In response to my blog in July several people have asked how to achieve an externally expressed frame without continually breaking the thermal envelope of the building.
Our view is don’t make the oak frame part of the thermal envelope because the only guarantee you’ll get is that it will leak somewhere at sometime. In how many places and how often will depend on the skill with which a system is fitted but all the systems we see are extremely complicated with lots of components. In other words they’re prone to human and component failure.
Although some ‘purists’ don’t like the idea, the best way to achieve current building regulations and get the appearance of an externally expressed frame is to use air dried oak cover boards over a complete external thermal envelope.
There are a number of products to which one can apply render and if the cover boards are fixed to the panels first the render then ‘fills’ between the cover boards so that they aren’t so obviously surface mounted. Be sure to use good thick cover boards to prevent cupping. Below are some pictures of a really well executed ‘externally expressed’ frame using this approach. This new oak framed house is in Twyford, Hampshire.
As an aside I find it difficult to see what’s ‘purist’ about an oak frame that uses numerous modern components to try and make it meet current regulations!