The effects of production technologies on the air permeability properties of cross laminated timber

Abstract

In building envelope, the cross laminated timber (CLT) is often used as air barrier layer. The objective of this study was to evaluate the impact of production technologies such as edge bonding, different initial moisture content (MC) of lamination, and number of lamination layers (3 and 5) on the air-permeability properties of cross laminated timber. Air leakage and crack growth in CLT panels were measured after the panels were conditioned in environments with different relative humidity (RH) in progressive steps from humid to dry environments (RH 70%→ RH 50%→ RH 30%→ RH 10%). The test results showed that the most effective technologies for avoiding large crack growth and air leakages through panels were to use 5 layers of laminations with bonded edges. Overall, it can be recommended that for the production of CLT panels it is advisable to use primarily a larger number of layers, at least 5, for smaller growth of cracks on panel surfaces and thereby avoid air leakages during the time of use. The use of bonded edge technology helps to ensure the avoidance of possible air leakage threats, but in the long-term, this beneficial effect might decrease as bond layers may rupture or cracks may form in the middle of laminations.