Warm fuzzy insulation

Figure 6. The thermal conductivities of a selection of materials typically used as insulation in construction.

Generally speaking, the effective insulating value of a wall is really determined by that of the insulation used. This was the case of the wall I discussed in my last post a few days ago. The thermal conductivities, λ, of some of the commonly used insulating materials can be seen in figure 6. You can see that they range roughly from 0.025 W/(m·K) to 0.060 W/(m·K). For any given type of insulating material there's a host of products made in different ways and they can have different λ values. In some instances, the different forms are necessary for particular applications, for example, the physical requirements for flooring components are quite different from those for walls. In the graph, the areas represented by the solid colors depict the best (lowest) and worst (highest) measured products in these groups. The lone values at the top of the columns are to be used for those particular products that remain untested by an approved facility.

At the right edge of the figure I've included some other materials of interest. Things such as porous concrete have better insulating properties compared to regular concrete but they're still a long way away from what is necessary for a Minergie-type house. Walls made of them would be too thick. In the area of bricks, there are perlite-filled ones which have very good insulating properties. Poroton-T7 is one that is actually appropriate for Minergie homes. A wall thickness of 42.5 cm satisfied the required U-value limit of 0.16[1] W/(m²·K) for the Minergie-P house BE-028-P. A blog (in German) about the construction of this house can be found here.

---

[1] If you're wondering why it's 0.16 and not 0.15 as I've been saying, I have to say that I don't know yet. I'm working on finding the answer.