ᐅ But should you install a controlled residential ventilation system?

Hello everyone,

We are in the final stages of planning our house; the floor plan is set, and the detailed construction planning will take place soon. It is a prefabricated house built with a timber frame construction and a prefabricated basement on a slope, meaning the front part of the basement is fully exposed above the slope.

So far, we have excluded the topic of mechanical ventilation with heat recovery, partly due to planning concerns (we are doing everything ourselves from the rough plumbing and electrical installation stages) and partly for cost reasons. However, in recent weeks, we have started to reconsider this, mainly for comfort reasons.

Long story short: Our question mainly concerns the routing of the ductwork, which would partially be installed within the floor structure. So far, we have planned for a floor buildup of 15cm (6 inches) on the ground floor. However, if we were to increase this to 18cm (7 inches) as our house manufacturer suggests, the clear floor height would decrease from 245cm (8 ft) to 242cm (7 ft 11 in) on the ground floor. This would bother me a bit. We cannot change the floor-to-ceiling height due to the zoning plan restrictions (maximum eave height fully utilized).

Now the question is: Is it really necessary to plan for 18cm (7 inches) because of duct crossings, or are there alternatives? For a suitable floor plan (here is our current one: https://www.hausbau-forum.de/threads/efh-in-Hanglage.12265/page-3#post-90366), could the ducts be routed only within the walls? And which mechanical ventilation system with heat recovery would you recommend for a living area of 180m² (1,938 sq ft)?

Thanks in advance for all the information!

Uwe

245 cm (8 ft) is already quite low – but would you really notice the 3 cm (1 inch) difference?

There are no intersecting pipes, but 18 cm (7 inches) is the minimum for 75 mm (3 inch) air ducts and concrete ceilings.

I had to experience this myself recently – I installed the pipes this weekend, and our basement ceiling is 18 cm (7 inches) – which was already borderline. Fortunately, the ground floor has 20 cm (8 inches) again, and that fits perfectly.

By the way, we have already exceeded our eaves height by about 6 cm (2.5 inches) – but no one can measure it anyway since we live on a sloping street. Where would you even measure there?

Our building authority is very strict. For the plot, a single-family house is specified, and from there we have 4m (13 feet 1 inch). We have already maximized our eaves height, exceeded it by 20cm (8 inches), and therefore lowered the house.

The question was whether to prioritize the knee wall height or the ceiling height, and the knee wall of 90cm (35 inches) won.

Because of this, we also have an open wooden beam ceiling with a thickness of 22cm (9 inches), which opens up the space again.

Uwe82 schrieb:

We have already reached the maximum eaves height, exceeded it by 20cm (8 inches), and therefore lowered the house. The question was: knee wall height or ceiling height, and the 90cm (35 inches) knee wall won.

Is that a wise decision? I think we should make sure to direct water away from the house, because we definitely don't want to bring it closer.

Regards, Bauexperte

Get a good natural disaster insurance policy (not to scare you) – unless your property is already located on higher ground.

The pipes can be embedded in the concrete ceilings. That has nothing to do with the floor structure.