Many years ago at University we learnt that old buildings 'breathe' and that old buildings perform thermally much better than the silly calculations the Government requires us to use to meet the building regs. Recent research by SPAB and STBA has shown that to be true.
If impervious insulation is fitted either internally or externally it is usually too much and by not allowing water vapour escape actually does more harm than good. There are a number of things that 'renovators' should NEVER do to buildings built, approximately, before WW2. Here are 5 of my favourite:
- Never fit UPVC windows without trickle vents or full-house mechanical ventilation system (MVHR).
- Repoint with lime mortar DO NOT USE cement mortar. The lime means the mortar moves and is permeable.
- Replaster with lime plaster as it is not impermeable.
- Repair the existing DPC, and ensure that the external ground level is a minimum of 150 mm below it, rather than replace with a useless chemical one.
- A new concrete floor and DPM will force the moisture into the walls and cause issues, try a ventilated and drained 'limecrete', or a 'suspended' timber, floor without a carpet.
If you would like help with bringing an old building back into having a useful life in the C21 please contact me at firstname.lastname@example.org or through my website www.kreativarchitects.co.uk. As a qualified conservation architect, it is what I do.