Which heating system would you choose for our planned new building?

Hello everyone,
I have read a lot in this good forum already, but somehow I am not making progress.
Maybe you can help me...

We (a couple in our mid-50s) are planning, possibly, to sell our semi-detached house (prefabricated house with about 115 sqm from 1999) and build a detached single-family house again.

The house will have approximately the following key data:

- Prefabricated house in panel construction, approx. 125 sqm on a slab foundation without a basement, U-value of the exterior wall about 0.14
- 2 persons (kids have left the house)
- Plot facing south
- New development area fully developed (gas available)
- KfW 55 is targeted in order to possibly get funding (but it is not absolutely necessary)

We have dealt extensively with the topic in recent weeks and have some non-binding offers. Accordingly, such a house costs us turnkey from about 230,000,- with standard heating.

We do not want to spend a lot, even though our current house is debt-free. But we are no longer getting younger. When selling the current house, we will have about 2/3 equity capital, so we would have to take out at least 1/3 in loans.

That is why I also pay attention to the topic of cost-effectiveness when it comes to heating. Because what good are the supposed super values of the different types of heating if the additional costs only pay off in 25 years and I am already lying deep in the ground on the last plot?

So, the following options are currently available to me:

1. Standard gas boiler (condensing) with underfloor heating (cost approx. 2,500,- gas connection costs for the house)
2. Nibe exhaust air heat pump F730 at no extra cost (so savings on the gas connection)
3. Air-water heat pump Elco S05 (COP value 4.0) extra charge 7,000,- (adjusted 4,500,- due to no gas connection)
4. Stiebel Eltron LWZ 304 integral extra charge 11,500,- (adjusted 9,000,-)
5. A brine heat pump Vaillant flexoCompact extra charge 10,900,- (adjusted 8,400,-)

For 1., 3., and 5., we would like to have a controlled ventilation system with heat recovery (Zehnder 350D), which would cost us about 2,000,- due to a promotion. For 2. and 4., we would not need this. A solar system for water heating for 1. would cost us about 3,500,-.

Some house suppliers promote this Proxon system (Proxon Zimmermann ventilation). I quickly rejected it after some research. I also have the concern with the Nibe system that I might pay more because I have to add electricity for heating in winter.

Currently, we pay 70,-/month for gas (condensing boiler and underfloor heating) in our current house with 2 people.
I would like to do without a gas connection, to be at least less dependent on one energy source. Photovoltaics appeals to me, but I think it is too expensive at the moment. I would have a conduit installed for preparation. Pellet heating is not an option due to lack of storage space.

My current conclusion:

I tend either to

1. Gas boiler without solar hot water plus ventilation system (total costs with gas connection about 4,500,-) or to the air-water heat pump from Elco plus ventilation system (total costs 6,500,-).

With 2. (Nibe exhaust air pump) I am very, very uncertain, although the architect thinks it is sufficient and economical. It would cost us no (!) extra charge and no gas connection at the house.

For which type of heating would you decide?
What makes sense and what is not worthwhile? (Environmental considerations not included)

Thank you in advance for your opinions!

Best regards
Frenzi

Definitely Var. 1

1 in such a way that heat generator 1 or 3 is chosen. But in any case underfloor heating, so that it could later be "arbitrarily" exchanged. For brine heat pump, the demand of the building is too small (small+well insulated) to make it worthwhile, I estimate.

Definitely Var. 1

Hi!

I agree with Mycraft.

Best regards
Thorsten

Provider 1 is out because with Eff 55 it’s clear from the start that he won’t manage with just a gas stove. My favorite is number 4, although I would have a serious word with the seller about his surcharge policy. I would throw their promotional ventilation right back at them. For 2 grand complete, you’ll never get a ventilation system in your life, unless somewhere beforehand a big markup was added. So it’s just smoke and mirrors. The Nibe itself is already a great device, but no longer state of the art (only freshis, basically the "simple" type of ventilation).

Provider 1 is out, because with Eff 55 it is clear from the start that he won't get there with just a gas cooker.

Hi Rübe,

I think that is not entirely correct factually. Only with a gas condensing boiler is correct, you won’t get there with that. You are right.

However:
Because it is very much possible to achieve Kfw55 according to the Energy Saving Ordinance 2014 with a gas condensing boiler device if additional solutions are implemented.

The relevant values for the Energy Saving Ordinance 2014 are Q_p and H_t.
Calculations are done individually for each building according to the Energy Saving Ordinance 2014. It is now the combination of insulation and system technology that determines the result in each case.

You can calculate it here down to the wire. If a controlled residential ventilation is planned by the TE anyway – I am curious what will come out.

For the exhaust air heat pump and other heat pump solutions, the heating load requirement should also be calculated precisely and the COP properly estimated based on the local situation.

With today’s prices for gas/heating electricity, for example, the air-to-water heat pump is more or less a zero-sum game.

kWh gas: 4.9 - 5.5 ct
kWh heating electricity: 19-21 ct
(here you can clearly see which COP you should achieve!)

In my opinion, a gas connection in the house also brings advantages:
a) Gas stove possible
b) Future heat/power generators can be retrofitted later (currently in its infancy)
Getting the gas connection laid during house construction for about 1,500-2000 euros is something I wouldn’t give up if I had chosen an air-to-water heat pump for my house.

The investment costs for a heat pump are generally actually higher than for a gas condensing boiler. The gas connection also doesn’t cost 4,500 euros – it’s more like 2,000 euros, and some energy providers even offer special deals.

Regards
Thorsten