Influence of the Water Vapour Permeability of Airtight Sheets on the Behaviour of Facade

Abstract

The air-tightness of the thermal envelope of buildings is one of the measures to reduce their energy demands in order to achieve global warming reduction targets. To this end, airtight sheets with different water vapour permeability characteristics are used. The different products studied are highly dispersed in terms of equivalent air thickness values, leading to confusion. After the analysis carried out, it is concluded that all airtight sheets are vapour barriers. To clarify whether or not these sheets are necessary as vapour barriers, a condensation analysis was carried out on 13 different facades for 3 climate zones with severe winters as defined in Spanish regulations. The results reveal that interstitial condensation occurs in only 7 of the 39 case studies, with the traditional facades of brickwork with render causing the greatest problems if the appropriate products are not used. In these cases, airtight sheets with water vapour barrier characteristics must be applied on the interior face of the insulating material. In all other cases (32), the airtight sheets must be permeable to water vapour if it is looked for a more breathable wall to water vapour and a better control of the interior humidity conditions.

Deterioration Mechanisms and Advanced Inspection Technologies of Aluminum Windows

“…The air permeability performance of aluminum windows has a great impact on indoor heat loss and energy efficiency [ 3 ]. The watertight performance of aluminum windows reflects their effectiveness in preventing the intrusion of rainwater into internal buildings [ 4 ]. Wind-load resistance refers to the ability of windows to withstand wind pressure without any mechanics-induced damage (e.g., cracking, local yield, and bond failure) or functional impairment such as loose hardware and opening difficulties [ 5 , 6 ].…”

Empirical Investigation of the Hygrothermal Diffusion Properties of Permeable Building Membranes Subjected to Variable Relative Humidity Condition

“…Building membranes have become essential components of building envelopes due to the many roles they play in modern construction systems, especially in framed construction [22,24]. They are used as an air control layer, a protection for bulk insulation-thermal control layers, as a water control layer and as a vapour control layer [2,25].…”