Spray Foam Attic Knee Wall

They are 2 4 construction kraft faced r 11 batts in the wall with the paper facing the drywall and a plastic vapor barrier in the knee wall attic.

Spray foam attic knee wall.

An attic space may be created behind a knee wall when constructing a bonus room in the area typically left as attic space. I suggest installing horizontally stacked r 19 unfaced fiberglass batt insulation across the back side anchored to the studs and then covered from roof. But you do so at the expense of floor space. Intumescent coatings are not always needed to coat spray foam in the attic in order to meet code thermal barrier requirements.

A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. If no access hatch into this space is required by other code stipulations there is no requirement for an ignition barrier on the spray foam behind a gypsum board knee wall because there is no access. Spray foam insulation is it a safe choice for your home indoordoctor. Kneewalls short walls under sloped ceilings are common in story and a half homes and in bonus rooms above garages.

Install blocking in the joist bays below the knee walls to prevent air flow under the knee walls. The higher the knee wall the greater the amount of useful wall space you create in your finished attic. If you want the attic to be outside then using foamboard on the attic side of the knee wall is a good idea. Third many side attic knee wall areas are very restrictive in accessiblity and working height.

Earlier this year i got a question about a home that had spray foam insulation in the attic. If spray foam insulation is used for the wall cavity insulation the spray foam can serve as the air barrier if it is at least 5 5 inches thick if open cell or at least 1 5 inches thick if closed cell spray foam insulation. Nothing unusual about that. You can use foam board to make baffles near your soffit vents and then blow in enough insulation to reach the r value you want.

A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents. If i place vertical runs of r 30 unfaced against the current plastic barrier i d use a perforated barrier to hold them in place. Although kneewalls can help turn attics into living space they often present insulation challenges most builders install fiberglass batts between the studs and some type of blown insulation between the floor joists. This makes is extremely difficult to install a rigid thermal barrier over the stud framing.

Using spray foam to create air barriers on exterior walls lapolla industries inc. You ll need to air seal all the penetrations and leaky spots like joists under the kneewall.