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Sunday, June 13, 2010

The house I'd like to build

We have just finished moving into a log home we built and it has great ambiance. There is nothing like all that wood. However, there is another type of house I would like to build. I'm not talking about the design. That is a very personal decision for each individual. I'm talking about a construction method. One that is about as cheap as it is possible to use to build a conventional house, very fast to construct and which should have tremendous thermal characteristics. It will also be virtually fire proof and exceedingly durable with very very little maintenance.

Let me diverge a moment. Close by there is a house built of Styrofoam. The blocks look like breeze (cinder) blocks but are very large. They are glued together. Vertical and horizontal steel is set into the central hollow (just as is done with cinder blocks) and the centre space is then filled with concrete. Of course, the outer face of such a house would be very vulnerable to all sorts of damage so they came up with a plaster that will go over the Styrofoam and provide a hard abrasion resistant surface. I think it contains vanadium glass strands to give it its strength. I mention this construction method just for the plaster. Keep in mind that it is possible to plaster over Styrofoam to protect it. Inside, you put on your preferred cladding.

The building system I have in mind uses conventional breeze block construction with steel reinforcing and with the blocks filled with concrete after construction. Nothing surprising here. Floors would be made of concrete slabs or using the U shaped reinforced beams that you lay out for a floor, suspended on the block walls and fill with concrete. Lots more thermal mass there.

 Here is where we diverge from conventional construction.

On the outside face you glue Styrofoam sheets - say 2" thick, over the whole outer surface. This includes the basement, if you have one, before back filling. You then plaster over the Styrofoam to protect it. You now have a huge thermal mass which is all 'inside' the house.

On the inside, you first paint the top 20cm and bottom 20cm of each wall a good dark colour such as black or dark green. You then glue 2 x 2 cm vertical wooden lysts to each wall at, say, 30 or 40cm centres. You attach the cladding of choice to these lysts, making sure that they join on a lyst. You could use a 4 by 2 lyst where cladding meets.   However, you leave a 5cm gap top and bottom. In other words, the cladding doesn't reach to the floor or the ceiling. Into this gap, you fit a nice looking grid of some sort that allows air to flow freely into the gap between the cement blocks and the cladding.

Of course you put in all the other good features such as awnings or overhangs that shade the summer sun but allow the winter sun to come in through large sun facing windows. You have air exchange windows which allow air exchange without loosing or gaining heat.  You install solar water heating and so forth. You may even have a log burner either on the main floor or basement.

The main point is that you now have a huge thermal mass which is available to smooth out the temperature variations in the house and all this thermal mass is inside. If the air in the house is warmer than the block wall, air will flow into the top gap, flow down the wall and out of the bottom gap and vice versa. Look back at the house I mentioned at the beginning which is built from foam blocks. It is extremely well insulated but has very little thermal mass inside the house. With this method, we have a house equally well insulated from the outside where insulation should be but with huge thermal mass. Other advantages are that the house is virtually fire proof. If it is reinforced adequately, it is extremely durable even to earthquakes, it is completely resistant to rot, and completely immune borers, mould and so forth. It is also arguably one of the fastest and cheapest types of building to construct and uses simple skills (block laying) that is widely available anywhere in the world.  As for attractiveness, this only depends on your overall design and the inner and outer cladding you put on the walls.  Your imagination is the only limit.

Happy house planning.

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