My eco-extension - Page 2

Student 07 · 01-06-13, 06:13 PM

Quote:

Originally Posted by charlesfl

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.

Hi,

I hope I can help clarify things. As Charlesfl stated the product is autoclaved aerated concrete block. The biggest manufacturer of it that I know of is Ytong. I was told it has an R value of just over 1 per inch, so Charlesfl's math above sounds right to me.

When remodeling our house in Germany I used AAC blocks for a bathroom wall on an upper floor. The product is lightweight, which made it possible to build the wall on an unsupported concrete floor. It is real easy to work with, you can saw it with a wood hand saw and sand it with sand paper, it can be worked like wood (but won't hold nails). If anybody uses it I would recommend you soak your blocks in water before applying mortar, otherwise it has a tendency to suck the moisture out of your mortar and weaken your joints.

S-F mentioned Airkrete. This product is actually a kind of spray foam (from what I have read). It is used to seal attics and other places that spray foam is used. The benefit of it is that it is supposed to be fireproof, rodent proof and holds it's R value forever.

These are two totally different products. I remember when I built our current house (in Oregon) I called around asking for AAC, you should of heard some of the replies I got.

mnbv69 really did a great job. The only thing I would recommend to him is to not underestimate the value of air sealing, especially now before all the walls, floors and ceiling are covered, and pay extra attention around windows and doors. In the future I am sure he will reap the benefits of the work he is putting into his project now. Thanks for sharing.

mnbv69 · 04-05-13, 03:16 AM

We've got a longer winter than usual in the UK this year -despite "summer time" kicking in last week temperatures are a good 10C below average - at around zero. Despite this my thermal slab floor has heated to 16C by solar gain alone so I'm quite happy with that.

I've been looking for a cheap "weather station" with a temperature probe to measure the floor temperature, indoor air and outside air; and some basic data logging facilities. No time to build from scratch right now, so I wondered if anyone has seen such a thing?

Mikesolar · 04-05-13, 05:26 AM

Ytong is the most widely used product in Germany and most of Europe and has been used for 80 years.

According to the company doc (in German) the heat transfer rate is about R50 for a 240mm block. There must be some difference between it and what is used in Britain if the same size block is R22.

When I build again, it may be worth it to get a container of the stuff from Germany.

04-05-13, 03:16 AM	#12
mnbv69 Lurking Renovator Join Date: Oct 2012 Location: UK Posts: 8 Thanks: 1 Thanked 2 Times in 2 Posts	We've got a longer winter than usual in the UK this year -despite "summer time" kicking in last week temperatures are a good 10C below average - at around zero. Despite this my thermal slab floor has heated to 16C by solar gain alone so I'm quite happy with that. I've been looking for a cheap "weather station" with a temperature probe to measure the floor temperature, indoor air and outside air; and some basic data logging facilities. No time to build from scratch right now, so I wondered if anyone has seen such a thing?

04-05-13, 05:26 AM	#13
Mikesolar Master EcoRenovator Join Date: Aug 2012 Location: Toronto Posts: 958 Thanks: 40 Thanked 158 Times in 150 Posts	Ytong is the most widely used product in Germany and most of Europe and has been used for 80 years. According to the company doc (in German) the heat transfer rate is about R50 for a 240mm block. There must be some difference between it and what is used in Britain if the same size block is R22. When I build again, it may be worth it to get a container of the stuff from Germany.