Most of the items included in the PHIUS+ Single Family Quality Assurance Workbook are the responsibility of the builder, but there are some items that concern the designer as well. Those items are collected in this section for emphasis, along with some other prescribed items. Please refer to the Workbook linked to above for additional information and adhere to these guidelines. If there are any inconsistencies with what appears in the Workbook and this Guidebook, please bring these to our attention.
The requirements below are listed according to section headings and numbering in the quality assurance workbook – references to Sections below may be referring to external documents rather than the PHIUS+ Certification Guidebook.
A passive house can have a woodstove, woodstove fireplace insert or sealed combustion gas fireplace vented to the outside, but the stove or fireplace box needs to be airtight. In an airtight house there is great danger of back drafting or for the fireplace/stove using the interior air for combustion. Therefore, the combustion intake air must be directly from the outdoors and independent of the interior air supply. Warning systems should be considered such as carbon monoxide detectors or depressurization sensors. If the building gets depressurized for some reason (one of the ventilator fans fails and the defect goes unnoticed) then, despite of all the precaution of airtight fire box and dedicated combustion air, back drafting could still occur and draw potentially life-threatening gases into the interior of the building.
Open and/or unvented fireplaces are prohibited in PHIUS+ projects. Per EPA Indoor airPLUS, this also applies to ethanol fireplaces.
Fireplace Disclaimer: The use of a fireplace/woodstove in a home can be dangerous due to the risk of carbon monoxide poisoning. The fireplace/woodstove specified for this home must be completely airtight to the room air. Combustion air must be provided by a dedicated pipe connecting to the outside. If smoke is seen to be leaking from the stove into the living area, immediately open all the windows, and discontinue using the stove. DO NOT LEAVE A FIRE BURNING UNATTENDED especially when going to sleep at night. Carbon monoxide detectors should be installed in locations so that they can be heard throughout the house. The Passive House Institute US|PHIUS or any of its employees are not responsible for any damage, injury or death caused.
3.5.2 Building Envelope
3.1a: Air Barrier Integrity: Air barrier is contiguous, including behind stairs, porch roofs, fireplaces, showers/tubs, attic knee walls, walls/ceilings adjacent to vented attics, and floors over unconditioned basements and vented crawlspaces. See ENERGY STAR Rater Field Checklist Section 2 for further details and criteria.
3.1b: Air Sealing: All penetrations (wire/pipe/HVAC/etc.) between conditioned and unconditioned space sealed, service chases capped at exterior, exterior/doors to garages weather-stripped, rough opening of doors/windows sealed, multifamily drywall shaft walls sealed at exterior, recessed lights ICAT and gasketed, etc. See ENERGY STAR Rater Field Checklist Section 4 for further details and criteria.
3.2: Insulation Quality Check: All insulated assemblies have achieved a RESNET Grade I cavity insulation level, or alternatively GII with continuous insulation. Per ES 1.3. Please see RESNET Standards Appendix A for information on insulation Grading.
3.3: Window Performance: Windows are ENERGY STAR certified, and/or triple-glazed with thermally broken frames/spacers, and meets project the design specs.
Per DOE ZERH footnote 13: Fenestration shall meet the applicable ENERGY STAR Windows Eligibility Criteria for U and SHGC, with the following exceptions:
- An area-weighted average of fenestration products shall be permitted to satisfy the U-factor requirements;
- An area-weighted average of fenestration products ≥ 50% glazed shall be permitted to satisfy the SHGC requirements;
- 15 square feet of glazed fenestration per dwelling unit shall be exempt from the U-factor and SHGC requirements, and shall be excluded from area-weighted averages calculated using the two bullets above;
- One side-hinged opaque door assembly up to 24 square feet in area shall be exempt from the U-factor requirements and shall be excluded from area-weighted averages calculated using the first two bulleted exceptions, above;
- Fenestration utilized as part of a passive solar design shall be exempt from the U-factor and SHGC requirements and shall be excluded from area-weighted averages calculated using the first two bulleted exceptions, above. Exempt windows shall be facing within 45 degrees of true South and directly coupled to thermal storage mass that has a heat capacity > 20 btu / ft3x◦F and provided in a ratio of at least 3 sq. ft. per sq. ft. of South facing fenestration. Generally, thermal mass materials will be at least 2 in. thick.
3.4: Vented Attic Reduced Thermal Bridging: Vent baffles installed in bays with soffit vents to prevent wind-washing; Insulation over top plates and under attic walkways/platforms ≥ R-21in CZ 1-5; ≥ R-30in CZ 6-8.
