ᐅ The dilemma of choosing...

Good evening, fellow home builders,

After gathering one opinion after another for days and consulting a heating engineer friend, choosing the right heating system is not getting any easier. I'd like to share some of the details and hear about your experiences 🙂

Parameters:

• New single-family house (solid construction, Poroton T8/T9, preferably monolithic)
• Style: townhouse, 2 full floors plus basement
• Approximately 150 m² (1,615 sq ft) of living space
• Plot with a slight slope
• There is a gas connection on the property
• Hipped roof with about 20° pitch, ridge line running roughly from NNE to SSW
• According to the local building consultant, the site (rocky) is not suitable for geothermal systems (collector), although no detailed study has been done yet
• Underfloor heating (according to the installer, the build-up is about 14 cm (5.5 inches) including floor covering)
• We would like to install a central ventilation system

Does the roof pitch exclude solar thermal systems? What heating system would you recommend here? I am mainly considering the economic aspect.

Perhaps you could also recommend a specific system (maybe one that complies with the current energy-saving regulations)? (Private messages are welcome).

I hope some of you dare to share your thoughts. I look forward to every reply.

Have a nice evening!

Maybe a small note: We would like to install a Swedish stove in the living and dining area (what is the forum’s opinion on this—would you prefer a pellet stove or a traditional wood stove)?

So many questions...

Gas with condensing boiler, air-to-water heat pump, or ground-source heat pump. Get quotes for all options. Is gas available on or near your property? If the site is fully connected to utilities, gas will most likely be the most cost-effective choice.

We have a 14 cm (5.5 inch) build-up only in the attic. The ground floor has a thicker build-up due to insulation. How is your foundation slab insulated?

Do you have a designer for the details? Is there an expert involved? You should definitely show them the construction service description before signing the contract.

satisfied schrieb:
Good evening, fellow home builders,

After gathering opinions from various sources for several days and consulting a heating specialist friend, choosing the right heating system is not getting any easier. I’ll share some of your experience here 🙂

Framework conditions:

• Newly built single-family house (solid construction, Poroton T8/T9, preferably monolithic build)
• Style: urban villa, 2 full stories plus basement
• Approximately 150 sqm (1,615 sq ft) living space
• Plot with slight slope
• Gas connection available on the property
• Hip roof with about 20° pitch, ridge line running approximately from NNE to SSW
• According to the local architect, the terrain (rocky) is not ideal for geothermal (collector) installation, but no detailed study has been done so far
• Underfloor heating (installer says buildup will be approx. 14cm (5.5 inches) including floor covering)
• We want to install a central ventilation system

Does the roof pitch rule out solar thermal?
What heating system would you recommend here? I’m primarily looking at the economic aspect.

Maybe you could specifically recommend a system (possibly one that also complies with the current energy saving regulations)? (Private messages are welcome).

I hope some of you dare to share your thoughts, I’m happy about every reply.
Maybe one more note: we’d like to install a Swedish wood stove in the living and dining area (what’s the forum’s opinion on this—pellet stove or traditional wood stove)?
So many questions...

Have a nice evening!

Hi,

You’re basically building according to the 2016 energy saving regulation (energy saving ordinance). However, you didn’t mention whether you’re going for a KfW house standard or not applying for KfW funding. That actually makes quite a difference! Which standard is planned? KfW 100, Energy Saving Ordinance 2016, or KfW 55/40/40+?

The systematics of the energy saving regulation are basically "system-neutral". Your house just has to meet the required criteria. This is generally—a rough summary—a combination of the building envelope/insulation plus the technology used (→ primary energy demand).

Balancing this out is difficult to do here in the forum, as it requires extensive calculations. Your architect and/or an energy consultant must handle this.

Solar thermal: It’s also possible on your roof.
Don’t expect too much from it. The relatively high investment is combined with relatively low yield. The combination of vacuum tube or flat-plate collectors (expensive!) with domestic hot water plus heating support promises the best yield, as these collectors have higher efficiency and work better even at low solar radiation in autumn and spring.
I personally only have solar thermal with domestic hot water support and conventional collectors due to KfW 70 certification at the time. Overall it’s just a nice gadget that was expensive and will never pay off financially. But it’s good for the environment and I enjoy it.
In my area, several urban villas with a 20-degree roof pitch have solar thermal systems.

Mechanical ventilation with heat recovery: This topic tends to spark debates. Personally, I never want to give up my mechanical ventilation system. It really impressed me. Your plan to install such a system is, in my opinion, good. Even my wife—after initial reservations—is now fully enthusiastic.

Gas connection: I am personally pro gas connection. That’s my own opinion. In the longer term, when my gas boiler breaks down, I plan to replace it with a system that can generate electricity as well (currently this technology is still in its infancy and very expensive).
Even if the gas supply is on the property, there are costs of several thousand euros before it reaches inside the house.

You will probably find it easier to meet the energy saving regulation requirements by equipping the house with a good air-to-water heat pump (COP > 3.3) or a ground-source heat pump. This can even be more or less cost-neutral since the higher device costs may be offset by savings from not extending the gas connection.
Since you planned underfloor heating, with its low supply temperatures that already favor an air-to-water heat pump. As said, your architect or energy consultant needs to confirm and calculate this in detail.

Wood stove: Ask 10 people and get 11 opinions.
Buy what you want and what you like, pellet or wood. Pellet stoves can be convenient as they are partly automated.
In a modern house: size it correctly, 5 kW is enough, otherwise you’ll quickly have a sauna. You probably want atmosphere and coziness, and not to lose heat through open windows to the garden from an oversized stove.
Forget saving money here. The efficiencies sound good on paper, but converted to energy content, both wood and pellets are more expensive than gas or electricity for an air-to-water heat pump. Only if you get wood cheaply or for free does it make sense financially.
A real fireplace—if you have space for it—is an alternative.
Apart from that, I don’t want to give up my wood stove. It’s my style of coziness to watch the flames when it’s running.
Let’s be honest—the stove is basically a lifestyle event, no more.

Best regards,
Thorsten

BeHaElJa schrieb:
Is the gas connection on your property or outside of it?

The gas connection is already on the property.

BeHaElJa schrieb:
How is your slab insulated?

I can’t say yet, I haven’t gotten to that stage.

BeHaElJa schrieb:
Do you have an expert involved? You should definitely show them the construction scope document before signing the contract.

What exactly is a construction scope document and an expert? 🙂

T21150 schrieb:
Which energy standard are you planning? KfW100 Energy Saving Ordinance 2016 or KfW55/40/40+?

Since I don’t think the additional investment is worth it, I’m currently not planning to apply for KfW funding, but maybe I’ll be convinced otherwise.

At what temperature does an air-to-water heat pump switch to fully electric heating?

Would a combination of controlled mechanical ventilation and an air-to-water heat pump (Viessmann offers such systems) powered by a photovoltaic system be a good choice?

Or is it more economical to use a condensing gas boiler and possibly expand it with a small air-to-water heat pump with photovoltaics? (This setup was recommended by my heating installer.)

Regarding pellet stoves: After looking at one, I think I’ll go back to a traditional wood stove. As Thorsten already said, it’s about the “atmosphere and coziness.” That effect is just stronger with a wood stove. Above all, I enjoy watching the fire.

satisfied schrieb:
At what temperature does an air-to-water heat pump switch to full electric heating?

When the pump is running, it consumes electricity... That's obvious, right? Or what do you mean by the question? Electricity is always required; otherwise, the heat pump won't work.