Friday, January 21, 2011

How not to insulate

Now that the kitchen in wrapping up (yes we still haven't "finished" that project), we are setting our sights on the basement.

The basement is unfinished. 85% of the walls are framed and insulated but nothing further.  In surveying the job, there is a lot of room for improvement on the insulation and I think most stems from the fact that who ever put it in probably did not understand how cavity insulation works.

Cavity insulation such as Roxul or fibreglass insulates well because in between all the fibres of poor insulating material is trapped air.   Air is a miserable conductor of heat especially in small pockets.

It is importenat then to fit the insulation into the cavity it was designed for.  If it is compressed, you squeeze out the air pockets and lose insulating power.  If you stretch it out you create larger air pockets that allow air to circulate and you lose insulating power.

In our basement, the goofs were all due to compressing the insulation.

In the exterior walls, they installed insulation intended for a 2x6" wall in a 2x4" wall.
Even with no wall coverings, the vapour barrier is already compressing the insulation. In the small section with wood paneling over it, they thought to add two 1" strips of wood.  But these strips cross over the front of the insulation and vapour barrier so really offer no relief.

In the ceiling over the old cold room, they installed insulation for 16" centres in a 12" spacing.  So with an extra 33% material the insulation is all squished and folded over.

In both these cases I am sure the renovator figured that more was better and was trying to improve the quality of their insulation but in the end really hurt it.

The key to proper installation is to trim to fit; there should be no gaps and no compression. This includes around receptacles, plumbing, window frames, etc.

Below is the picture of our kitchen. It took some patience to get it proper fit but it is so important that the job is done right.

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