ᐅ New Single-Family Home Construction | Choosing the "Right" Heating System
Created on: 14 Jun 2017 07:19
Z
zehn0813
Good morning!
Clearly, there is no perfect heating system. But which one could be the right choice for us?
In connection with the construction of a new single-family house with 170m² (1830 sq ft) of living space, 1.5 stories, the initial requirement given to the architect was that it should meet the KfW55 standard to qualify for subsidies. At the same time, we were very interested in the ground-source heat pump – even though it is expensive. Furthermore, a controlled mechanical ventilation system was a must, and the photovoltaic system should at least be prepared.
After digging deeper into the topic, it is now clear that the KfW55 standard will not be achieved. We just miss the target value for the average transmission heat loss.
With 8cm (3 inches) more insulation in the exterior walls, we would meet the standard, but this would reduce the living space since the building footprint is almost fully used. According to our architect (who is also the energy consultant), the additional costs would be around €2,000, but the annual heating savings would be only about €30.
Moreover, from a financing perspective, adhering to the KfW55 standard no longer makes sense for us.
Nonetheless, we initially continued planning to install a ground-source heat pump. We have always felt uneasy about an air-source heat pump, and with a gas condensing boiler, we were somewhat bothered by the solar thermal system on the roof, which is required for the renewable share under the KfW55 standard.
By now, we have the thermal insulation verification of the building and the heating load (~7.5 kW) is known. We also received initial offers for both a ground-source heat pump and an air-source heat pump. And now, we are reconsidering again!
I’ll try to summarize the comparison briefly:
Ground-source heat pump: ~€18,000 (including multifunction storage tank)
+ Deep drilling: ~€10,000
- Subsidies (BAFA and NRW Progress): ~€6,000
Total: ~€22,000
Air-source heat pump: ~€16,500 (including multifunction storage tank)
We do not have an offer yet for a gas condensing boiler including a suitable storage tank, but roughly it seems to be about €10,000 (including storage and installation). Along with the costs for the chimney and gas connection, we would at most break even compared to the air-source heat pump.
Since we will no longer meet the KfW55 standard but only need to comply with the Energy Saving Ordinance (EnEV), we do not require solar thermal anymore. The building envelope, however, is close to KfW55 standard – so it is very tight.
Setting aside the intangible value and ecological considerations, the additional costs of the ground-source heat pump somehow no longer make sense! This brings the gas condensing boiler back into play, especially since the heating load is very low due to the building envelope.
We are really torn and would appreciate any feedback on our perspective.
Best regards,
zehn0813
Clearly, there is no perfect heating system. But which one could be the right choice for us?
In connection with the construction of a new single-family house with 170m² (1830 sq ft) of living space, 1.5 stories, the initial requirement given to the architect was that it should meet the KfW55 standard to qualify for subsidies. At the same time, we were very interested in the ground-source heat pump – even though it is expensive. Furthermore, a controlled mechanical ventilation system was a must, and the photovoltaic system should at least be prepared.
After digging deeper into the topic, it is now clear that the KfW55 standard will not be achieved. We just miss the target value for the average transmission heat loss.
With 8cm (3 inches) more insulation in the exterior walls, we would meet the standard, but this would reduce the living space since the building footprint is almost fully used. According to our architect (who is also the energy consultant), the additional costs would be around €2,000, but the annual heating savings would be only about €30.
Moreover, from a financing perspective, adhering to the KfW55 standard no longer makes sense for us.
Nonetheless, we initially continued planning to install a ground-source heat pump. We have always felt uneasy about an air-source heat pump, and with a gas condensing boiler, we were somewhat bothered by the solar thermal system on the roof, which is required for the renewable share under the KfW55 standard.
By now, we have the thermal insulation verification of the building and the heating load (~7.5 kW) is known. We also received initial offers for both a ground-source heat pump and an air-source heat pump. And now, we are reconsidering again!
