Passive House Design
Chicago, IL
Ruchira Sardesai
Passive house design for a 2 storey home in Chicago, IL
Key design Information:
• Climate zone 5A, Bucktown, Chicago, IL.
• Envelope Area = (411 ft2 x 2 + 1160 ft2 x 2) = 3142 ft2
• iCFA = 2065.5 ft2(688.5 ft2 x 3)
• Bedrooms = 4 (per program)
• Occupants = 5 (4 bedrooms + 1 person)
• PHIUS CORE Source Energy Criteria = 2,975 kWh/person x 5 people = 14,875 kWh/year
PHIUS Design Checklist:
General
1: Building oriented east-west with shorter sides facing north and south. See page 3 for the orientation and layout of rooms
2: 2 parking spaces with detached garage provided with 4 bedrooms for 5 occupants. See page 3 for additional details on how the program was fulfilled for the clients
3: Largest % of windows is on east & west facades – 18.3% each. South façade has 13.2% and north façade has the least windows with only 6.3%. Total window area is 12% of the envelope.
4: Operable insulated roller blind shades provided on windows, see pages 5 and 6. Shading on east, west and south sides only.
5: Garden style conditioned basement used which is 4’ above grade
6: Mechanical room located on north side at the center of the layout 52 ft2 in size and shown on page 3
7: The basement provided is conditioned as per EPA Indoor airPLUS for climate zone 5A.
8: Passive radon system shown on page 5 as per EPA Indoor airPLUS v2 (EPA zone 2)
Enclosure:
9: Minimum PHIUS prescriptive wall R-value of 37; typical wall section with R-value calculation on page 7
10: Minimum PHIUS prescriptive roof R-value of 68; typical roof section R-value calculation on page 7
11: Minimum PHIUS prescriptive floor/slab value of 19/24; typical section with R-value calculation on page 7
12, 13, & 14: Wall, Roof, and Floor construction shown on page 7.
15: U-value of 0.12 shown on page 7 (Zola Thermoclad III tilt & turn windows)
16: Window frame u-value – 0.18 and thermally broken detail showed on page 7
17: SHGC of 0.456 shown on page 7 (Zola Thermoclad III tilt & turn windows)
18: Window installation detail shown on page 7.
19: Height of tallest window shown on page 4
20: Thermal bridge free design shown for wall, roof, floor, and window; 0.006 Btu/hr.ft.F noted.
21, 22, & 23: Details for the wall-first floor, wall-second floor, and wall-roof designed to be thermal bridge free and shown on page 7.
24, 25, & 26: Airtight envelope design, noting 0.06 cfm50/ft2envelope area shown on page 3,4,7.
Mechanical Ventilation:
27 & 28: Balanced ventilation calculations shown on page 8 with design
Balanced heat recovery ventilator - Zehnder Novus F 300 with up to 95% heat recovery and equipped with automatic electric resistance defroster.
29: Heat recovery system is up to 95% efficient with a maximum volumetric flow of 177 cfm of air at an external pressure of 0.8 "wc. Humidity heat exchanger fitted with anti-microbial polymer membrane is capable of recovering both heat and significant amount of humidity.
30: MERV 13 filter indicated on page 8
31: Cfm calculations for balanced ventilation capacity shown on page 8 and ventilation unit chosen according to 108 cfm capacity.
32: Ventilation supply and exhaust ducts indicated for all rooms on page 8.
33: Fresh air has been supplied to all bedrooms at 22 cfm and 42 cfm for the Master bedroom
34: Placement of supply and exhaust diffuser shown on page 8. Supply diffusers placed at junction of wall and ceiling to maximize Coanda effect to improve fresh air distribution. All exhaust diffusers on far side of room for proper intake.
35: 6” for trunk and 4” for branch ductwork shown on page 8
36: Duct layout kept as compact as possible for the room layout; smooth and straight and specified on pages 8
37: ERV exhaust diffuser is 10’-5” from the cooking top surface; detail shown on page 8
38 & 39: Intermittent, direct exhaust specified for the cooktop on page 8. Ventilator is located next to the exterior wall, in the conditioned kitchen. Exhaust from the ventilator is greater than 10’ from the ERV intake duct.
40, 41, & 42 & 43: Specifications for ERV ductwork are called out on page 8. Ducts are insulated to R-10 with vapor tight wrap, are installed 10’-0” above grade to be above the expected snow line and are indicated to be air and watertight; intake and exhaust for ERV are 17’ apart and on opposite sides of the building, have weather and critter protection.
44: Insulation specified for trunk ducts and around the entire mechanical room on page 8
45: All interior doors with louvres to maintain 1 pascal pressure difference between rooms – called out in general notes on page 8.
46: Space conditioning and ventilation systems are separate; insulation on ventilation ducts does not apply.
47: Domestic Hot Water system - Rheem - PROPH50 T2 RH375-SO Hybrid/Electric Heat Pump 45 Gallon Water Heater. Source: https://www.energystar.gov/productfinder/product/certified-water-heaters/
•Energy Star rated.
•First-hour rating at 125°F outlet temp (gallons/hr) of 67
•Electric Usage at 125°F outlet temp (kWh/yr): 846
•Uniform Energy Factor (UEF): 3.88
•Recovery Efficiency per UEF test method (%): 430
48: All DHW piping home run back to tank. All piping to be run through conditioned space and insulated to R-5 Any penetration through the conditioned envelope like hose bibs or the supply line would be sealed airtight.
49: Distance from the hot water tank to the floor 2 bath is estimated to be 30’-0” because it will be run through the ceiling to remain in a conditioned space. For a half inch pipe, at 1.89 ounces per foot, the total volume stored is 56.7 ounces, or 0.44 gallons which is <0.5 gallons as per DOE ZERH v2 criteria.
