Multifamily Passive House: Into the Weeds

Transcription

1 Multifamily Passive House: Into the Weeds

2 Controlling Cooling Loads in Multifamily Passive House Jordan Dentz, Vice President, PHI CPHC Thomas Moore, PHIUS CPHC The Levy Partnership, Inc., New York City Building Technology Energy Services Building Research

3 Context Challenge Strategy

4 Context URBANIZATION, DENSITY & ENERGY USE INTENSITY

5 Archetype

6 Renewables Systems Inner Loads Enclosure Form Site Time & Cost to influence

7 NYC Urban Infill Site

8 NYC Urban Infill Site

9 PH Site Conditions

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11 Renewables Systems Inner Loads Enclosure Form Site Time & Cost to influence

12 PH Site Conditions Form & Surface to Volume Ratio Narrow E W streets (in Manhattan) Neighboring buildings with adiabatic condition on west and east Lot Size Approximately 25 x 100 Height Restrictions at approximately 4 6 stories before variance Surface to volume ratio is established Low Building Wind Exposure with two sides exposed Solar exposure on north and south only Azimuth 210 (slight North East orientation) Little control over form and siting No sun in winter, No shade in summer

13 Multifamily PH and Energy Use Intensity Urban infill site decreases greenfield development Increased urban density and low EUI are some of the benefits of the urbanization trend Multifamily PH is an effective means to reduce EUI Dense multifamily results in some added challenges for balancing heating and cooling loads in Passive House Energy Use Intensity (EUI) is expressed as energy per square foot per year. It's calculated by dividing the energy consumed by the building in one year (kbtu or kwh) by the total gross floor area of the building. (Energy Star, 2017)

14 The Challenge BALANCING HEATING & COOLING DEMAND

15 Multifamily PH Case Studies 6 residential units 20 residential units 10,000 ft 2 1 commercial unit 17,000 ft 2

16 Manage heating load/demand Adiabatic site conditions make the heating demand and load easy to meet until you start tweaking to meet cooling targets Approximate R and U ranges based on case studies: Above grade wall R 30 Roof R 68 Slab Below Grade Wall Window Frame R 5.5 R Btu/hr ft 2 F 0.20 Btu/hr ft 2 F Frame to Wall Psi value U window Installed 0.15 Btu/hr ft 2 F Solar Heat Gain Coefficient Window to Wall ratio 12 15%

17 Passive House Criteria Heating Demand Cooling Demand Heating Load Cooling Load Heating Load Cooling Load OR Heating Demand Cooling Demand Primary Energy Air tightness 0.08 CFM/ft 2 Primary Energy Air tightness 0.6 ACH50

18 Heating and Cooling Balance Pre certified energy model indicates that cooling demand is the toughest threshold Heating Demand: 4.3 kbtu/ft 2 yr Cooling Demand: 4.9 kbtu/ft 2 yr Heating Load: 3.9 Btu/hr ft 2 Cooling Load: 4.5 Btu/hr ft 2 Source Energy: 6200 kwh/per/yr Need to manage the cooling demand with enclosure, inner loads, and systems Heating Demand Cooling Demand Heating Load Cooling Load Modeled Space Conditioning Energy Required Space Conditioning Energy Overage of Space Conditioning Energy Source Energy

19 Strategies

20 Enclosure

21 Window to Wall Ratio Window to wall ratio (WWR): 12 15% Reduce unnecessary glazing at bulkheads, and for common areas Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

22 Below Grade Conditions Heating Demand Cooling Demand What does a multifamily Passive House have in common with a naked mole rat? Reduce below grade insulation, use ground as heat sink in summer, reduce cooling demand Reductions in above grade insulation assemblies have minimal impact on cooling demand Heating Load Cooling Load Source Energy

23 Nighttime Natural Ventilation Nighttime natural ventilation through operable windows reduces cooling demand Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

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25 Solar Heat Gain Coefficient Heating Demand Cooling Demand Heating Load Cooling Load Lower the SHGC to reduce cooling demand Minimal impact on heating demand because you probably don t get much winter sun anyway Source Energy

26 Window Reveal Depth Increased window reveal depth maintains views, daylighting, but reduces solar gain Subtle but impactful to cooling demand Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

27 Window Blinds Heating Demand Cooling Demand Heating Load Include interior blinds to reduce solar gain and decrease cooling demand Modeling protocol results in typical solar shading coefficients of Cooling Load Source Energy

28 Internal loads

29 Appliances Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

30 Clothes dryers Exhaust dryers get a bum rap. They increase heating demand and heating load BUT they also reduce cooling demand! Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

31 Bi Level Lighting Bi level lighting with occupancy sensors in common spaces reduces internal gains Target LPD 0.3 W/ft 2 Original LPD 0.6 W/ft 2 Final LPD 0.39 W/ft 2 Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

32 Elevator An efficient elevator will reduce internal gains and cooling demand LED cab lighting with occupancy sensors Auto fan shut off Regen Power back elevator drive Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

33 Exercise equipment Self powered exercise equipment (i.e. no treadmills) will reduce miscellaneous electrical loads, internal gains and cooling demand Elliptical Stationary bike Weights Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

34 Systems

35 Domestic Hot Water Reduce DHW pipe length will deliver less heat to the building Recirculation controls for central system Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

36 Mechanical Ventilation Decrease in energy recovery efficiency will: increase the heating demand negligible impact on cooling demand Heating Demand Cooling Demand Heating Load Cooling Load Source Energy

37 Impact to Cooling Demand Cooling Demand Threshold Cooling Demand Baseline Nightime Nat Ventilation redcued to 0.1 ACH Central DHW with 300' re circ No interior blinds WWR increase (100' glazing added to S) SHGC increased from 0.38 to 0.5 No Bi Level Lighitng (0.6 W/sf) 4" underslab No Powered gym equip (MELs) Elevator Standard Drive, standard lighting, continous fan Ambient Walls on West and East Federal min efficient appliances ERV efficiency 75% Exhaust Dryer Window Reveal Depth increased to 8" (kbtu/ft 2 yr)

38 Thank You Jordan Dentz