How To Insulate Roof Rafters With Celotex

Install the insulation flush with the bottom of the rafters making sure that it does not fill the entire rafter depth.

How to insulate roof rafters with celotex.

Where the benefits of over rafter insulation want to be enjoyed while still creating a useable room in the roof space it s possible to insulate over and between the rafters. I wish to use celotex 50mm between the rafters 70 x 150mm up to the 2m height. Ensure that the insulation boards fit tightly between the rafters. Kingspan with a warm roof the usual process is to split the insulation into two layers.

Not insulating between the rafters above this space thus creating a huge air space. Cut the insulation boards to size using a sharp knife or fin toothed saw. The saint gobain insulation uk u value calculator gives you instant access to calculating a proposed insulation thickness and product options or giving an indicative calculation on a proposed construction detail. There will also be kooltherm k7 pitched roof board between the rafters image credit.

Although there are many different circumstances that may call for insulating roof rafters the means to determine the necessity for insulating rafters remains the same. Due to the thermal bridging effect of the timbers the overall thickness of insulation used to achieve a low u value is not as efficient as over rafter insulation only. Insulate the flat roof 75mm celotex fixing plasterboards to the cross supports creating a ceiling. As for insulating below the joists an insulating laminate insulation bonded to plasterboard such as celotex pl4000 or a separate rigid pir insulation board finished with a separate sheet of plasterboard can be securely fixed to the joists to provide an internal finish to the roof.

If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of. Alternatively battens can be secured to the underside of the. Once up at roof level the between rafter boards can be cut accurately to fit the rafter spacings. Depending on the specifics of the roof it may be possible to fully fill the rafter depth or in most cases leave a 25mm or 50mm air gap between the top face of the insulation and the.

We used kingspan thermapitch tp10 zero odp which is a 100mm thick rigid board. Being lightweight they do not impose significant additional loads on existing structures.