Insulate Hip Roof

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.

Insulate hip roof.

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. The rafters are 2x8 s. Do not use plastic sheeting in this case.

Why not consider a hot roof instead. 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. Nail 1 furring along every rafter side against the roof deck. Rigid foam sheeting has an r value ranging from r 5 to r 10 per inch of thickness.

Originally we insulated with the pink fluffy stuff. This has the added advantage of bringing any ductwork in the attic into the building envelope and it s becoming an accepted practice. It typically has 3 variations. Why do you want to vent the roof.

In a warm roof structure the insulation is placed above or above and between rafters in order to avoid heat loss and energy transfer. At hot roof design problems. If there is a floor you will need to remove it to properly insulate the roof rafters. Rigid foam board is just above the roof deck or an exterior insulation option.

The roof overall is 26 x8 and the max height where it meets up with the house is maybe 2 2 1 2 high. 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. 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. It s essentially impossible to effectively vent hips.

Place the plastic sheeting on top of the rolled insulation. Bare foam board one sided sheathing board or double sided which is also reference as structural insulated panels. The later is used in new construction as the interior board serves as an inner wall.