Insulation Under The Roof

Arguably the most popular pitched roof solution installing insulation between and under the rafters uses the depth of the structural timbers to best effect.

Insulation under the roof.

A vent baffle should be installed between the insulation and the roof decking to maintain the ventilation channel. The insulation boards are best fitted under the roof structure whilst the mineral wool can be inserted between the beams of the roof. An efficient room in a roof in a new build property where over rafter insulation is not desirable. The materials used to insulate under the roof include batts of mineral or glass wool insulation held in place by battens of wood attached to and across the rafters alternatively polystyrene.

Water is insulation s enemy. Consider using high density r 30 batts which are as thick as r 25 batts but fit into 2x10 framing. It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow. The quest for greater energy efficiency in buildings has led to increasing interest and need for insulation improvements in hvac equipment more airtight construction new materials and assemblies.

You can also add rigid foam insulation under the rafters which adds r value and eliminates thermal bridging through wood rafters. Senior engineer manager at icynene john broniek makes the case for the unvented attic assembly and why insulating the underside of the roof makes sense.