Insulation For Flat Roof Without Attic

To insulate a flat roof internally using insulated plasterboard.

Insulation for flat roof without attic.

You can expect to pay about 55 100 sq ft. New rules and practical interpretation. Rolls are easy to transport and can be cut to the length you need. For a 1 inch board equivalent of 6 r value.

In most cases it should be possible to insulate each rafter space all the way down to the eaves and over the top of the exterior wall. 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. 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. While expensive the best insulation is polyiso rigid foam.

This means lowering the height of the ceiling but may be a better option than insulating externally. 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 helps resist moisture that can lead to mold or mildew and provides increased sound and thermal insulation. Water is insulation s enemy.

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. Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. It is top quality and the most cost effective product for your flat roof. We recommend having at least 20 r value worth of material for optimal energy efficiency.

For such constructions the principles and benefits of unvented attic construction are similar to that occurring in a single family residence. Insulation on the floor of the attic figure 1. 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. Box out light fixtures.

It creates a breeding ground for mold and mildew and ruins the air trapping pockets that block heat flow. Seal any roof vents into the parts of the attic that are not heated.