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Research Project Summary Review of Energy Rating for Windows Brittany Hanam MASc EIT Al Jaugelis BSc Arch March 2013.

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Presentation on theme: "Research Project Summary Review of Energy Rating for Windows Brittany Hanam MASc EIT Al Jaugelis BSc Arch March 2013."— Presentation transcript:

1 Research Project Summary Review of Energy Rating for Windows Brittany Hanam MASc EIT Al Jaugelis BSc Arch March 2013

2 Agenda Background to the study Energy Rating Study methodology and energy findings Thermal comfort issues Conclusions

3 Energy Rating (ER) originally developed in 1989 Some early ER-qualified products were associated with discomfort and dissatisfaction in some markets Concerns about validity of ER, given changes to house archetypes, technology advances, and original assumptions Oct CSA A440.2 Task Group recommended new research to validate ER parameters, but effort stalled due to lack of funding at NRCan In 2011 RDH proposed a study to investigate ER BC Homeowner Protection Office (HPO) assembled coalition of funding partners from across Canada Background

4 Included all parties with keen interest in the subject All points of view represented Cooperative effort promoted mutual understanding, with possibilties for future collaboration Funding partners

5 ER is generally valid for ranking the relative energy efficiency of windows and sliding glass doors, with some exceptions ER is better at ranking energy performance of windows than U-value alone Comfort issues related to unwanted solar heat gain and high U-values are better understood Clarified limitations of ER and recommended guidelines for its use Final Report released Bonus: resulted in follow-on study of Passive House windows, North American vs. European simulation methods, currently underway Outcome of study

6 What is the Energy Rating?

7 Canadian measure of window/glass door energy performance defined in CSA A440.2, Fenestration Energy Performance Single number rating Evaluates both solar gains (SHGC) and losses due to transmittance (U-value) and air leakage For low-rise residential applications vertical applications only, no skylights What is the Energy Rating?

8 To rate winter window performance dont just measure heat loss through windows... Conduction through glass and frame (U-value) Air leakage... ADD heat gained from the sun The ER concept: include the sun

9 ER equation in CSA A440.2: Simplified Equation: The ER calculation Solar Heat Gain ConductionAir Leakage

10 Voluntary Program Two Compliance Paths: ER or U-Value ENERGY STAR qualification requirements Windows Zone Heating Degree-Day Range Compliance Paths Energy Rating (ER)orU-Value Minimum ER Max. U-Value 0.35 Btu/h-ft²-F (2.00 W/m²K) Max. U-Value Btu/h-ft²-F (W/m²-K ) Minimum ER A <= or0.32 (1.80)13 B > 3500 to <= or0.28 (1.60)17 C > 5500 to <= or0.25 (1.40)21 D > or0.21 (1.20)25

11 Study methodology and energy findings

12 Hourly energy simulations performed using the program DesignBuilder (EnergyPlus engine) Several archetype houses – sizes, enclosures, etc. Cities from across Canada selected to represent various climate zones Various window types - investigate different combinations of U-values and SHGCs Study used whole building energy simulations

13 Representative WindowU-Value [Btu/hr-ft 2 -F] SHGCER ASHRAE 90.1 Compliant, Aluminum Frame High U-Value / High SHGC Low U-Value / High SHGC High U-Value / Low SHGC Low U-Value / Low SHGC different windows in the study, 5 representative Actual study looked at 23 different windows Will show results for 5:

14 Representative WindowU-Value [Btu/hr-ft 2 -F] SHGCER ASHRAE 90.1 Compliant, Aluminum Frame High U-Value / High SHGC Low U-Value / High SHGC High U-Value / Low SHGC Low U-Value / Low SHGC Actual study looked at 23 different windows Will show results for 5: 23 different windows in the study, 5 representative

15 Cooling energy low relative to heating and total energy Relation between heating, cooling, and total energy Vancouver

16 Lower U-value & higher SHGC generally result in lower energy use Relation between heating, cooling, and total energy Lowest Third Second Vancouver Fourth

17 Generally higher ER results in lower heating energy consumption, with some exceptions Energy simulation findings: ranking Increasing ER

18 Good correlation between energy consumption and ER Energy simulation findings: energy consumption

19 Orientation affects potential solar heat gain Energy simulation findings: window orientation

20 Window shading affects solar heat gain Energy simulation findings: window shading

21 In a typical house, low U-value & high SHGC result in lowest energy consumption in houses Cooling energy use is low relative to heating and total energy High ER generally good indication of lower heating and total energy consumption Factors affecting solar heat gain Window to wall ratio Orientation Exterior shading Summary of energy simulation findings

22 Thermal Comfort

23 How to measure thermal comfort? ASHRAE Standard 55: Thermal Comfort Conditions for Human Occupancy 6 primary factors affect thermal comfort: Air temperature Radiant surface temperature Humidity Air speed Metabolic rate Clothing insulation Windows and thermal comfort

24 Main factors that affect thermal comfort: Air temperature Radiant surface temperature Study explored: Operative temperature Window surface temperature Windows and thermal comfort

25 Operative Temperature: Balance of surface temperature and air temperature ASHRAE acceptable range of operative temperature based on research studies Operative temperature

26 Hourly energy simulations – extract window surface temperature, air temperature, operative temperature Defined comfort parameters: Operative temperature 19 ° C to 25 ° C Surface temperature 15 ° C to 30 ° C Count number of hours outside this range Thermal comfort: methodology

27 Operative temperature example: Vancouver bedroom Similar trend for other locations Thermal comfort: methodology

28 Representative WindowU-Value [Btu/hr-ft 2 -F] SHGCER ASHRAE 90.1 Compliant, Aluminum Frame High U-Value / High SHGC Low U-Value / High SHGC High U-Value / Low SHGC Low U-Value / Low SHGC representative windows from 23 in the study Actual study looked at 23 different windows Will show results for 5:

29 Warm hours correlate with high solar gain products, across all climate zones Thermal comfort: operative temperature High SHGC Windows Low SHGC Windows

30 Cold hours more significant in colder climates Cold surface temperatures related to high U-value Thermal comfort: operative temperature High U-value Windows

31 Cold hours correlate with high U-value Compare with number of operative warm hours Thermal comfort: surface temperature U-0.16U-0.5U-0.35

32 Overheating a function of high SHGC, not high ER Overheating discomfort related to project-specific conditions Orientation Exterior shading Window to Wall Ratio Low SHGC reduces overheating when no external summer shading present Low U-value lowers surface temperature, leading to greater comfort year round, esp. winter Thermal comfort summary

33 Study conclusions

34 Higher ER generally results in lower heating energy consumption in typical Canadian houses ER is generally better at ranking energy performance of windows than U-value alone ER does not correctly rank windows: In the far north due to lower solar gain in the winter months Primarily oriented in one direction With high window-wall ratios With exterior winter shading Overheating is a function of solar heat gain, not ER, and comfort can be managed with summer shading or A/C ER is not suitable for MURBs with high window to wall ratios (>40%) due to overheating and cooling energy use Study conclusions

35 Keep both U-value and ER paths in codes and ENERGY STAR program Need to educate consumers on how to select the best windows for their particular situation, considering all factors that are important to them Atypical homes and site-optimized energy performance design should use both U-value and SHGC characteristics for selecting windows ER Study Recommendations

36 Questions?


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