I’ll try to summarize the comparison briefly:
Ground-source heat pump: ~€18,000 (including multifunction storage tank)
+ Deep drilling: ~€10,000
- Subsidies (BAFA and NRW Progress): ~€6,000
Total: ~€22,000
Air-source heat pump: ~€16,500 (including multifunction storage tank)
We do not have an offer yet for a gas condensing boiler including a suitable storage tank, but roughly it seems to be about €10,000 (including storage and installation). Along with the costs for the chimney and gas connection, we would at most break even compared to the air-source heat pump.
Since we will no longer meet the KfW55 standard but only need to comply with the Energy Saving Ordinance (EnEV), we do not require solar thermal anymore. The building envelope, however, is close to KfW55 standard – so it is very tight.
Setting aside the intangible value and ecological considerations, the additional costs of the ground-source heat pump somehow no longer make sense! This brings the gas condensing boiler back into play, especially since the heating load is very low due to the building envelope.
We are really torn and would appreciate any feedback on our perspective.
Best regards,
zehn0813
The gas boiler, including solar heating for hot water, will cost around 10,000 euros (about 10,000 USD) with a branded unit. Additional costs would be for the gas connection, which is roughly 1,500 euros (about 1,500 USD) here.
The air-to-water heat pump does not save enough to cover its higher price, I am sure of that. Economically, the gas boiler is the better choice. Karsten
The air-to-water heat pump does not save enough to cover its higher price, I am sure of that. Economically, the gas boiler is the better choice. Karsten
Why should a ground-source heat pump be more expensive than an air-to-water heat pump?
€10,000 for the drilling is quite a lot—do you have a specific quote or a price estimate? How deep is the drilling? A €6,000 subsidy from progress NRW suggests around 100 meters (330 feet) depth, which is rather shallow for 7.5 kW, but at the same time, a €10,000 drilling cost would be way too expensive for that depth.
Our architect also estimated much higher costs for this (assuming it’s the premium option, so it must be expensive and padded with a safety margin). If you're interested in a ground-source heat pump with a probe, just call a couple of drilling companies. Getting a price estimate with the heating load takes about five minutes on the phone.
Why do you need to increase insulation thickness by 8 cm (3 inches) when you just miss the KfW 55 standard? An extra 8 cm is quite a lot. If you’re just barely missing the target, switching EPS (expanded polystyrene) to WLG 032 (Neopor) might be enough—without adding thicker insulation.
But KfW isn’t really worth it anyway. Additional effort from inspectors and the loan conditions have become more expensive again just a few days ago, so for us, it’s off the table for good.
€10,000 for the drilling is quite a lot—do you have a specific quote or a price estimate? How deep is the drilling? A €6,000 subsidy from progress NRW suggests around 100 meters (330 feet) depth, which is rather shallow for 7.5 kW, but at the same time, a €10,000 drilling cost would be way too expensive for that depth.
Our architect also estimated much higher costs for this (assuming it’s the premium option, so it must be expensive and padded with a safety margin). If you're interested in a ground-source heat pump with a probe, just call a couple of drilling companies. Getting a price estimate with the heating load takes about five minutes on the phone.
Why do you need to increase insulation thickness by 8 cm (3 inches) when you just miss the KfW 55 standard? An extra 8 cm is quite a lot. If you’re just barely missing the target, switching EPS (expanded polystyrene) to WLG 032 (Neopor) might be enough—without adding thicker insulation.
But KfW isn’t really worth it anyway. Additional effort from inspectors and the loan conditions have become more expensive again just a few days ago, so for us, it’s off the table for good.
To be honest, the heating load seems quite high to me.
7.5 kW for 170 m² (1,830 ft²) would be about 45 W/m² (4.2 W/ft²).
We are at 35 W/m² (3.3 W/ft²)...
Is there a basement or attic included that isn’t counted in the living area?
What type of wall and roof construction do you have?
