Cold Flat Roof Insulation Between Joists

As there are two types of flat roofs available that require different types of insulation the methods used.

Cold flat roof insulation between joists.

The underside of the rafters in this case will need to be finished with a suitable vapour control layer vcl and plasterboard to provide a suitable internal finish to the roof. Cold deck roof a cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. This method of insulation can also be used to upgrade the thermal performance of an existing roof without affecting the waterproofing system. How to insulate a flat roof.

This quetion is to do with warm roofs and cold roofs presumably the 50mm of insulation on the underside of joists would act as the vapour barrier if taped sealed correctly or if insulation between joists a vapour barrier i e. This is used for refurbishment e g. Poly to the underside of joists. Alternatively battens can be secured to the underside of the joists and gmw fitted between these in much the same way as between the main roof joists.

It is preferred to have the bulk of the insulation between the. In the warm flat roof construction there is insulation packed into every possible space where air can flow. The rule of thumb for foil faced boards like thermapitch tp10 or kooltherm k7 in this scenario is that you can have no more insulation under the joists than you have between the joists. Great videos thanks for sharing.

It allows insulation to be added without having to replace the waterproofing on. Refurbishing an existing timber joisted flat roof which has no insulation. Where insulation depth is restricted by the flat roof construction it may be necessary to install the roof insulation between and below the joists to create a cold deck structure. The insulation is below the deck but above the plasterboard.

The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof. A cold flat roof is one where the insulation is between or between and below the roof joists. The majority of domestic cold flat roofs use insulation between and under the joists. No ventilation is required for these types of roofs.

Insulation is placed in between the joists underneath the roof surface above. A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation.