ᐅ Hot Water Only with a Heat Pump?

I need some expert advice: We are building a single-family home, building permit/planning permission from 2015, 115 sqm (1,237 sq ft) of living space, no basement, 7.5 sqm (81 sq ft) utility room. Now we are considering the heating system investment: either a gas condensing boiler using propane (no natural gas available), but the roof orientation is not ideal for solar thermal. Or an air-to-water heat pump? Our planner recommended a compact unit from Viessmann 😉, but a heating specialist told me that the hot water storage tank would not be sufficient and that he would definitely add a separate storage tank. Besides the investment costs, we also want to keep the utility room usable for other purposes and not fully occupied by technical equipment. What would you recommend? Thank you for your answers!

Neubau-2016 schrieb:
I need some expert advice: We are building a single-family house, building permit from 2015, 115 sqm (1,237 sq ft) living space, no basement, 7.5 sqm (81 sq ft) utility room. Now we are facing the question of heating system investment: either a gas condensing boiler running on liquid gas (there is no natural gas available), but the roof orientation is not optimal for solar thermal systems. Or an air-to-water heat pump?? Our planner recommended a compact unit from Viessmann 😉. However, a heating specialist told me that the water storage tank would not be sufficient and advised installing an additional tank next to it. Apart from the investment costs, we also want to keep the utility room available for other uses and not fill it entirely with technical equipment. What would you recommend? Thanks a lot for your answers!

Hi, we have about 110 sqm (1,184 sq ft) living space, no basement, KfW70 standard.

Our utility room has 4.96 sqm (53 sq ft) and despite all the technical equipment (including a Pluggit Avent 310 controlled residential ventilation system with heat recovery, which also takes up space), it is still very usable if you consider some clever solutions.

We use a Buderus GB-172 gas condensing boiler for heating.

The solar thermal collector faces east. It’s not optimal but only reduces output by about 5–8% compared to south orientation. Don’t expect too much from solar thermal. Hot water costs are generally not that high; the savings you get from solar thermal usually don’t cover the investment, interest, and repayments.

We have a 300-liter (79-gallon) hot water storage tank. It’s a stratified storage tank because of the solar thermal system. Usable volume in winter is about 150 liters (40 gallons). The rest, at the bottom, is cold water reserved for the solar thermal system (which is inactive during that time).

It depends on what hot water volume the offered Viessmann air-to-water heat pump provides. For a full bath, count on 100–150 liters (26–40 gallons), which can be used up quickly. I usually keep hot water at 45°C (113°F). When I take a bath (large tub), I temporarily raise it to 60°C (140°F) because otherwise the hot water runs out while bathing. So the heating specialist’s advice to install an additional storage tank could definitely be very practical.

Best regards,
Thorsten

Hello Thorsten,

Are you otherwise satisfied with the GB 172?
Doesn’t it have an integrated stratified storage tank? Your solar thermal system is only on the east side, so you charge your storage with the morning sun?

Thanks and best regards

Hi Bortel,

I am very satisfied with the GB-172. The price-to-performance ratio is excellent.

The storage is separate. The GB-172 is compact and wall-mounted.

The east side: Charges from the morning into the afternoon.

Best regards,
Thorsten

Thank you