Fine Home Building Insulating Knee Walls Roof Vented Roof

If you choose an air permeable insulation like fiberglass or cellulose most building codes require the roof assembly to include a ventilated air gap directly above or directly below the roof sheathing.

Fine home building insulating knee walls roof vented roof.

Floor area is 1200 sq ft. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. The third shows the baffle extending up into the roof attic. A vented attic where insulation is placed on an air sealed attic floor is one of the most underappreciated building assemblies that we have in the history of building science.

The house was built in 2001 and now only has batt insulation on backside of drywall of knee. We prefer cellulose but we use fiberglass sometimes too. The ridge is about 40 feet long and there is currently a ridge vent but no other roof vents no soffit vents and no gable vents. Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist.

Unfortunately the space on the unconditioned side of the knee wall often is not well sealed or insulated and the wall structure by itself does not provide enough of a thermal barrier to adequately maintain the temperature of the conditioned side of the knee wall in a vented non conditioned attic. Of 4 companies i called i finally got a quote andwhat they propose is to install vent baffles on underside of roof osb and then fg batt insulation. My 1914 house needs to be re roofed this summer but i am at a loss re ventilation. If you ve got a roof over your latest building project chances are you ve also given some thought to roof venting.

Sloped roof assemblies can be insulated with a wide variety of insulation materials including spray foam fiberglass batts or blown in cellulose. I installed baffles between the roof and insulation shown to allow for the air to flow from the soffit to the roof attic as shown in the second picture. There are arguments about shingle life over a hot roof vs vented but shingle color is more significant and as already stated one can install ventilation chutes. The first picture is looking up at the angled roof of the knee wall.

Blown insulation in the knee wall and top attics. The standard roof ventilation requirement used in building codes and asphalt roofing manufacturers calls for 1 square foot of net free ventilation area for every 300 square feet of ceiling area attic floor area when vents are evenly divided half of them high on the roof at the ridge gable or a high roof and half low on the roof at. The shortest distance from the top of the knee wall to the top of the outside wall beneath is still along the roof line and you avoid having to insulate the floor behind the knee wall. So i ll start by saying something that might sound controversial but really isn t.

I live in peachtree city ga and have a house with 9 of these knee wall areas i need to properly insulate. 15 articles and videos from the fhb archive that will take you through every step of the roof venting process.