ᐅ Is nighttime temperature setback still effective in a KfW 55 apartment?
Created on: 11 Nov 2024 10:52
K
KaEfWehHello everyone,
Last year, we bought an apartment in a six-unit building that was completely renovated to meet the KFW55 energy efficiency standard. The apartment is located on the first floor (1st floor) and is well insulated within the building, with heated units both above and below.
Unfortunately, district heating with standard radiators was installed, so there is no underfloor heating. We can still easily reach 22°C (72°F) on thermostat setting 3, so everything is fine for now.
Our district heating transfer station in the basement was adjusted by the installer to reduce the flow temperature during the night setback period from 10 p.m. to 6 a.m., which means the supply temperature is lowered accordingly. I’m wondering whether this really leads to any significant energy savings in such a well-insulated building.
Measuring this directly is not as straightforward with district heating as it is with a heat pump, where I can simply log electricity consumption. Therefore, I would be interested in hearing about practical experiences—does it make more sense to keep the heating running continuously once a certain insulation standard is reached?
The installer says the night setback makes sense, but since this is a makeshift installation, I wouldn’t be surprised if it was set that way just because “that’s how it’s always been done.”
Last year, we bought an apartment in a six-unit building that was completely renovated to meet the KFW55 energy efficiency standard. The apartment is located on the first floor (1st floor) and is well insulated within the building, with heated units both above and below.
Unfortunately, district heating with standard radiators was installed, so there is no underfloor heating. We can still easily reach 22°C (72°F) on thermostat setting 3, so everything is fine for now.
Our district heating transfer station in the basement was adjusted by the installer to reduce the flow temperature during the night setback period from 10 p.m. to 6 a.m., which means the supply temperature is lowered accordingly. I’m wondering whether this really leads to any significant energy savings in such a well-insulated building.
Measuring this directly is not as straightforward with district heating as it is with a heat pump, where I can simply log electricity consumption. Therefore, I would be interested in hearing about practical experiences—does it make more sense to keep the heating running continuously once a certain insulation standard is reached?
The installer says the night setback makes sense, but since this is a makeshift installation, I wouldn’t be surprised if it was set that way just because “that’s how it’s always been done.”
Lower average indoor temperature due to a nighttime setback initially means less heat demand in kWh.
A nighttime setback can be omitted if thermal mass (such as underfloor heating) causes a delay, or if the setback simply does not occur.
An actual reduction in room temperature only happens if the heating curve is set so that the nighttime heating water temperature is low enough that the provided room heat is indeed lower than what is required for the normal target room temperature.
Practical example: If the daytime supply temperature is set to 50°C (122°F), but 40°C (104°F) would be sufficient, a nighttime setback of 10 K (10°C / 18°F) in the room makes no difference and therefore no energy savings.
The downside of a nighttime setback is seen in systems that suffer significant efficiency losses at the higher supply temperatures needed during reheating because a higher heating water temperature is required.
Due to the supply water connection, the control of your supply temperature is relatively irrelevant to efficiency and the required heat demand in kWh. The heat meter only measures the difference multiplied by cubic meters.
With a correctly adjusted heating curve, a small saving from a nighttime setback may be possible even in a KfW 50 standard building. However, this is paid for by lower room temperatures. The absolute savings, though, will be low.
A nighttime setback can be omitted if thermal mass (such as underfloor heating) causes a delay, or if the setback simply does not occur.
An actual reduction in room temperature only happens if the heating curve is set so that the nighttime heating water temperature is low enough that the provided room heat is indeed lower than what is required for the normal target room temperature.
Practical example: If the daytime supply temperature is set to 50°C (122°F), but 40°C (104°F) would be sufficient, a nighttime setback of 10 K (10°C / 18°F) in the room makes no difference and therefore no energy savings.
The downside of a nighttime setback is seen in systems that suffer significant efficiency losses at the higher supply temperatures needed during reheating because a higher heating water temperature is required.
Due to the supply water connection, the control of your supply temperature is relatively irrelevant to efficiency and the required heat demand in kWh. The heat meter only measures the difference multiplied by cubic meters.
With a correctly adjusted heating curve, a small saving from a nighttime setback may be possible even in a KfW 50 standard building. However, this is paid for by lower room temperatures. The absolute savings, though, will be low.
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