ᐅ Sizing of Air-to-Water Heat Pumps for New Construction

Smirnoff1983 schrieb:

Not considering geothermal energy?

That was not an option under consideration. Why do you ask, and with what intention?

OWLer schrieb:

Not up for discussion. Why and with what intention do you ask?

We are slowly moving forward with the planning for our house construction, and I’m considering whether to insist on geothermal heating or an air-to-water heat pump. The more you read, the more uncertain you become. The type of heating system is not a decision you change daily. I can replace a toilet model every day for a few euros, but the heating system will need to run for several years, and mistakes in planning can quickly become very costly.

When we bought the plot of land, I contacted the responsible authority beforehand to check whether deep drilling is allowed. This was confirmed, and I was told there were no objections. After that, we also chose our land accordingly. It wouldn’t make sense to buy a plot if the building project doesn’t fit the local development plan or zoning regulations (building permit / planning permission).

When I researched this back in 2019, I frequently read about the efficiency problems of air-to-water heat pumps at low temperatures. The advantage of deep drilling is the constant ground temperature. But when I read posts here in the forum, almost 99% mention using an air-to-water heat pump or a trench collector. Even in the new subsidy program from 2021, I no longer see support for geothermal drilling.

We don’t want a trench collector because we would need to be very careful about planting (root depth) in the area. Although we have plenty of space with over 1000m² (10,760 sq ft), at the moment, I can’t really get enthusiastic about it.

I completely ignored the issue of noise from an air-to-water heat pump since we only have fields on two sides and no neighbors. So noise would not be a problem for us.

The disadvantage of deep drilling is the higher upfront cost.

However, no one can predict the temperatures for the next 20–25 years. For example, this winter in northern NRW, we had -23°C (-9°F), and in 2012 it was -16°C (3°F). Nobody knows what future winters will bring, and I would prefer not to have to keep warm in winter using the electric backup heater.

The trench collector is ideal for your situation. You don’t need to worry about root depth because the collector is installed at around 180cm (6 feet).

Joedreck schrieb:

The trench collector is ideal for your situation. You don’t need to worry about root depth because the collector is installed at about 180cm (6 feet)...

1.8m (6 feet)??? 😳 I always thought the collector was usually buried at around 1m (3 feet). Do you have any tips on what I should look for to learn more about this topic?

Won’t the entire soil be dug up and the layers (topsoil/fill soil) mixed in the process?

As of today, in my opinion, the air-to-water heat pump is the second most cost-effective heating option after gas heating, considering both investment and operational costs. At the time, we deliberately limited our decision to either gas or a heat pump.

Geothermal energy is not approved by our water authority. The ground loop collector was always of interest to me, but it was dismissed due to the funding conditions from BAFA at the time. It either wasn’t allowed or the required DIY work for the trench would have been too complicated.

With a well-designed underfloor heating system (have a professional calculate the room-by-room heating load!) and the right heat pump selection, operation and costs should be very favorable in the current climate. In OWL, it is usually fairly mild in winter (except this year), so the electric backup heater only needs to assist in exceptional cases. I expect winters to be warmer rather than colder in the future, which will improve the efficiency of the air-to-water heat pump. If it turns out to be the opposite, I would reconsider the ground loop collector afterward. The technology can be relatively easily replaced if the underfloor heating is installed optimally. Very roughly estimated, the additional cost of the ground loop collector plus heat pump might equal the extra expense of drilling.

Especially when leveraging collective knowledge on the internet, it’s possible to implement good and affordable solutions during reinvestment without involving the general contractor, in case the air-to-water heat pump turns out to be the wrong choice due to climate factors.

Best value for money if you do not want gas: air-to-water heat pump

We are slowly approaching the planning phase for our house construction, and I am wondering whether to insist on geothermal energy or an air-to-water heat pump.

As always with questions like this, my advice is:
More important than the heat source is the insulation of the house and the proper design of the underfloor heating and the heat pump.
If that is not right, even the best heat source won’t be of any use.