Insulating A Flat Roof From Outside

In a nutshell you would sandwich 130mm of solid insulation between two decks allowing to place a vapour barrier on top of the first deck.

Insulating a flat roof from outside.

To produce a hot roof rigid insulation is fitted outside above the weatherproofing. Rigid foam panels are available in thickness. Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses. Materials used to make insulation in these three types include mineral wool fiberglass cellulose fiber vermiculite styrofoam polystyrene and polyurethane.

Cold roof a very bad idea. Why its important to insulate your flat roof. Whatever new flat roof covering you choose epdm rubber kemper. However most cathedral ceilings and low slope flat roofs are insulated roof assemblies.

Not cheap but needs to be done right either way. You would only do this however if replacing the roof covering on top and you have the height above the roof to do this. With this kind of roof the insulation follows the slope of the roof. Or insulate partially on the exterior side of the roof sheathing with an air control layer insulate in the rafters bays control the vapor diffusion and re work the fascia soffit etc.

The correct method for a flat roof is under the current regulations to have a warm roof. Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. This is then covered with a further weatherproofing layer. Insulated roof assemblies can be vented or unvented.

Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior. They lose loads of heat and are prone to leaking causing the materials to deteriorate. A roof over a vented unconditioned attic does not need to include any insulation. The material that works best depends largely upon preference in a given situation.

Fur down the rafters for more r value after evaluation air seal insulate and control the vapor diffusion. I explain problems with insulating a roof using the warm and cold roof construction methods. Warm deck flat roof insulation is now the standard way to insulate a flat roof click to enlarge flat roofs for example on extensions bathrooms and dormer windows are not the best of ideas. When you have an un insulated roof you have to live with.

The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation. While insulation for a flat roof is expensive and can account for as much as 25 of the total installation cost there are a number of important benefits to having it in place.