How To Insulate A Flat Roof Ceiling

Creating a void between the old ceiling and new is better but ideally you need to eventually consider insulating the top of the concrete roof with solid insulation and a better covering grp or epdm.

How to insulate a flat roof ceiling.

Vapor barriers are usually made from polyethylene film asphalt laced building paper or paper backed aluminum. It should be of the maximum available thickness. It s what s called the cold roof principle. Can a flat roof be insulated from inside from the ceiling of the area below.

The target should be to achieve a u value of 0 25w m2k or better. The typical u value of an existing uninsulated flat roof is 1 5w m2k. There are two main types of flat roof that require different approaches to installation. If you have a flat garage roof and an attic above you can install the garage insulation from below using a standard ladder.

Flat concrete roofs are generally not ventilated since the ceiling internally is generally a plaster and skim coat directly to the underside of the cold concrete. Insulating a roof from inside is technically feasible. The correct method for a flat roof is under the current regulations to have a warm roof. 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.

Bypasses are anywhere that there is a break in the insulation. On new build or replacement pitched roofs the ideal build up would be insulation fitted over and then between the rafters giving a big boost for airtightness image credit. Insulation between ceiling rafters there are only 2 types of insulation that should be used for this method. However if you have a cathedral style garage roof you will need a scaffolding to get into the upper areas of the roof.

With flat roof insulation a vapor barrier should sit between the joists and ceiling panels and the insulation on top. Insulation is placed in between the joists underneath the roof surface above. The reason is because it is very difficult to properly ventilate a flat space because air does not generally move in a straight line. This system was often used in the past but is not recommended nowadays.

Kingspan with a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. Insulation material is placed on top of the roof rather than in between the ceiling and the decking.