Insulating Existing Flat Roofs

Composite insulation works in flat and low sloped roofs with a variety of roof coverings.

Insulating existing flat roofs.

Insulation material is placed on top of the roof. I want to insulate below a flat roof without removing the existing ceiling. Here we share the most common mistakes people make when installing flat roofing insulation. Insulating a flat roof presents a challenge even for experienced roofers and home builders.

To produce a hot roof rigid insulation is fitted outside above the weatherproofing. 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. The target should be to achieve a u value of 0 25w m2k or better. This method requires the use of 150mm thick insulation between the rafters and a 50mm air gap to prevent cold bridging occurring.

Composite insulation reduces the need for a cover board when applying different membrane roof coverings. Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. Insulating a flat roof is a task that must be done during construction. 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.

There are several different methods for insulating roofs and walls alike but with a flat roof you have to worry about water getting in. You will be unable to pass your building or extension through required. Cold roof a very bad idea. Alternatively existing insulation material may be reused when a new roof is installed if it s still in good enough condition.

The existing ceiling is sound but provides no insulation. 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 chances of water seepage with a slanted roof are less simply because water is designed to run off and does not.

The typical u value of an existing uninsulated flat roof is 1 5w m2k. 1 the first method is to use rigid insulation. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. Roofing insulation is one of the most important and misunderstood building components.

There are many different types and installation methods out there along with a lot misinformation about which products offer the greatest energy savings.