1.The thermal performance ofThe thermal performance of traditional windows andtraditional windows and practical measures to reducepractical measures to reduce heat loss and air leakageheat loss and air leakage Paul BakerPaul Baker Glasgow Caledonian UniversityGlasgow Caledonian University Centre for Research on Indoor Climate & HealthCentre for Research on Indoor Climate & Health Paul.Baker@gcal.ac.ukPaul.Baker@gcal.ac.uk 11

2. 22 IntroductionIntroduction 27% of the UK27% of the UKs carbon dioxide emissions can be attributed to thes carbon dioxide emissions can be attributed to the energy used in peopleenergy used in peoples homes.s homes. A third of the COA third of the CO22 emissions from the average home could be savedemissions from the average home could be saved by adopting simple energy saving measures.by adopting simple energy saving measures. Achieving further reductions in carbon emissions from UKAchieving further reductions in carbon emissions from UK households to meet the UK Governmenthouseholds to meet the UK Governments 60% target is a majors 60% target is a major challengechallenge 3. Scottish distribution of dwellingsScottish distribution of dwellings 33 Figure 1: Age of Dwelling (Scottish House Condition Survey Key Findings for 2005/6) 17% 13% 25% 25% 20% 0% 5% 10% 15% 20% 25% 30% Pre-1919 1919-1944 1945-1964 1965-1982 Post 1982 4. National Home Energy Ratings of Scottish housing stockNational Home Energy Ratings of Scottish housing stock by age as a percentage of the total housing stock (SHCS 2005/06)by age as a percentage of the total housing stock (SHCS 2005/06) Poor % Moderate % Good% Pre-1919 2.4% 10.6% 3.9% 1919-1944 0.5% 7.5% 4.9% 1945-1964 0.7% 13.0% 11.2% 1965-1982 0.5% 12.6% 12.1% Post 1982 0.0% 5.1% 15.2% TOTAL 4.1% 48.6% 47.2% 44 53% of dwellings in Scotland may be considered to have only53% of dwellings in Scotland may be considered to have only moderate or poor energy efficiencymoderate or poor energy efficiency PrePre--1919 are the largest proportion with poor rating1919 are the largest proportion with poor rating 5. 55 Traditional Buildings:Traditional Buildings: Refurbish or Replace?Refurbish or Replace? Traditional buildings are viewed as energy inefficient.Traditional buildings are viewed as energy inefficient. TheThe operationaloperational carbon emissions of new buildings are lower thancarbon emissions of new buildings are lower than traditional buildings.traditional buildings. However, traditional buildings already embody carbon.However, traditional buildings already embody carbon. Energy is required for demolition and disposal of waste, and toEnergy is required for demolition and disposal of waste, and to produce and transport new building materials.produce and transport new building materials. Existing building also have cultural and societal value.Existing building also have cultural and societal value. 6. The challengesThe challenges Improve the housing stock in response to climate change andImprove the housing stock in response to climate change and reduce COreduce CO22 emissionsemissions Improve comfort and lower energy bills for occupantsImprove comfort and lower energy bills for occupants Maintain our architectural heritageMaintain our architectural heritage The options for upgrading the thermal performance are particularThe options for upgrading the thermal performance are particularlyly limited for prelimited for pre--1919 dwellings with solid wall constructions.1919 dwellings with solid wall constructions. 66 7. Traditional WindowsTraditional Windows Traditional single glazed windowsTraditional single glazed windows -- easiest option for replacementeasiest option for replacement with modern double glazing?with modern double glazing? Traditional windows are often considered to be draughty, prone tTraditional windows are often considered to be draughty, prone too condensation and hard to maintain.condensation and hard to maintain. But, with good care and maintenance traditional windows will outBut, with good care and maintenance traditional windows will outlastlast modern replacements and should be considered as a sustainablemodern replacements and should be considered as a sustainable resource.resource. However, the heat lost through a single glazed window is aboutHowever, the heat lost through a single glazed window is about twice that through a double glazed window meeting the currenttwice that through a double glazed window meeting the current Building Standards targets.Building Standards targets. 77 8. OptionsOptions Secondary glazingSecondary glazing most effective option to preserve existingmost effective option to preserve existing traditional windowstraditional windows Little information on the performance of more traditional (andLittle information on the performance of more traditional (and cheaper) methods of reducing heat loss, such as, draught proofincheaper) methods of reducing heat loss, such as, draught proofing,g, shutters, blinds and curtains.shutters, blinds and curtains. This paper quantifies the effectiveness of relatively simple meaThis paper quantifies the effectiveness of relatively simple measuressures to improve the thermal performance of traditional windows byto improve the thermal performance of traditional windows by DraughtDraught--proofingproofing Blinds, curtains, & shuttersBlinds, curtains, & shutters Secondary glazingSecondary glazing Replacing single glazed panes with double glazingReplacing single glazed panes with double glazing 88 9. 