Construction and building materials vol:18 issue:1 pages:49-59
In order to investigate the hygrothermal performance and durability of well-insulated cold zinc roofs, a total of four cold zinc roofs with a low U-factor [U<0.25 W/(M-2&BULL;K)] were constructed in a test building at the KU Leuven, Belgium. This paper presents the hygrothermal performances measured in the four roofs during an exposure period of 28 months. The zinc roofs with a specific design and careful workmanship exhibited a satisfactory thermal performance. The moisture content in the wood deck generally stayed below 20% by weight. However, the moisture situation at the underside of zinc sheeting was bad in all four roofs studied. We found that the strong undercooling of the zinc sheeting was the main cause for the bad moisture situation observed. Even a combination of a low air exfiltration and a good roof cavity ventilation rate did not eliminate or reduce the condensation at the underside of zinc sheeting. (C) 2003 Elsevier Science Ltd. All rights reserved.