A few people have been asking when I’ll get to start building, what needs to be done first.

Well, first of all we must wait at least 36 days after getting a building permit. But there’s no way I could have started so soon anyway, so that’s not a problem. Right now, I’m redrawing the plans, turning them into workable plans to send to contractors to get price offers. I’m also working on writing specificiations and measuring and counting every single thing so that I can get nicely detailed price offers. I’ve made some price estimates based on that and so far it looks like I should fit within my budget.

Last week, we did a bit of surveying on site, the get the exact height of the neighbours’ houses.

A couple of months ago, I also had a cone penetration test done to get the geotechnical properties of the soil. Basically, they push a cone into the ground at a fixed rate and measure the resistance.

As you can see on this chart, there’s a soil layer with a decent bearing capacity at a depth of about 2.5m, which is rather deep. This means I can’t use the type of foundations that are traditonally being used as those foundations usually start at a depth of about 1.2m. Foundations to a depth of 2.5m are rather expensive so we calculated if I could use a general floor slab instead. Since the structure of the house is rather lightweight, this should work. So basically, I’m going to have a reinforced concrete slab of about 25cm that spreads the load from the structure over the entire surface. Because it’s spread over an entire surface, the pressure isn’t quite so high and the house won’t set too much (4cm according to calculations).

Other calculations that must be done now are the ones relating to the energy efficiency of the house. It’s going to be a passive house, I have to determine now how thick to make the walls, how much insulation to put in, etc. One of the main characteristics of a passive house is that the building must not use more than 15 kWh/m² per year (4746 btu/ft² per year) in heating and cooling energy. There’s special software to calculate this. Considering it’s part of my daytime job, I can do these calculations myself and don’t need to pay anyone else to do them for me. This also means I can play with it a bit more.

This is what I have so far.

The pink shows I’m at 14! So yay, the house meets the required standards. I still have to fill in a whole lot of other things (such as type of heating, shading, electrical appliances) and only then will I get my value for the other characteristics.

The blue line on this chart shows the total energy losses for each month (via walls and ventilation). In yellow are the solar gains, the grey is the heating demand. It shows that’ll get to switch off my central heating in the beginning of March and leave it off till November. I haven’t yet put in the shading effects from the surrounding buildings and the solar screens, which is why the solar gains in summer are quite high in this chart. I plan on calculation the summer comfort using dynamic software, to see what I need to do to prevent overheating in summer.