ᐅ Is a reinforced concrete slab without a service void feasible?

Hello friends of homebuilding,

I am new to this forum and have just spent a few hours reading various threads here. My wife and I live in Berlin and are currently planning the construction of a small house (80m2 (860 sq ft) of living space) in Brandenburg. We already own the plot, the architect is working on the plans, and the structural engineer will be involved soon... We are optimistic!

The house should be built as economically as possible and will basically be used only as a second home. We prefer a timber frame construction. I have two questions about this:

— Is it possible to build a timber frame house without an INSTALLATION LEVEL? Does this necessarily mean that all electrical outlets have to be surface-mounted? The cables running inside would then penetrate the vapor barrier, right? And every time we hang a picture or fix something on the wall, the screws or anchors would inevitably pierce the vapor barrier? From a cost perspective, omitting the installation level seems sensible at first, but is this just a short-term view that could lead to damage faster than we expect?

— What does it mean for the VENTILATION if, as mentioned, we only live in the house part-time? If we are sometimes away for weeks and cannot ventilate the house, would a controlled mechanical ventilation system be advisable or even necessary? Or is there another way to handle this?

I look forward to your feedback and tips (and please be patient as I enthusiastically familiarize myself with these many complex topics related to homebuilding).

Best regards from Berlin,
Erwin

Hello

In my opinion, building without an installation level is not sensible. The potential sources of error are too numerous. However, this could save on a mechanical ventilation system with heat recovery. I would also argue that it does not make sense financially, since additional insulation is also being installed. A small mechanical ventilation system designed according to DIN standards would be more practical.

Olli

Erwin_M schrieb:

— What does it mean for the VENTILATION if we only live in the house part-time, as mentioned? If we are sometimes away for weeks and cannot ventilate, would a controlled mechanical ventilation system be advisable or even necessary? Or is there another solution?

If you are not there, no or less moisture is produced, so ventilation is not necessarily required. However, I would still recommend planning for some form of slight mechanical ventilation.

For a small house, few rooms, or an open floor plan, decentralized units are a good option and not overly expensive. It also doesn’t need to cover every room. Ventilation without heat recovery is less common nowadays but could be suitable here—options include window frame ventilators, central exhaust, and supply air vents or similar.

Near Berlin, there is a ventilation consultancy where you can listen to and get advice on various decentralized units with heat recovery. If you are planning a gas heating system, a ventilation system with heat recovery might make it possible to avoid a less efficient solar thermal system, provided the energy savings calculation supports this.

I personally still have a small rental apartment that sometimes stays empty for extended periods. I would really appreciate having ventilation there. People still shower, cook, etc., and before leaving you should ventilate thoroughly, which isn’t always feasible—the moisture remains. In a small airtight apartment, this is critical. When returning, the windows have to be fully opened.

boxandroof schrieb:

If you are planning a gas heating system, you might be able to avoid the less practical solar thermal system by using a ventilation system with heat recovery, provided the energy performance calculation allows it.

Thank you for your feedback, @boxandroof! Could you please explain this part in more detail? And could you name the ventilation company near Berlin?
Thank you very much and best regards,
Erwin

wrobel schrieb:

There are too many potential sources of errors. But that could then save the need for the controlled residential ventilation system.

Hi @wrobel, thanks for your feedback and explanation. I understand the connection between the installation layer and the sources of errors – which ones exactly do you see there, and how do you mean that this could allow for skipping the controlled residential ventilation system?
Thank you very much and best regards,
Erwin

Gas heating alone is no longer permitted under the energy saving regulations. Typically, solar thermal systems are installed alongside gas to provide domestic hot water, as this is the most cost-effective option. Without this requirement, solar thermal is not economical and I would prefer to replace it with something more practical. Some home builders offer their standard houses with controlled ventilation and gas heating, but without solar thermal. From what I have read in forums, most energy consultants or those preparing the energy saving regulation documentation find this challenging. It is possible, but it also depends on the rest of the house. For example, as far as I know, gas heating with controlled ventilation alone is not sufficient to meet KfW 55 standards.

Erwin_M schrieb:

And the ventilation company near Berlin, can you name it?

Please search briefly online, I do not want to promote anyone here.

Erwin_M schrieb:

Installation layer and potential sources of error – exactly what do you see, and how do you mean that controlled ventilation could be omitted because of this?

If the building envelope is leaky, you don’t need mechanical ventilation.