3.5: Slab Edge Insulation: For slabs on-grade in CZ 4-8, 100% of slab edge insulated to ≥ R-5 at the depth specified by the 2009 IECC
Per ENERGY STAR Rev 09 Rater Checklist footnotes 14 & 15:
a. Consistent with the 2009 IECC, slab edge insulation is only required for slab-on-grade floors with a floor surface less than 12 inches below grade. Slab insulation shall extend to the top of the slab to provide a complete thermal break. If the top edge of the insulation is installed between the exterior wall and the edge of the interior slab, it shall be permitted to be cut at a 45-degree angle away from the exterior wall. Alternatively, the thermal break is permitted to be created using ≥ R-3 rigid insulation on top of an existing slab (e.g., in a home undergoing a gut rehabilitation). In such cases, up to 10% of the slab surface is permitted to not be insulated (e.g., for sleepers, for sill plates). Insulation installed on top of slab shall be covered by a durable floor surface (e.g., hardwood, tile, carpet).
b. Where an insulated wall separates a garage, patio, porch, or other unconditioned space from the conditioned space of the house, slab insulation shall also be installed at this interface to provide a thermal break between the conditioned and unconditioned slab. Where specific details cannot meet this requirement, partners shall provide the detail to EPA to request an exemption prior to the home’s certification. EPA will compile exempted details and work with industry to develop feasible details for use in future revisions to the program. A list of currently exempted details is available at: energystar.gov/slab edge.
3.6: Above-Grade Wall Reduced Thermal Bridging: AGWs achieve at least one of the strategies for Reduced Thermal Bridging listed in Section 3.4 of the ENERGY STAR Rater Field Checklist (Rev 09)
- Most PHIUS+ Projects will easily meet this requirement. Where any doubt or question exists about the strategy to meet this requirement, see the ENERGY STAR Rater Field Checklist (Rev 09) footnotes relating to section 3.4.
3.7: Other Thermal Bridging/mitigation strategy identification: Note any other meaningful thermal bridges observed on the project, as well as thermal bridging mitigation strategy identification. Special effort should be made to clearly document such bridging and mitigation strategies, or where such details are missed.
- PHIUS+ Rater shall discuss the presence of known thermal bridges with CPHC prior to inspection, as well as specific mitigation strategies.
Any significant bridging observed on a project not accounted for by the CPHC must be brought to the attention of PHIUS immediately.
18.104.22.168 Fresh Air Supply
- Fresh air (OA) supply to bedrooms is required:
- Provision must be made to supply fresh air to all bedrooms in dwelling units.
- Dedicated ventilation ductwork is best practice.
- In the case of ventilation ductwork integrated with heating/cooling ducts, ERV should remain in balance under all fan speeds of the heating/cooling air handler, and said air handler fan must be designed to run continuously by default.
22.214.171.124 Ventilator Defrost
A pre-heater defrost (or ground loop pre-heater) is required for ERVs where the ASHRAE 99.6% design temperature is below the manufacturer’s claimed minimum operating temperature, rather than relying on re-circulation defrost.
- If the unit can maintain the required fresh air ventilation rates with the unit in partial recirculation mode, then this is acceptable. So basically, the unit needs to have enough boost to maintain the same typical fresh air ventilation rate as it would at higher temperatures.
- The ASHRAE 62.2-2010 Table 4.2 effectiveness factor calculation should be used to determine the required boosted intermittent rate, in the case that the cycle time is more than 3 hours.
- See this article: https://homes.lbl.gov/ventilate-right/intermittent-ventilation-runcycles
Intermittent fan flow rate = 𝑐𝑜𝑛𝑡𝑖𝑛𝑢𝑜𝑢𝑠 𝑓𝑎𝑛 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 / (𝑒𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑛𝑒𝑠𝑠 𝑓𝑎𝑐𝑡𝑜𝑟 ε) 𝑥 (𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑜𝑛−𝑡𝑖𝑚𝑒 𝑓)
continuous fan flow rate = Required whole-building ventilation rate for the house or apartment if the system was operated continuously
f = Fractional on-time for whole-building ventilation, or the percentage of time the whole-building ventilation equipment will operate in one duty cycle (the length of one complete on/off cycle).
𝛆 = Ventilation Effectiveness for Intermittent Fans from Table 4.2 in ASHRAE Standard 62.2.
