Most times, when we come upon a fenestration that’s been bricked up we can safely ignore the ‘hole’ and assume that its the same wall construction as the rest of the element. But every so often that rule can fall foul of an auditor who decides that the ‘hole’ is too different or too big a proportion of the wall it’s in to be ignored….
If the ‘bricking up’ has been done to a poor standard and/or is obviously not of the same construction as the surrounding wall then a fenestration or alternative wall type needs to be applied. For example, I’ve just assessed an old Victorian office property with a 1990’s extension to the rear (cavity wall construction with a flat bitumen felt roof on an insulated light timber deck) in which three windows have been removed and single leaf blocks used to seal the fenestrations. The blocks have been set on the outer leaf of the surrounding wall, leaving the cavity and the inner leaf of the wall exposed to the interior space. Obviously the thermal performance of this light solid block wall is very different from the cavity brick wall around it and as such needs to be identified as an alternative wall type. The proportion of the whole element given over to these bricked up windows might be a consideration but at what proportion of the whole wall is it appropriate to ignore these bricked up windows…?
So what about damaged skylights that have had a sheet of marine ply screwed in place with lead flashing or flashing tape over to make the cover weather proof but offering only minimal thermal performance, little better than the glassfibre or polycarbonate skylight it replaces. This can’t realistically be treated as the same as the roof structure and ignored but it’s also not a skylight/window with solar gain impacts on the space below. An opaque window type or another roof type – but which?
As always guidance from AB’s is contradictory and it seems down to luck of the draw whether your auditor agrees with you or not.