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Roof Types
A typical single ply roof system comprises structural support (generally not installed by the roofing contractor), a deck providing continuous support, a vapour control layer (if required), thermal insulation (if required) and a waterproof membrane covering with aesthetic traffic or load resistant finish (if required).
Membrane roof systems are generally divided into the following types, according to the position in which the principal thermal insulation is placed:
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The Warm Roof
The principal thermal insulation is placed immediately below the roof covering, resulting in the structural deck and support being at a temperature close to that of the interior of the building.
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The Inverted Warm Roof
This is a variant of the warm deck roof, in which the principal thermal insulation is placed above the roof covering, resulting in the roof covering, structural deck and structural support being at a temperature close to that of the interior of the building. Generally the principal insulation is secured by ballast. However, proprietary lightweight systems are available, which do not rely on ballast.
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The Cold Roof
The principal thermal insulation is placed at or immediately above the ceiling, resulting in the roof covering and structural deck being substantially colder in winter than the interior of the building. The structural support will typically bridge between the high and low temperature zones of the construction. It is very difficult to insulate a cold roof system to current mandatory levels, without increasing the risk of condensation accumulation within the system. In addition, the requirement for uninterrupted external air circulation limits the application of the system, where abutting elevations or changes in building geometry occur. It is therefore not a recommended option. If an existing cold deck roof is refurbished, it is important to ensure that the ventilation requirement is achieved, whether or not the level of insulation is to be increased.
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Other Roof Types
Many roofs combine the features of two or more of the roof types described above. Examples include structural decks with high thermal insulation properties combined with additional insulation and existing roofs to which thermal insulation is added. However, once assessed in terms of their thermal and water vapour transmission characteristics, such roofs will generally fall into one of the categories described above. In some constructions, the waterproofing layer is placed between two layers of insulation, combining the properties of warm roof and inverted warm roof construction. This form of construction is generally known as a ‘duo roof’.
Roof gardens or ‘green roofs’ (see SarnaVert green roofs) typically comprise a roof system of either warm deck or inverted warm deck construction, with drainage, reservoir, filter and growing medium layers placed above.
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© 2006 Sarnafil Ltd. Legal Disclaimer
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