Compriband - Magical tape

For a house to have good thermal performance, you need insulation and airtightness. A company called Wuerth provides a magical component called Compriband, which we are using to seal our windows.

Regular Japanese window frames are the antithesis of this as the aluminium is a great conductor. Also, sliding windows, while great at saving space, defy airtightness. This is just looking at the window moving within the window frame; there must also be no gap between the frame and the house, and whatever is filling that gap should insulate.

The problem is what to do with this gap between the window frame and the house, and German manufacturers Weurth have come up with a tape called Compriband, which can be fitted around the window before it is installed, and it then expands after installation to fill the gap with foam and provide an airtight membrane on the inside.

The tape is passed around the whole window frame. It should be cut diagonally at the join, to ensure the seal. Also, at each corner, there needs to be some extra length.

Getting into the corners

One piece of advice the manager of Pazen gave to me was to look into the corners. When the Compriband tape is applied, each corner needs a little extra length, so that the tape can expand to fill the corner, and the insulation is complete and the airtightness maintained. The picture above is what the corners should look like, with the Compriband filling the gap. In one case, it looks like no extra length was given at the corner.

In another case, although it looks like extra length was given, there is some daylight visible at the corner, so the Compriband has not filled its gap.

You can follow Wuerth Japan's blog here
And see a range of their products from their Japanese website here.