ᐅ Gas boiler without solar panels – from when is this allowed?

Hello everyone,

we are currently building a new house with 220m² (2,368 sq ft) plus a 110m² (1,184 sq ft) basement, of which 80m² (861 sq ft) is heated. The project is being completed without KfW funding and currently without an energy consultant. The attic is not finished. The walls are made of 36.5 cm (14 inches) bricks with a U-value of 0.09 W/m²K, windows are triple-glazed, the roof is insulated with 60 mm (2.4 inches) wood fiberboard, and the collar beams are insulated with 35 cm (14 inches) of mineral wool, as is the roof slope.

The house has a mechanical ventilation system with heat recovery and a geothermal heat exchanger.

Up to now, we had planned a gas boiler combined with solar thermal, but this is not economical when comparing the additional costs for solar thermal with the gas price. Until now, we believed that gas heating was only allowed in combination with solar thermal. My question is: is this really the case?

Would it possibly be allowed, with a precise calculation, to install a gas boiler alone? My research so far suggests that, especially due to the mechanical ventilation system, this might be permitted. However, I would prefer not to hire an energy consultant who might conclude that it is not possible, and then we would have wasted the cost.

We are currently undecided between a standalone gas boiler (if allowed) or a fuel cell system because of government incentives. We have ruled out gas plus solar thermal.

Thank you very much and best regards

PS: No, there is no architect or general contractor managing this. Although it costs us a lot of time, it is working well at the moment.

Chilledkroete schrieb:
Until now, we believed that gas was only allowed in combination with a mechanical ventilation system with heat recovery. My question is— is that correct?

No, it is basically also possible with controlled residential ventilation.

However, the house still has to comply with the energy-saving regulations, and this must be documented as well.

Chilledkroete schrieb:

We are currently building a new house with 220m² (2,368 sq ft) plus a 110m² (1,184 sq ft) basement, of which 80m² (861 sq ft) is heated.

...

PS: No, there is no architect or general contractor managing this. It does take a lot of our time, but it is currently working quite well.

I don’t believe you have started construction yet. If you had, you would have gone through the permitting process, which is not possible without a thermal insulation certificate outlining the building services used. Also, this would have failed due to the absence of a qualified person authorized to prepare planning documents.

Therefore, regarding your P.S., it seems that the time has come when this approach is no longer working very well.

However, controlled residential ventilation alone is usually not sufficient. So, in principle, it involves controlled residential ventilation plus additional compensatory measures.

And yes, I know that for many, controlled residential ventilation alone was enough, but in those cases, the house was already better positioned from the start due to other adjustments that had been made beforehand.

Mycraft schrieb:

And yes, I know that for many, just the controlled residential ventilation was sufficient, but in those cases, the house was already better positioned from the start through other adjustments that had been made earlier.

What kind of adjustments would those be, for example? Something like thicker insulation under the slab, etc.?

Insulation measures, improved basic equipment, lower primary energy demand, and so on.