ᐅ Request for Evaluation of Heating and Ventilation Concept for a New Single-Family House

Hello everyone,

We are planning to build a detached single-family house, about 160 sqm (1,722 sq ft), on an 1100 sqm (11,840 sq ft) plot at the edge of town with a slight slope on slate soil. We are aiming for approximately a KfW 70 energy efficiency level, although with the current interest rates we are not relying on the related subsidies. Overall, our planning is going quite well, but when it comes to heating and ventilation, we are unsure if our plan really makes sense. Therefore, we appreciate your opinions on this 🙂

In general, we want to build and operate the house simply and cost-effectively, and it would be great if we could do this with a clear conscience for the environment. Our idea:

- A fairly well-insulated building envelope (see above), without it becoming a bottomless pit.
- Air-to-water heat pump
- Pellet stove in the living room
- Controlled mechanical ventilation (with heat recovery)
- Underfloor heating

The idea is that the air-to-water heat pump supplies most of the heat for the house, and the pellet stove in the living room provides extra support when it gets very cold outside. Ideally, this would happen automatically—so that the pellet stove switches on as soon as the outside temperature drops to a certain value, e.g., -3°C (27°F).

Here are a few questions for you experts:

1. Does this concept make sense as a whole?
2. Or would it be better / simpler / more cost-effective overall to use gas for purchase, operation, and maintenance?
3. Should the pellet stove in our setup be water-bearing (hydronic) or not?
4. Should the controlled mechanical ventilation system include heat recovery, or is that not necessarily required? Does a central or decentralized system make more sense here?
5. How can I find someone who can plan, recommend, offer, and install the right equipment for this setup (and not just the products that provide them with the highest commission)?

Thank you very much for your opinions—and Happy New Year in advance 🙂

A double heat generator is not worth it.
A pellet stove is therefore not worthwhile at all.

Personal amateur opinion:

1. No, you are investing in two residential units when one would be sufficient.

2. There are opinions that KfW 70 standard and gas heating in 2016 are either not feasible or only achievable with extreme effort.

For example, building experts have not been able to clearly explain this yet.

But it’s not possible without a solar thermal system, and if you go that route, you might as well consider a heat pump.

I find ground source heat pumps interesting because the additional money is better invested there than in a solar thermal system or an additional pellet stove.

Especially if the plot allows for a horizontal ground collector (preferably a trench collector).

3. That only makes everything worse.

4. I recommend a central mechanical ventilation system with heat recovery.

What makes sense is up to each individual, as there are different priorities.

5. Contact several heating system installers / mechanical and electrical planning consultants.

Hello,

Why isn’t a pellet stove worthwhile? But for example, a heat pump or a gas boiler might be? Having two water-based heat generators is obviously not practical.

I don’t think ground or trench collectors are effective in slate soil.

I would reduce everything to one water-based heat generator. Think about how you want to heat. With a pellet stove, the heat generator is located in the living area, creates minimal dirt and effort. Combined with a buffer tank and thermal solar system, it can serve as the sole heating source. I have had good experiences with the products from a manufacturer in Tübingen, including in my own home. Heat pumps and gas systems are less demanding.

Olli

Thanks in advance for your answers. I agree with wrobel – I’m ruling out surface or trench collectors because of the slate ground. Besides, in 15 years, when the heat pump breaks down and needs to be replaced, there will probably be something else that can no longer use all the collectors buried in the garden. An air-to-water heat pump can be replaced more easily.

Regarding the additional pellet stove in the living room: partly it’s a “luxury,” we like having a stove, and a wood stove is too much work and mess, so pellet. I thought that if it’s going to be a luxury, it should at least be somewhat practical – meaning that it could (with or without water heating?) help reduce the load on the heat pump on cold days.

Does this not make sense?

Get some quotes made – I’d be interested to know what your total costs come to. Feel free to post them here – we do have comparisons related to gas. Deep drilling and surely someone will also bring up your air-to-water heat pump.

I would be concerned that this might become very, very uneconomical.