of Ireland, Department of

Communications, Energy and Natural

Resources (DCMNR), 2007. Government

"White Paper Delivering a Sustainable

Energy Future for Ireland". [Internet]

DCERN. Available at:

http://www.dcmnr.gov.ie/Energy/

Energy+Planning+Division/Energy+

White+Paper.html

OLeary, F., Howley, M., and OGallagher,B., 2006. Energy in Ireland 1990-2004,

Trends, issues, forecast and indicators.

Dublin. Sustainable Energy Ireland.

United Nations Framework Convention

on Climate Change (UNFCCC), 1997.

The Kyoto Protocal. [Internet]. UNFCCC.

Available at: http://unfccc.int/resource/

docs/convkp/kpeng.html

1 A passive house is a building, for which

thermal comfort (ISO7730) can be

achieved solely by post-heating or post-

cooling of the fresh airmass, which is

required to fulfill sufficient indoor air

quality conditions (DIN 1946) - without a

need for recirculated air. Source:

http://www.passivhaustagung.de/

P a s s i v e _ H o u s e _ E / p a s s i v e h o u s e _

definition.html

2 See http://www.passiv-on.org/

3 See http://www.passiv.de/07_eng/ news/

CEPHEUS_final_short.pdf

Irelands first Passive House, Wicklow.

Source: MosArt Architecture.

The OLearys embark on their passive house project.



13/48

SECTION TWO

How to Design & Speciy a Passive House in I reland


14/48

This section introduces the passive

house building design process as well asexplaining the balance between energylosses and gains. It also provides anoverview o the various building systemsand technologies typically employed ina passive house and presents the PHPP

sotware used or energy balancecalculations. The design andspeciication o the example prototypepassive house in the Irish climatedeveloped as part o these guidelines

will be covered in greater detail inSection 3.

2.1 Building Design Processor a Passive House

Clients BrieThe design o a passive house willtypically commence with developing a

brie with the Client, whether this is aamily wishing to build a single rural

dwelling, a Local Authority progressing ahousing scheme or a commercialdeveloper proposing a mixed residentialproject. The brie would typically outlinethe Clients practical requirements interms o space unctions and density

and also their preerred image orconcept or the building(s). Clientsinterested in building a passive housewill oten have carried out aconsiderable amount o research on the

subject and so will already be relativelywell inormed regarding the beneits oliving in a passive house.

Site Visit

A site visit is important to (thus reducingthe potential or achieving a glazedsouth acing aade) identiy thepresence o structures, landorm orevergreen trees which might castshadows on the house during the short

winter days when the sun is low in the

sky. It may happen that the best viewsrom the site are to the north suggesting

the placement o large glazing areas onthe northern aade in order to optimisethe best view. All orientation optionsmust be considered by the designer atthis stage - the house must not only

unction well in terms o energyeiciency but also in terms o optimisingthe potential o the site and itssurroundings.

Sketch DesignThe next phase o the design process isto develop a sketch design or the house.

The basic principles o passive housedesign will greatly inorm thedevelopment o the initial design. Anideal approach would be to have thelongest aade o the house acing

south, a bias o glazing towards thesouthern elevation with reduced glazingarea on the northern elevation and acompact orm in order to minimisesurace to volume ratio. Shading devicesmay be required in order to protect

against the risk o overheating insummer and the aesthetic integration othese are essential. In terms o internallayout, it is preerable to organise, wherepossible, amily rooms and bedrooms on

the southern elevation with utility roomand circulation spaces on the northernelevation where availability o sunlight is

not so critical.

Initial Evaluation o Energy PerormanceOnce the sketch design has beenapproved by the client, it is important to

test the energy balance o the housedesign using the Passive House PlanningPackage (PHPP). The essential elementso the design are entered into thespreadsheet U-values o walls, loors,

roo and glazing as well as orientation,

volume, and size o the house. This willprovide an early indication o whether

the Passivhaus Standard is beingachieved. I the space heat requirementis signiicantly above the threshold o15kWh/(m2year) then the building willhave to be modiied whether in terms o

improved U-values, reorganisation oglazing or adjustment o orm. Thedesigner should intuitively know howimprovements can best be achievedwhile broadly remaining true to the

agreed sketch design. I the space heatrequirement is signiicantly less than thethreshold level, then it might be possibleto increase the U-values and thereoresave on insulation costs. Care should betaken to note other perormance

indicators calculated by the sotware,such as requency o overheating, or

example.

Detailed Design and Speciication

The design o the house is nextdeveloped to the level o detail requiredto apply or planning permission.Typically this would not require allconstruction details but it is wise toconsider the various technologies at this

stage in order to avoid diiculties lateron. The type o construction will need tobe considered, whether timber rame,concrete, externally insulated masonry,insulated concrete ormwork, straw bale,

etc as well as the space required orservices such as solar panels, largedomestic hot water tank, mechanicalventilation equipment with supply andexhaust ducting. The speciication osuch services might be outside the

expertise o the house designer and itmay be required to commission theservices o a Mechanical and ElectricalEngineer. It is also critically important toplan ahead in terms o airtightness and

9

How to Design & Speciy a Passive House in Ireland


15/48

cold bridging detailing as these otenrepresent the most challenging aspectso passive house design. The detaileddesign should be re-tested in the PHPPsotware to ensure that the Passivhaus

Standard is achieved. At this stage all therequired data ields have to becompleted as accurately as possible

(details of the PHPP tool datasheets isoutlined in section 2.3.1). This mightrequire some minor redesign o the

initial house design. The Client shouldbe kept inormed at all times o thedecisions being made by the designteam and have the opportunity tosuggest alterations should the need

arise.

