ᐅ Create an insulated utility room for the gas boiler in the attic.

A safer option is a climate membrane that is vapor permeable in warm weather but seals in cold conditions. This way, any moisture can dry out if necessary. The price is higher but manageable. We used Climoplus DB FEX XL. Not because others are bad, but because it was available in stock. One roll costs about 70 euros. It covers approximately 40 m² (430 sq ft).

We will take whatever the building materials supplier has in stock.

We will use 160mm (6.3 inches) insulation with a thermal conductivity of 0.035.

How should the floor connection be executed? Should the membrane be taped to the exterior tongue-and-groove boarding? That wouldn’t make the assembly airtight... Or do the outer tongue-and-groove boards need to be removed, and the membrane taped underneath to the interior wall (aerated concrete)?

The living space is supposed to be airtight anyway since the main insulation will be installed in the ceiling by the general contractor.

In our rented apartment, the heating system and hot water tank are also located in the attic, and we had a very unpleasant experience this week. My boyfriend went to the bathroom at night, and water started leaking through the ceiling. A pipe connection behind the heater had come loose, and it leaked for about an hour before we noticed. Approximately 6 cubic meters (210 cubic feet) of water flowed out, and now three apartments need renovation. The plumber said he doesn’t understand why so many people want to have these systems in the attic because it always causes serious problems when something goes wrong. Maybe this is something to keep in mind. Of course, you always hope that nothing like this will happen.

This is a worst-case scenario, and having the boiler in the ground-floor utility room is clearly better.

Regarding the membrane: apply it to the boards using a generous bead of this membrane adhesive. The bead should be continuous without gaps. This ensures sufficient sealing.

Tina mit K schrieb:

In our rental apartment, the heating system and hot water tank are also located in the attic, and we had a very unpleasant experience this week. My boyfriend went to the bathroom at night, and water started leaking through the ceiling. A joint in the water pipe behind the heating system had come loose, and it flowed for about an hour before we noticed. Approximately 6 cubic meters (212 cubic feet) of water leaked out, and now three apartments need to be renovated. The plumber said he doesn’t understand why so many people want to have this setup in the attic, as it always causes serious problems when something goes wrong. Maybe this is something to consider. Of course, you always hope such things don’t happen.

Did you have a drip pan with a drain installed under the system?

Golfi90 schrieb:

Did you have a bathtub with a drain installed under the system?

Nope. Not that I know of.