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.
Thank you all for the valuable discussion. It has definitely helped me make significant progress!
I have understood this much. The idea was to use electric underfloor heating instead of temporary supplemental heating by electric towel warmers or infrared heaters. Thanks to you, I now realize that this is neither energy-efficient nor economical!
Since we are building to KfW 40 Plus standards, we are logically planning for a 7.5 kWp photovoltaic system + 7.5 kWh battery storage, so that ideally the general electricity demand is fully covered and the heat pump electricity demand is partially met by self-generated power:
Self-consumption about 4,000 kWh (1,800 kWh direct use + 2,200 kWh from battery storage)
Total electricity consumption about 6,500 kWh (3,500 kWh general use + 3,000 kWh heat pump) minus 4,000 kWh self-consumption = 2,500 kWh at heat pump electricity tariff = 525.15 EUR per year or 43.76 EUR per month according to an online comparison portal.
Too good to be true?
After our discussion here, my feeling is that it now makes the most sense to continue planning with an air-to-water heat pump and underfloor heating, and to control the supplementary heating in the master and kids’ bathrooms, for example, with infrared mirror heaters.
Mycraft schrieb:
@DaSch17
In addition to everything already mentioned, keep in mind that every extra degree of indoor temperature in winter directly impacts your wallet. Manufacturers usually only provide consumption values for the commonly used 19, 21, or 22°C (66, 70, or 72°F). Sorry, but that is not warm enough for everyone in winter. The supposed "savings" from turning off heating in some rooms actually cause the opposite effect because the surrounding rooms then need more heat, effectively heating the unheated spaces (since the entire building envelope is heated). For example, an electric underfloor heating system in bathrooms (in a non-passive house) is a bad idea — unless there is also a conventional underfloor heating system installed underneath to provide basic warmth.
Hot water consumption has already been mentioned. Every liter (approximately 0.26 gallons) counts here as well. It’s best to install as much heat recovery as possible.
No question, heat pumps are great technology — if the house, location, and user behavior are suitable.
T_im_Norden schrieb:
Yes and no, because you still need to supply the same amount of heat to the room, and the supply temperatures are the same as with a regular underfloor heating system.
Since electric underfloor heating often has little or no screed coverage, the heat transfer distance is shorter and it heats very little thermal mass (screed).
That means the room cools down faster when the heating is off, and the heat is transferred more quickly to the room when it’s on. I can't say exactly by how much it’s faster, but due to the low supply temperatures, I don’t think the difference is very large.
I have understood this much. The idea was to use electric underfloor heating instead of temporary supplemental heating by electric towel warmers or infrared heaters. Thanks to you, I now realize that this is neither energy-efficient nor economical!
Since we are building to KfW 40 Plus standards, we are logically planning for a 7.5 kWp photovoltaic system + 7.5 kWh battery storage, so that ideally the general electricity demand is fully covered and the heat pump electricity demand is partially met by self-generated power:
Self-consumption about 4,000 kWh (1,800 kWh direct use + 2,200 kWh from battery storage)
Total electricity consumption about 6,500 kWh (3,500 kWh general use + 3,000 kWh heat pump) minus 4,000 kWh self-consumption = 2,500 kWh at heat pump electricity tariff = 525.15 EUR per year or 43.76 EUR per month according to an online comparison portal.
Too good to be true?
After our discussion here, my feeling is that it now makes the most sense to continue planning with an air-to-water heat pump and underfloor heating, and to control the supplementary heating in the master and kids’ bathrooms, for example, with infrared mirror heaters.
T
T_im_Norden23 Jul 2020 12:06Regarding heating system planning:
Underfloor heating -> Proper planning is the most important aspect; any mistakes made here cannot be corrected afterwards. Low supply temperatures, sufficiently large heated areas, bathrooms possibly with wall heating.
Therefore, study the topic carefully.
Heat generator -> Suitable for the building’s energy demand, with modulating technology and as low a minimum output as possible.
Underfloor heating -> Proper planning is the most important aspect; any mistakes made here cannot be corrected afterwards. Low supply temperatures, sufficiently large heated areas, bathrooms possibly with wall heating.
Therefore, study the topic carefully.
Heat generator -> Suitable for the building’s energy demand, with modulating technology and as low a minimum output as possible.
DaSch17 schrieb:
Since we are building to KfW 40 Plus standards, we are logically planning with 7.5 kWp photovoltaic panels plus a 7.5 kWh battery storage system, so that ideally, the general electricity demand is fully and....Why only 7.5 kWp? Fully covering your roof should be your goal.
Lumpi_LE schrieb:
3 MWh for heating seems quite a lot, or are you building a palace?
Otherwise, make the photovoltaic system as large as possible and not just 7.5 kWp.
A special electricity tariff for heat pumps is usually pointless. 180 m² (1937 sq ft) living area
T_im_Norden schrieb:
Regarding heating design:
Underfloor heating -> Proper planning is the most important; any mistakes here cannot be easily corrected later.
Low flow temperatures, sufficiently heated surface area, possibly wall heating in bathrooms.
Therefore, study the topic carefully.
Heat generator -> Should match the building’s energy demand, use modulating technology, and have as low a minimum output as possible. So, instead of infrared heating, could you hang a standard water-based flat panel radiator in the bathrooms and connect it to the heat pump system?
Heinz2k schrieb:
Why only 7.5 kWp? Your principle should be to cover the whole roof. We were told that if the photovoltaic system is too large, you overproduce energy which essentially goes to waste once the battery storage is full (especially in the warmer months). Also, I read somewhere that the ratio between battery storage and photovoltaic capacity should be about 1 kWp = 1 kWh.
So should we go for a larger photovoltaic system after all?
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