Space Conditioning:
From PHIUS 2021 Performance Criteria Calculator (v. 3.1)
•Annual Heating Demand = 5.9 kBtu/ft2 x 2065.5 ft2 = 12,186 kBtu/year
•Annual Cooling Demand = 3.4 kBtu/ft2 x 2065.5 ft2= 7022 kBtu/year
•Peak Heating Load = 4.6 Btu/ft2 x 2065.5 ft2 = 9,501 Btu/hour
•Peak Cooling Load = 1.5 Btu/ft2 x 2065.5 ft2 = 3098 Btu/hour
50 & 51: Heating and cooling system are three Fujitsu - H-Series : AOUG09LZAH1 Mini-split Heat Pump mounted to the wall in common areas to facilitate air movement to all floors. Outdoor Unit Model – N/A; Indoor Unit Model - ASUG09LZBS. Nominal rating of 15,400 Btu/hr heating, 9,000 Btu/hr cooling. SEER of 33.1, COP @ 5°F of 2. Outdoor units mounted to the north exterior wall 10’-0” above grade to prevent snow from covering condenser. Specs used from Energy Star Energy Efficiency products list: https://www.energystar.gov/productfinder/
52: Thermostat for basement heat pump located in center of the building outside mechanical room; thermostat for floor 1 heat pump located in kitchen on the service chase wall; thermostat for floor 2 located in lounge area.
53: Fujitsu - H-Series Mini-split Heat Pump is rated at 15,400 Btu/hour at 5°F.
54: Fujitsu - H-Series Mini-split Heat Pump is rated at 9,000 Btu/hour at 82°F.
Additional Items:
55: Passive Strategy Narrative:
a. The building volume was kept as compact as possible to prevent heat loss through surface area while ensuring sufficient room sizes for the occupants.
b. The area of the windows was 12% of the total envelope area to prevent weak spots in the envelope. Window area - (10 windows x 21.25 ft2 + 10 windows x 11.25 ft2 + 5 windows x 6 ft2 + 2 windows x 11.33 ft2 = 377.66 ft2 and total envelope area - (411 ft2 x 2 + 1160 ft2 x 2) = 3142 ft2
c. Insulated operable roller shutters were provided on all windows except the north side to allow the occupants to limit heat gain during the day and to add an additional layer of insulation at night. Windows on the south façade are naturally shaded by the adjacent building during the winter, the blinds are used during the summer when the sun angle is high.
d. The roof pitch was oriented in the north-south direction with an angle of 41.8 degrees which is the optimal year-round angle for harvesting solar energy and the roof overhang acts as a shade for the windows on north and south facades.
56: A dedicated junction box (40A, 208/240V) was provided in the garage for electric vehicle charging.
57: A photovoltaic system was included in the design and is on the roof of the house facing south direction; page 5/6
58: The project is pursuing PHIUS CORE 2021; a renewable energy procurement strategy is therefore not required.
OUTDOORCONDENSER UNITSFORTHREE MINI-SPLITHEATPUMPS ANCHOREDTOEXTERIOR WALLAT10'ABOVEGRADE
PASSIVERADON MITIGATIONEXHAUSTPIPE EXTENDS12"PASTROOFLINE ASPEREPAINDOORAIRPLUSV2 (EPAZONE2)
NORTH&EASTSIDEELEVATION
SCALE:3/16"=1'
NOSHADINGPROVIDEDTO WINDOWSONNORTH FACADE
PVPANELSCOVERING 250SQ.FTOFROOF AREA>110SQ.FTAS REQUIREDBYDOEZERH PV-READYCHECKLIST
ROOFANGLEAT41.8 DEGREESTOOPTIMIZE SOLARENERGY HARVESTING THROUGHOUTTHE YEARFORCHICAGO
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-3'WX3'9"H
10"WIDEVERTICAL SHADINGFOREAST& WESTFACADES
INSULATEDOPERABLE ROLLERBLINDSHUTTER
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-5'8"WX3'9"H
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-3'WX2'H
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-5'8"WX2'H
NORTHELEVATION EASTELEVATION
SOUTH&WESTSIDEELEVATION
SCALE:3/16"=1'
PVPANELSCOVERING 250SQ.FTOFROOF AREA>110SQ.FTAS REQUIREDBYDOEZERH PV-READYCHECKLIST
ROOFANGLEAT41.8 DEGREESTOOPTIMIZE SOLARENERGY HARVESTINGTHROUGHOUT THEYEARFORCHICAGO
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-3'WX3'9"H
INSULATEDOPERABLE ROLLERBLINDSHUTTER
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-5'8"WX3'9"H
ZOLATHERMOCLADIII TILT&TURNWINDOW WINDOW-3'WX2'H
10"WIDEVERTICAL SHADINGFOREAST& WESTFACADES
SOUTHELEVATION WESTELEVATIONGeneralnotes: 1.AllOSBsheathingseamsaretapedandsealed
First/Secondfloorassembly
9.5"IJoistswithfibreglassbattinsulation30
WALL SECTION
SCALE: 3/8" = 1'-0"
5/8"Shingles
3/4"Airvent
9.5"EPSrigidinsulation
15"Blowninfibreglassinsulation
Rafter
MetalFlashing
Soffitvent
Topplate
Rigidinsulation
Metalflashing Woodtrim
Overinsulationatsillandlintel
ofwindowinstallation<0.006Btu/hr.ft.F forthermalbridgefreedesign
TaperedRigidinsulation
Airtight'red-line'envelope layer<0.060cfm50persq.ft. ofenvelopearea
Perforateddrainpipe
