Insulation For Flat Roof Without Attic

You can expect to pay about 55 100 sq ft.

Insulation for flat roof without attic. Staple plastic or foam baffles to the roof sheathing near the eaves to keep the material away. Try a spray foam insulation kit to fill cavities gaps cracks expansion joints and other sources of air leaks. For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence. The type that is right for your flat roof insulation job depends upon the state of the roof expert opinion on the best type and your budget.

Depending on your climate you ll need r 30 to r 49 to meet code which is 5 to 8 1 2 inches of polyiso rigid foam which is r 6 per inch. Roof types the various types of roofs found on homes sheds garages and other buildings fall into one of the following categories. The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow. Because most flat roofs don t have an attic crawl space or venting the insulation must go underneath the roof s covering on the exterior of the home or be placed on the inside of the home.

It is important to note when insulation is on the floor of the attic the space between the insulation and the roof deck must be vented to the exterior. New rules and practical interpretation. But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used. You probably don t have to meet code of course retrofitting insulation on a funky old house but it s not a bad thing to strive for.

We recommend having at least 20 r value worth of material for optimal energy efficiency. This insulation strategy has not changed in recent code iterations and is not discussed in this article. It helps resist moisture that can lead to mold or mildew and provides increased sound and thermal insulation. For a 1 inch board equivalent of 6 r value.

Insulation on the floor of the attic figure 1. For the same reason insulation shouldn t touch the roof s underside. Condensation control is most often accomplished by installing rigid foam above the roof deck or by installing air impermeable spray foam insulation directly against the underside of the roof deck. Rolls are easy to transport and can be cut to the length you need.