Note: Table 4.2 is different in ASHRAE 62.2-2007 and ASHRAE 62.2-2010.
126.96.36.199 Balanced Ventilation Requirements
A whole-building mechanical ventilation system is required to be installed.
The system shall have at least one supply or exhaust fan with associated ducts and controls. Local exhaust fans can be part of a whole-house ventilation system.
In the Energy Star framework, the ventilation system type is characterized as either “Supply”, “Exhaust”, or “Balanced”.
For PHIUS certification, regardless of type, the ventilation system must meet one of the following requirements for balance:
- Total measured supply and exhaust airflows are within 10% of each other. (Use the higher number as the basis of the percentage difference.)
- The total net pressurization or depressurization from the un-balanced ventilation system does not exceed 5 Pa. The net pressurization/depressurization that the ventilation system imbalance causes on the building is determined using the multi-point air-tightness test results graph.
In the case of “Supply” or “Exhaust” systems:
A ventilation system design with supply fans only or exhaust fans only will generally require dedicated openings in the envelope (with dampers) for make-up air in order to meet the balance requirements, because of the air-tightness requirement on the building overall. Such make-up air inlets or outlets must appear in the design documentation for pre-certification.
In the case of “Balanced” systems with heat or energy recovery devices:
If the exhaust or supply air flow exceeds the exhaust air flow by more than 10%, the associated additional infiltration or exfiltration must be accounted for. It will be assumed that this unconditioned airflow will be continuous at the same rate as the difference between the supply and exhaust air flows.
In WUFI Passive, this should be added under 'Ventilation Rooms>Exhaust Ventilation' as an 'other exhaust appliance' running for 525,600 minutes/year.
- It is recommended that the ventilation system is capable of at least 0.3 ACH (based on the net volume) at its maximum setting. It is not required.
1.3a: All ventilation air inlets located at least 10' ("stretched-string distance") from known contamination sources.
- Examples of contamination sources include: plumbing vents, bath/kitchen exhaust vents, combustion exhaust, vehicle exhaust. Exception: ventilation air inlets in the wall at least 3 ft. from clothes dryer exhaust or contamination sources exiting through the roof.
- Please note that ERV/HRV exhaust is not necessarily a "contaminant". Thus it is not subject to this provision. However, exhaust/intake separation shall meet manufacturer specifications.
1.3b: All ventilation air inlets located minimum 5' from ventilation exhaust outlet, recommended 10'.
1.4: Ventilation air inlets are at least 2' above grade and/or roof deck, and are not obstructed by snow, plantings, outdoor equipment, etc. at the time of inspection.
- Care should be taken by projects to position fresh air inlets additional appropriate distance above grade or roof deck where snow loads or plantings may be a greater concern
1.5: Ventilation air comes directly from outdoors, not from adjacent dwelling units, common spaces, garages, crawlspaces or attics.
1.6: Outside air passes through a minimum MERV 8 filter prior to distribution, is changed at final and home is ventilated prior to occupancy.
1.7: Outside air filter is located to facilitate regular service by the occupant and/or building superintendent
1.8: Air-sealed, class 1 vapor retarder shall be installed over all air-permeable insulation (such as fiberglass duct wrap) on ventilation ducts connected to outside
1.9: Bedrooms are pressure balanced to achieve a Rater-measured pressure difference of no more than 1Pa with respect to the main body of the house/apartment when all bedroom doors are closed and just the ventilation system is operating at 24/7 design speed
1.10: Fresh air supply to all bedrooms. Example, supply to living room only, in a one-bedroom apt, is not acceptable.
1.11: Rater-measured bathroom exhaust rates meets one of the following: >=20cfm continuous or 50 cfm intermittent
1.12: Direct exhaust bath fans ENERGY STAR rated; <= 1 sone
1.13: Rater-measured kitchen exhaust rates meets one of the following: >=25cfm continuous, 100cfm intermittent for range hoods, or 5ACH based on kitchen volume
1.14: If kitchen exhaust connected to ERV/HRV, register is min. 6' from cooktop and MERV 3 or washable mesh filter for trapping grease, and recirculation hood over range.
1.15: Clothes dryer is a condensing/heat pump dryer, or exhaust dryer with exhaust ducted to the outside.
A minimum of MERV 8 filtration is required for all ventilation systems, as well as ducted heating/cooling systems. MERV 12 or higher is recommended for filtration of the ventilation air.
