Essah, E A; Sanders, C H; Baker, P and Kalagasidis, A S (2009) Condensation and moisture transport in cold roofs: Effects of roof underlay. Building Research & Information, 37(2), pp. 117-128. ISSN 0961-3218
Abstract
Cold pitched roofs, with their form of construction situating insulation on a horizontal ceiling, are intrinsically vulnerable to condensation. This study reports the results derived from using a simulation package (Heat, Air and Moisture modelling tool, or HAM-Tools) to investigate the risk of condensation in cold pitched roofs in housing fitted with a vapour-permeable underlay (VPU) of known characteristics. In order to visualize the effect of the VPUs on moisture transfer, several scenarios were modelled, and compared with the results from a conventional bituminous felt with high resistance (200MNs/g, Sd = 40m). The results indicate that ventilation is essential in the roof to reduce condensation. However, a sensitivity analysis proved that reducing the overall tightness of the ceiling and using lower-resistance VPUs would help in controlling condensation formation in the roof. To a large extent, the proposed characteristic performance of the VPU as predicted by manufacturers and some researchers may only be realistic if gaps in the ceiling are sealed completely during construction, which may be practically difficult given current construction practice.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | air leakage; air tightness; cold pitched roofs; condensation; ham-tools; permeability; roof design; vapour-permeable underlay |
| Index terms: | manufacturer, ventilation, pitched roof, permeability, air tightness, package, housing, roof, moisture transfer, sensitivity analysis, modelling, insulation |
| Subjects: | thermal systems, architectural elements, contractual arrangements, material properties and characteristics, construction type, environmental engineering, environmental hazards, design practice, air quality, analytical methods, building materials, practitioner |
| Topics: | Design Practice, Construction Materials, Procurement, Construction Technology, Sustainability, Engineering Principles, Roles and Professions |
| Descriptive scope: | 2 PC |
N.B. Descriptive scope is a count of how many of the five facets of empirical research are indicated by the words used in title, abstract and keywords. It is not intended as a judgement on the research; merely a count of the kind of word we would expect to indicate Phenomenon, Concepts, Theoretical framing, Empirical techniques, Analytical techniques. If all five are present, then a code of “5 PCTEA” will indicate this. If you feel the coding for this record is questionable, we welcome discussion around the terms we matched or the way we categorized them. The facet you would expect may not be coded, or a facet may be coded inappropriately. This can also bear on a larger question, of which facets should be treated as defining in construction management research. Please get in touch, and we will look at it. More details here