ᐅ Exotic combination: wood pellets plus exhaust air heat pump?

Hello,

First of all, thank you for providing a platform for questions like this.
I have the following issue that I’m trying to solve and hope to get some tips from the experts here.

I’m interested in a house but haven’t bought it yet.
- Viebrockhaus, so-called 3-liter house, haha. Built in 2000
- Very good quality in terms of bathrooms, floors, and materials
- Two upper floors totaling 200sqm (2,150 sq ft) with a mansard roof and a fully finished basement including an office of about 90sqm (970 sq ft)
- Now here’s the thing, hold on to your hats: the electricity bills are easily around 400€ per month, and depending on the year they use between 10,000–12,000 kWh annually. All electric, mind you. For two people!
- Radiators throughout the house. No underfloor heating! Two fireplaces, but their chimneys are located exactly opposite the technical room. They do have flaps to the hallway as well.
- Heating system: 2 x exhaust air heat pumps, Nibe Fighter 600 or 610, for the living area and one Nibe Fighter 315 for the basement/office.
- Central exhaust ventilation system from relevant rooms, with decentralized air supply openings in every room.

Clearly, the system is so inefficient that it probably runs on electric heating cartridges 90% of the time. Plus, the ventilation has to be on; otherwise, there is no efficiency at all.

I want to reduce these high costs. I’ve read that you can tweak the system with timers and turning ventilation mostly off, or trick the temperature sensors, etc. But I think all that is neither effective nor practical.

IDEA:
- Since there is LOTS of space in the technical room in the basement, including a large storage area, I’m considering installing a suitable wood pellet boiler. The chimney draft is external. The appearance doesn’t bother me.
- Combined with a modern exhaust air heat pump like the Nibe F135, which would only run occasionally.
To keep the ventilation going—I’m afraid of mold otherwise—the house was very dry and didn’t feel stuffy.
The viewing was on a 35°C (95°F) day, so it was blazing hot inside, obviously because warm air is drawn in.

What do you think about this, or is it nonsense? Would solar thermal for hot water be better? I have also thought about keeping the old Nibe just to run the ventilation function. What I don’t want is to break up 200sqm (2,150 sq ft) of flooring to install underfloor heating.
That rules out oil/gas/air-source/geothermal heat pumps.
I have also considered photovoltaic panels to cover the huge electricity costs, but that would be like casting pearls before swine and still wouldn’t be enough.
Maybe someone here has another tip.

THANK YOU VERY MUCH!
Frank

If the energy standard is good and radiators including piping are already installed, I would consider a conventional air-to-water heat pump. You’ll need to do the calculations.

Unfortunately, that is exactly the misconception most brainwashed salespeople have.
A modern air-to-water heat pump operates optimally at a very different operating point, but with these temperatures, I can’t get the radiators warm enough to heat a house.
In other words, with a modern air-to-water heat pump, I am so inefficient under these conditions that I might as well keep the old setup. It only really works with fuel-based systems.
The question is, what do you do about the ventilation...

Why is gas excluded? Gas heating with radiators is absolutely fine.

RockyFranco schrieb:

Unfortunately, this is exactly the misconception of most brainwashed salespeople.
A modern air-to-water heat pump operates optimally at a completely different operating point, but with these temperatures, I can’t get the radiators warm enough to heat a house.

There is no misconception. It depends on the insulation standard and the available heating surface of the radiators. Only you and/or the heating engineer/planner can determine that. And if the radiators work with a supply temperature of 35°C (95°F), then why not a heat pump?
What does your calculation look like (heating load, room-by-room, etc.)?

In the next few weeks, I will also be converting an apartment in a two-family house from oil to heat pump heating—new low-temperature radiators will be installed as part of this. Accompanied by insulation measures. The conditions will then be right for me.

Joedreck schrieb:

Gas with radiators is absolutely fine.

Much simpler and more reliable than the heat pump I mentioned. If necessary, even with a tank in the garden, when a gas pipeline is not available.