ᐅ Heating: Partial Knowledge, Conflicting Advice, Uncertainty

Hello everyone,

We will start building our single-family house (220 sqm (2,370 sq ft) living area plus basement) at the beginning of 2018.

Basically, we do not prioritize any KfW standards. Initially, we planned to install a gas boiler (gas connection already included in the land price) with solar thermal and a tiled stove with a water jacket in the living room.

A week ago, we had an appointment with a heating engineer. He told us that this setup would not comply with certain building regulations (energy saving ordinance? 30% renewable energy requirement?). He said that we would either have to use a heat pump or pellet heating system or, in addition to the above configuration, install a central ventilation system.

Following this, we researched the topic and were leaning toward a “heat pump + photovoltaics” solution.

Today, another heating engineer came by. He said that gas with solar thermal is no problem if properly designed and recommends it to any homeowner with an existing gas connection.

So, what is actually correct? What is really advisable?

Hmm, this is difficult because there isn’t really a clear recommendation. The tricky part is that this topic also depends heavily on personal preferences and priorities. In the end, it comes down to what matters most to you. If you want to be as (though not completely) independent as possible from rising energy costs, then only a heat pump (e.g., geothermal) combined with photovoltaic panels and possibly a storage system makes sense. However, if overall lower installation costs are more important and energy prices are secondary, then I would choose gas and solar thermal systems.

Since we don’t have access to gas where we are, the decision was easy—we are installing a heat pump with photovoltaic panels and storage. Regarding advice from installers, each will only recommend what they are familiar with, and unfortunately, heat pumps combined with photovoltaic systems are still unfamiliar territory for many because proper system design and further adjustments are more complex than gas plus solar thermal.

The decision is indeed not easy, as each option has its advantages and disadvantages.

Is it correct that using gas combined with solar thermal energy currently does not comply with building regulations (energy saving ordinance??)?

cybergnom schrieb:
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Is it correct that with gas plus solar thermal energy, I cannot meet the current building regulations (energy saving ordinance??)?

This cannot be answered as a simple yes or no, since it depends on calculations. Often, better insulation is sufficient, but then the ratio of walls to windows must be considered.
If he is actually referring to the 30% renewable energy requirement of the 2016 energy saving ordinance, then solar alone probably won’t be enough.
Adding a mechanical ventilation system with heat recovery should be sufficient, but in my opinion, it is something you should have anyway.
Considering the size of your house, manual ventilation is not practical and should be planned for!

P.S. Your fireplace probably won’t be enough for this, right?!?

We also have gas and solar thermal systems and had to install a mechanical ventilation system (which we wanted to do anyway).

Best regards,
Sabine

According to our energy calculation, it was tight but possible to operate using only gas and solar energy for domestic hot water. Integrating solar into the heating system would be a potential next step; alternatively, connecting a fireplace to the heating system or using controlled mechanical ventilation...

There are several options, and a specific energy calculation should be done for your house.