Strategies for Energy Efficiency in Buildings: 2012/2013 Overview

1. Gestão de energia: 2012/2013 EnergyinBuildings Prof. Tânia Sousa taniasousa@ist.utl.pt

2. EnergyConsumption in Buildings • Buildingsaccount for 40% of total energyconsumption in theEuropeanunion • Whatabout Portugal? • In 2010 the final consumptionofservices + domestic sector represented 55% ofthe final energyconsumption • Do youthinkthatthefractionofprimaryenergywouldbehigherorlower? Why?

3. Energy Consumption in Buildings • Mosteffectivestrategy to reduceenergy use in buildings (Harvey, 2010): • Reduceheatingandcoolingloadsthrough a high-performance envelope • highdegreeofinsulation, windowswithlow U values in coldclimatesandlow solar heatgain in hot climates, externalshadingandlowairleakage • Meetthereducedload as much as possibleusingpassive solar heating, ventilationandcoolingtechniqueswhileoptimizingthe use ofdaylight • Use themostefficientmechanicalequipmentto meettheremainingloads • Ensure that individual energy-using devices are as efficient as possible and properly sized

4. Energy Consumption in Buildings • Howmuchenergyreduction can weachieve? • Passive house standard: heating 15kWh/m2 per yearcooling 15 kWh/m2 per yearTPE  120 kWh/m2 per yearn50 ≤ 0.6 / hour From 220 kWh/m2/year to 20-40 kWh/m2/year Triple-glazedwindowswithinternalvenetianblinds & mechanicalventilationwith 82% heatrecovery

5. Energy Consumption in Buildings • Howmuchdoes itcost?

6. Buildings – High Performance Envelope • Theeffectivenessofthethermal envelope dependsofinsulationlevels in thewalls, ceilingandbasement • Insulationlevelscontroltheheatflowbyconduction & convectionthroughthe exterior andthe interior • U value (W/m2/K), theheattrasnfercoefficient, isequal to theheatflow per unitareaand per degreeofinside to outsidetemperaturedifference • The U valueof a layerofinsulationdependsonitslengthandtypeof material

7. Buildings – High Performance Envelope • Theeffectivenessofthethermal envelope dependsofinsulationlevels in thewalls, ceilingandbasement Themosthighlyinsulatedhouseshave U=0.1-0.2 W/m2/K Blown-in celluloseinsulation (fillsthe gaps) Foaminsulation Vaccuminsulationpanels

8. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheinsulationlevelsofwindows • Windows offersubstantiallylessresistance to thelossofheatthaninsulatedwalls • Single glazedwindowshave a typical U-valueof 5W/m2/K which can bereduced to to 2.5 and 1.65W/m2/K withdoubleand triple glazingbecauseoftheadditionallayersofair • The U-valueof 2.5W/m2/K ofdoubleglazedwindowscan bereducedto 2.4W/m2/K and2.3W/m2/K withArgonandkrypton • Doubleand triple glazingvaccumwindows can reducethe U value to 1.2 and0.2W/m2/K

9. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsonthegain/lossenergybyradiation • Windows permit solar energy to enterandlossofinfraredradiation • Lowemissivitycoatingsreflect more (reduce SHGC), i.e., reduceheatgains in summerandwinter • Lowemissivitycoatingscan reducelossofheatbyinfraredradiation • Thesolar heatgaincoefficient, SHGC, isthefractionof solar radiationinicidenton a windowthatpasses throughthewindow

10. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheairleakage • The net heatflowdue to anairexchangeat rate ris: • Thestackeffectpromotesairleakage • Coldairissuckedintothelowerpartandwarmairexits throughtheupperpartthroughcraksandopeningsbecauseitislighter. • Stackeffectcan account for up to40% ofheatingrequirementsoncoldclimates • Thewindeffect

11. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheairleakage • Carefulapplicationof a continuousairbarrier can reduces rates ofairleakageby a factor of 5 to 10 compared to standard practice (enforcementofcarefulworkmanshipduringconstruction) • Buildingswithverylowairleakagerequiremechanicalventilation(95% oftheavailableheatin thewarmexhaustaircan betransfered to theincomingcoldair) to keep indoor airquality

12. Energy Balance in Open Systems • Heat Exchangers: • Used in power plants, air conditioners, fridges, liquefication of natural gas, etc • Transfer energy between fluids at different temperatures Direct Contact Heat Exchanger Counter-flow Heat exchanger Direct Flow Heat Exchanger

13. Buildings – The role ofshape, form, orientationandglazed % • Buildingshape & form • Havesignificantimpactsonheatingandcoolingloadsanddaylightbecauseoftherelationbetweensurfaceareaand volume • Whichone minimizes heattransferbyconductionandconvection? • Buildingorientation • For rectangular buildingstheoptimalorientationiswiththelongaxisfacingsouth • Why?

