ᐅ Design of Underfloor Heating for a KfW 55 Energy-Efficient House with a Ventilation System

dream2023 schrieb:

Basically, I would have also tended to go for a 15 cm (6 inches) installation spacing in the living and sleeping areas. That’s not possible with the planned system. Reducing everything to 12 cm (5 inches) might be a bit overdoing it...

Just a silly question: How do you come up with 6/12/18 cm (2.4/5/7 inches) installation spacings? No staple or studded panel is designed for these distances. Usually, you talk about 5, (7.5), 10, or 15 cm (2, 3, 4, or 6 inches). When I read about such spacings, and that most of it should even be installed at 18 cm (7 inches), it really annoys me. Nearly 20 cm (8 inches) was state of the art 30 years ago, but not anymore today. Nowadays, you should generally plan for 10 cm (4 inches) spacing or, where necessary, 5 cm (2 inches) (bathrooms). This requires minimal additional effort (+ material) but leads to a) significantly lower flow temperatures, which feel better and are more efficient, and b) allows comfortably maintaining 22 degrees Celsius (72°F) in living spaces with well-designed planning.

You discuss these topics with a qualified planner. Wrong approach: A qualified planner asks about your wishes. In your case, the cheapest solution for the builder is installed – it will get warm, sure, but that’s like comparing a Dacia to a Mercedes. Both will get you from point A to point B but with very different levels of comfort (only the price difference for the car is significantly higher).

KarstenausNRW schrieb:

Just a silly question. How do you arrive at installation spacings of 6/12/18cm? No stapler plate or studded membrane is designed for such distances. Usually, people talk about 5, (7.5), 10, or 15cm. When I see these spacings, especially with a large part planned at 18cm, it really bothers me. Almost 20cm was state of the art 30 years ago, but not today. Nowadays, you should generally plan with 10cm spacings, or 5cm where necessary (bathrooms). This only costs a minimal additional effort (+ material), but a) leads to significantly lower supply temperatures, which feels better and is more economical, and b) allows for comfortably maintaining properly planned 22 degrees Celsius (72°F) in living areas.

You discuss these issues with a qualified planner. Wrong: A qualified planner asks about your wishes. In your case, the cheapest solution for the builder is installed – it will warm up, but it’s like comparing a Dacia to a Mercedes. Both get you from point A to B, but with very different comfort levels (although the price difference for the car is much more significant).

I don’t know. Apparently, this studded membrane is designed exactly like that. The site manager said that at least I can’t just switch to a different system than the one planned for the heating. I have heard several times now that these installation spacings are quite unusual.

Daniel-Sp schrieb:

Hello,
a temperature difference from 24°C (75°F) to 15°C (59°F) is not achievable with KfW 55 standard. If implemented as planned, you would end up heating the adjacent rooms through the already unheated bathroom.
It’s better to plan for 24°C (75°F) in the bathrooms and 22°C (72°F) in the rest of the rooms.
Will a mechanical ventilation system with heat recovery be installed?

A mechanical ventilation system with heat recovery will be installed.
The site management was really unhappy about my skepticism. I don’t think they are open to major changes.

dream2023 schrieb:

The construction management was really unhappy about my skepticism.

They are used to that and you just have to accept being a bit unpopular. They know their usual characters and are aware of who tends to do better work and who doesn’t. That’s why they also know that corrections will be needed when the buyer/homeowner is actively involved and pays attention.

If I understand correctly, the calculation is based on a flow temperature of 35 degrees Celsius (95°F). That seems too high for me. I would calculate using a flow temperature of 30 degrees Celsius (86°F).

hanse987 schrieb:

That’s too high for me. I would have the supply temperature calculated at 30 degrees Celsius (86°F).

That may be well and good, but what’s the outcome supposed to be? According to calculations, there’s already a deficit at 35 degrees Celsius (95°F) in the bathroom. If you calculate with 30 degrees Celsius (86°F) now, the deficit will only get bigger, and then the original poster either has to accept that the bathroom will only reach around 21 degrees Celsius (70°F), or the heating installer won’t install the system.