99 Laboratory StudiesLaboratory Studies -- ObjectivesObjectives Determine the benefits of various options on reduction of heat lDetermine the benefits of various options on reduction of heat lossoss through glazing of a sash & case windows provided by Historicthrough glazing of a sash & case windows provided by Historic Scotland (HS).Scotland (HS). Measure the benefits of draughtMeasure the benefits of draught--proofing.proofing. 10. 1010 Historic Scotland Window 1.89m (h) x 1.06m (w) 11. 1111 Laboratory StudiesLaboratory Studies ThermalThermal PerformancePerformance Tests performed in environmental chamber usingTests performed in environmental chamber using in situin situ heat fluxheat flux measurements on glazing.measurements on glazing. Approach justified since NPL guarded hot box measurements on HSApproach justified since NPL guarded hot box measurements on HS window indicate that 72% heat lost through glazing.window indicate that 72% heat lost through glazing. The reduction in heat using the various option compared withThe reduction in heat using the various option compared with basebase measurement on single glazing only.measurement on single glazing only. Surface temperature measurements also made to determine USurface temperature measurements also made to determine U-- values and assess impact on thermal comfort.values and assess impact on thermal comfort. 12. 1212 GCU Environmental ChamberGCU Environmental Chamber 13. 1313 Cold Room 2C Warm Room 22C Windows mounted in 300mm thick insulated panel Environmental ChamberEnvironmental Chamber window #1 window #2 insulated frame 14. 1414 Heat Flux MetersHeat Flux Meters Sensor area Guard area Sensor area Guard area 15. 1515 Test SequenceTest Sequence 0 5 10 15 20 25 21-May 22-May 23-May 24-May 25-May 26-May 27-May Temperature[C] 0 10 20 30 40 50 60 70 80 HeatFlux[W/m2 ] Warm Cold Heat Flux Set up test, e.g. change option to curtain Allow conditions to stabilise Use data for analysis 16. 1616 Options testedOptions tested Heavy curtains.Heavy curtains. Timber shutters (salvaged traditional panelled shutters)Timber shutters (salvaged traditional panelled shutters) Modified traditional shutters, with insulation inserted into panModified traditional shutters, with insulation inserted into panels andels and covered with 6mm plywood. The insulated area of the shutters iscovered with 6mm plywood. The insulated area of the shutters is 55%.55%. Modern roller blind.Modern roller blind. Modern roller blind, covered with a low emissivity film.Modern roller blind, covered with a low emissivity film. Victorian blind fitted to the top of the recess formed by the wiVictorian blind fitted to the top of the recess formed by the windowndow case pulley stiles at the side of the upper sash.case pulley stiles at the side of the upper sash. AA thermalthermal Duette honeycomb blind manufactured by HunterDuette honeycomb blind manufactured by Hunter Douglas Europe b.v.Douglas Europe b.v. Secondary glazing system with lowSecondary glazing system with low--e glazing.e glazing. Window reWindow re--glazed with Slimlite lowglazed with Slimlite low--e double glazed panes,e double glazed panes, manufactured and installed by Fountainbridge Windows Ltd.,manufactured and installed by Fountainbridge Windows Ltd., Edinburgh.Edinburgh. 17. 1717 Heavy Curtains Traditional ShuttersHeavy Curtains Traditional Shutters 18. 1818 Insulated Shutters with SpacethermInsulated Shutters with Spacetherm 19. 1919 Modern Roller BlindModern Roller Blind Blind with lowBlind with low--e foile foil appliedapplied 20. 2020 Victorian Blind Honeycomb BlindVictorian Blind Honeycomb Blind Metallised interior of honeycomb 21. 2121 LowLow--e Secondary Glazinge Secondary Glazing 22. 2222 ResultsResults The effect of the various options on the heat loss through the gThe effect of the various options on the heat loss through the glazinglazing was estimated as follows:was estimated as follows: The reduction in heat lossThe reduction in heat loss compared directly with the test oncompared directly with the test on glazing only.glazing only. A centre of pane UA centre of pane U--valuevalue, calculated from the average heat flux, calculated from the average heat flux meter reading and surface temperature difference between the outmeter reading and surface temperature difference between the outerer glazing surface and the inside (roomglazing surface and the inside (room--facing) surface of the curtain,facing) surface of the curtain, shutter or blind with a correction for the standardised internalshutter or blind with a correction for the standardised internal andand external surface resistances.external surface resistances. A correction was also applied for the thermal resistance of heatA correction was also applied for the thermal resistance of heat fluxflux meter.meter. Uncertainty of UUncertainty of U--values is 0.3 W/mvalues is 0.3 W/m22 K.K. 23. 