Cold Flat Roof Insulation Between Joists

This method of insulation can also be used to upgrade the thermal performance of an existing roof without affecting the waterproofing system.

Cold flat roof insulation between joists.

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. The insulation is below the deck but above the plasterboard. Flat roof dormer the traditional cold deck flat roof system is to install the insulation between and under the joists with ventilation below the timber deck. 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.

The majority of domestic cold flat roofs use insulation between and under the joists. 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. Last year we bought a barn that was converted in the 1980 s. Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior.

Tlx silver can be used to reduce the thickness of additional insulation required between the joists to help ensure a ventilated gap is maintained between the insulation and the deck. This is used for refurbishment e g. Poly to the underside of joists. It already has foil backed insulation in the roof but only 35mm and we would like to increase this without taking the roof off as it s simply too expensive.

The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation. Great videos thanks for sharing. 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. 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.

No ventilation is required for these types of roofs. Here the roof deck is maintained at the same temperature as the external conditions hence cold deck roof. 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. We ve watched your video on youtube and wonder if you could give us some advice please.

A cold flat roof is defined by insulation being installed between and if necessary underneath the timber joists.