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Abstract
Air leakage through the building envelope joints is usually one of the main reasons why airtightness targets are not achieved. The objective of this study was to analyse the air leakage of joints filled with polyurethane foam and its influencing factors. Wooden test specimens (54 in total) with planed, sawn and plastic-coated cavities and two cavity thicknesses were filled with three different polyurethane foams and tested according to standard EN 12114. The surface type and thickness of the joint had a significant effect on the air leakage of joints filled with polyurethane foam. In laboratory conditions, a consistent and very low air leakage rate was obtained with planed timber surfaces. Joints with plastic-coated and sawn timber surfaces performed worse, on average, by a factor of two or more and contributed to very variable airtightness, with up to 28% and 50% of the test specimens failing the airtightness testing. On the basis of the high ‘failure rate’, polyurethane foam may classify as a not completely trustworthy solution in guaranteeing the airtightness of construction joints. A comparison of estimated and previously measured overall airtightness of an entire building envelope showed dependency on ‘failure rate’ rather than on average measured leakage rate.
Highlights
An airtight and well-insulated building envelope is a key factor for achieving the requirements set for nearly zero energy buildings becoming mandatory in the European Union (EU) from the year 2021
It has been shown that the overall airtightness of new buildings has improved significantly [1,2,3], the actual leakage rate and its variation is strongly related to overall quality assurance mechanisms and local building techniques [1,4], especially for window-related air leakages [5]
The airtightness properties of foam joints have been previously tested and these foams have been proved to be almost airtight [13] and perform satisfactorily at the window–wall interface in cavity brick walls [14], the current study showed that the airtightness of actual joints could vary a lot and depends strongly on many parameters
Summary
An airtight and well-insulated building envelope is a key factor for achieving the requirements set for nearly zero energy buildings (nZEB) becoming mandatory in the European Union (EU) from the year 2021. Increased insulation thickness in timber constructions creates a serious risk of moisture accumulation inside the construction and deterioration of the building structure, if air leakages are not minimised or avoided. This is especially important in the case of timber constructions where the materials are more sensitive to extensive moisture and deterioration. It has been shown that the overall airtightness of new buildings has improved significantly [1,2,3], the actual leakage rate and its variation is strongly related to overall quality assurance mechanisms and local building techniques [1,4], especially for window-related air leakages [5]
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