14. Buildings – The role ofshape, form, orientationandglazed % • Glazingfractions • Highglazingfractionsincreaseenergyrequirements for heatingandcooling • Thereislittleadditionaldaylightingbenefitoncetheglazedfractionincreasesbeyond 30-50% ofthe total façadearea • Housesize • Thelivingarea per familymemberincreasedby a factor of 3 between1950 and 2000 in the US

15. Buildings – (almost) Passive solar heating, ventilation & cooling • EvaporativeCooling:

16. Buildings – Passive (almost) solar heating, ventilation & cooling • Thermalinducedventilation & cooling: EarthPipecooling LargeAtria

17. Buildings – Passive (almost) solar heating, ventilation & cooling • Windinducedventilation & cooling: Windcatcher

18. Buildings – Passive (almost) solar heating, ventilation & cooling • Passive Solar Heating & Lighting Shading Light tubes Light shelves

19. Buildings: MechanicalEquipment • In evaluatingtheenergyefficiencyofMechanicalEquipmenttheoverallefficiencyfromprimary to usefulenergyshouldbetakenintoaccount • Thisisparticularlyimportant in the case ofusingMechanicalEquipmentsthat use electricity (producedfromfossilfuels)

20. Buildings: MechanicalEquipment for heating • Furnaces • heatairand distribute the heated air through the house using ducts; • are electric, gas-fired (including propane or natural gas), or oil-fired. • Efficiencies range from 60 to 92%(highest for condensing furnaces) • Boilers • heat water, and provide either hot water or steam for heating; • heat is produced from the combustion of such fuels as natural gas, fuel oil, coal or pellets. • Efficiencies range from 75% to 95%(highest for condensing boilers)

21. Buildings: MechanicalEquipment for heating & cooling • Electrical-resistance heating • Overall efficiency can be quitelow (primary -> useful) • Heat-Pumps • Overall efficiency can be quite good • It decreases with T • Air-source and ground-source • For cooling & heating • District Heating/Colling • For heating & cooling • Users don’t need mechanical equipment

22. Buildings: MechanicalEquipmentfor cooling • Chillers • Produce cold water which is circulated through the building • Electric Chillers: use electricity • Absorption chillers: use heat (can be waste heat from cogeneration) • Electric chillers, COP = 4.0-7.5 (larger units have a higher COP) • Absorption chillers, COP = 0.6-1.2

23. Buildings: HVAC Systems • Ventilateandheator cool bigbuildings • Allairsystems: airat a sufficientlow (high) T and in sufficient volumes iscirculatedthroughthebuilding to remove (add) heatloads • CAV: constantair volumes • VAV: variableair volumes • Airthatiscirculated in thesupplyductsmaybetakenentirelyfromtheoutsideandexhausted to theoutsidebythereturnductsor a portionofthereturnairmaybemixedwithfreshair • Incomingairneeds to becooledanddehumidified in summerandheatedand (sometimes) humidified in winter • Restrictairflow to ventilationneedsand use additionalsystems for additionalheating/cooling • Heatexchangersthattransferheatbetweenoutgoingandincomingairflows

24. Buildings: MechanicalEquipment for waterheating • Electricaland natural gasheaters • Efficiencyof natural gasheatersis 76-85% • Efficiencyofoilheatersis75-83% • Thereisheatlossfromstoragetanks • Point-of-use tanklessheatershavelossesassociatedwiththepilot light • There are systemsthatrecoverheatfromthewarmwastewaterwith45-65 % efficiencies

25. EuropeanDirectives • EuropeanDirectivesontheEnergy Performance ofBuildings • Directive 2002/91/EC of the European Parliament and Council (on the energy performance of buildings): • http://ec.europa.eu/avservices/video/videoplayer.cfm?ref=I048425&videolang=en&sitelang=en • This is implemented by the Portuguese Legislation RCCTE and RCESE • Directive 2010/31/EU of the European Parliament and Council (on the energy performance of buildings)

26. Directive 2010/31/EU: Aims • Reductionofenergyconsumption • Use ofenergyfromrenewablesources • Reducegreenhousegasemissions • Reduceenergydependence • Promotesecurityofenergysupplies • Promotetechnologicaldevelopments • Createopportunities for employment & regional development • Links withaimsof SGCIE?

