Energy Efficiency - Putting Old Buildings To The Test

College of Estate Management:

Annual Conservation Alumni CPD Lecture

ENERGY EFFICIENCY:PUTTING OLD BUILDINGS TO THE TEST

Douglas Kent BSc(Hons), BSc, MSc, MRICSTechnical and Research Director,

Society for the Protection of Ancient Buildings

MY BACKGROUNDBuilding surveyorOld buildingsSPAB independent charityAimsPeriods of buildingMembership

CONTENT

Introduction

Energy Efficiency

Alternative Paints for Exterior Timber

INTRODUCTION

INTRODUCTION

Why is SPAB undertaking research:

•Wasn’t it behind much bad LC19th Restoration?

•Don’t we avoid experimentation?

•Isn’t SPAB practical?

•Aren’t old buildings already tried & tested?

INTRODUCTION

User requirements:

Roman Durability Convenience Beauty

Georgian Firmness Commodity Delight

Today Technology Function Aesthetics

Plus: Cost (including the environmental cost)

Conservation requirements (‘extra client’)

INTRODUCTION

Need to respond reasonably to changing user requirements otherwise:

•Old buildings otherwise perceived as liability – have continually evolved•Others more likely to suggest unsympathetic approaches, particularly where commercial interests

INTRODUCTION

Research not incompatible with conservation:

•Understanding buildings is a vital prerequisite

•Sometimes in laboratory, though not always viable

•Owners seek evidence

So, Morris not turning in his grave!

ENERGY EFICIENCY

ENERGY EFFICIENCY

Three main strands of research involving traditional buildings constructed in a range of materials, eg: limestone, brick, granite and cob:

•U-values•Building Performance Survey•Hygrothermal Modelling

ENERGY EFFICIENCY

‘Traditional’ buildings (pre-1919):

•Solid•Breathable (no DPCs etc)•Often non-standardised

ENERGY EFFICIENCY

Risks:

•Aesthetic (eg: SWI)•Loss of fabric (eg: windows & glass)•Colder, damp buildings become warmer, damp ones ...

‘Green Deal’ initiative:

•Government (DECC) finance mechanism for 30 approved measures, including solid wall insulation

•Integrated with Energy Company Obligation (ECO)

•Biggest home improvement scheme post WWII

•Went live 28th Jan 2013 – despite lack of traditional building specialists

ENERGY EFFICIENCY

But:

•EPCs no longer when listed building sold•A-G ratings•Beyond EPBD•Much dubious advice•SPAB view

ENERGY EFFICENCY

U-values

ENERGY EFFICIENCY

Aim:

•Real cf calculatedU-values (heat transmittance)

Method:

•External thermocouple

•Internal heat flux & surface temp sensor

•Probe coming

Example result (Taunton):

•Lime plaster 15mm

Granite 400mm

Cement render 13mm

Lime rough-cast 25mm

•Calculated U-value

2.56W/m2K

•In situ U-value 1.75 W/m2K

ENERGY EFFICENCY

Results:

• Mean U-value heavyweight homogenous walls 1.31W/m2K (DECC now 1.5 cf BRE’s 2.1)

• Calculations underestimate in 77% of cases - sometimes 3 times better than expected

Conclusions:

• Inadequately identified materials of unknown quantities with doubtful thermal conductivity data

ENERGY EFFICIENCY

Building Performance Survey

ENERGY EFFICIENCY

Aim:•Assess range of buildings pre- & post-thermal upgrading (DNP & EH help)

Method:•U-values, air tightness, moisture behaviour & indoor air quality

Three so far post-upgrading

ENERGY EFFICENCY

U-value example result (Drewsteignton):

•100mm polyisocyanurate (PIR) board insulation• 1.24W/m2K•87% reduction in heat loss

U-value results:•68-70% Shrewsbury house (40mm wood fibre insulation) (cf 87% at Drewsteignton)• Discrepancy between measured and calculated U-values post-renovation minimal

