When having your flat roof repaired or installed, the question of insulation methods will inevitably arise. Your two main options for effective insulation of your property are a cold flat roof, or warm flat roof design.
Pencast – Cold Roof Construction Pencast – Warm Roof Construction It is perhaps surprising, and certainly unfortunate that some building professionals, and contractors are under a misapprehension as to the precise requirements in order to achieve warm roof, and, or cold roof construction.
The Cold Deck is the most common but also the least thermally efficient design of roof insulation. In the case of a flat roof the roof deck and waterproof membrane are supported on joists, the internal ceiling is attached to the underside of the joists and should have a vapour barrier to stop condensation penetrating the internal decor.
RR-0404: Roof Design. Joseph Lstiburek. ... In cold and very cold climates selecting a roof deck condensing surface temperature criteria of 45°F is very conservative. ... Unvented Flat Roof Assembly—There is no potential for condensation on the underside of the roof sheathing until interior moisture levels exceed 50% RH at 70°F; ...
Traditional cold deck flat roof. Traditionally, flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck.
THE HOUSEHOLDER’S GUIDE TO FLAT ROOFING. ... This type of construction has the insulation above the roof deck, thus keeping the deck ‘WARM’. This is usually ... BASIC DESIGN WARM AND COLD ROOFS Householder’s Guide to Flat Roofing In a flat roof, the waterproofing is always supported by a structural roof deck. This is usually a timber ...
Cold flat roofs are found in many homes around the UK, though they are not recommended these days and are actually banned in Scotland. Cold roofs involve the thermal installation being installed between the joists and below the structural deck.
The Cold Deck is the most common but also the least thermally efficient design of roof insulation. In the case of a flat roof the roof deck and waterproof membrane are supported on joists, the internal ceiling is attached to the underside of the
Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction, this videos show detailed drawings how a cold flat roof is constructed.
A note to consider before construction: if insulation is installed below the flat roof deck this is called a “cold” roof. Generally, roofers discourage this method for cold climates because it can promote condensation and requires ventilating the roof, which may be difficult to do in small or tight spaces.
A cold roof construction will normally comprise of a structural deck on joists or purlins with a ceiling layer fixed to the bottom of the joists/purlins thereby creating an air layer or cavity within.
For most domestic purposes a warm deck flat roof is superior to a cold deck. Converting a cold flat roof into a modern warm deck roof can be surprisingly economical. Provided the existing roof is in a good state of repair and has a suitable structure a warm deck overlay can be applied.