Insulate Hip Roof

Do not use plastic sheeting in this case.

Insulate hip roof.

Why not consider a hot roof instead. This has the added advantage of bringing any ductwork in the attic into the building envelope and it s becoming an accepted practice. Place the plastic sheeting on top of the rolled insulation. In the case of a cold roof structure the insulation is placed between or between and under the rafters or at ceiling joist level and the roof is ventilated by leaving a 50mm gap above the insulation which vents air to the outside.

If there is a floor you will need to remove it to properly insulate the roof rafters. In a warm roof structure the insulation is placed above or above and between rafters in order to avoid heat loss and energy transfer. Rigid foam sheeting has an r value ranging from r 5 to r 10 per inch of thickness. At hot roof design problems.

Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. That is insulate the bottom of the roof deck with closed cell foam. If the plastic sheeting is in pieces overlap the pieces by 8 inches and staple it in place directly to the roof rafters and the wall. The later is used in new construction as the interior board serves as an inner wall.

Rigid foam board is just above the roof deck or an exterior insulation option. Originally we insulated with the pink fluffy stuff. To get the most r value with the least thickness use batt insulation with higher r value per inch in combination with rigid foam insulation. It s essentially impossible to effectively vent hips.

Why do you want to vent the roof. The rafters are 2x8 s. It typically has 3 variations. Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam.

Cut and insert 1 or thicker high r foam insulation sheets r 8 per inch against the furring giving a 1 or greater air path between the insulation and the roof deck under the cathedral ceiling. What is the best way to insulate and more importantly ventilate an addition with a hip roof and a very low pitch. Nail 1 furring along every rafter side against the roof deck.