Hello Tim,
When I read this, the provider told us that the ventilation and exhaust system will be installed in the HAR (room is about 8sqm). It can also be installed in the attic, but then it would need better insulation, which would cost about 3500 EUR extra (since currently only Energy Saving Regulation 2009 insulation).
HAR sounds plausible, a purely controlled ventilation and exhaust system doesn’t need that much space; I can’t assess the extra cost for insulation in the attic, it depends, for example, on the roof shape, height to the ridge/size of the attic, whether the standard stairs lead into the attic, etc. When installing such systems in the attic, you need to think ahead – what if this system needs to be replaced someday?
Does that mean if I add a solar system to the ventilation and exhaust system, only a relatively "small" additional cost of about 3000 EUR arises? I always thought this item was much higher...
Sort of :) I mentioned two different systems. Tecalor TVZ is the designation for the controlled ventilation and exhaust system with heat recovery – costs around EUR 9,000. The combined unit is called Tecalor THZ 303 integral with or without the addition “SOL” – costs without SOL about EUR 10,000, with SOL about EUR 13,000. The combined unit includes the following technologies: air-water heat pump, controlled ventilation and exhaust with heat recovery and either a solar system or not, depending on choice. If I remember correctly, Buderus offers similar technology at comparable prices; since we rarely work with Buderus, I don’t have the type designations at hand.
If you now decide on the above controlled ventilation and exhaust system with heat recovery and a separate air-water heat pump, costs of about EUR 14,000 will arise. If you decide from the start on the combined unit, it will be either EUR 10,000 without SOL or EUR 13,000 including SOL. For the integral system, note that it requires a lot of space; measured from the wall it extends about 80 cm into the room and it needs a possibility for supply and exhaust air at a distance of 3.5 m.
One more note, since I can no longer edit:
- Exterior walls: 36.5 cm (Poroton T9)
- Interior walls: 11.5 cm (11 cm WLG040)
The only thing that in my opinion would be missing for a KfW70 standard would be the extra floor slab insulation and the air-water heat pump?
The building envelope as a whole – including the triple glazing and roof structure – initially provides the basis for KfW 70. Only with the use of renewable energies – assuming the individual components are coordinated accordingly – does a certified KfW 70 efficiency house result.
Insulation under the floor slab in a solidly constructed single-family house is generally only necessary if you opt for gas condensing boiler with solar and controlled ventilation. With both of these last-mentioned technologies and detached construction, meeting KfW certification can often be very tight.
I have already explained to you that you will not cover the ancillary costs. I would like to ask you – since you are looking for decision support here – to have the documents of your preferred provider reviewed externally and independently and possibly also to consider external construction supervision in this context. We can only answer partially here because we do not have the same knowledge of your documents as you do. Therefore, all answers – including mine – are only partial and without guarantee ;)
** All prices I have mentioned are understood to be surcharges – the usually available gas condensing boiler plus solar system have been offset.
Best regards