Heat loss around windows

I've just surveyed a lovely old Welsh stone cottage.  It was interesting in being warm and dry - and had just had UPVC windows fitted all round.  Now I know I don't like these, but in this case, they are doing a good job - the windows are warm, and are not losing heat.  What is very obvious though is that heat is being lost AROUND the windows, through the reveals. This is very typical of such solid walled buildings.  Most heat actually does get lost around the windows, not through them.  You can see here that where the wall is very thin - heat is able to leak around the frames.  This is the cause of the very common mould and mildew patches around windows - often we see little areas of mould in the corners or on the reveals at the bottom. 

How do we stop this?

The best way to prevent heat loss in window reveals is to insulate them.  In an old solid walled building, it's almost certain that modern gypsum or cement plaster will now be present - so we first chop everything off - take it back to clean stone or brick.  Then we re-plaster using a hemp lime mix - hemp is a really good insulator, and added to the lime, gives it good qualities.  Thicken it as much as possible into the window frame, and you will find heat loss is then minimised.

This is actually a major issue in old houses - heat is not lost through the main walls - but window openings are a big contributor to heat loss.  The devil is in the detail - and in this case, going back to old technology like hemp lime, is a really good way to keep your solid walled 'old' house cosy and warm.


Recent News
RICS prove they don't understand damp

I've just seen this staggeringly incompetent blog on the RICS website.  This is the kind of mis-information that is being fed to homeowners all over the country - and...

Pete's on BBC Radio 4 now!

Pete recently did an interview on BBC Radio 4 - You and Yours - which investigated a case history of failed cavity wall insulation.

An Irish client and his magnificent restoration blog

Our client, John, wanted help with this restoration - it led to this great blog.

It's Condensation Season!

The phone is running off the hook with calls about condensation. Find out how to solve your issues.

The Haynes Manual for Period Property

Ian Rock has written another of his great books.  This one is even better - We've helped Ian with this one and there's loads of photos of our guys doing timber frame work.  A great book, with lots of practical information you need if you have an old home.  Treat yourself and buy this - you won't regret it!

Share this page

If you've found this site useful, please share it with your friends!

Website by twoclicks