Checklist: Installing Insulation the right way

By Maggie Leslie on 03/22/2010

There are many types of insulation. The most common type is batt, or blanket-type insulation (typically fiberglass). This is the least expensive but requires careful installation to ensure 100-percent coverage. Blown types, such as fiberglass, cellulose (made from recycled newspaper) and foams are more easily installed, and each one does a good job of filling in gaps, cracks and areas around pipes and wiring. Foams have an added benefit: They air seal all the gaps and cracks in the walls for more of an airtight outcome. Below is an insulation installation checklist.

• Insulation is installed to be in full contact with the air barrier (the Sheetrock to the inside and the sheathing to the outside). If the insulation is not encapsulated by a rigid material on all six sides, it will not insulate properly.
• Insulation is installed to fill 100 percent of every cavity.
• If batts are installed, the batt is cut to fit around all plumbing, heating and electrical penetrations and other obstacles. It is split to go behind and in front of wires and plumbing. This is done in such a way as to fill all cavity spaces and gaps, while not compressing the insulation.
• The space behind electrical boxes is fully sealed and insulated.
• If faced (Kraft or paper) batts are used in walls or cathedral ceilings, the flanges are stapled to the face of the studs or rafters, not the side of the surface facing into the cavity (this is known as inset stapling).
• Attic insulation extends all of the way to the exterior edge of the top plate of the wall below without compression. Roof-framing details, such as raised-heel trusses or oversized trusses, must allow for this.
• Insulation baffles are installed to prevent overblow into soffits and to prevent wind-washing through the insulation. This means that baffle height is no less than the thickness of the insulation.
• Attic-access openings (hatches or pull-down stairs) are insulated to at least R-30 and weather-stripped to prevent air movement between the attic and the living space. The insulation is glued or stapled to prevent misalignment. This is a great application for rigid foam.
• Floor insulation is in continuous contact with the subfloor above. It should provide continuous coverage, with no compression of the insulation and with no gaps. Batt insulation is cut to fit around pipes, blocking and bridging and other obstacles, so as to provide the full R-value in all spaces (the measure of how well your insulation resists heat flow).
• Band joists are insulated to at least the level of exterior walls and cover the entire band-joist area.
• Walls between conditioned space and attic space, such as knee walls in bonus rooms, have a rigid material on the attic side, preferably rigid-foam insulation, which will prevent air flow through the wall cavity and allow the R-value of the wall insulation to perform as intended. This rigid material is sealed with caulk or spray foam at all connections to the framing.
• Single-ply headers are used where possible to allow for insulating headers above windows and doors. Headers are insulated by using rigid foam sheathing as a spacer instead of plywood or oriented strand board, either between or on one side of double headers.
• Interior/exterior wall intersections are framed using ladder T-walls in order to maximize the area of insulation on the exterior wall.
• Outside and inside corners: Two-stud corners or “California” corners are used to decrease lumber use and increase insulation levels, compared to typical practice. Wood nailers and/or drywall clips are used to ease the installation of exterior and interior finishes.

Sources for this checklist include Advanced Energy System Vision Guidelines, Southface Energy Institute Technical Bulletins, HealthyBuilt Homes program guidelines and Energy Star guidelines for homes and indoor quality.

[Maggie Leslie is program director of the WNC Green Building Council. She can be reached atmaggie@wncgbc.org or at (828) 254-1995.]