Tender Documents and DrawingsOnce planning permission has beengranted, a more detailed set o technicaldrawings will be required in order to

enable the construction o the house. Ashighlighted above, the emphasis will beon detailing o junctions betweendierent elements o the building,practical requirements or minimising

heat loss through cold bridging,planning or airtightness and thelocation and routing o services. Thesizing o the ventilation equipment,back-up space heating, solar domestichot water system, as well as details o

controls or space and water heating andventilation, will have to be speciied atthis stage. The detailed drawings andspeciication can then be issued ortender to competent contractors.

Site OperationsThe detailed design o the passive housemust now be realised on-site and qualitycontrol is paramount to achieving thestandard envisaged in the PHPP

sotware. The most challenging aspectwill typically be achieving the required

level o airtightness, as this is greatlyaected by the quality o cratsmanshipon site. The challenge becomes all themore diicult i the building contractorhas no prior experience o building tothe Passivhaus Standard. More

challenging again is the commonpractice o the house built by direct

labour and without an experiencedsupervisor with overall responsibility toachieve the high standards set.

It will usually be necessary to engagespecialist Sub-Contractors to supply andinstall such elements as the ventilationequipment, solar system, back-upheating systems and controls.

Post Construction TestingThis is the inal stage to determinewhether the constructed dwellingactually meets the air-tightness

requirements o the PassivhausStandard. The air-leakage must notexceed 0.6 air changes per hour using50Pa overpressurisation andunderpressurisation testing. Anindependent inspection and testing

body should conduct the testingactivities. It is important to undertakethis test as soon as the airtight layer iscomplete so that any leaks can berectiied. When the house does not meet

the requirements urther testing may berequired.

2.2 General Principles: HeatEnergy Losses & HeatEnergy Gains

2.2.1 Passive House Building

Envelope

The building envelope consists o allelements o the construction whichseparate the indoor climate rom the

outdoor climate. The aim o the passive

10

Roof Loss 30%-35%

Flue Loss

VentilationLoss 25%

Window Loss 15%

Floor Loss 7%-10%

Loss throughWalls

25%-30%

Areas of Heat Loss in Homes

Comparison typical building fabric heat loss patterns

in a detached dwelling, excluding ventilation and

infiltration. Source: SEI.

Figure depicting 2005 Building Regulation standard required for insulation and required insulation to meet the

Passivhaus Standard in Ireland. Source: UCD Energy Research Group.

Thermographic image illustrating difference in heat

loss through building envelope in a conventional and

passive house building.


0

0.05

0.1

0.15

0.2

0.25

0.3

321

U-valueW/m

K

TGD Part L

Passive House

Walls RooFloor

2

Thermal transmittance (U-value)

relates to a building component or

structure, and is a measure o the rate

at which heat passes through that

component or structure when unit

temperature dierence is maintained

between the ambient air temper-

atures on each side. It is expressed in

units o Watts per square metre per

degree o air temperature dierence

(W/m2K).

Source: Building Regulations Technical

Guidance Document, Part L Conserv-

ation of Fuel and Energy 2005.


16/48

house is to construct a buildingenvelope that will signiicantly minimiseheat loss and optimise solar and internalheat gain to reduce the space heatingrequirement to 15KWh/(m2year).

The ollowing building envelopeparameters are undamental in thisprocess:

1. Well insulated building envelope

2. High energy perorming windowsand doors

3. Minimised heat loss through thermalbridging

4. Signiicantly reduced structural airiniltration

5. Optimal use o passive solar andinternal heat gains

Building Envelope InsulationMany building methods can be used inthe construction o a passive house,including masonry, lightweight rames(timber and steel), preabricated

elements, insulated concrete ormwork,straw bale and combinations o theabove. The prototype house presentedin this publication (details in Section 2and 3) illustrates both masonry andtimber rame construction as

representative o most typically usedbuilding methods or dwellings inIreland.

Continuous insulation o the entire

thermal envelope o a building is themost eective measure to reduce heatlosses in order to meet the PassivhausStandard.

A thermographic image is used toillustrate the dierence between thewell and poorly insulation levels in ahouse. Heat loss through the buildingenvelope is highlighted by the green,yellow and red colouring. The amount o

radiation emitted increases with

temperature, thereore warm objectsstand out well against coolerbackgrounds. In the passive house someheat is lost through windows but heatlost through the external wall is very low.In the conventional building, on the

other hand, there is heat loss rom theentire building envelope, especially

through windows.

Insulation o the building envelope can

be divided into our distinct areas:external wall, loor, roo and windows.Existing passive houses in Central andNorthern European countries have beenachieved with U-values or walls, loorsand roos ranging rom 0.09 to 0.15

W/(m2K) and average U-value orwindows (including glazing and windowrames) in the region o 0.60 to 0.80W/(m2K). These U-values ar exceedthose currently required under the Irish

Building Regulations, with the mostmarked dierence pertaining towindows, wall and loor.

A sensitivity analysis using the Passive

House Planning Package (PHPP), v2004,sotware was undertaken using a rangeo U-values or the timber rame andmasonry constructions o the prototypehouse using climate data or Dublin. In

all options tested the same data wasinput into PHPP or air-tightness0.6ac/h@50Pa, ventilation andminimised thermal bridging. Various

parameters were tested in order todetermine, or example, the required

level o U-values or the buildingenvelope in the Irish climate, and toascertain whether it would be possibleto use double glazing and still achievethe Passivhaus Standard in Ireland. Theresults are: Option 1 being the most

energy eicient house and Option 8being the least energy eicient. Anoutline description o each o the eight

11

Irish Building Regulations, ElementalHeat Loss Method (BuildingRegulations Technical GuidanceDocument Part L, Conservation oFuel and Energy 2005).

