ᐅ Where is it most worthwhile to exceed the requirements of the energy-saving regulations?

Hello,

we are currently planning a solid construction house, and there is some financial flexibility available. Now I am wondering if it would be possible to improve the energy efficiency of the house beyond the originally planned minimal compliance with the 2016 Energy Saving Ordinance requirements. This is not necessarily about return on investment, as I assume that is negative in most cases anyway. It’s more about where it makes the most sense to upgrade the house so that the money isn’t completely wasted and there may also be some comfort benefits (e.g., cooler indoor climate during heatwaves, etc.). The usual KfW subsidies are not attractive for us, so meeting a KfW standard is not the goal.

Conditions planned so far:
- 2 full floors, no basement
- Solid construction with 36.5cm (14.4 inches) Poroton air-filled blocks (requirement: walls should not become thicker)
- Central controlled ventilation system with heat recovery (for comfort reasons)
- Gable roof insulated at the roof structure instead of the upper floor ceiling
- Solar system likely unfavorable due to the roof pitches facing 22° west and east
- Heating with an air-to-water heat pump

What would be the most “sensible” options?
- Poroton blocks with some kind of filling?
- Better insulation under the ground slab?
- Ground-source heat pump? (groundwater level is quite high, is that even possible?)
- Modulating/variable capacity air-to-water heat pump?
- Better windows?
- Better roof insulation?
- Other suggestions?

Or to ask differently, what would you consider the most sensible balance between the Energy Saving Ordinance and KfW 55 standards?

Looking forward to your responses.

Best regards

Hausbauer schrieb:

and there is still some financial leeway.

Don’t you need a buffer for earthworks or fixtures?

If photovoltaic or solar thermal systems are not cost-effective (we still have the mandatory solar thermal system on the east roof), I would choose an air conditioning system and a covered terrace for a "wish list" option, provided there is sufficient electrical capacity and enough windows installed in the house.
Otherwise, I don’t think anything will pay off. For savings of 5–10 €/month, there is no need to invest thousands.

But I’m not a professional, so I’m looking forward to further suggestions.

As long as the feed-in tariff for photovoltaic systems is still available, it makes sense to go with an east/west roof orientation as well. Whether the tariff will be discontinued is unclear but possible.

The most sensible investment I see here, besides photovoltaics, is investing in thorough planning of the heat pump and underfloor heating system: have a room-by-room heating load calculation done and research a lot yourself on how to avoid errors with heat pumps in order to give clear instructions to the contractors. This is more beneficial than pursuing a higher energy standard.

Insulate more where it is cost-effective or where you will not have access later. Is insulation planned under the slab? It is also advisable to avoid large imbalances in the heating load between individual rooms. For example, the ground floor and upper floor should be insulated to a similar level, whether good or poor. With a typical floor plan, this is usually the case.

Ground source heat pump: look into horizontal trench collectors.

Hausbauer schrieb:

What do you think would be the most practical combination of the Energy Saving Ordinance and the KfW 55 standards?

None at all. Subsidies are, secondly, a bonus; they are meant to cover only the additional investment costs but not to overcompensate. And first, they are all or nothing. "Almost KfW 55" is, in terms of funding, the same as "no KfW 55."

Hausbauer schrieb:

We are currently planning a solid construction house, and there is still some financial leeway.

Don’t worry: when planning turns into building, that financial leeway will disappear effortlessly as if by magic.

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Hausbauer schrieb:

- Better roof insulation?

This is where I would start, together with a controlled ventilation system or air conditioning, to keep the attic nice and cool during the height of summer.

Upgrade to geothermal heating and/or photovoltaic systems, possibly air conditioning – but first, install external (smart) shading.

Upgrading monolithic wall constructions is quite expensive, and the added value is not that significant anyway.

You could also upgrade the windows to aluminum frames. Although this does not provide any energy efficiency benefits, it does offer higher quality.