3.5.4 Heating, Cooling & Domestic Hot Water
See Appendix C for ASHRAE-55 based evaluation of when a cooling system is recommended.
Heating/Cooling Distribution – Ducted systems only
2.4: All return air passes through a min. MERV 8 filter which is located to facilitate regular service by the occupant and/or building superintendent
2.6: Equipment selected to keep relative humidity < 60% in “Warm-Humid” climates OR install additional dehumidification. Exception: Climate Zones 4-8 3B, 3C and the portions of 3A and 2B above the white line as shown by IECC Figure 3012009
2.7: Bedrooms are pressure balanced to achieve a Rater-measured pressure difference of no more than 3Pa with respect to the main body of the house when all bedroom doors are closed, all heating/cooling air handlers are operating at full speed and ventilation system is operating at design speed
2.8: Ducts and air handlers located entirely within building thermal envelope
Combustion Safety and Condensation Management
4.1: Combustion heating/water heating systems located within the buildings' pressure boundary are sealed combustion, direct-vent appliances
4.2: Natural draft fireplaces are not installed
4.3: Installed fireplaces and woodstoves have a combustion air inlet connected to the firebox
4.4: No unvented combustion fireplaces installed in home
Domestic Hot Water Systems
6.4: Continuous, time, or temperature-based hot water recirculation systems not installed.
6.5: Hot water temperature-rise test.
For more information, see the EPA Watersense Guide for Efficient Hot Water Delivery Systems. Download the associated design-aid calculator here.
WUFI Passive hot water distribution entries also support this calculation.
3.5.5 Lights, Appliances, & Renewables
1.1: 80% of lighting fixtures are ENERGY STAR qualified or ENERGY STAR lamps (bulbs) in minimum 80% of sockets Renewable Energy Systems
Note: PHIUS has moved to requiring homes to be solar PV-ready regardless of average daily solar radiation (kWh/m2/day). PHIUS+ projects are not exempt even if daily average solar radiation for the site is less than 5 kWh/m2/day. This rule is in effect as of April 2016.
4.3: If solar photovoltaic (PV) system not installed, document home's compliance with the DOE ZERH Home PV-ready checklist:
4.3B: Home has adequate roof area within +/-45° of true south based on table below
|CFA||Min roof area within +/-45° of true south|
4.4: If either of the above is false, the home is not required to meet the following requirements:
4.4A: Provide code-compliant documentation of the maximum allowable dead load and live load ratings of the existing roof; recommended: allowable dead load rating can support an additional 6 lbs/sq. ft. for future solar system.
4.4C: Install a 1” metal conduit for the DC wire run from the designated array location to the designated inverter location (cap and label both ends)
4.4D: Install a 1” metal conduit from designated inverter location to electrical service panel (cap and label both ends)
4.4E: Install and label a 4’ x 4’ plywood panel (or alternatively blocking) area for mounting an inverter and balance of system components.
4.4F: Install a 70-amp dual pole circuit breaker in the electrical service panel for use by the PV system (label the service panel)
3.5.6 Water Management and Indoor Air Quality
Water/Moisture Managed Site/Foundation
1.1: Patio/porch slabs/walks/driveways sloped ≥ 0.25"/ft from home to edge of surface or 10 ft; backfill tamped and graded ≥ 0.5"/ft from home for 10'. See footnote 2 of the ENERGY STAR Water Management System Builder Requirements Rev. 09
1.2: Layer of aggregate or sand (4 in.) with geotextile matting & capillary break beneath all slabs using either: ≥ 6 mil polyethylene sheeting, lapped 6-12 in., or ≥ 1 in. extruded polystyrene insulation with taped joints. Exceptions to the aggregate OR sand requirement: (Not applicable in EPA Radon Zone 1)
- Dry climates, as defined by 2009 IECC Figure 301.1. (Also exempt from capillary break requirement)
- Areas with free-draining soils – identified as Group 1 (Table R405.1, 2009 IRC) by a certified hydrologist, soil scientist, or engineer through a site visit.
- Slab-on-grade foundations
1.3: Basements/crawlspaces insulated, sealed, dampproofed and conditioned. Exceptions:
- Homes built in areas designated as flood zones (conditioned crawlspaces not recommended for use in flood zones).
- Raised pier foundations with no walls.
- Dry climates, as defined by 2009 IECC Figure 301.1.