Maximum average elemental U-value

W/(m2K)

Pitched roo, insulation horizontalat ceiling level 0.16

Pitched roo, insulation on slope0.20

Flat roo 0.22 Walls 0.27 Ground Floors 0.25 Other Exposed Floors 0.25 Windows and roo lights 2.20

*Regulations due to be updated in 2008

Light filled room in a passive house.


Light, bright and airy.


Windows on the northern elevation should ideally be

small. Source: MosArt Architecture.

Comparison of the interior surface temperature depending on the type of glazing.

Source: Internorm, fensterLichtund Leben catalogue 2007/2008, pp.91.


17/48

options analysed is provided. Only theirst our achieve the PassivhausStandard set or space heating(delivered energy) o 15 kWh/(m2year)treated loor area:

Option 1 - U-value 0.10 W(m2K) or allbuilding elements combined withtriple gazed windows with averageU-value (including glazing and

window rames) o 0.80 W(m2K)results in space heating requirementsigniicantly below the standard

required o 15 kWh/(m2 year).

Option 2 - (This is the option that has

been used in the design o theprototype passive house in Ireland aspart o these Guidelines), with U-value 0.15 W(m2K) or all buildingenvelope elements combined withtriple glazing. The results show space

heating requirement below thePassivhaus Standard.

Option 3 - All building envelopeelements with U-value o 0.10

W(m2K) combined with an eicientdouble glazed unit with low U-value1.1 W/(m2K) achieves the PassivhausStandard.

Option 4 - U-value 0.175 W(m2K) orexternal walls and U-value 0.15

W(m2K) or all other buildingenvelope elements, coupled withtriple glazed windows. The result isexactly at the threshold o thePassivhaus Standard but was not

used or the prototype house as thereis no margin in site operations.

Option 5 - U-values or walls, rooand loor employed in the Irish

Building Regulations, Elemental HeatLoss Method (Building RegulationsTGD Part L, Conservation o Fuel and

Energy 2005) combined with tripleglazed windows, ailing to achievethe required standard.

Option 6 - also a ailure is thecombination o U-value 0.10W(m2K)or building abric in combinationwith standard double glazed units.

Option 7 - U-values 0.15 W(m2K) orwalls, roo and loor as the prototypehouse but with standard doubleglazing U-value 2.20 W(m2K) which

comes way above the Passivhaus

Standard. Option 8 - U-values or walls, roo

and loor employed in the IrishBuilding Regulations, Elemental Heat

Loss Method (Building RegulationsTDG Part L, Conservation o Fuel andEnergy 2005) and standard doubleglazed units underachieving thePassivhaus Standard.

Thermal ConductivityThermal conductivity (-value) relates to

a material or substance, and is a measureo the rate at which heat passes througha uniorm slab o unit thickness o thatmaterial or substance, when unittemperature dierence is maintainedbetween its aces. It is expressed in units

o Watts per metre per degree (W/mK),(Building Regulations TechnicalGuidance Document Part L,Conservation o Fuel and Energy 2005).Insulation materials or walls, roos and

loors vary in terms o thermalconductivity. Typical conductivities ordierent insulation materials areincluded below as well as theapproximate thickness required in orderto achieve a U-value o 0.15 W(m2K) and

0.10W(m2K). (Table 4)

Typical insulation materials used inIreland include mineral wool,polystyrene, polyurethane, polyiso-

cyanurate, sheep wool and hemp.Dierent insulation materials suitdierent types o construction

12

Note: Advantages and disadvantages

of using triple glazed windows are

discussed in detail in section Windows

& Doors)

Note: Results presented here are

indicative only and should be used as

starting point for specification of a

passive house dwelling in Ireland.

Meeting the Passivhaus Standard must

be tested and verified with the PHPP

software for the specific dwelling

design.

Option U-Values o

ext. wall U-Values o roo

U-Values o

foor

Average

U-Value o

windows and

doors

Space heating

requirement

1 0.10 W(m2K) 0.10 W(m2K) 0.10 W(m2K) 0.80 W(m2K) 8 kWh/( m2a)








Table 3: Sensitivity analysis of the passive house prototype house in Ireland outline test results for eight options. Source: MosArt Architecture.


18/48

application and it is important to use thematerial best suited or the situation. Forexample, cellulose insulation is suitableor use in an open attic space where itwill ill completely between ceiling joists

in comparison with rigid insulationwhere there is a high risk o thermalbridging unless cut perectly to it

snuggly between the joists. Conversely,a high density rigid insulation is bettersuited under a loor slab compared with

insulation that easily compress or areaected by moisture.

The U-value o the construction isdetermined by the conductivity o

materials and components used romthe internal surace to the externalsurace o the thermal envelope.Examples o typical constructionmethods and materials used or theprototype passive house in Ireland are

illustrated later in Section 3.

Windows & DoorsThe recommended approach to thedesign o a passive house is to have

avoid excessive area o north acingglazing and place relatively largewindows acing south or due south. Thisis in order to minimise heat lossesthrough the north acing elevation,which receives no direct sunlight, while

maximising ree solar heat gains on thesouth. An advantage o large windows isan increase in interior day light levels

which in turn reduces the need or use oelectricity or artiicial lighting and also

ensures a more pleasant natural light-illed living environment.

There is, however, a balance to beachieved between heat losses throughthe glazing and solar heat gains through

the south/east/west acing windows.When designing a passive house, PHPPsotware should be used to calculate theheat losses and heat gains taking intoaccount building orientation, areas o

glazing and speciic types o glazing so

the optimum balance o glazing or eachpassive house design can be reached.

