ᐅ Timber Frame Construction – Include a Service Cavity or Not?

Hello,

we are about to embark on the adventure of building a house and are planning to construct a timber frame house to KfW 55 standard.

One company has recommended an installation cavity for the exterior walls (“Useful to never compromise the airtightness of the house”), while another strongly advises against it (“Not necessary at all – just takes up space!”).

We are still undecided on the ideal wall construction. What should be considered regarding the airtightness of the walls? How about any later installation work? What are your experiences?

Best regards
TiBiHaus

Hello

Definitely include it.
Or do you want to seal every outlet and switch box as well as all cable penetrations airtight?

Olli

Would that really be the case? A provider who works without an installation floor said that an air draft issue would not occur...

The contractor mentioned airtight installation boxes that make it straightforward to achieve airtightness. That sounds plausible to me at first. But how does it work when modifying the installation later on?

Of course, exactly the same, except that the (slightly more expensive) airtight box only makes sense if it is installed properly – and pulling cables afterwards is always somewhat problematic. I would also recommend the installation level if there is enough space.

Good luck

K1300S

If you want to install something later on (pulling cables), and there is no installation level present, just make sure not to damage the vapor barrier. The sockets are already inside the “airtight” space anyway. If you know the wall construction and work carefully, there is no problem. And if the vapor barrier does get damaged, simply repair it with the appropriate system tape.

How often does this actually happen in practice? It’s better to plan for more sockets than fewer during the design phase—because you can never have too many.