ᐅ New Single-Family Home Built to KfW55 Standard – Which Heating System to Choose?
Created on: 19 Jul 2020 12:19
T
Traube348
Hello everyone,
I have read many articles and would now like to benefit from the extensive knowledge of the members here.
A brief overview of my building project:
- Single-family house with approximately 160sqm (1,722 sq ft) of living space
- No basement, 2 full floors with an unfinished attic
- Relatively large window areas and an open-plan design with a staircase in the living area
- Underfloor heating throughout the house with tile flooring
- KfW 55 standard with timber frame construction
- A wood-burning stove will be installed
Unfortunately, I have little experience in this area and rely on recommendations from others regarding heating.
On the ground floor, we have a utility room of 8sqm (86 sq ft) where we would like to accommodate all the technical equipment.
The builder recommends installing a central ventilation system, which we would like to do.
Now to my question:
There is a gas connection in our building area, and a friend told me we should definitely heat with a gas boiler. To meet the KfW standard, according to the energy consultant, we still need to install 9sqm (97 sq ft) of solar panels on the roof.
A heating engineer friend advises: choose an air-to-water heat pump – split system Weishaupt LS 8-BREK – so you can avoid the solar requirement.
I have requested quotes for both options from different heating engineers, and they come out roughly the same in price.
Since I have heard many statements opposing air-to-water heat pumps, I tend to prefer gas.
However, the main challenge is the limited space in the utility room. In addition to the heating system, the two-flue fireplace, and the ventilation system, the electrical control cabinet as well as the washing machine and dryer are also planned to be located there.
Is there anyone who has faced a similar space issue?
What would you recommend?
Thank you very much in advance for your help.
I have read many articles and would now like to benefit from the extensive knowledge of the members here.
A brief overview of my building project:
- Single-family house with approximately 160sqm (1,722 sq ft) of living space
- No basement, 2 full floors with an unfinished attic
- Relatively large window areas and an open-plan design with a staircase in the living area
- Underfloor heating throughout the house with tile flooring
- KfW 55 standard with timber frame construction
- A wood-burning stove will be installed
Unfortunately, I have little experience in this area and rely on recommendations from others regarding heating.
On the ground floor, we have a utility room of 8sqm (86 sq ft) where we would like to accommodate all the technical equipment.
The builder recommends installing a central ventilation system, which we would like to do.
Now to my question:
There is a gas connection in our building area, and a friend told me we should definitely heat with a gas boiler. To meet the KfW standard, according to the energy consultant, we still need to install 9sqm (97 sq ft) of solar panels on the roof.
A heating engineer friend advises: choose an air-to-water heat pump – split system Weishaupt LS 8-BREK – so you can avoid the solar requirement.
I have requested quotes for both options from different heating engineers, and they come out roughly the same in price.
Since I have heard many statements opposing air-to-water heat pumps, I tend to prefer gas.
However, the main challenge is the limited space in the utility room. In addition to the heating system, the two-flue fireplace, and the ventilation system, the electrical control cabinet as well as the washing machine and dryer are also planned to be located there.
Is there anyone who has faced a similar space issue?
What would you recommend?
Thank you very much in advance for your help.
Lumpi_LE schrieb:
For an air-to-water heat pump in a KfW55 house, 175 liters (46 gallons) is definitely too small.
We have 300 liters (79 gallons), 2 adults, 2 children – and usually, that’s not enough for 24 hours. With gas, it doesn’t matter because it simply reheats. With an air-to-water heat pump, especially when combined with photovoltaics, you want to use midday heat and sunlight. Also, a heat pump can’t recharge the storage tank in just 15 minutes. Our house will probably be built to KfW40plus standards. We’re not big bath users. From what I’ve read on various sites, 175 liters (46 gallons) should be sufficient.
Tolentino schrieb:
You are both talking about hot water storage tanks. @Joedreck is referring to (gas boiler +) solar thermal systems, while you are probably referring to an air-to-water heat pump (possibly combined with photovoltaic, but that is independent). Joedreck explains in the post you quoted why the hot water tank needs to be properly sized for solar thermal systems.
This is irrelevant if solar thermal is not used. Thank you for the clarification
H
hampshire20 Jul 2020 15:38We have an approximately 200-liter (53 gallons) heat pump water heater for two people. The children’s apartments each have a tankless water heater – once the boys move out, these units will only be used occasionally, as an office, guest room, or holiday apartment, and when we are older, as a ground-floor, accessible bedroom or apartment for a “life assistant.” In other words: mixing systems is also possible.
As always, the sizing depends on both the demand and the technology used, as @Tolentino and @Joedreck write.
We found the KfW standards unsuitable for us and therefore built independently of them.
As always, the sizing depends on both the demand and the technology used, as @Tolentino and @Joedreck write.
We found the KfW standards unsuitable for us and therefore built independently of them.
P
pagoni202020 Jul 2020 15:54So, in our old house, we had a 200-liter (about 53 gallons) storage tank for hot water with a 2+2 setup, plus our parents living in the separate apartment. The oil heater back then probably heated the water much faster than a heat pump does today (at least that's what I assume), right? However, in 25 years, we never had a single hot water issue.
I think when one person is bathing, usually no one else is showering at the same time, and even if that happens, 200 liters is quite a lot. As I said, it really depends heavily on individual usage patterns, as in most cases.
In recent years, we also installed solar panels for hot water on the roof, but the storage tank was not enlarged, it stayed at 200 liters. During summer, the solar system would sometimes release some water, but in the end, that didn’t cause any problems. At least, that was my experience and the information provided by the heating engineer.
Of course, it might feel nice to have a buffer tank, but you have to reheat that buffer every time, even if you only need it in extreme, rare cases. In my opinion, that doesn’t make much sense.
I think when one person is bathing, usually no one else is showering at the same time, and even if that happens, 200 liters is quite a lot. As I said, it really depends heavily on individual usage patterns, as in most cases.
In recent years, we also installed solar panels for hot water on the roof, but the storage tank was not enlarged, it stayed at 200 liters. During summer, the solar system would sometimes release some water, but in the end, that didn’t cause any problems. At least, that was my experience and the information provided by the heating engineer.
Of course, it might feel nice to have a buffer tank, but you have to reheat that buffer every time, even if you only need it in extreme, rare cases. In my opinion, that doesn’t make much sense.
Ybias78 schrieb:
What are the costs for such a system? Is 20,000 € enough? All in, including installation, scaffolding, planning and permitting, accessories, etc., it was 18,000 € net.
With an air-to-water heat pump, you can often end up paying double the heating costs in a new building compared to gas, even with correct pipe spacing and heat load calculation. Only through personal optimization can this be balanced out. It’s unfortunate but often the reality.
Actually, the best heating technology is still pellets. Reliable, affordable, and flexible. Underground storage tank in the garden, ready to go.
With a heat pump, you also face the major risk of electricity price increases. No energy source becomes more expensive as quickly as electricity.
Actually, the best heating technology is still pellets. Reliable, affordable, and flexible. Underground storage tank in the garden, ready to go.
With a heat pump, you also face the major risk of electricity price increases. No energy source becomes more expensive as quickly as electricity.
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