It has been illustrated above that the useo windows and doors with average U-values o 0.8 W/(mK) can be combinedwith U-values or opaque elements o0.15 W/(mK) to comortably achieve the

Passivhaus Standard in Ireland. There area number o advantages in usingwindows with average U-values o 0.8W/(mK) as well as highly insulateddoors, principally the assurance o a

comortable indoor climate due to thelower cold radiation heat transer at thesurace o the glass. One will not sense adrop in temperature standingimmediately adjacent to this standard owindow, unlike the experience o

standing next to a conventional doubleglazed unit with U-value, or example o2.2 W/(m2K). An added beneit o using

highly energy eicient windows anddoors includes signiicant draught

reduction due to the act that they havetypically two seals or gaskets (comparedwith conventional double glazed unitswhich oten have only one) as well asexcellent sound insulation. Finally,

natural convection which is driven bytemperature dierence between theinside ace o the glass and the roominterior is much reduced with which inturn will reduce cold air lows andthermal discomort.

The sensitivity analysis or a passive

house dwelling in Ireland (showed inOption 3), achieves the PassivhausStandard yearly space heatingrequirement with extremely eicientdouble glazed windows with a U-value

no greater than 1.1 W/(mK). When usedin a passive house, however, they mustbe used in conjunction with very low U-values or all other elements o thebuilding envelope. This may negate anyinancial saving in not using more

eicient glazing as well as compromise

the thermal comort level in the house.

Typically triple glazed window units areused in passive houses in Central andNorthern Europe. The Passivhaus Institut

has certiied a range o glazing and doorunits suitable or use in passive housebuildings. Although it is not aprerequisite to use certiied passivehouse products (http://www.passiv.de) ina passive house, choosing approved

products means the validity o technicaldata has been tested and veriied by anindependent certiier. The principlecharacteristics and advantages o usingtriple glazed windows in a passive house

are listed below, or both windowglazing and rames:

Glazing Three panes o glass separated by

special low-conductivity spacers

eliminates the risk o condensation atthe bottom o the glass in coldweather (which may lead to rottingo timber rames over time).

High solar energy transmittance (g50) which allows solar radiation topenetrate the glass and contributetowards heating o the dwelling.

A low emissivity (low-e) coating onthe inside o the outer two paneswhich reduces solar re-radiation backout through the glass. It should benoted that a sot coat has slightly

better U-value but a hard coatglazing has higher solar trans-mittances.

Insulating gases between the glasspanes, typically argon or krypton,

which help to reduce heat escapingthrough the glass.

Frame The rame must be well insulated and

also be thermally broken. Even wood

conducts heat and a thermallybroken timber window rame willresult in much lower heat losses thana solid one.

There will typically be two weathergaskets on triple glazed windowsused in a passive house dwelling, theprimary unction o the outer onebeing or weathering with the innerone serving to improve airtightness.

The majority o these types owindows open outwards which iscommon place in Continental Europe

13

Insulation MaterialType

Thermal

conductivity W/mK

Thickness or

U-Value o 0.15

W(m2K)

Thickness or

U-Value o 0.10

W(m2K)

Polyisocyuranate orpolyurethane

0.023 145mm 220mm

Polystyrene, sheep wool 0.035 220mm 340mm

Cellulose, Hemp andRockwool

0.04 250mm 400mm

Wood 0.13 825mm 1,250mm

Table 4: Conductivity of insulation materials and approximate thickness to achieve specific U-value for external

walls. Source: MosArt Architecture.


19/48

however, there are models o inwardopening windows being developedwhich will soon be available in theIrish market. One advantage ooutward opening windows is that

they dont intrude in the room spacewhich may be important in morecompact dwellings.

Triple glazing window rames aretypically much wider and strongerconstruction than their conventional

double glazing counterparts.

Triple glazed windows with low-emissivity coating and insulatedwindow rames will have improvedU-values compared to double glazedwindows, resulting in less heat loss.

However with triple glazing the solarenergy transmittance (gs), that is, theamount o solar energy entering

through that glazing, is somewhatreduced compared to double glazingdue to the eect o the additional

layer o glass. The requirements othe Passivhaus Standard is to useglazing with minimum solartransmittance o 50% or higher.

The use o larger areas o glazing on the

south elevation is helpul in maximisingthe amount o sunlight available in theshort days o winter. It must beremembered, however, that highlyenergy eicient windows allow less

daylight (visible light transmittance) intoa building than a normal double glazedwindows without e-coating. Lighttransmittance is an optical property thatindicates the amount o visible lightbeing transmitted through the glazing.It varies between 0 and 1 (0 to 100%

light transmitted) with the higher thelight transmittance value the more lightis transmitted. A double glazed windowwith low-e coating will transmit 72% ovisible light. A triple glazed energy

eicient window will transmit 65% ovisible transmittance (these areindicative values only - actual valuesdepend on the manuacturers speciic-ation).

In a conventionally constructed house in

Ireland radiators are typically positionedunder windows in order to heat the coldair entering through the single ordouble glazing. In a passive houselocating radiators beneath windows issimply not required as the heat load is

transerred throughout the house viathe mechanical ventilation system. Thishas the added beneit o enablingunobstructed use or placing urnitureagainst all external walls.

Thermal BridgingThermal bridging (i.e. un-insulated jointsbetween walls, loors/walls, ceilings/adjacent walls, windows/walls etc) areweak points o the building envelope

and cause unwanted losses o energywhich should be eliminated orsigniicantly reduced to a degree thatthe associated heat losses becomenegligible.

A thermal bridge increases heat lossthrough the structure, and in someextreme cases this may cause suracecondensation or interstitial conden-sation in the structure. Surace mould

growth or wood rot may be theconsequences o a thermal bridge.Typical eects o thermal bridges are:

Signiicantly increased heat losses.