27. Directive 2010/31/EU: Principles • The establishment of a commonmethodology to compute EnergyPerformace • includingthermalcharacteristics, heatingandairconditioninginstalations, renewableenergies, passive heatingandcooling, shading, natural light and design

28. Directive 2010/31/EU: Principles • Set MinimumEnergy Performance Requirements • Requirementsshouldtake intoaccountclimaticand local conditionsandcost-effectiveness

29. Directive 2010/31/EU: Principles • Energy Performance Requirementsshouldbeapplied to newbuildings & buildingsgoingthrough major renovations

30. Directive 2010/31/EU: Principles • Set SystemRequirements for: energy performance, appropriatedimensioning, controlandadjustment for TechnicalBuildingSystems in existingandnewbuiildings

31. Directive 2010/31/EU: Principles • Increasethenumberofnearly zero energybuildings

32. Directive 2010/31/EU: Principles • Establish a systemofEnergyperformacecertificates. • Energy Performance certificates must beissued for constructed, soldorrented to newtenants • Buildingsoccupiedbypublicauthoritiesshould set na example (ECO.AP in 300 publicbuildings in Portugal)

33. Directive 2010/31/EU: Principles • Regular maintenanceofairconditioningandheatingsystems • Independent experts

34. Implementationofthedirectives • Directive 2002/91/EC was implemented with: • Directive 2010/31/EU was not yet implemented • DL 78/2006, the National Energy Certification and Indoor Air Quality in Buildings (SCE). • DL 79/2006, Regulation of HVAC Systems of Buildings (RSECE). • DL 80/2006, Regulation of the Characteristics of Thermal Performance of Buildings (RCCTE).

35. RCCTE - Aims RCCTE – Aim • General aims: • Methodology for computingenergyperformaceofbuildings • Set minimumenergy performance standards • ImplementEnergyCertificationofbuildings • SpecificAims: • Limitation of annual energy needs for heating, cooling, domestic hot water and primary energy • Limitation of heat transfer coefficients • Limiting of solar factors • Installation of solar panels

36. RCCTE – DomainofApplication RCCTE – Domain of application • Buildingsthat RCCTE applies to:

37. RCCTE – Indoor & Outdoor Conditions RCCTE - Outdoor conditions Reference Indoor conditions • 20ºC in heating season • 25ºC and 50% relative humidity in the cooling season • Consumption of 40 liters of water at 60ºC/occupant . day Reference Outdoor conditions: • Portugal is divided in winter and summer climatic zones

38. RCCTE – Outdoor Conditions RCCTE - Outdoor conditions Reference Outdoor conditions:

39. RCCTE – Outdoor Conditions Climate • HeatingDegree-days are: • Where: • Tb is the desired indoor temperature (20ºC) • Tj is the temperature outside the hours j • The Degree-days are calculated for an entire year • For example, to Lisbon, for Tb = 20 º C, heating degree days are 1190 º C.day. Knowing the heating season is 6 months (180 days), the average daily GD (GDI) will be 6.6 º C.

40. HeatingDegreeDays – a comparison

41. RCCTE – Outdoor Conditions Climate • Outdoor projecttemperature • The outside project temperature is calculated on a cumulative probability of occurrence of 99%, 97.5%, 95% and 90%. • A cumulative probability of occurrence of 99% means that in summer the temperature indicated is exceeded only in probabilistic terms, 1% of the time, ie, 30 hours per year (e.g. Lisbon).

42. Nominal Annual Needs of Useful Energy for Heating Nic Nic≤Ni Ni Thecorrespondingmaximumpermissible Nominal Annual Needs of Useful Energy for Cooling Nvc Nvc≤Nv Nv Thecorrespondingmaximumpermissible Nac Nominal Annual Energy needs for Domestic Hot Water Nac≤ Na Na Thecorrespondingmaximumpermissible Nominal Annual Energy needs for Primary Energy Ntc Ntc≤Nt Nt Thecorrespondingmaximumpermissible RCCTE – Fundamental thermalIndices RCCTE – Indices e parameters • Thethermalbehaviorofbuildingsischaracterizedusingthefollowing fundamental thermalindices:

43. RCCTE – Additionalparameters RCCTE – Indices e parameters • Thethermalbehaviorofbuildingsischaracterizedusingtheparameters: more demanding for harsherwinters more demanding for harshersummers Additionalparameters Heattransfercoefficientsofwalls U Umax Thecorrespondingmaximumpermissible Heat Transfer Coefficients of Thermal Bridges 2 x Umax Solar factor offenestration (for windowsnotfacing NE-NW witharea > 5%) Fs Fsmax Thecorrespondingmaximumpermissible

