Insulating A Roof Without Felt

Add a preinstalled membrane to absorb and release the condensation as it forms with the natural weather cycle.

Insulating a roof without felt.

Roofing felt may be necessary for use with your shingles to meet a class a fire rating when shingles are evaluated for their fire ratings it is done on a small test deck with the roofing felt underlayment in place without this underlayment the shingles alone may not meet the class a fire requirements. Insulate and try to keep from reaching the dew point. Roofing felt was introduced primarily to act as a secondary barrier against wind driven snow and rain but its use also causes a reduction in air movement within the roof space particularly if the roofing felt is impervious and this effect is often compounded by the introduction of insulation. I would lean toward adding rigid foam either on top of the roof or on the inside under the joists if reducing headroom isn t a problem.

Loft insulation against rafters on an old roof with no felt lining under the tiles i want to make more use of the loft space and ideally want to insulate and board up the roof to create an clean insulated space. Depending on your climate you ll need r 30 to r 49 to meet code which is 5 to 8 1 2 inches of polyiso rigid foam which is r 6 per inch. When the home inspector checked the roof he found that the new shingles were installed without a layer of felt. The roof can usually be insulated under the rafters with sheet insulation and incorporate a vapour barrier.