Decreased interior surace temper-ature which may result in highhumidity in parts o the construction.

Mould growth cause by warminternal air condensing on coldsuraces.

All o the above situations can beavoided in houses built to thePassivhaus Standard. The Passivhaus

Standard or linear thermal trans-mittance () should not exceed 0.01W/(mK). This requires the buildingdesigner to identiy and locate allpotential thermal bridging in theconstruction, careul speciication anddetailing o those elements providing

where possible a continous layer oinsulation, as well as care being taken toexecute those elements on site as perdesign details.

Designing and building a passive housein Ireland requires the development o

construction details that go ar beyondguidance provided (to avoid excessiveheat losses and local condensation) inBuilding Regulations Technical Guidance

Document Part L, Conservation o Fueland Energy 2005. Building practitionerscould reer to the accredited con-struction details speciically developedor passive house building published in

Germany Thermal Bridge-Free Con-struction (PHPP 2007, pp.96). Thermal

14

Cross section though a triple glazed insulated window

and frame. Source: MosArt Architecture.

The risk of internal condensation is dramatically

reduced. Source: MosArt Architecture.

The quantity which describes the heat

loss associated with a thermal bridge is

its linear thermal transmittance ().This is a property o a thermal bridge

and is the rate o heat low per degree

per unit length o bridge that is not

accounted or in the U-values o theplane building elements containing

the thermal bridge.

Source: SEI, Dwelling Energy Assess-

ment Procedure (DEAP) 2005 edition,

version 2, pp.55


20/48

bridging can be tested and veriied inthe PHPP sotware as the design o thepassive house building is beingdeveloped.

Structural Air-Tightness and Draught-ProoingBuilding an airtight or leak-ree structureis imperative to achieving the PassivhausStandard. I there are gaps in the

building structure then uncontrolledamounts o cold external air caniniltrate the building. Achieving a highlevel o air-tightness eliminates colddraughts and associated comort losses.It also prevents condensation o indoor

moist, warm air penetrating thestructure, and possible structuraldamages due to decay, corrosion androst.

Air-tightness is achieved by careulapplication o appropriate membranesand tapes or wet plastering in concreteconstruction within the buildingenvelope. A great deal o attention mustbe paid to detailing and workmanship in

order to ensure that the airtight layer iscontinuous all round the building,especially around junctions betweenwalls and loors, roo, windows, doors,etc. Penetrations o the airtight layer bymechanical and electrical services must

be properly sealed.

The air-tightness o a building can beaccurately measured by carrying out ablower-door test. The test involves

placing a powerul an suspended in acanvas sheet within a door opening andoperating the an at very high speedsthereby creating either negative orpositive pressure within the house. Bysucking air out o the house, or

example, a negative pressure is createdwith the result that external air will besucked in through any gaps or cracks inthe building envelope. The pressureused or such tests is 50 Pascal which can

be accurately set by the blower door

equipment.

When undertaking the test it is usuallyquite easy to identiy major leaks due to

the presence o a strong draught whichcan be elt by the hand or, or smallerleaks, can be detected by athermographic camera. The cause othese draughts can then be sealed withappropriate materials as the test is being

undertaken. It may also happen that the

leaks in the envelope are very minor andthereore diicult to locate. In thesesituations it is typical to reverse thedirection o the an and suck air into thehouse putting it under positive pressure.Odorless smoke can then be released

into the building and leaks can beobserved rom the outside where the

smoke appears through the envelope. Itis important to notiy the ire service iyou are carrying out such a test in case it

is mistakenly reported as a house ire bypassers by.

The Passivhaus Standard is reachedwhen there are less than or equal to 0.6air changes per hour @50Pa pressure.

The most critical issue regarding testingor airtightness is timing during thebuilding process. It is important thatremedial measures can be carried out in

order to remedy any leaks or cracks. Thetest should be carried out beore secondix carpentry, or example, when thereare no skirting boards or window boardsitted and where the junctions coveredby such materials are still accessible and

can be sealed. The test should also becarried out ater all mechanical andelectrical services, that need topenetrate the building envelope, havebeen installed. Otherwise, installing

such services ater the test couldseverely compromise the airtightness othe building.

In a typical Irish house built inaccordance with building regulations

TGD Part F 2002 the method in whichhabitable rooms are ventilated is usuallyvia a hole in the wall or ventilator in thewindows o 6,500mm2 itted with a

controllable grille. Such means oventilation can result in large amounts ocool external air iniltrating the buildingdepending on wind speed and pressure.In a passive house, on the other hand,the supply o resh air is provided by a

whole house mechanical ventilation

system with heat recovery whichnegates the necessity or openings inthe wall or windows. Thereby draughtsare eliminated and structural air-

tightness is not compromised.

In developing the building design it isvery important to anticipate dierentialmovement and decay o adhesives andchemical bonds by detailing junctions

which will assist in maintaining an

15

Infrared image of the interior of a passive housewindow. All surfaces (wall structure, window frame,

and the glazing) are pleasantly warm (over 17C). Even

at the glass edge, the temperature does not fall below

15C (light green area).

Source: Passivhaus Institut, http://www.passiv.de from

the passive house Kranichstein).

For comparison, a typical older double glazed windowis shown. The centre of glass surface temperature is

below 14C. In addition, there are large thermal

bridges, particularly where the window meets the

external wall. The consequences are significant radiant

temperature asymmetry, drafts, and pooling of cold air

in the room. IR-photography: Passivhaus Institut.

Source: Passivhaus Institut, http://www.passiv.de from

the passive house Kranichstein).

Timber Frame I-Beam construction reducing thermal

bridging. Source: Passivhaus Institut, Germany.


