ᐅ New Construction and Heating Question: Ground Collector or Air Source

Hello everyone,
I’m new here and would like to say hello 🙂
Like most of you, I plan to start building a house next year. The construction method will be a solid masonry house with 36cm (14 inches) thick walls and about 170 square meters (1,830 square feet) of living space. The house will be located in the Swabian Jura region.

An important factor now is the type of heating system. I do not want to use fossil fuels, and wood (pellets) is initially ruled out as well.
Therefore, it will be a heat pump. Due to the soil conditions, drilling is not possible. So basically, only ground collectors or air remain as options.

At the moment, I am seriously considering an air-source split unit. However, has anyone had experience with this over several years, especially at low temperatures around -15°C (5°F)?

I would appreciate hearing about your experiences.

Best regards,
speer

Hello,

speer schrieb:
..Therefore, only ground collectors and air remain as options. At the moment, I am considering an air split unit.

I have designed systems for heating load design temperatures down to -14°C (7°F). A decision can usually be made only once the specific climate location and building parameters are known. Here, the cumulative frequency of ambient temperatures within the 1°C (2°F) temperature band from the heating load design temperature up to the heating limit plays a role, i.e., what percentage of the expected annual heating demand occurs at low temperatures. In general, air-source heat pumps are less efficient than brine (ground loop) systems in terms of annual performance factor (APF), and this difference becomes more pronounced the less favorable the climate location is! Also, defrosting the evaporator consumes energy.

However, in buildings with very good thermal insulation, controlled mechanical ventilation with heat recovery, and thus low heating loads, the annual performance factor is no longer the decisive factor, as the overall demand is correspondingly low. If an air-source heat pump is suitable, fully modulating split units are the first or only choice.

For brine systems, the costs for ground loop installation are often significant. Therefore, trench collectors are often preferred when self-installation work is possible. For purely professional installation, this usually does not make much sense. Ground (surface) collectors also have some disadvantages: impact on vegetation, large area requirements (restricting land use), and depending on the design, possible frost build-up until mid-spring.

Best regards

speer schrieb:
...The problem is always: who can you trust.

That is often the key question. It is not wrong if the person who plans or calculates has nothing to do with sales. That way, a major conflict of interest is already avoided.

speer schrieb:
.... I think I will look for an independent energy consultant and discuss everything with him personally again.

Not only energy consultants. This is not a protected professional title! Even a building materials supplier can be an energy consultant. A building services engineer/energy consultant/construction engineer in one person, with experience in the single-family home sector, would be the right contact.
And start early. Don’t wait until the architect has planned the building and then try to “fix” it afterwards!

Best regards