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For New Residential Construction
Adopted by the MIAQC
Board of Directors on
Copyright 2003 –
General Concern for Residential Air Quality in
The purpose of this document is to highlight those practices that need to occur during new residential construction to minimize the likelihood of poor air quality in a residential property. It is in checklist format, and is meant to be used in conjunction with other, more comprehensive building science resources. For every checklist item in this document, there are extensive building science resources that provide detailed “how-to” guidance. The checklist has been sequenced to the actual residential construction process – from site selection and design considerations, to finishing details and building occupant considerations.
Tip: Examples of outside resources include:
· Energy & Environmental Building Association’s Builder’s Guide to Cold Climates. Published with support from the U.S. Department of Energy’s Building America Program. See www.eeba.org.
· Standard 62.2, Ventilation and Acceptable Indoor Air Quality In Low-Rise Residential Buildings, published by the American Society of Heating, Refrigeration & Air-Conditioning Engineers. See www.ashrae.org.
This document is designed
for new residential construction in
Guiding Principles of This Document:
There are a number of key guiding principles that apply to indoor environments, including new residential construction.
1. There is a well-established link between indoor pollutants and occupant health. (See MIAQC policy statement on the health basis for recommendations)
2. The principles for achieving a healthy and productive residential indoor environment are simple. The goal is an environment that is:
(See MIAQC policy statement on Indoor Air Quality)
3. While the methods to achieve these goals may vary, the primary best practice tools are:
§ Prevention or Elimination of Pollutants (source control)
§ Proper Ventilation
§ Thermal and Humidity Control
§ Proper operation of the structure by the building owner
§ Proper use of the structure by the building occupants
(See MIAQC policy statement on Indoor Air Quality)
4. There is a significant relationship between energy efficiency measures and indoor air quality in the residential construction process. (See MIAQC policy statement on energy efficiency and indoor air quality)
5. Individual building components and subsystems must be considered collectively in terms of their interaction with each other and their joint IAQ impact on occupants and building performance. Failure to consider these interactions increases the risk for structural issues and systems failures that can result in health and safety concerns for residents. (See MIAQC policy statement on a Whole Building Approach to Indoor Air Quality)
6. Building an IAQ healthy home does not necessarily cost more. While the installation of some features may initially be more expensive, they are essential for the health of the residential occupant, and have long-term value for energy efficiency and increased comfort. The recommendations that follow should never be sacrificed due to expense.
7. Building an IAQ healthy home requires the equal involvement of the builder (and the builder’s subcontractors), the designer, and the homeowner.
A dry or
drainable site is necessary to prevent moisture intrusion and subsequent
biological contamination in the home.
There is a
link between the quality of the outdoor air and the quality of the indoor
air. A site located away from
significant sources of outdoor air pollution is preferred. (Examples: high traffic areas, industry, dry cleaners,
bus-idling yards, etc.)
The building and site must provide effective drainage measures to control both surface water and sub-grade water and prevent it from entering the building.
¨ The finish grade on all sides of the building must be sloping away from the building to prevent water intrusion. Guideline: 4 inches of pitch for every 10 feet.
¨ Water from gutters and downspouts should be directed away from the building either above or below grade
¨ On building sites with excessive sub-grade water, a drainage system must be installed on the up-slope side of the site to divert water away from the home site.
Tip: Options include a curtain drain, retaining pond, or swale.
Uncontrolled Air leakage:
¨ The foundation should be made as airtight as possible. Use waterproof caulking and sealants to prevent air from moving in or out of the foundation.
Handling & Storage of Building Materials:
Building materials that get wet and stay wet during the construction process are at risk for subsequent mold growth in the home.
¨ Keep building materials delivered to the site protected from rain and snow.
¨ Intrinsic moisture from the materials used in the construction process (concrete, joint compound, paint, etc.) must be given a means of drying out. Be careful not to “trap” moisture in the components of the building.
§ Complete frame of house before delivery of weather sensitive materials.
§ Installing bituthane on full roof surface is an excellent means of protecting home while waiting for roofing completion/installation. (Refer to manufacturer’s specifications to prevent over-exposure of this material.)
§ Dry lumber to 15% moisture content or less before covering. If lumber shows signs of mold growth, use a HEPA vacuum and detergent wash, then dry to 15% moisture content. Sand if needed after drying to remove surface mold.
All cladding will leak, and should not be considered a functioning part of the drainage plane. Cladding is primarily an aesthetic, visual detail.
¨ A properly installed and sealed drainage plane is essential to prevent water and moisture from leaking into the structure and coming in contact with the frame and insulation of the building. It also serves as the primary means for moisture to flow down, off and away from the building.
¨ If house wrap is used as a drainage plane, all seams should be properly overlapped and taped or sealed so that it is continuous.
¨ Penetrations for windows/doors, vent hoods, water spigots, chimneys, and wires must be sealed to the drainage plane.
¨ All windows and doors must be properly flashed and sealed.
¨ For wood and fiber cement siding, create a space between siding and drainage plane (a “rain screen”) to allow for drainage of water down and out, and allow moisture to dry from the back of the siding.
