Condensation occurs when water vapor in the air condenses from a gas into a liquid (dew point), and usually occurs when there is enough of a temperature difference between the air itself and the surface it lands on. This can happen on any cold surface and is worse in humid environments such as kitchens or bathrooms. The most apparent form of condensation is surface condensation, this is seen all around us in our homes and offices (as seen on cold window and door handles in winter)

Another form of condensation is Interstitial condensation, this uses this same principle in how it is formed, however, it occurs when the moist air vapour penetrates through the elements of a building’s fabric, experiencing a temperature difference along the way and condensing not on the surface, but within the building fabric itself. Therefore, interstitial condensation is unseen and can be eating away at the structure from the inside if not dealt with swiftly, and properly. This type of condensation is also found in cavity wall construction as well as cold roof construction where cold air meets the warm air from the building. This will deposit water in the insulation layer and this itself becomes soaked, losing its’ thermal properties and efficiency. This then has a knock-on effect of cooling the wall and / or roof, then condensation will form on the inside face of the plasterboard over time. These usually takes the form of mould and appears as black spots on the plasterboard surface.

Overtime, if not treated correctly, the roof structure will begin to rot and failure of roofs may become an issue. This is a real problem where timber has been used as the main structural frame of the roof.

You will see from the images accompanying this article, that with a cold roof construction a ventilation space above the insulation is required to vent the water vapour that will form within the roof structure. This water vapour will soak into any timber over time causing decay. It is a continuous process of water vapour forming and is a particular issue in the UK climate in the colder, darker months when condensation is common place. Dealing with this is paramount to ensure longevity and performance of a roof structure. Many clad under roofs we see today will have condensation forming in this way and will quickly fail. 

A warm roof construction will work to move the dew point to the outside of the structure and ensure the warm and cold air streams don’t mix within the roof space. This eliminates the need for ventilation under the roof deck and therefore the risk condensation altogether. The Prefix WARMroof®, (as a true warm roof) will do just that, the insulation is sat outside the roof structure, and between the rafters, to ensure the whole structure is kept warm and that interstitial condensation is not present within the structure. The Prefix WARMroof® requires no additional ventilation under the tiles and/or roof deck.

With no risk of rot or excessive expansion and contraction the Prefix WARMroof® will provide customers with a fit and forget product that is best in class. 

To request a brochure pack or to get a quote call our team: 01254 871800 or email enquiries@prefixsystems.co.uk