046. Ready for the wood envelope

Since my last update, the scaffolding has been installed in preparation for the wood envelope. The wall elements will be moved into place with the crane and the installers will have the scaffolding to walk around on to access the exterior of the thing. Now we're just waiting for a few clear days.

Figure 39. The concrete shell has been treated against water penetration and extruded polystyrene insulation panels have been mounted. In the foreground is the roof of the technical room, soon to become the floor of the garage. Figure 40. View from the other side. Figure 41. Closer look at the ducts for the ventilation system.

045. Concrete foundation

The concrete foundation and retaining walls were completed before the winter holidays. Here are a couple of photos showing them at different parts of the process.

Figure 37. Concrete foundation/shell. The black stuff is a bituminous paint. Figure 38. Most of the backfilling had been done by the time I took this photo. In the foreground the top of the rainwater reservoir tank can be seen. A little patio will be built on top of the area.

Walls of wood and concrete compared

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.

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[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.