Attic Knee Wall Ventilation

Old school roof vents which look like rectangles on the roof work pretty well too.

Attic knee wall ventilation.

Although kneewalls can help turn attics into living space they often present insulation challenges. Intake vents located at the lowest part of the roof under the eaves allow cool. Kneewalls short walls under sloped ceilings are common in story and a half homes and in bonus rooms above garages. 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.

Most builders install fiberglass batts between the studs and some type of blown insulation between the floor joists. Ventilating knee wall attics is challenging. With that said it s important to allow outdoor air to enter the attic. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of 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. 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. 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. Rather than leaving this space empty homeowners can fill it with insulation for additional thermal protection.

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. Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls. Filling the space behind the knee walls with insulation helps to lock in your home s thermal energy. The peak attic is insulated above the bedroom ceiling and has gable end vents at each end.

Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities. Install insulation without misalignments compressions gaps or voids in all knee wall cavities.