21/48

airtight layer or the lie o the building.Many excellent details, or example, canbe ound at the website o the ScottishEcological Design Association(www.seda2.org/dfa/index.htm). It is also

important to use membranes andplasters that are both airtight but alsovapour diusing which allow moisture

within the structure to escape to theoutside thereby reducing the risk ointerstitial moisture and the threat o rot

and decay over time.

Passive Heat GainsPassive heat gains in a passive house area result o the combination o solar gainsand internal gains.

Solar Heat GainsPassive solar gain is optimised byproviding an east-west alignment to the

building, i possible on the site, resulting

in the longest aade acing south, andby placing the majority o the glazingtowards the south. Very high qualitywindows (average U-value 0.8W/m2K)

acing south will have a positive thermalbalance - it will have more heat gainthan heat loss throughout the year.Results o a recent parametric study by J.Schnieders o the Passivhaus InstitutClimate Data or Determination o

Passive House Heat Loads in NorthwestEurope illustrates the relationshipbetween the area o south acing glazingand the space heat demand or a passivehouse dwelling located in Ireland(measured climate data or Birr used).

The parametric study uses the irstpassive house built by Dr. Wolgang Feisto the Passivhaus Institut as a case studybuilding, shown below. It can be seenthat the space heating demand initially

decreases quite steeply with increasingsouth acing glazing. There arediminishing returns rom increasing thearea o south acing glass, however, andthere eventually comes a point wherethere is little or no beneit in providing

more south acing glass as the net heatloss is greater than the heat gains overthe year.

There is no optimal ratio o glazing toloor area that can be used as a rule othumb in deciding what proportion o agiven aade should be glazed. The area

o glass has to be determined as part othe design veriication procedure usingthe PHPP sotware.

Internal Heat GainsA passive house is very eicient atutilising ree internal heat gains romdomestic household appliances, kitchenand utility equipment, electronicequipment, artiicial lighting, and

occupants. Heat losses rom stoves orboilers also contribute towards the

overall space heating requirement aslong as they are positioned within thebuilding envelope. Occupants o the

building also contribute to the heat load- a human continuously emits 100W oheat when stationary. A amily o ivepersons, thereore, can emit 0.5KW oheat. This may seem like a small amountbut it equates to approximately one

third o the total space heat load or theprototype passive house presented inSection 3.

Risk o Overheating

Placing extensive areas o glass on thesouth acing aade in a well insulatedand air-tight dwelling may lead tooverheating in warm sunny days. ThePHPP sotware will alert the designer toany risk o overheating by calculating

the requency o overheating expressingthis as a percentage o the year in whichthe internal temperature in the houserises above 25oC. I requency otemperatures over the comort limit o

25oC exceeds 10% o the year, additionalmeasures or reducing overheatingshould be included in the dwelling. Toprevent uncomortable indoortemperature in a passive house dwelling

it is recommended to speciy shadingdevices (blinds, overhangs or awnings,etc.) which allow low sun to enter thehome in winter but prevent the high sunentering in summer.

In the irst Irish passive house in Wicklowshading was not in place on the southacing glazing during the irst summerand the house did overheat. A balconywas installed ahead o the second

summer, which signiicantly reduced therequency o overheating. In mid-summer when the daylight hours arelong the sun only enters the buildinglater in the day while during winterwhen the daylight hours are short the

low sun completely illuminates theentire interior o the building.

In the temperate climate in Irelandwhere external temperature rarely

exceeds 25oC, the risk o overheating

16

Correctly insulated house avoiding thermal brid.

Source: Passivhaus Institut, Germany.

Timber frame house pre-cladding fitted airtight

membrane. Source: Passivhaus Institut, Germany.

Continuous Airtight Membrane.

Source: IG Passivhaus Osterreich Innovative Passivhaus

projekte.

There are two measurements used to

deine airtightness, namely cubic

metres o air per square metre o

external envelope per hour (m3/m2h) or

air changes per hour (ac/h). While the

measured result or the ormer is

generally 20% greater than that o the

latter, the dierence is practice greatly

depends on the building orm.


22/48

should be avoided by careulconsideration o shading devices,provision o openings or natural

ventilation in combination with thermalmass inside the dwelling (exposedconcrete loor; masonry wall, etc.). In

some cases the mechanical ventilationsystem could be used to distribute reshair throughout the building by switchingto a summer bypass setting. Thishowever should be avoided where

possible as the ventilation system willconsume electricity resulting inincreased primary energy. The dwellingdesigner should employ passivecoolingstrategies to minimise overheating.

2.2.2 Passive House Building

Systems

As explained earlier a passive housedoes not need a conventional space

heating system o radiators orunderloor heating to maintain acomortable indoor climate. Instead,typically, the ollowing building servicesare required in a passive house:

Mechanical ventilation system withheat recovery which provides most othe space heat requirement.

Back-up system capable o heatingthe air passing through the dwellingvia mechanical ventilation. Typicaluel sources or the back-up systeminclude biomass, gas, and in someinstances electricity (or example

green electricity rom renewablesources). Since the demand or spaceheating in a passive house dwelling isvery low, the back-up system is usedto provide hot water, either

throughout the year or during winteri a solar water heating system is usedduring summer.

Each o these items is dealt withseparately in greater detail below.

Given the lengths to which the designerand builder go to in terms o ensuring a

highly insulated building envelope,excellent air-tightness and minimalthermal bridging, it is important that thebuilding services in a passive house areas energy eicient as possible. This is

especially critical in the case o themechanical ventilation heat recoverysystem. Thereore, the required

eiciency o the mechanical ventilationsystem with heat recovery or a passivehouse dwelling is 75%. It is also very

important to consider comort, healthand saety issues in the design o thebuilding services or a passive house,ensuring or example that the back-upheating system is adequately sized to

deal with extreme weather conditions;that ilters in the ventilation equipmentare replaced regularly and that there is aresh air supply or any combustiondevices such as a boiler. These and other

issues are dealt with in greater detailbelow.

