Yes, You Can Have Too Much Insulation.

Boring but vital grill

You can have too much insulation. Especially if you live in a 200 year old house. 

Our local, friendly (and distinguished) restoration architect, who lives in a fully restored but reasonably chilly and draughty old listed house, has told us on several occasions that a great many problems for old houses are caused by sealing them up (just like the government tells you) and then heating them up. I've heard the same advice from another specialist in old houses and their challenges.

'You don't know how often somebody buys an old farmhouse that has been sitting there for years with fairly minor problems of damp, loose slates, etc. The new owner has a full restoration job done, but in the process, a builder who has only ever dealt with new houses, seals everything up in a misguided attempt at insulation. Then, within a couple of years, all hell breaks loose in the form of rot and mould of various kinds.'

Government advisory services don't seem to know much about old houses either, so with the best will in the world, they will be telling you to insulate everything. Which will, indeed, make your house warmer and more economic to run. What it may also do, unless you are very, very careful, is store up endless troubles for the future.

Above is a deeply boring picture of a grill on the outside of our house, which sits on a village street. Most of our houses have them. Over the years, the level of the pavement had risen and almost covered these grills over. It took a fair bit of agitating to get them uncovered. But they're vital.

These old houses more or less sit on the ground, with a small space between the floor and the earth or 'solum' as it's called here. (I didn't know that was a term used more in Scotland with that particular meaning until I looked it up, and found it in a Scots dictionary!) It's always a source of amusement to us that you could probably build a multi storey car park on the foundations of any new extension, while the main house itself sits comfortably on the ground, held up by the memory of its own, admittedly immensely thick stone walls.

But it is vital to have a current of air passing through that small space under the house. It's what keeps the house healthy. Block it up and you're asking for trouble.

Not a lot of people know that. Even young professional surveyors don't seem to know it.
Better to live in a slightly draughty old house and wear more clothes or wrap yourself in blankets than turn your house into a sealed box.

Lots of listed houses.