2323 TCold TWarm Surface glazing temperatures 24. 2424 TCold TWarm Surface glazing temperatures 3 1025.617.0 1 + = Q TT U sesi 25. 2525 Reduction in heat lossReduction in heat loss 14% 28% 22% 36% 45% 51% 58% 62% 60% 63% 66% 75% 77% 55% 0% 20% 40% 60% 80% Curtains Victorian Blind Modern RollerBlind Duette honeycombblind Modern RollerBlind + Foil Shutters Blind & Shutters Blind,Shutters & Curtains Insulated Shutters SecondaryGlazing SecondaryGlazing & Curtains SecondaryGlazing & Shutters SecondaryGlazing & Insulated Shutters Double glazing 26. 2626 Effect of Closing Shutters 0 10 20 30 40 50 60 70 80 90 100 21-Apr 22-Apr 23-Apr 24-Apr 25-Apr 26-Apr 27-Apr 28-Apr HeatFlux[W/m2 ] Glazing only + Shutters Fitting Shutters 27. 2727 UU--ValuesValues 5.4 3.2 3.2 3.0 2.4 2.3 2.2 1.8 1.6 1.6 1.7 1.3 1.1 1.0 1.9 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Glazing only Curtains Victorian Blind Modern RollerBlind Duette honeycombblind Modern RollerBlind + Foil Shutters Blind & Shutters Blind,Shutters & Curtains Insulated Shutters SecondaryGlazing SecondaryGlazing & Curtains SecondaryGlazing & Shutters SecondaryGlazing & Insulated Shutters Double glazing U-value of Glazing + Option [W/m2K] 28. 2828 Airtightness MeasurementsAirtightness Measurements The airThe air--tightness of the window was measured bytightness of the window was measured by depressurisation with both test rooms at 22depressurisation with both test rooms at 22ooC.C. Measurements were made:Measurements were made: Before and after draughtBefore and after draught--proofing by Ventrollaproofing by Ventrolla After installation of secondary glazing.After installation of secondary glazing. 29. Airtightness MeasurementsAirtightness Measurements 2929 WindowWindow Pressure Difference - P Flowmeter Differential Pressure Gauge Variable fan/fow control Air Flow - Q 30. 3030 0 10 20 30 40 50 60 70 80 0 5 10 15 20 25 30 35 40 45 50 PRESSURE DIFFERENCE DP [Pa] AIRFLOW[cu.m/h] HS WINDOW AS RECEIVED HS WINDOW AFTER DRAUGHT-PROOFING HS WINDOW DRAUGHT-PROOFED + 2ndry GLAZING 31. 3131 ResultsResults Professional draught proofing reduces air leakage by 86%Professional draught proofing reduces air leakage by 86% compared with the ascompared with the as--received conditionreceived condition The addition of the secondary glazing system provides a furtherThe addition of the secondary glazing system provides a further reduction in air leakagereduction in air leakage A trickle vent with an area of 4000mmA trickle vent with an area of 4000mm22 (Section 3.14 SBS 2007) has(Section 3.14 SBS 2007) has an air leakage about 5 x that of the draught proofed window.an air leakage about 5 x that of the draught proofed window. Whole window UWhole window U--value measurements by NPL show no significantvalue measurements by NPL show no significant difference before & after draught proofingdifference before & after draught proofing 32. 3232 In situIn situ measurements at Lauristonmeasurements at Lauriston Place, EdinburghPlace, Edinburgh Shutters & SecondaryShutters & Secondary Glazing TestedGlazing Tested Shutters similar performance toShutters similar performance to laboratory testslaboratory tests Secondary glazing resultSecondary glazing result (2.3W/m(2.3W/m22 K) higher than theK) higher than the environmental chamber result.environmental chamber result. 33. 3333 Effect of closing shuttersEffect of closing shutters 3RD FEBRUARY 0 10 20 30 40 50 60 70 00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 HEATFLUX[W/m2 ] 0 2 4 6 8 10 12 14 16 18 20 TEMPERATURE[C] HEAT FLUX ROOM TEMPERATURE EXTERNAL TEMPERATURE Shutters CLOSED Shutters OPEN Shutters CLOSED 34. 3434 ConclusionsConclusions All measures have significant benefits.All measures have significant benefits. Shutters are most effective of traditional methods particularlyShutters are most effective of traditional methods particularly withwith addition of insulation.addition of insulation. Improved blind designs also have potential to reduce heat lossImproved blind designs also have potential to reduce heat loss -- roller blind with lowroller blind with low--e foil facing glazing very effective (but note foil facing glazing very effective (but not attractive?)attractive?) High performance secondary glazing and replacement doubleHigh performance secondary glazing and replacement double glazed panes offer improved thermal performance throughout theglazed panes offer improved thermal performance throughout the day.day. Careful installation of the secondary glazing also results in imCareful installation of the secondary glazing also results in improvedproved airair--tightness.tightness. All measures offer improved thermal comfort due to higher surfacAll measures offer improved thermal comfort due to higher surfacee temperatures compared to single glazing alone.temperatures compared to single glazing alone.