Ventilated Wooden Claddings - A Field Investigation

This paper presents the setup and some preliminary results of measurements on different wooden claddings on a test house at the field station of NBI (Norwegian Building Research Institute) and NTNU (Norwegian University of Science and Technology). The field station is located at Voll in Trondheim, Norway. The object of this investigation is to increase the understanding of the relation between micro climatic conditions and the responding performance of wooden claddings, according to orientation, design of ventilation gap and material qualities. Ventilation behind the cladding is varied by using different sizes of the inlet and outlet of the air gap behind the cladding. Different material qualities are tested by using fast and slow grown spruce. Both unpainted and painted claddings are included in the tests. Temperature and moisture content are measured in several positions on the cladding boards. The meteorological climate is carefully recorded. The investigation includes measurements of wind-driven rain, both in the open field and at the wall. The time of wetness (TOW) at the external surfaces is also recorded. Some preliminary measurement results from the first year of measurements are given in the paper. The measured moisture content in the wood claddings demonstrate the influence of ventilation gap design. When the cladding is heavily exposed to driving rain, free air gap openings will give the lowest moisture content in the cladding, whereas in a dry climate situation closed air gap openings will give the driest wood cladding.