ᐅ Comparison of Geothermal Heat Pump and Air-to-Water Heat Pump

Your construction company or energy consultant can calculate that for you.

The goal is to increase insulation and reduce the heating load enough so that the heat recovery ventilation (HRV) system of the controlled residential ventilation achieves the 15% share.

This then counts as a compensatory measure.

T_im_Norden schrieb:

Your construction company or energy consultant can calculate that for you.

It basically comes down to increasing the insulation and keeping the heating load low enough so that the heat recovery from the mechanical ventilation system covers the 15% requirement.

This then counts as a compensatory measure.

Mechanical ventilation with heat recovery plus gas boiler including solar thermal system and 36.5 cm (14 inches) brickwork plus passive house windows will be tight for KfW55, right? As far as I have heard, 9.9 kWp photovoltaic doesn't really help for KfW55.

I can’t tell you if that works with KfW. I’m building without KfW and therefore only have to comply with the Energy Saving Ordinance.

T_im_Norden schrieb:

Your construction company or energy consultant can calculate that for you.

It basically comes down to increasing the insulation and keeping the heating demand low enough so that the heat recovery of the controlled mechanical ventilation covers the 15% share.

This then counts as a compensatory measure.

Thank you for the information!

Hello,

interesting topic, I’ll join the discussion.

We have 18 years of experience with ground-source heat pumps in two different houses. Always using surface collectors in the garden (vertical ground probes weren’t available back then). Our experience has been consistently positive.

We are currently planning our new build, KFW55 without mechanical ventilation, timber frame construction. The builder’s standard is an air-to-water heat pump (Nibe or Viessmann). According to him, this is currently the most sensible option (gas with solar collectors is almost the same price but considered old-fashioned, ground-source heat pumps are significantly more expensive and hardly pay off anymore at KFW55 level).

I’ve read here that the price difference isn’t that big. However, I didn’t quite understand the calculation:

Ybias78 schrieb:

The subsidy has increased to 35% (all ground-source heat pump costs). I’ve also heard from many general contractors that the extra costs are around €8,000. That seems about right. You get around €4,000 more in subsidies. So roughly €4,000 additional cost.

The subsidy is 35%, so on €8,000 extra costs that would be €2,800, not €4,000, but anyway. What worries me in our situation:
- high effort for drilling (permits)
- plot too small for surface collector

So… air-to-water heat pump. According to the builder: with a seasonal performance factor of about 4.5 compared to 5.5 for a ground-source heat pump, I have roughly 18% higher electricity costs per year with an air-to-water heat pump. With total costs around €1,000 per year, that is acceptable.

What bothers me more is the “rumor” that air-to-water heat pumps are prone to issues and have a short lifespan… does anyone have experience with this?

I don’t mind the outdoor unit much. We also have a less attractive side of the house behind the carport, adjacent to the utility room.

My idea is to install a (small-sized) stove inside. With appropriate temperature sensors and motorized valves on the underfloor heating, I could cover the cold winter period with it. From experience with the slow-reacting underfloor heating system, we want to have a stove anyway.

I’ve read that spacing of 10cm (4 inches) instead of 15cm (6 inches) for the underfloor heating loops only costs a few hundred euros extra. Is that true? How much does it improve performance and reduce the supply temperature?

Regards, Andreas

neo-sciliar schrieb:

Hello,

interesting topic, I’ll join in here.

We have 18 years of experience with brine-water heat pumps in two different houses. Always with ground collectors in the garden (horizontal trench collectors were not available at that time). The experiences have been consistently positive.

We are currently planning our new build, KFW55 standard without mechanical ventilation, timber frame construction. The builder offers air-water heat pumps (NIBE or VIESSMANN) as standard. According to him, this is currently the most sensible choice (gas with solar collectors is nearly the same price but outdated, brine-water heat pumps are significantly more expensive and barely pay off anymore at the KFW55 standard).

Now I read here that the price difference is not that big. Although I did not understand the calculation:

The subsidy is 35%, so for additional costs of €8,000 it would be €2,800, not €4,000, but anyway. What holds me back (in our situation) are:
- High effort for drilling (permits)
- Too small plot for horizontal trench collector

So... air-water heat pump. From my builder’s perspective: with a seasonal performance factor of about 4.5 versus 5.5 for a brine-water heat pump, I have 18% higher electricity costs per year with an air-water heat pump. With total costs around €1,000 per year, that is bearable.

What bothers me more is the “rumor” that air-water heat pumps are prone to faults and have a short lifespan… does anyone have experience regarding this?

I’m not much bothered by the outdoor unit. We also have a less attractive side of the house behind the carport, adjacent to the utility room.

My idea is: we will install a (small-sized) stove in the house. With proper temperature sensors and actuators on the underfloor heating, I could bridge the cold winter period. Based on experience with the slow response of underfloor heating, we want to have a stove anyway.

I read that reducing the spacing of underfloor heating pipes from 15cm (6 inches) to 10cm (4 inches) only increases the cost by a few hundred euros. Is that true? What is the gain in quality and reduction in supply temperature?

Best regards, Andreas

Good questions. How was it with the ground collectors? Did you have any restrictions due to those (no planting, etc.)?