Hello everyone,
we are currently building – at the moment we are dealing with the heating system. Our energy consultant calculated the energy demand of our house (which is supposed to meet KfW 70 standards), and we took this information to the heating installer. We received an offer for a heating system that feels oversized to me.
My question/request at this point is whether anyone can assess if the system is reasonably sized or not...
According to the energy certificate, the house will have a final energy demand (per year) of 8.6 kWh/m² (2.7 kWh/ft²) for heating and 6.1 kWh/m² (1.9 kWh/ft²) for hot water. The building volume is just under 1000 m³ (35,315 ft³) and the usable floor area is given as 319 m² (3,434 ft²).
The heating system is supposed to be a brine/water heat pump (using deep geothermal boreholes) that heats via underfloor heating. An offer was made for a 14 kW heat pump...
Can anyone estimate from these values whether a 14 kW heat pump is correctly sized? Is it even possible for the heating installer to size the system based on this information, or are important details missing?
Thank you very much for your help!!!
Bonagel
we are currently building – at the moment we are dealing with the heating system. Our energy consultant calculated the energy demand of our house (which is supposed to meet KfW 70 standards), and we took this information to the heating installer. We received an offer for a heating system that feels oversized to me.
My question/request at this point is whether anyone can assess if the system is reasonably sized or not...
According to the energy certificate, the house will have a final energy demand (per year) of 8.6 kWh/m² (2.7 kWh/ft²) for heating and 6.1 kWh/m² (1.9 kWh/ft²) for hot water. The building volume is just under 1000 m³ (35,315 ft³) and the usable floor area is given as 319 m² (3,434 ft²).
The heating system is supposed to be a brine/water heat pump (using deep geothermal boreholes) that heats via underfloor heating. An offer was made for a 14 kW heat pump...
Can anyone estimate from these values whether a 14 kW heat pump is correctly sized? Is it even possible for the heating installer to size the system based on this information, or are important details missing?
Thank you very much for your help!!!
Bonagel
Here is my input on this topic. I would appreciate your assessment:
Our air-to-water heat pump has a capacity range of 3.5 to 7.0 kW.
We built a solid, energy-saving standard house without controlled ventilation, with (including basement) 226 heated square meters (2,433 square feet). No KfW funding. Underfloor heating. Household of 4 people.
The heating system seems undersized to me. Am I correct? Neighbors have smaller houses and larger units from the same manufacturer.
The installer calculated a standard building heating load of 7,828 W, which is more than what the air-to-water heat pump can provide. The domestic hot water heating is not yet included, as far as I understand the calculation.
Have I misunderstood something, or has the installer really undersized the system?
Can I insist on an upgrade?
I am concerned about high electricity costs due to frequent use of the electric backup heater.
Thanks in advance.
Our air-to-water heat pump has a capacity range of 3.5 to 7.0 kW.
We built a solid, energy-saving standard house without controlled ventilation, with (including basement) 226 heated square meters (2,433 square feet). No KfW funding. Underfloor heating. Household of 4 people.
The heating system seems undersized to me. Am I correct? Neighbors have smaller houses and larger units from the same manufacturer.
The installer calculated a standard building heating load of 7,828 W, which is more than what the air-to-water heat pump can provide. The domestic hot water heating is not yet included, as far as I understand the calculation.
Have I misunderstood something, or has the installer really undersized the system?
Can I insist on an upgrade?
I am concerned about high electricity costs due to frequent use of the electric backup heater.
Thanks in advance.
It depends on how the calculation was done, as well as how your house is positioned and oriented, how often you are at home, where your house is located, and so on...
In general, you can say that it works if the calculation is correct. If an air-to-water heat pump is oversized, it will short cycle frequently, and you will end up using more electricity.
Skipping a mechanical ventilation system with heat recovery is definitely a mistake; in that case, you should be careful not to over-ventilate when it’s around -16°C (3°F).
I have a heating load of 5400 W, the pump is 5 kW, and it hasn’t needed that full power even for a few days at -14°C (7°F).
In general, you can say that it works if the calculation is correct. If an air-to-water heat pump is oversized, it will short cycle frequently, and you will end up using more electricity.
Skipping a mechanical ventilation system with heat recovery is definitely a mistake; in that case, you should be careful not to over-ventilate when it’s around -16°C (3°F).
I have a heating load of 5400 W, the pump is 5 kW, and it hasn’t needed that full power even for a few days at -14°C (7°F).
How many square meters do you have?
We installed 4 decentralized ventilation units for peace of mind. However, I don't think we will miss having a mechanical ventilation system with heat recovery. We wanted to build conservatively. Poroton bricks. Natural hydraulic lime plaster everywhere. No external thermal insulation composite system (ETICS) / no external wall insulation. My wife ventilates diligently. The indoor climate should be fine.
We installed 4 decentralized ventilation units for peace of mind. However, I don't think we will miss having a mechanical ventilation system with heat recovery. We wanted to build conservatively. Poroton bricks. Natural hydraulic lime plaster everywhere. No external thermal insulation composite system (ETICS) / no external wall insulation. My wife ventilates diligently. The indoor climate should be fine.
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