- Marine climates, as defined by 2009 IECC Figure 301.1, if no air handler or return ducts are installed in the crawlspace
1.4: Class 1 vapor retarder not installed on interior side of air permeable insulation in exterior belowgrade walls. See footnote 7 of ENERGY STAR Water Management requirements
1.5: Drain or sump pump installed in basements and crawlspaces; sump pump covers mechanically attached with full gasket seal or equivalent. See item 1.1 of IAP specs
1.6: Drain tile installed at basement/crawlspace walls, with the top of the drain tile pipe below the bottom of the concrete slab or crawlspace floor. See footnote 8 of ENERGY STAR Water Management requirements
Water Managed Walls/Roofs
2.1: Flashing at bottom of exterior walls with weep holes included for masonry veneer and weep screed for stucco cladding systems or equivalent system
2.2: Fully sealed continuous drainage plane behind exterior cladding that laps over flashing in Item 2.1 and fully sealed at all penetrations. Additional bond-break drainage plane layer provided behind all stucco and non-structural masonry cladding wall assemblies.
- See footnote 9 & 10 of ENERGY STAR Water Management requirements
2.3: Window and door openings fully flashed. Apply pan flashing over the rough sill framing, inclusive of the corners of the sill framing; side flashing that extends over pan flashing; and top flashing that extends over side flashing or equivalent details for structural masonry walls.
2.4: Step and kick-out flashing at all roof-wall intersections, extending ≥ 4” on wall surface above roof deck and integrated shingle-style with drainage plane above; boot / collar flashing at all roof penetrations." Intersecting wall siding shall terminate 1 in. above the roof or higher, per manf. recommendations. Continuous flashing shall be installed in place of step flashing for metal and rubber membrane roofs.
2.5: Non-slab on-grade homes shall have gutters/downspouts with discharge on sloping final grade ≥ 5 ft. from foundation. See footnotes and additional details from ENERGY STAR and IAP for other circumstances. See item 1.7 of IAP specs and footnotes 3, 13 & 14 from ENERGY STAR Water Management requirements
2.6: Self-adhering polymer-modified bituminous membrane at all valleys & roof deck penetrations AND in CZ 5+, over sheathing at eaves from the edge of the roof line to > 2 ft. up roof deck from the interior plane of the exterior wall. See footnote 3 & 15 of ENERGY STAR Water Management requirements
2.7: Piping in exterior walls insulated with pipe wrap.
Water Managed and Low-Emitting Building Materials
3.1: Hard-surface flooring in kitchens, baths, entry, laundry and utility rooms AND carpet not installed within 2.5 ft. of toilets, tubs, and showers.
3.2: Cement board or equivalent moisture-resistant backing material installed on all walls behind tub and shower enclosures composed of tile or panel assemblies with caulked joints. Paper-faced backerboard shall not be used. See footnote 16 of ENERGY STAR Water Management requirements.
3.3: In Warm-Humid climates, Class 1 vapor retarders not installed on the interior side of air permeable insulation in above-grade walls. Except at shower and tub walls. See footnote 7 of ENERGY STAR Water Management Requirements.
3.4: Materials w/ visible signs of water damage/mold not installed; framing members/insulation products w/ high moisture content not enclosed. See footnotes 17 &18 of ENERGY STAR Water Management Requirements
3.5: All composite wood products, interior paints/finishes, carpet/carpet adhesive/padding certified low-emission. See IAP construction specs for Section 6.
Radon, Pest & Combustion Pollutant Mitigation
4.1: Radon-resistant features installed in Radon Zone 1 homes in accordance with IAP Construction Specification 2.1.
*Passive radon systems are highly recommended in Radon Zones 2 & 3.
See EPA Consumers Guide to Radon Reduction for more details.
4.2: Corrosion-proof rodent/bird screens installed at all openings that cannot be fully sealed (Exception: dryer vents)
4.3: Emissions standards met for fuel-burning and space-heating appliances; CO alarms installed in each sleeping zone (e.g., common hallway) according to NFPA 720. Except at shower and tub walls. See footnote 7 of ENERGY STAR Water Management Requirements.
4.4: Multifamily buildings: Smoking restrictions implemented AND ETS transfer pathways minimized. See item 1.7 of IAP specs and footnotes 3, 13 & 14 from ENERGY STAR Water Management requirements.
4.5: Attached garages: Door closer installed on all connecting doors AND in homes with exhaustonly whole-house ventilation EITHER a 70cfm exhaust fan installed in garage OR a pressure test conducted to verify the effectiveness of the garage-to-house air barrier. See IAP spec for details.
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