Insulating A Flat Roof From Outside

Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior.

Insulating a flat roof from outside.

The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation. Not cheap but needs to be done right either way. Rigid foam panels are available in thickness. Materials used to make insulation in these three types include mineral wool fiberglass cellulose fiber vermiculite styrofoam polystyrene and polyurethane.

I explain problems with insulating a roof using the warm and cold roof construction methods. Why its important to insulate your flat roof. Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation. When you have an un insulated roof you have to live with.

Fur down the rafters for more r value after evaluation air seal insulate and control the vapor diffusion. This is then covered with a further weatherproofing layer. 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. Unfortunately too many dwellings suffer from this problem.

To produce a hot roof rigid insulation is fitted outside above the weatherproofing. With this kind of roof the insulation follows the slope of the roof. Cold roof a very bad idea. Reduce extreme temperature fluctuations inside your home.

The correct method for a flat roof is under the current regulations to have a warm roof. However most cathedral ceilings and low slope flat roofs are insulated roof assemblies. 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. You would only do this however if replacing the roof covering on top and you have the height above the roof to do this.

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. Insulated roof assemblies can be vented or unvented. A roof over a vented unconditioned attic does not need to include any insulation.

They lose loads of heat and are prone to leaking causing the materials to deteriorate. Use rigid foam insulation panels on your flat roof before applying the final roof covering or inside the house before adding sheetrock or paneling.