ᐅ Setting up a mechanical ventilation system with heat recovery for an energy-efficient home (KfW 70 standard) combined with underfloor heating

Hello everyone,

after living in our new house for a few days now, I’m wondering if our heating system is set up optimally.

It consists of a gas boiler with a 100-liter (26-gallon) hot water tank and a mechanical ventilation system with heat recovery.
The entire ground floor has underfloor heating, while upstairs only the bathroom does.
The other rooms are equipped with panel radiators.

My friends and I both work and leave the house early, around 7:00 a.m., returning only around 6:00 p.m.

Currently, we have the system programmed so that the heating/ventilation system/pump/hot water start about one hour before we’re home and turn off when we leave, or at 10:00 p.m. in the evening, except on weekends.

Does it make sense to set the system up this way?
Considering that underfloor heating is quite slow to react.

The question is, what is more efficient: generating energy only when needed, taking into account that the system cools down in between, or maintaining a constant temperature and using just one time window per day.

Some practical experience would be helpful, thanks!

We have two time slots set by our heating technician. Daytime and nighttime temperature reduction by 4 degrees. Or was it 3 degrees? Now it is at least 4. We only adjusted the times a bit: in the afternoon from 2 p.m., and on weekends from 12 p.m., we set it to 22 degrees. At night, it is 18 degrees. But our new builds don’t really cool down anyway.

By the way, congratulations on moving in. It took us about a month in January to settle on our temperature settings.

Thank you!

Then it should be almost perfect.

So, after a few days, I think we have found a very good balance regarding temperatures and comfort.

I know this is a somewhat specific question, but maybe you can still share some figures.
It’s about daily gas consumption. What do you typically use?
We heat the ground floor, which is completely open plan, about 45m² (480 sq ft), as well as the two bathrooms. The office and bedroom are only minimally heated.

On average, we use around 4-5 m³ of gas per day, which is about 1500 kWh per month, given the current heating season and outdoor temperatures.

What about you? Are these values realistic?

Thanks and best regards

The values are realistic. At the end of November, we recorded a consumption of about 3 m³ (cubic meters) (approximately 106 cubic feet) ourselves (readings taken several times for personal reasons).
Last month, the usage was noticeably higher, as I see: 5.7 m³ (about 201 cubic feet). It was also very cold outside most of the time.

PhoenixDH schrieb:

The office and the bedroom are heated minimally.

What does that mean in numbers?

Regards, Yvonne

So, in the rooms that are already warm at 21-22°C (70-72°F), I would estimate the other rooms to be around 19°C (66°F).
Heating set to level 2

You also have to consider that the house was built in August.

I would have guessed around 60€ for gas, which should be about right when calculated over the year.