Insulating Existing Flat Roofs

There are several different methods for insulating roofs and walls alike but with a flat roof you have to worry about water getting in.

Insulating existing flat roofs.

Flat roofing insulation is included in the costings put together by installation companies when quoting for a new roof. I ve built a timber frame to support a new plasterboard ceiling below the existing one. The target should be to achieve a u value of 0 25w m2k or better. Insulating a flat roof presents a challenge even for experienced roofers and home builders.

Here we share the most common mistakes people make when installing flat roofing insulation. Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. This is then covered with a further weatherproofing layer.

There are many different types and installation methods out there along with a lot misinformation about which products offer the greatest energy savings. 1 the first method is to use rigid insulation. You will be unable to pass your building or extension through required. The chances of water seepage with a slanted roof are less simply because water is designed to run off and does not.

Alternatively existing insulation material may be reused when a new roof is installed if it s still in good enough condition. Insulating a flat roof is a task that must be done during construction. The existing ceiling is sound but provides no insulation. There is only a small gap between this ceiling and a concrete roof cold roof felt covered.

The typical u value of an existing uninsulated flat roof is 1 5w m2k. Insulation material is placed on top of the roof. Roofing insulation is one of the most important and misunderstood building components. Composite insulation reduces the need for a cover board when applying different membrane roof coverings.

To produce a hot roof rigid insulation is fitted outside above the weatherproofing. Cold roof a very bad idea. This method requires the use of 150mm thick insulation between the rafters and a 50mm air gap to prevent cold bridging occurring. Retrofitting flat roof insulation is a difficult task and often a messy one that involves pulling up the waterproof layer that finishes off the deck so as to put flat roof insulation in underneath.

Hack n stack sealed foam board between the rafters would be better since it s at least an air impermeable insulation but even that would require a vent gap below the roof deck to meet code and you d still be under r38 on that 2x6 rafters unless you fattened it out per holladay s recommendation.