My eco-extension
 

I've spent 2012 getting this built, a 70m2 side extension to my house in the UK. I've made it as green as I can afford- from aircrete blocks and 100mm glassfibre cavity insulation (the blocks are apparently made from power station ash and the insulation from old bottles).
It's partly passive solar; with a concrete ground floor slab heated by a large 6m2 south-facing door. Naturally it will be instrumented!
Looking forward to getting data on energy use when we move into it in early 2013.
http://i1147.photobucket.com/albums/...n/Untitled.jpg

Interesting addition. What made you want to add the extra area? How is it insulated?

We bought the house at a good price with the intention of extending and also improving the existing property. So the extension gets us an extra bedroom, kitchen and bathroom which we need for a family.

Insulation in the extension is, from bottom to top:
-150mm PIR "celotex" foam under the concrete ground floor;
-walls are 100mm aircrete, 100mm glassfibre, 100mm aircrete;
-attic is 300mm glassfibre.
-The door and windows are 28mm double-glazed with coated glass.

These exceed the current UK building regs/codes, but not by that much - they are quite demanding now.

Do you know the R-value of the new wall? I'm not familiar with aircrete.

I think it's UK talk or maybe a brand for these.
Aerated Concrete Block/ACC
Sort of like the glassfibre for fiberglass type talk.
Power station ash would likely be flyash from using coal.

My understanding is that airkrete is an injectable material and when cured it isn't actually concrete like. I gather it's a bit like a sponge. I don't really understand any of what's said about this building envelope.

Almost all homes in the UK are built with a type of concrete or masonry block. They used to be clay and if you picture the garden clay walls with holes running horizontally, you get the picture. Then there was a parging placed on the inside and outside of the block which created an air pocket of insulation. Often this was the only structure/insulation but since the 80s PIR (polyurethane foam) and rockwool has been used on the outside, then a facing brick or heavy parge. There is a lot of variations on this and the Germans came up with "Ytong" which is an aerated concrete block that you can make any type of structure and the holes are now placed vertically. It is sold here by "Hubel" and has a good insulation value.

I was in Germany a few years ago and I watched some builders basically tossing up from one floor to the next, a concrete looking solid block. Turns out it was a 4" solid PIR with a stucco coat on all sides, maybe 8" by 24" by 4" thick. This went on the outside of the Ytong as more insulation and the wall structure is about an R50 for a 14" thick wall. It was a really cool way to build.

http://en.wikipedia.org/wiki/Autocla...rated_concrete

ww.youtube.com/watch?v=KH5yg3SWXx8

Mikesolar, yes that's the material - aka AAC, an aerated block that comes in a range densities and therefore strengths. A 440x220x100mm block weighs about 7kg.

As to the "R" value , not sure about this in US units but my wall of two blocks separated by a fully filled cavity of 100mm rockwool has an overall "U" of about 0.25 W/mK. About a quarter of this comes from the blocks.

I've mostly used thinjoint mortar (as featured in the video above)- this means the mortar joints are only 3mm thick. I chose this as its quicker than traditional mortar as there's a time saving in mixing a smaller quantity of mortar (and lifting it up!), and it's easy to build more accurately. There's some stainless steel reinforcement strip in there as well but that's another story. We cut a lot of these blocks using a hand saw; very selfbuild friendly!

Autoclaved aerated concrete block (AAC)

R-value (US) = RSI × 5.678263337 and RSI (SI) = R-value × 0.1761101838 and R = 1/U

0.25 W/mK = R value US of 5.678 X 1/0.25 = 5.678 X 4 = 22.7 R value for wall.

Some places list AAC has an "effective" R value of up to 3.9 but my figures indicate a real R value of approximately 1.25 per inch depending on density. Effective R value use the mass of the concrete to store heat for higher effective R under certain conditions.

"real" R-value is unimportant here, effective is what matters but most engineers can't figure out how to do a heat loss with only masonry. They grossly oversize the boiler. My double brick house has a lower cost to heat than the average 2x6 stud wall construction with fibreglas insulation so that makes it an "effective" R20 or so. The real insulative value of a 2x6 stud wall with air barrier and vapour barrier is about R13, if you are lucky.