{"id":23263,"date":"2016-03-21T14:08:54","date_gmt":"2016-03-21T14:08:54","guid":{"rendered":"https:\/\/www.pbctoday.co.uk\/news\/?p=23263"},"modified":"2016-03-22T10:08:51","modified_gmt":"2016-03-22T10:08:51","slug":"photonair-gives-interstitial-condensation-cold-shoulder","status":"publish","type":"post","link":"https:\/\/www.pbctoday.co.uk\/news\/energy-news\/photonair-gives-interstitial-condensation-cold-shoulder\/23263\/","title":{"rendered":"PhotonAir gives interstitial condensation the cold shoulder"},"content":{"rendered":"

Mark Seddon, a director at Thermic Technology outlines why thermal performance should be a clear consideration when thinking of insulation…<\/span><\/h2>\n

Weighing up the pros and cons between achieving better thermal performance and risking condensation is a fundamental requirement for many of today\u2019s new build and refurbishment roofing projects. \u00a0Yet by cutting through the technical jargon, it\u2019s not such a complex decision to make. Here Mark Seddon, of Thermic Technology talks about the importance of considering low resistance underlays in your insulation choices.<\/p>\n

Synthetic breather membranes first emerged in northern Europe more than 15 years ago and following research by the BRE (Building Research Establishment) and BSi (British Standards Institution) it was established that a requirement of vapour resistance of below 0.25 MN.s\/g would classify a true breather membrane for use in warm roof and cold non-vented applications. It was also agreed that a higher vapour resistance than this carries a risk of interstitial condensation forming.<\/p>\n

It\u2019s important to understand the definition of condensation and in particular interstitial condensation. While most would understand that condensation is the process of water vapour in the air condensing from a gas into a liquid, interstitial condensation is different. Interstitial condensation is a form of structural damping that occurs when warm, moist air penetrates inside a wall, roof or floor structure, reaches the dew point and\u00a0condenses\u00a0into liquid water.<\/p>\n

Interstitial condensation can cause deterioration of the building fabric, through corrosion, rot and decay. It can also reduce the thermal resistance of materials thus adversely affecting energy efficiency.<\/p>\n

For the new generation of insulating breather membranes thermal resistance is important but vapour resistance is even more critical and the magic 0.25 MN.s\/g should not be overlooked.<\/p>\n

When assessing such risks within a warm pitched roof, designers should take the following inter-related factors into account:<\/p>\n