Figure 4. Two different above-ground wall constructions. Numbered elements are: 1 ‐ Interior wall surface. 2 ‐ Support structure. 3 ‐ Vapor retarder. 4 ‐ Insulation. 5 ‐ Post. 6 ‐ Wood fiberboard. 7 ‐ Ventilation gap. 8 ‐ Exterior cladding. 9 ‐ Exposed concrete.
In my last post I claimed that we were expecting the exterior walls of our house to be a minimum of 35 cm (14") thick to achieve the required heat transfer coefficient (U-value). I had also remarked that massive construction – masonry or concrete – would result in thicker walls, a few things being equal. Well, I ran some numbers through for a couple of wall types[1] I found in a compendium[2] of such things.
First I picked out the wall types seen in the figure. Then I chose the same material (Steinwolle[3] of the fiberglass persuasion) for insulation in both cases and I increased the thickness of this until the U-value dropped to 0.15 W/(m2 K). The total thickness of the wall in the case of the wood construction turned out to be 35.5 cm and 40.0 cm in the case of exposed concrete.
[1] There must be a couple of hundred wall element combinations possible! If you think I'm exaggerating, you can download a PDF of the Bauteilekatalog by clicking here.
[2] There are some decent free online tools with which one can calculate the U-values of different building components. I used this one here. Available in German and French. But wait, there's more! The tool also estimates the grey-energy embodied in the structures and 'environmental impact points' to help in the decision making process. More about these at some later date.
[3] Steinwolle is made from mostly natural mineral raw materials while Glaswolle has about a 70% recycled-glass content.
Hi ersatz
ReplyDeleteHave you seen the difference between Wi2 und Wi3.
There is no one at same insulation and thinkness.
wellingtonia
Wellingtonia:
ReplyDeleteThe thickness of item 5 (the post) in my figure (the Riegel) changes in the 4 cases pictured in the Katalog pages 58 and 59. The fixe Schicht is what they call it and it has the values 12 cm, 14 cm, 16 cm, 18 cm. I used the 12 cm version. Did I understand your question?
Hi ersie
ReplyDeleteor ersatz
Sorry I mean Wi1
http://www.bauteilkatalog.ch/202.asp?id=30759872&katalog=EKG%20Elementgruppen%20light&typ=-131912444&lng=DE
und Wi3
http://www.bauteilkatalog.ch/202.asp?id=84153340&katalog=EKG%20Elementgruppen%20light&typ=1133814&lng=DE
at same insulation and thickness.
In construct Wi1 there is a wooden plank over the whole thickness of insulation.
In construct Wi3 - at same insulation 18 and 12 cm to the same U-Wert of 0.15 !!
On page 58 to 59 at the pdf-datei.
In my projekt I plan same construction as Wi1 and calculatet with an other Lambda - than only insulation.
Wellingtonia
The only difference I could find is that the UBP (Umwelt Belastung Punkten) is about 8% lower for the Wi 1 compared to the Wi 2/3. But I would think there might be a small difference in the U-Wert in the two cases because in the Wi 1 case it looks like there could be a Wärmebrücke-type situation with the plank being 30 cm thick when compared to the Wi 2/3 case. I have to think about it carefully.
ReplyDeleteBy the way, for the Hinterlüftung gap does it make sense to use 1.5 cm? What about the gap (item 2 in my drawing - support for the Innenverkleidung)? I didn't include these in the thickness and it looks like the wood wall will actually be about the same as the concrete wall. This surprises me.
Another question: isn't a vapor retarder or air barrier required in the concrete construction as well?
Hi Z
ReplyDeleteInteresting details - isn't it ?
If you can build one construction with "thru going" planks - it's easier and stable.
Upright planks you can use for receptive of loads.
To get a good air ventilation behind the outside wall, there is a distance of 40 mm necessary.
The gap on the inside will be ok.
The differenc is the water vapor diffusion.
Ventilatet air behind inside or outside wall and the wall itself, won't be calculated into the heat transfer coefficient (U-Wert).
The insideair and the outsideair are by the insulation at the same teperature like in- or outside !!
The concrete construktion you will build with beton - beton is like a vapor barriere so you dosn't need one.
Further questions ??
To a coffee on a weekend ??
Why not.
Wellingtonia
Wellingtonia: Thank you for your input. I've written another post on the topic, with some more details. I have many, many questions about many, many topics! We should meet for coffee sometime. Are you planning to go to the Immomesse in St. Gallen?
ReplyDelete