44. RCCTE – Fundamental thermalIndices: Heating Heating Heating: Maximum Allowable Needs (Ni) [kWh / (m2.year)] FF ≤ 0.5 :: Ni = 4,5 + 0,0395 GD 0,5 < FF ≤ 1 :: Ni = 4,5 + (0,021+ 0,037FF) GD 1 < FF ≤ 1,5 :: Ni = [4,5 +(0,021+ 0,037FF) GD] (1,2 – 0,2 FF) FF > 1,5 :: Ni = 4,05 + 0,06885 GD Form factor: FF = ( (Aext) +  ( Aint))/V GD :: Degreeday (ºC * day) more demanding for smaller FF Nic < Ni Heating: Nominal Needs (Nic) [kWh / (m2.year)] Nic= (Qt + Qv – Qgu) / Ap Qt = 0.024 x GD x  (A x U) Qv = 0,024 (0,34 x R x Ap x Pd) x GD to keeptheTint = 20ºC duringtheheatingseason Qt: heat loss by conduction & convection through the surrounding Qv: heat losses resulting from air exchange Qgu: solar gain and internal load

45. Current average residential heating energy use (Harvey, 2010) • 60-100 kWh/m2/yr for new residential buildings in Switzerland and Germany • 220 kWh/m2/yr average of existing buildings in Germany • 250-400 kWh/m2/yr for existing buildings in central and eastern Europe • For Lisbon the maximum heating allowable needs are: • Passive house standard: 15 kWh/m2/yr

46. RCCTE – Fundamental thermalIndices: Cooling Cooling Cooling: Maximum Allowable Needs (Nv) [kWh/(m2.year)] V1 (North) : Nv = 16 V1 (South) : Nv = 22 V2 (North) : Nv = 18 V2 (South) : Nv = 32 V3 (North) : Nv = 26 V3 (South) : Nv = 32 Açores : Nv = 21 Madeira : Nv = 23 Cooling: Nominal Needs (Nvc) [kWh / (m2.year)] Nvc = Qg * (1 - ) / Ap (kWh/m2year) Qg : Total gross load (internal + walls + solar + air renewal) : Load Factor Nvc < Nv to keeptheTint = 25ºC duringthecoolingseason

47. RCCTE – Fundamental thermalIndices: Hot Water DomesticHotWater Domestic Hot Water: Maximum Allowable Needs (Na) [kWh / (m2.year)] Na= 0,081 MAQSnd/Ap MAQS : Reference consumption (40 liters per occupant) nd : Reference n. of days with DHW (residential:365) N. of occupants: T0=2; TN=n+1 1 m2 solar panel collector per occupant or 50% of available area if solar exposition is adequate Domestic Hot Water: Nominal Needs (Nac) [kWh / (m2.year)] Nac = (Qa/ηa – Esolar – Eren)/Ap Qa: Conventional useful energy requirements ηa: Efficiency of the conventional systems ESolar: Contribution of solar thermal panels for DHW Eren: Contribution to other renewable for DHW Qa : (MAQS * 4187 * T * nd) / (3 600 000) (kWh/year) Maqs = 40 l /occupant . Day*nº occupants T : 45º (15ºc  60ºc) Nac < Na

48. RCCTE – Fundamental thermalIndices: PrimaryEnergy Primaryenergy Primary energy: Maximum Allowable Needs (Nt) [kgep/(m2.year)] Nt= 0,9 (0,01Ni + 0,01 Nv + 0,15 Na) Primary energy : Nominal Needs (Ntc) [kgep/(m2.year)] Ntc= 0,1 (Nic/ηi)Fpui + 0,1 (Nvc/ηv)Fpuv + NacFpua Fpu : Conversion factor from final energy to primary energy Electricity: Fpu = 0.290 kgep / kWh Fuels: Fpu = 0.086 kgep / kWh In the absence of more precise data consider, eg: Electrical resistance = 1 Boiler fuel gas = 0.87 Heat Pump = 3 (cooling) and 4 (heating) Ntc < Nt

49. Energy Performance Certificate Energylabel • EnergyLabelling: R = Ntc / Nt R A A+ Newbuildings (licensedafter 2006) B- B 1 C D 2 Oldbuildings E F 3 G

50. RCESE - Aims RCCTE – Aim • General aims: • Methodology for computingenergyperformaceofbuildings • Set minimumenergy performance standards • ImplementEnergyCertificationofbuildings • Regular inspection of boilers and air conditioning in buildings • SpecificAims: • Limitation of annual energy needs for heating, cooling, and primary energy • Limitation of heat transfer coefficients • Limiting of solar factors • Maintenance of HVAC systems • Monitoring and energy audits