What IS a thermal envelope?

Its pretty simple really… It’s the space between inside your whare and outside and it's this gap where the majority of warm air escapes, taking your hard-earned cash with it.

In most houses it’s the space between the inside wall and outside wall, the place where the insulation gets stuffed into. Now the goal is to seal this space so no warm air gets into it from inside keeping all that heat trapped for your enjoyment.

BUT not all houses have this thermal envelope wonderfully sealed shut. Here are a list of places you should check where heat can leak out…


Make sure your windows fit well and have tight seals. If you’re building a house or renovating look into having double-glazing installed. This can reduce the amount of cold air allowed inside.

But you know the easiest and most cost-effective way to reduce heat loss from your windows is to put up curtains or blinds! Make sure though that the curtain reaches from jamb to jamb and from the top of the window to the windowsill or floor.


Hot air rises, so a well-insulated attic can prevent a lot of heat loss (and can save you up to 40% on your power bill!)

The chimney


Draughts can often sneak inside under doors that have not been properly fitted. Also be wary of dog flaps and mail slots sucking all the lovely warm air out. Draught-stopping devices can be brought at your local hardware store in all different shapes and sizes and are an easy and cheap solution to this problem.

Replace old doors as wooden doors crack with age

Light fixtures and/or power outlets

Silly things like the holes made for power lines in your house can make a big difference on how well your house retains heat. They are easily fixed – your local hardware store will sell putty that can be plugged into any hole.