I want to install a vent for loft ventilation and also install a sun tunnel through a gable wall, to help light a severely under-illuminated upstairs room (not going with a window, for reasons of privacy, thermal performance, cost, ease of installation and reversability).
Thinking I'm going to need holes of 6" diameter or more. I can't see this being a structural problem, but presumbly there's a diameter beyond which there would be trouble with insurers, mortgage providers, selling the house etc. (and, in the extreme, catastrophic failure of the supporting wall) so would like to know how to find out what this limit might be.
Answers for other countries' regulations also welcome. (Will be upvoted but not accepted.)
EDIT: the exterior walls are made out of reconstructed stone bricks. I assume there is another layer of brick behind, forming a cavity wall, and the wall is structurally signficant, not just a facade (the house was constructed in the mid '90s). Then of course a layer of plasterboard. No electrics nearby that I know of and no plumbing.