Mechanical Heat Recovery Ventilation(MHRV)An airtight house requires a well-designed mechanical ventilation system

to provide good indoor air quality. Apassive house is ventilated using amechanical system which incorporatesair to air heat recovery (mechanicalventilation heat recovery, or MVHR).

17

Climate Data for the Determination of Passive House Heat Loads in Northwest Europe.

Source: J. Schnieders, Passivhaus Institut.

No more than 0.6 air changes/hour at 50 Pascal

pressure should be observed in accordance with the

Passivhaus Standard. This should be checked for

compliance with a blowerdoor test which will

immediately highlight leaky areas. Air-tightness can be

achieved through the use of membranes, roofing felts

and plasters combined with sealants and vapour

diffusing resistant materials.


Location of overhang and balcony.


Lighting contributes towards internal heat gains.


0

4

6

810

1

14

16

18

0

4

0 10 0 30 40 50 60

Area South Facing Windows [m2]

SpaceHeatDemand/HeatLoad

Space Heat Demand [kWh/(m2a)]

Heat Load [W/m2]

Ireland - Birr

U-Value Wall = 0.175 W/(m2K)

U-Value Window = 0.85 W/(m2K)

Deep roo overhang shadesupstairs windows

Balcony shadesdownstairs windows


23/48

Exhaust air is extracted rom rooms thattypically produce heat, moisture andunwanted smells such as kitchens andbathrooms. Beore this air is expelled tothe outside it passes through a heat

exchanger where the heat is transerredto the incoming resh air, therebyeliminating the need to completely heatthe resh air as it enters the building. It isimportant to highlight that the staleexhaust air and clean resh air do not mix

in the heat exchanger and thereorethere is no risk whatsoever o whatmight be reerred to as sick buildingsyndrome. Rather, the stale air and cleanair is channelled through closely spaced

but separate narrow sleeves in the coreo the heat exchanger.

The beneits o having a whole-housemechanical heat recovery ventilation

system (MHRV) are many, including:

Constant supply o the correct

amount o resh air to all habitablerooms thereby reducing CO2 levelsand removing the cause o stuinessand tiredness.

Simultaneous extraction o moisture-laden air rom bathrooms, utilityrooms and kitchens as well asventilating noxious gases and

unwanted smells i present.

A lowering in humidity levels

reducing mould and ungus that mayappear over time and decreasingdust mite levels.

System Eiciency

The eiciency o the heat exchanger inthe MHRV determines the amount oheat that can be recovered rom theexhaust air and, thereore, has a verysigniicant inluence on the additional

space heating that may be required in apassive house. The aim is to use thewarm exhaust air to raise the temper-ature o the cool resh air to provide orthermal comort all around the house.

On a night where outside temperaturesare below reezing, the resh air shouldbe raised to, or example, 18oC, havingpassed through the MVHR. Theeiciency o sensible heat recoveryshould exceed 75% or the nominal

range o low rates speciied or the unitwhen measured in terms o the supply-air side temperature ratio as described inEN 13141-7:2004.1 Speciiers anddesigners should be wary o products

claiming extraordinary eiciency rates o95% or higher. The saest route is to

install equipment that has beenindependently tested and veriied bysuch bodies as the Passivhaus Institute.

The graph above is based on actualtesting o the irst Irish passive house in

Wicklow. It illustrates, or example, howmechanical ventilation ensures goodindoor air quality by removing the highconcentrations o a tracer gas that wasdeliberately released into the house aspart o the test procedure. In less than

1.5 hours the air quality in the house hadreturned to normal.

Recommended Ventilation RateAccording to the Passivhaus Institut, theappropriate air change rate or dwellingsis between 0.3 and 0.4 times the volume

o the building per hour, with a generalrecommendation o leaning toward thelower rate. This maintains high indoor airquality while ensuring a comortablelevel o humidity and maximizingenergy savings.

18

Photo depicting how the low winter sun enters the

room below the overhang/awning/balcony.


Schematic of the supply air ducts, the extract air ducts

and the heat exchanger within mechanically

ventilated house. Source: Passivhaus Institut.

The sommer-bypass can be used for cooling in the

summer if needed. Source: MosArt Architecture.

Photo depicting how the house is shaded from the high

summer sun by the overha ng/awning/balcony.


Graph depicting how mechanical ventilation ensures a good indoor air quality by removing the high concentrations

of tracer gas that were inserted into the house under test conditions. Source: UCD Energy Research Group.

IR

Concentration

Hours


24/48

The PHPP sotware suggests that 30m3

per person per hour should be providedto dwellings to ensure good air quality.These two measurements can be used tochoose an appropriately sized machine

or dierent dwelling designs. Taking theprototype house presented later inSection 3 as an example, an occupancy

o 5 persons would require 150m3 oresh air delivered to the house per hour.In terms o extract, the PHPP sotware

uses the ollowing rates or dierentroom types as deault values, kitchen =60m3h, bathroom = 40m3h, shower =20m3h and WC = 20m3h. In the prototypehouse these total 140 m3h which is close

to the supply volume which will ensurethat the whole house system will bebalanced. The supply and extractvolumes can be accurately set by using adigital anemometer and adjusting thevalves on the vents in each room as

required.

Adjustment o Fan Speed and ExchangeRateMost MVHR machines have dierent

settings or dierent circumstances.These are oten reerred to as a partysetting, where there are a lot o peoplein the house and where additional reshair is required, and holiday setting,where the house is being let vacant and

the low o air is reduced. The ormer othese settings will use more energy andalso decrease the level o humiditywhereas the latter will use less energyand perhaps lead to an increase in

humidity.

