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Talk by Douglas Kent at the CEM Carpenters' Hall CPD event – 14 February 2013
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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