ᐅ Combination of air-to-water heat pump + solar thermal system + stove, or stove and air-to-water heat pump only

Hello forum,

I am currently planning the construction of a new KfW40 single-family house.
The expert’s calculation resulted in the following (summary):
Heated building volume = 532 cubic meters
Usable floor area = 170 square meters
Qp-new building = 29 kWh/(sqm per year)

The construction company’s offer includes the following technology
(where KfW was only calculated with the heat pump):
Novelan heat pump LAD 5 (air-to-water heat pump)
Compact Station Dual 180-liter (47-gallon) domestic hot water tank
+
optional solar thermal system
SPE1 with 2 Roth collectors (2 x 2.52 sqm (27 sq ft))
including a 400-liter (106-gallon) water tank.
If the solar thermal system is installed, the 180-liter (47-gallon) heat pump tank would likely be removed.

I am generally aware that both systems are rather designed for the summer months and show weaknesses in winter, but nevertheless, the extra cost for the solar system (€4,800) seems reasonable to me for ideological reasons… purely from a financial standpoint, it will probably never really pay off.

For the winter months, I am considering connecting the planned wood stove with water heat exchanger to the central water storage tank. For this purpose, something like a Novelan/Alpha Innotec MFS 600-liter (158-gallon) multifunctional storage tank would probably be necessary.

What do you think, is this all nonsense or somewhat justifiable?
Or just take the heat pump with a small water tank plus a regular stove for the living room (which is already planned, as mentioned)?

No ST—especially not for 5,000 euros 🤨, no water-bearing stove—if you want to ease your ecological conscience, better buy green electricity—you’ll have done more for the environment.

Hello

As you already mentioned, some system components don’t work well together here.
However, the idea of adding a fireplace stove to the heat pump makes sense.
Or a stove combined with solar thermal systems also works. First, consider how you want to heat your home and how much effort you are willing to invest.
Is the desire for a stove serious and long-term? Maybe pellets?

Olli

Good morning and thank you very much for your responses.
Of course, I forgot the most important basic information:
Household of 3-4 people.
Underfloor heating throughout the entire house.
Controlled ventilation system with heat recovery.
The wood-burning stove is included for coziness; whether it will be water-based or not is still under discussion.

Assuming solar thermal is removed, and the heat pump and stove remain:
What type and size of hot water storage tank would be appropriate?
I have read that for the heat pump, rather a smaller tank (for example, the available 180 liters (48 gallons)) is advisable.
For the stove, on the other hand, a larger tank (600-1000 liters (160-260 gallons)) might make more sense?

The small storage tank by the heat pump is for domestic hot water (I find it too small), and the large one by the stove is for the heating system water.

So you need both 😉

We have a 150-liter (40-gallon) tank for the hot water connected to the air-to-water heat pump. So far, I would say it is neither too large nor too small.

We decided against installing a wood stove with a water heat exchanger and thus a second tank. On one hand, I wanted to avoid the extra effort; on the other hand, I preferred an independent heating system that I can operate without electricity in an emergency.