Most test methods in wood protection rely on exposure of single or multi-component test units with comparison to similar units treated with control treatments of known performance in service situations. Such methods are usually excellent in providing information about relative performance against single vector biodeteriogens, but can be lacking in providing data about performance in a service environment. This, of course, is the case in most component testing across many industries and applications.
In an effort to provide more detailed information about the effects of various treatments and coatings on wood windows in service, the Building Research Establishment in the U.K., during its existence at the Princes Risborough Laboratory constructed and closely monitored window performance in a "window wall" test house. Later, the Forest Research Institute in New Zealand in the 1960s used a simplified version of this to develop similar data on the performance of treated radiata pine windows.
The methodology basically measures both biodeterioration, and the effects, concurrent or otherwise of exposure to moisture (liquid or vapor) and weathering, as well as other causal agents such as insect attack. Gravimetric and multi-directional dimensional changes are measured, as well as the effects, if any, of the window glass integral to the window units. Each window unit is fully removable for periodic inspection, while continous output readings can be achieved in some setups.
The method has been further refined to provide a test protocol for outdoor exposures of both windows and doors. In one case it has been used as a test bed for termite attack on treated windows place in an untreated framing situation.