Fine Home Building Insulating Knee Walls Roof

Blown insulation in the knee wall and top attics.

Fine home building insulating knee walls roof. Insulating only the attic roof rafters and the walls at the end of the attic is one method some use to insulate the knee wall area underneath but carson dunlop author of principles of home. Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation. Few building materials have been embraced by so many builders as rigid foam insulation certainly there are builders who avoid it but rigid foam can be used everywhere from beneath a basement slab to the rooftop and that versatility gets it into a lot of residential projects. Rake walls it s easier to handle than plywood or thermo ply and still gives you an r 19 r121 assembly.

We prefer cellulose but we use fiberglass sometimes too. Another alternative for knee walls conditions is to remove and reinstall the batt insulation to qii standards. 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. In finished attic rooms with or without dormer insulate 2a between the studs of knee walls 2b between the studs and rafters of exterior walls and roof 2c and ceilings with cold spaces above.

There are many ways to build an insulated sloped roof. 2d extend insulation into joist space to reduce air flows. We reduced the air leakage nearly 50 on this house in shaker heights without insulating the walls. Then cover that same area with an r 8 fsk affixing it using cap nails.

There are several common types of rigid foam insulation each with different pros and cons. In tight attics or odd shaped wall conditions i e. Insulating the knee wall with rigid foam keeps stone and cement which are poor insulators from conducting cold and dampness into the greenhouse. Added bonus the floor of this knee wall leaked too so there is a line of foam just above the floor joist.

An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot. Enough of each tie remained exposed to anchor the stone facing to the concrete wall.