Is an energy-efficient house with a heat pump, photovoltaic system, and water-carrying fireplace sensible?

Hello everyone,

I am currently planning to renovate the inherited parental home into a KfW efficiency house.

For the system technology, an air-water heat pump including photovoltaic is planned. Additionally, the large kitchen/living/dining area (70 sqm) is to be heated with a fireplace, as we like the ambiance and can obtain wood very cheaply and have storage options. We are considering installing a water-bearing fireplace connected to the outside air and then combining it with the heat pump via a buffer storage. This way, we want to compensate for the low efficiency of the heat pump at cold to very cold temperatures.

The total living area is about 200 sqm, which should be completely heated by surface heating (underfloor heating). Due to the renovation already planned, we are flexible in the design of heating pipes, etc.

Has anyone had experience with the combination of heat pump/photovoltaic/buffer storage and water-bearing fireplace in an efficiency house? Is this combination sensible? Is the control of the system technology manageable with this combination or too prone to errors?

Any tips and experiences would help me here, as we are still in the early planning phase.

Hi,

we had this in our old house: a brine-water heat pump with a water-circulated fireplace stove. In advance: it works, but: the control is extremely difficult. And it already gets complicated during the planning:
- how large is the room that the stove heats directly? Where is the stove located (in the middle?)?
- keep in mind, you need water pipes for the buffer storage to and from, fresh water and wastewater to the stove.
- you need a buffer storage, at least 80 liters per kW of stove
- stove selection must be well matched to the size of the rooms (ratio of water to direct output roughly equal to the ratio of directly and indirectly heated rooms)

But with exactly this large buffer storage your heat pump can only cope to a limited extent: it prefers none at all. After all, it is supposed to heat the floor and not a buffer storage.

How exactly did you imagine the concept? Is there someone at home who "feeds" the stove all day? Because by transporting the heat, it "consumes" wood a lot. And below 65°C water temperature nothing reaches the buffer storage, meaning you always have to keep the temperature between 65 and 90 degrees.

In the harsh winter you will notice that you hardly "feed" the buffer storage. At night, when it is especially inefficient, the heat pump will then turn on again.

I advise you (this is how we have it now in the new house):
- photovoltaic system instead of water circulation: heat a small buffer storage via the heat pump during the day
- small stove for coziness

If you have questions, ask :-)

I would see it similarly. Drive the heat pump directly into the underfloor heating without a buffer. A small stove in the living room for "fire watching." In well-renovated houses or new buildings, definitely pay attention to the heating output of the stove. I have already seen new buildings with <5 kW building heating load and at the same time a >10 kW stove in the living area. Then in winter you can sit with open windows and 30°C while watching TV ;)

I would see it similarly. With a heat pump directly feeding into the underfloor heating without a buffer. A small stove for "watching the fire" in the living room. In well-insulated houses or new builds, definitely pay attention to the heating capacity of the stove. I have already seen new builds with <5 kW building heat load and at the same time a >10 kW stove in the living area. Then you can sit in winter with the windows open and 30°C while watching TV ;)

because I keep reading this: the heating value of the stove depends on the load of wood – the specified kW values are maximum values. If I put a piece of Ta/Fi into a 22 kW stove, then I heat with 1 kW and have nice radiant heat and flame play.

because I keep reading this: the calorific value of the stove depends on the wood loading - the specified KW values are maximum values. If I put a piece of Ta/Fi into a 22KW stove, then I am heating with 1 KW and have nice radiant heat and flame play.

But unfortunately, you also have to clean the glass of the fireplace regularly, because they only burn clean if the fire burns properly.

Hello everyone, I am currently planning to renovate the inherited parental home into a KfW efficiency house. For the system technology, an air-to-water heat pump including photovoltaics is planned. In addition, the large kitchen/living/dining area (70 sqm) is to be heated with a fireplace because we like the ambiance and can get wood very cheaply and have storage options. We are considering installing a water-bearing fireplace connected to the outside air and then combining it with the heat pump using a buffer storage tank. This way, we want to compensate for the low efficiency of the heat pump at cold to very cold temperatures. The total living area is about 200 sqm, which should all be heated by surface heating (underfloor). Due to the renovation already planned, we are flexible in the design of heating pipes etc. Has anyone here already had experience with the combination of heat pump/photovoltaics/buffer storage tank and water-bearing stove in an efficiency house? Is this combination sensible? Is the control of the system technology manageable with this combination or too error-prone? Any tips and experiences would help me here since we are still in the early planning phase.

My parents have had an air-to-water heat pump with a water-bearing fireplace for over 15 years and are very satisfied with it (living-dining room where the fireplace is located is about 50 sqm). By the way, they have normal radiators, as the house is a prefabricated house built in 1990. The stove is turned on from about 0 degrees Celsius. Unfortunately, I cannot say anything about photovoltaics etc.