Attic Knee Wall Ventilation

The peak attic is insulated above the bedroom ceiling and has gable end vents at each end.

Attic knee wall ventilation.

With that said it s important to allow outdoor air to enter the attic. If you can gain access to the triangular attic behind the kneewall it s often possible to inspect the rafter bays to see if the builder included ventilation baffles. Sometimes though there are no soffits. The upstairs bedrooms are built inside the roof with a peak attic above the bedroom ceiling and knee wall attic spaces behind the bedroom walls.

Install insulation without misalignments compressions gaps or voids in all knee wall cavities. Filling the space behind the knee walls with insulation helps to lock in your home s thermal energy. Rather than leaving this space empty homeowners can fill it with insulation for additional thermal protection. Most builders install fiberglass batts between the studs and some type of blown insulation between the floor joists.

Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. What happens then is that the batts don t make contact with the air barrier the drywall air moves through and around them and they fall out of the attic kneewall. Kneewalls short walls under sloped ceilings are common in story and a half homes and in bonus rooms above garages. I read lots of guides and blogs understanding that roof deck sheathing needs to be ventilated from soffits at bottom edge of roof preferable to ridge or gable end vents.

The problem with many kneewalls is that they have fiberglass batt insulation with nothing covering them on the attic side as shown in the photo below. Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities. Although kneewalls can help turn attics into living space they often present insulation challenges. Ventilating knee wall attics is challenging.

Intake vents located at the lowest part of the roof under the eaves allow cool. If these are absent they can sometimes be added by sliding them in place above the batts especially if the sloped section of roof is relatively short.