It is not advisable to constantly run theequipment on the lower setting just tosave energy when the house isoccupied. MHRV machines uses

surprisingly little energy given theimportant role that they play in thepassive house. The PHPP sotware usesstandard value 0.45Wh or every m 3

transported air sotware in the

calculation o electricity due to MHRV.When designing a passive house inIreland the speciic an power should becareully considered as the electricityconsumed or ans has direct impact interms o primary energy perormance

and energy labelling, the BuildingEnergy Rating (BER), recently introducedto Ireland. Thereore, speciic an poweror ans should be less than 1w/l/s.

Winter and Summer ModeThere are generally two ventilationmodes in a passive house: SummerMode and Winter Mode. In winter, theMHRV uses the heat in the exhausted air

to warm the incoming resh air. Insummer, a bypass in the equipment canbe set to open automatically (controlled

by thermostats) such that the incomingresh air is not heated. Alternatively insummer natural cross ventilation may be

used and the MHRV system can beswitched o.

Insulation and Positioning o Duct Workand VentsIit is very important to adequatelyinsulate the supply air ducting so that

there is minimal loss o temperature indelivering warm air around the house.The thickness o insulation generallyused in passive houses is between 6cm

and 10cm or ductwork. It is alsopreerable to locate the ducting within

the thermal envelope and to keep piperuns as short as possible by ideallypositioning the MVHR unit in the centreo the house. This requires careulplanning at a very early stage o building

design.

Vents are normally placed in the ceilingbut can also be placed in the wall inecessary. The air inlets are typicallydesigned to spread the air horizontallyacross the ceiling, minimizing down-

ward drats. There should be a gap eitherunder or over the door o each room toenable the easy movement o air romone room to the next. I doors are ittedtight without such a gap, rooms withexhaust vents would be under negative

pressure and rooms with supply airunder positive pressure.

NoiseFan and valve noises can be almostcompletely eliminated by sound controlmeasures (e.g. vibration isolation

mounts, low air speed and acousticlining in ducts). The grilles on ventsgenerally guide incoming air along theceiling rom where it uniormly diusesthroughout the room at velocities that

are barely perceptible. I the ventilationequipment is operating on a highsetting (Party Mode) the noise o theequipment and the air low may be morenoticeable. MVHR machines aregenerally housed in a well insulated

19

A pellet stove is at the hearth of an Irish passive house.


The ventilation system can be used in a sealed closet todry clothes. Source: MosArt Architecture.

Supply air ducts should be well insulated.


Ceiling air supply vent.



25/48

casing and noise should not be a criticalissue.

Maintaining Good Air QualityIt is important that attention is paid to

regular replacement o air-ilters or bothincoming and exhaust air. Filters areused not only to provide clean air or theoccupants but also to ensure that theheat exchanger is not clogged with dust

and other matter. I the ilters are notregularly replaced (or example every sixto twelve months) and they themselvesbecome clogged with dirt the MHRV willhave to work harder to provide the samevolume o air to the house, thereby

increasing the speeds o the ans and,ultimately, using more energy. Incountries where this system is relativelynew, occupants may not be aware o thismaintenance need and indoor air qualitymay suer as a consequence. Equipment

diers with respect to the types o iltersused, some have to be replaced whileothers can be washed and reused.

Sometimes the extractor hood in thekitchen is connected to the MHRVequipment to extract kitchen smells and

to use the waste heat rom cooking towarm the incoming resh air. In suchinstances, it is very important that thehood is itted with a high quality ilterthat can easily be cleaned or replaced in

order to prevent the built up o grease inthe ducting system which could be a ire

hazard.

What happens in the event o a powerailure?I there is a loss o electricity (and the

dwelling has no back-up generator) theventilation system will stop working andthe supply o resh air will be cut o. Ipower is lost or a short while (orexample a ew hours), then there is likelyto be no noticeable dierence in indoor

air quality. I the loss o power isprolonged, the simple solution is toopen the windows and to create natural

cross low ventilation through thebuilding.

Back-up Heating System

As previously highlighted in theseguidelines, space heating requirementin a passive house is so low that there isno need or a traditional space heatingsystem. The optimal way to transer the

small amount o required heat through-out the house is through the mechanical

ventilation system. This section o theguidelines will provide an overview othe typical back-up heating systemsused in passive houses to providethermal comort .

Space heating demand in a passivehouse is typically met through passivesolar gains (4060%), internal heat gains(2030%) and the remainder (1040%)needs to be provided rom building

systems.

The PHPP sotware will accuratelypredict the ollowing two measure-ments or each passive house design:

Annual Space Heat Requirement -this measures the amount o energythat is needed to maintain acomortable indoor temperature,speciied in kilowatt hours per square

metre o treated loor area per year,

or kWh/(m2year).

Heat Load - this measures the

capacity o the space heating systemrequired to maintain comortableindoor temperatures at any one time,speciied in Watts per square metre otreated loor area, or W/m2.

For the prototype house the annualspace heat requirement is15kWh/(m2year) equating to approx-imately 1,650 KWh over an entire year(the house measures 110m2 in treated

loor area). This would equate to 155litres/year o oil, 160m3/year o mains gasor 350kg/year o wood pellets (in bags)at a cost o approximately 92/yearwhen using oil, 55/year when using gas(without standing charges or gas or

345/year with standing charges) or97/year when using wood pellets. Unitprice: heating oil 5.62c/kWh; mains gas3.39c/kWh standing charges 256/year;wood pellets - in bags 5.92c/kWh.

Source: SEI, Dwelling Energy AssessmentProcedure (DEAP) 2005