KFW70 heat pump, underfloor heating, ventilation system, and photovoltaic

Hello everyone

we are planning the construction of a KFW70 house and would like to install an air heat pump with underfloor heating and a photovoltaic system.
For this, we would like to have your professional opinion regarding the required size of the pump. The house is planned to have about 140 sqm of living space.

Furthermore, we would like to have a fireplace in the living room.

Now I am unsure whether we definitely need a ventilation system for this house to keep it free of mold.

Is the risk really given if, for example, we go on vacation and do not ventilate regularly, or is that more the case with passive houses?

Thank you in advance for your help!

Best regards, Silke

Hello,

...we are planning to build a KFW70 house and would like to install an air heat pump with underfloor heating and a photovoltaic system.

Kfw 70 and Proxon probably do not fit well together, unless you want to live with high consumption costs in the long run!

...For this, we would like your professional opinion regarding the required dimension of the pump. The house should have about 140 sqm of living space.

For this, a TGA planning is needed or you rely on the unreliable statements of sellers

...Now I am uncertain whether we definitely need a ventilation system for this house to keep it free of mold

not necessarily, however significant comfort with "normal" use, heat recovery possible => sometimes one performance level smaller (cheaper) for a weekend, savings on room heating surfaces, hydraulics, so that the additional costs relativize overall.

best regards

Hello, KfW 70 and Proxon probably do not fit well, unless you want to live with high consumption costs in the long term! For this, you need TGA planning or you rely on the unreliable statements of sellers not necessarily, however, significant comfort with "normal" use, heat recovery possible => sometimes a heat generator one performance level smaller (cheaper), savings in the room heating surfaces, hydraulics, which relativizes the additional costs overall.

regards

What do you mean by Proxon?

What do you mean by Proxon?

Apparently, a post got "shifted" here. How that happened is a mystery to me!

l.g.

We are planning to build a KFW70 house and would like to install an air-to-water heat pump with underfloor heating and a photovoltaic system.

Furthermore, we would like to have a fireplace in the living room.

Now I am unsure whether we definitely need a ventilation system for this house in order to keep it free of mold.

Is the risk really present if, for example, we go on holiday and the house is not ventilated regularly, or is this more of an issue with passive houses?

I can only share a layman’s opinion and experiences with you: we also have a KFW70 (actually an unconfirmed 55) house with an air-to-water heat pump, controlled residential ventilation with heat recovery, underfloor heating, and photovoltaics. In our case, the photovoltaics are connected to household electricity and not to the heat pump supply, so they have nothing to do with the heating.
Controlled residential ventilation is worth the money for us. Of course, there are costs for filters and especially electricity, but the luxury is great. Whether your house will mold without controlled residential ventilation, nobody can tell you. It depends on how much moisture will be in the house if you don’t ventilate. That is speculation. Most of my neighbors have KFW70 and no controlled residential ventilation and after 2.5 years no mold. However, this statement will not help you if the walls in your house mold after 2 years.
We also planned a fireplace; we only installed the chimney flue, the stove is still missing. Since it is always quite warm in our house anyway, the fireplace is only for aesthetic reasons, which we have put aside so far. A water-bearing fireplace would have become uneconomical for us due to the technology to be installed and the hydraulics.
Ventilation system and fireplace is a topic on its own. On our ventilation system, you can easily connect a pressure monitor that switches off the system in case of negative pressure. You should discuss this in advance during planning.

Hello Wastl,
your post almost sounds like the answer I am looking for. We are currently planning and want to build a prefabricated house through Bien-Zenker.
The floor area is 70m² ground floor, 70m² logically upstairs where the bedrooms and bathroom are. Since our house is not the biggest, a WFKA from Proxon was recommended to us, which can also provide cooling in the summer. I have read that it can cause problems with a floor area over 90m² and is not really designed for that. Since we are not sensitive to cold, I hope that according to the calculations the WFKA will be sufficient for us. The house is a KFW70 passive house. In the bathroom, I want to lay underfloor heating separately under the tiles; we have that now only for warm feet in winter, which is enough for us.
Theoretically, one should or must no longer have to ventilate the house manually, only my wife likes to open the windows too much. I assume we will rarely use the system. Does anyone else have a PROXON WFKA?