Conclusion:• New insulation single most important factor affecting heat loss & known quantity and conductivity data• Air-trapping layers effective

ENERGY EFFICIENCY

ENERGY EFFICENCY

Air infiltration example result (Shrewsbury):

•From 11.4 to 8.5m3h-1m-2 @ 50Pa•0.8ach to 0.6ach through infiltration at ambient temperature•Reflects benefit of secondary glazing

Air tightness test results:• A further property, Riddlecombe, showed little change but was already very air tight• Testing (including IRT) confirmed air leakage around beams, loft hatches & older windows

Conclusions:• Better than the min 10m3h-1m-2 in AD L1A 2010• Riddlecombe below 0.4-0.5ach which may present problems without extra ventilation

ENERGY EFFICIENCY

ENERGY EFFICIENCY

Moisture behaviour example result (Drewsteignton):

•Flatter temperature gradient•Decline in surface & sub-surface moisture levels post-upgrading• However, dewpoint margins decreased at depth

Moisture behaviour results:

• Similar results for dew point margins with IWI at Shrewsbury (40mm wood fibre cf PIR boards) but no RH rise at depth

Conclusion:

•Shows moisture-buffering benefits with wood fibre (‘breathable’) insulation reduce risk of interstitial condensation

MOISTUREi/c can calc DP margin (ie temp drop req to reduce DP), ie degree of risk to fabric from m presentD&R DP margin convergence unlikely to be summer cond as vap press differential unchanged. RH in 2 but not Shre – reflects m buffering and vapour-open nature of internal isnualtion

ENERGY EFFICIENCY

ENERGY EFFICIENCY

Indoor air quality (CO2), comfort & fabric risk example result (Drewsteignton):CO2 unchanged•Temp & RH plotted against comfort/risk index

ENERGY EFFICIENCY

Indoor air quality (CO2), comfort & fabric risk example result (Drewsteignton):CO2 unchangedTemp & RH plotted against comfort/risk index slight improvement

Indoor air quality (CO2), comfort & fabric risk results:

CO2: Little change because reflection of not just air tightness but occupancy levels

Comfort & fabric risk: Indoor air temperature increased in two cases, RH in two

Conclusion:

•Wet finishes a factor?

•Might lime suppress mould & fungus?

ENERGY EFFICIENCY

Hygrothermal Modelling

ENERGY EFFICENCY

Aim:

•Simulate condensation risk pre- & post-upgrading

Method:

•BS EN ISO 13788 (Glaser) & more advanced BS EN 15026-compatible software (WUFI Pro 5.1)

Results:

• BS EN ISO 13788 ignores liquid moisture movement &, consequently, failure caused by insertion of VCLs

• WUFI requires better materials and climatic data

ENERGY EFFICIENCY

Energy efficiency research implications:

• BR 443 & SAP 2009 need revision as U-values the basis of building energy assessments, legislation & policy

•Can significantly improve energy efficiency of traditional buildings but what are the limits – 0.4W/m2K & 0.4-05ach?

• DECC needs to address this before full deployment of the Green Deal

ENERGY EFFICIENCY

ALTERNATIVE PAINTS FOR EXTERIOR TIMBER

ALTERNATIVE PAINTS

Aim:•Identify most durable alternatives to lead paint (with TPF, NT & others)•Changing demand & legislation•35 paint systems - range

Method:•IAW BS EN 927 at PRA•Colour, flaking, mould etc

CONCLUSION•The key to good building conservation is using evidence-based practice to deliver known outcomes

• The need for continuing high quality research is particularly important when it comes to reducing carbon emissions from our stock of traditional buildings – some 25% of the total

•Knowledge, though, complements, & is not a substitute for, experience & judgement

SPAB:• 020 7337 1644• www.spab.org.uk• @spab1877

Project (Saffron Walden): • http://thespab.wordpress.com• @DouglasDKent