ᐅ Gas or air-to-water heat pump. Requesting assistance.

Created on: 8 Jun 2016 07:41
P
pb1989
Hello,

We have been researching heating systems online for a long time.
We are getting desperate and hope you can help me.
We are building a single-family house in Berlin Mahlsdorf.
125 m² (1,345 sq ft).
It is a 30 cm (12 inch) masonry wall (including insulation) built with Ytong system prefabricated panels.
Completely with underfloor heating and no basement.
Gable roof.
I once did a quick heating load calculation online, which was about 8.6 kW (realistic).

The builder has provided an offer for a gas condensing boiler with heat recovery.

A cost-neutral offer for an air-to-water heat pump from Thermia Atec Total 9.

With the air-to-water heat pump, we would also save on the gas connection, and we would receive a credit of 2,500 for the heat recovery.

Please help me with the decision.
If you need more details, please let me know which ones. Thank you in advance.
L
Legurit
12 Jun 2016 19:33
The sad truth is that even professionals often tend to follow the “more is better” and “more safety means fewer complaints” approach when it comes to heating system sizing... at least based on our experience.

Now I’m reading this... you get credited 2500 € and they won’t install a mechanical ventilation system with heat recovery? That’s really not ideal – I would install mechanical ventilation regardless of the heating type... just the thought of letting expensive heated air escape through the window at -10°C (14°F), especially when using an air-to-water heat pump where heating costs are high, because otherwise you can’t control humidity properly...

Go with gas and double-check whether it really needs to be 30cm (12 inches) – because it probably can’t be, at least not with Ytong blocks.
S
Saruss
12 Jun 2016 19:47
That could be the case. It was stated as 30cm (12 inches) total including insulation, and a 17cm (7 inch) aerated concrete block with 12cm (5 inches) insulation might work, also considering structural requirements. After all, it’s probably not a two-story building.
L
Legurit
12 Jun 2016 20:54
17cm (7 inches) aerated concrete... well, why not – it just wouldn’t be my choice.
S
Saruss
12 Jun 2016 21:57
Everyone is free to build however they prefer. It's a matter of personal taste. I also use 17.5cm (7 inches) aerated concrete blocks and am satisfied with them. On top of that, there is mineral wool insulation and then very solid facing bricks, which makes a significant difference.
L
Legurit
12 Jun 2016 21:59
That's how I know it as well – double-shell construction; we also had the choice between aerated concrete or calcium silicate blocks. But single-shell with external thermal insulation composite systems (ETICS) would probably feel too drafty for me.
S
Saruss
12 Jun 2016 22:34
The thermal and sound insulation is somewhat weak, but other than that, I don’t think it’s really a problem.

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