Insulating A Flat Roof Without Ventilation

There is a common misconception that flat roofs are difficult to insulate.

Insulating a flat roof without ventilation.

Cold roof a very bad idea. Hot roofs have the roof deck then insulation then the roofing material. This misconception is so strong that some people actually choose to not get flat roofs because they are worried about the roofs not being properly insulated. Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses.

The material that works best depends largely upon preference in a given situation. Flat roof insulation cross section a great example of this is powerdeck f insulation board which is both rot resistant and highly durable. Since you currently do not have ventilation and it sounds like you have access to the attic the most cost effective insulation technique you can use is to spray closed cell foam using spray foam kits around the perimeter of the roof between the roof surface and the ceiling to a nominal depth of at least 2 inches to prevent air infiltration. The old roof was tar and gravel so the switch to tpo should show significant change.

However in many situations the insulation may need to be primarily or entirely below the flat roof membrane and between the roof joists if so what are the best options. Should i leave out the soffit vent. I have an insulation factor of about 8 10 plus the reflectivity of the white tpo. Ventilation is necessary to allow moisture accumulated inside to escape.

Depending on the weather and usage of the roof during its lifespan the insulation board may still be in a good enough condition to re use when the time arrives to replace the roof itself. When renovating an older home whose roof rafters are only 2x6 really 5 1 2 x 1 5 in dimension the available space for insulation and ventilation is limited therefore limiting the options for a combination of good under roof ventilation and high insulation r values in the cathedral ceiling. How much ventilation does a flat roof need. It depends on where the insulation is installed.

Proper ventilation in flat roofs. Is there any advantage to trying to get any insulation in between the 2 8 rafters. A cold roof or hot roof. This is then covered with a further weatherproofing layer.

Insulating a flat roof requires ventilation above the insulation. Also there is a soffit vent but none at roof peak. The answer depends on the type of roof you have. To produce a hot roof rigid insulation is fitted outside above the weatherproofing.

It also lets hot air escape in the summer.