¨ Install insect screen at the base of the rain screen to prevent pests from entering the home.
Tip: Use “cedar breather” when installing cedar shingles. Use 1” x 3” vertical strapping when installing clapboards.
¨ It is critical that both an air and vapor barrier be installed to prevent air and moisture from leaking in or out of the home in an uncontrolled manner. These are generally combined as one product, but can be installed as two separate systems.
Tip: As noted in previous sections of this document, it is important to consider installation of the air and vapor barriers throughout the construction process.
¨ It is important to consider the wall between the house and an attached garage as an exterior wall. Insulation, air, and vapor barriers should be installed in the same manner as any other exterior wall so that the garage is “thermally separated” and sealed off from the house, greatly reducing the risk of pollutants from the garage entering the house.
Air barriers serve to keep outside air outside and inside air inside, thereby eliminating points where condensation can occur. Air barriers should be:
¨ Continuous and connected to previously installed portions of the air barrier (see Foundations and Framing sections of this document.)
¨ Located within building envelope
¨ Seal all penetrations.
¨ Applied to warm side of insulation (for
¨ Continuous and connected to previously installed portions of the vapor barrier (see Foundations and Framing sections of this document.)
¨ Seal all penetrations
Tip: Have sealant tape and expandable foam available for subcontractors to repair any penetrations to either barrier. Explain to them the importance of doing so.
controlled ventilation system must be installed in all new residential
¨ A fully-ducted heat recovery ventilation system is preferred.
· It removes stale air and pollutants from the entire home.
· It provides fresh air to the entire home.
· It reduces energy costs
· It increases occupant comfort.
Tip: Installation of a fully-ducted heat recovery ventilation system is more expensive up front, but yields long-term energy savings.
¨ All ductwork must be mechanically fastened and properly sealed (not duct tape)
¨ All ductwork must be protected from construction debris.
¨ It is possible to ventilate a home with an exhaust-only ventilation system comprised of:
· Bathroom fans vented to the outdoors, never to the attic
· Kitchen fans vented to the outdoors.
· A means for allowing fresh, outside air to enter the home
All gas oven/range
appliances must have a range hood direct vented to the outside.
¨ All clothes dryers should be vented to the outside to prevent high moisture levels in the home
fossil fuel, a sealed-combustion heating unit (direct vented to outside) is
preferred so there is no pathway for carbon monoxide (CO) to enter the
home. This includes all wood-burning
appliances as well as gas burning appliances used for heating. For non-sealed combustion units, a
de-pressurization test should be conducted to determine if make-up air is
required and to ensure proper operation of the appliance venting system.
¨ Combustion appliance outdoor vents have a code-regulated setback from exterior windows, doors, overhangs, etc. to prevent infiltration of combustion by-products from entering the home. Refer to manufacturer’s specifications for setback details.
¨ If using a ducted forced hot air system – use high efficiency filters and install registers in walls rather than floors to minimize intrusion of dust and particulates into registers and keep the air in the home cleaner.
¨ Never use unvented gas and kerosene heaters indoors.
¨ Never install plumbing in outside walls
Tip: Consider insulating cold water pipes that may be prone to condensation in summer months.
¨ Seal all plumbing penetrations passing through the air and vapor barriers.
¨ Test the plumbing systems before finishing the interior to maintain access to repair leaks and to prevent water damage to porous materials.
¨ Seal all penetrations of electrical wires with caulk and foam
Install air tight
outlet boxes in exterior walls and insulated ceiling
behind and air seal electrical panels that are installed on exterior walls
¨ When a recessed lighting fixture penetrates the vapor barrier, use insulation-contact (IC rated) recessed lighting fixtures.
¨ Use low or no-VOC paints and finishes
Tip: Delay occupancy by 3-4 weeks to allow for off-gassing of VOC’s (volatile organic compounds) from paints and finishes. If you cannot delay occupancy, keep the heat at 70 degrees Fahrenheit and open windows 1-2 inches to increase ventilation.
¨ If using particle board cabinetry or furniture, seal exposed edges to prevent off-gassing of VOCs (volatile organic compounds) or consider using or purchasing solid wood cabinetry and furniture.
¨ Never install carpet in an area likely to get wet
¨ Damage to the air and vapor barriers must be sealed and repaired before covering.
Landscaping schemes can sometimes contribute to air quality problems in a home. Plants, shrubs and trees placed too close to the building can contribute to moisture problems and provide easy access points for pests to enter the home.
¨ Foundation plantings should be set away from the dripline of the roof and at a minimum of 24 inches away from the foundation at full maturity.
Tip: Place a two-foot wide strip of pea-stone or non-woody mulch, with landscape cloth
underneath, to discourage insect and rodent infestation and prevent vegetation from growing next to the foundation.
¨ Shade trees should be set far enough away from the home to prevent pest access and eliminate foundation damage from root penetration.
¨ Exterior vents should be kept free of obstacles
¨ Finish grade should be no less than 8” away from any wood surfaces