What is the point of building an energy efficient extension on to a nightmarishly energy inefficient house?

Because its better than building and energy inefficient extension onto an inefficient house.

Thats not to say you should'nt also upgrade the existing.

I like the approach of comparing the overall energy efficiency of the building before and after the extension rather than applying overly strict standards to the "new bit". I think the test should be that the building after should use no more energy for space heating than it did before (preferably less). I mean in absolute terms not per m2.

i am doing this

however, it's not all bad.

We live in a VERY draughty old stone barn. We are upgrading the existing (to some extent) and building a very efficient extension.

The 'NEW' accommodation will form about 50% of the house.

The way it works, is that the internal arrangement will be shuffled a bit to make all the 'living' accommodation - living room, family room/office and kitchen - very efficient, and all the bedrooms in the old draughty bit.

We insulate where we can, draft seal where we can, and most importantly, dont heat it much. i like to sleep in the cold.

So, warm bit efficient and 18 degrees, cold bit less efficient and 14 degrees.



This is clearly a lot better than building an extension to match the existing spec, or flattening it and starting again. Its 150 years old now, and has a good 150 or more left!