It could also be that the mechanical ventilation with heat recovery was not taken into account, which would increase the heating demand due to ventilation heat loss.
I would ask to see the heating load calculation.
7.5 kW for 170 m² (1,830 ft²) would be about 45 W/m² (4.2 W/ft²).
We are at 35 W/m² (3.3 W/ft²)...
Is there a basement or attic included that isn’t counted in the living area?
What type of wall and roof construction do you have?
It could also be that the mechanical ventilation with heat recovery was not taken into account, which would increase the heating demand due to ventilation heat loss.
I would ask to see the heating load calculation.
Nordlys schrieb:
The gas boiler including solar thermal for hot water heating will cost around 10,000 (currency), using a brand-name unit. Additional costs would be for the gas connection, about 1,500 euros here.
The air-to-water heat pump does not pay off its extra cost, I’m sure of that. Economically, the gas boiler makes more sense. KarstenFor us, it’s 2,500. So my assumption that the costs for the air-to-water heat pump are comparable or even lower is not far off, especially since the ST is already included in the cost.
I had incorrect information regarding the assumption that the ST wouldn’t be needed.
Mycraft schrieb:
If the gas connection doesn’t require extra work…then yes, it’s definitely the cheapest option…No extra work needed. The connection via the multi-utility entry point is supposed to cost 2,500.
Alex85 schrieb:
Why would a brine heat pump be more expensive than an air-to-water heat pump?
10,000 for the drilling is quite a lot. Is there a concrete offer or price indication? How deep? 6,000 subsidy with Progress NRW suggests about 100 meters depth, but that’s a bit low for 7.5 kW, and at the same time 10,000 for drilling seems too expensive for that.
Our architect also estimated much too high costs (assuming that the brine heat pump is the premium variant, so it must be expensive and therefore a buffer was added). If you’re interested in a brine-water heat pump with probe, just call two drilling companies. Getting a price indication with heating load takes 5 minutes on the phone.I have a concrete offer for deep drilling. 160 meters (2x80m) – going deeper than 100 meters has other consequences.
Progress subsidy is 10 euros per drilling meter. In addition, there is a 4,500 subsidy from BAFA.
Alex85 schrieb:
Why do you have to increase insulation thickness by 8 cm when you barely miss the KfW55 standard? An extra 8 cm is significant. If it’s just barely missed, for EPS insulation it might be enough to switch to WLG032 (Neopor) without thicker insulation at all.
But KfW doesn’t really pay off anyway. Extra costs for the assessor and the loan conditions just became more expensive a few days ago and it’s definitely off the table for us.We are building a classic wall assembly with sand-lime brick, mineral wool insulation, an air gap, and facing brickwork. That results in 47 cm total thickness with 16 cm (6 inches) exterior wall insulation.
“Barely” means we undershoot the target for the average transmission heat loss by only 21.6%, whereas 30% would be required to meet the KfW55 standard.
matte1987 schrieb:
To be honest, the heating load seems quite high to me.
7.5 kW for 170 m² (about 1,830 ft²) is around 45 W/m² (about 13.9 Btu/h·ft²).
We are at 35...
Is there a basement or attic included that is not counted as living space?
What is your wall/roof assembly?
Could it also be that the mechanical ventilation system wasn’t considered and the ventilation heat loss increases the heating demand that much?The primary energy demand according to WSNW is 19 kWh/(m²·a) (about 6,000 Btu/(ft²·year)).
The footprint is just under 230 m² (about 2,475 ft²). Living area is 170 m² (about 1,830 ft²). It’s a 1.5-story house with an expanded attic.
matte1987 schrieb:
I would ask to see the heating load calculation... There is no heating load calculation yet. The 7.5 kW is a rough estimate from the company to produce an offer.
The exact calculation is to be made after the contract is awarded.
I am neither enthusiastic nor satisfied with this. It feels like “buying a pig in a poke.”