ᐅ KfW40 house offer with heat pump and mechanical ventilation with heat recovery— is it worth it?
Created on: 25 May 2019 21:19
Q
querys_
Hello everyone,
Today I received a house offer from a prefabricated house supplier.
They list the exhaust air heat pump Nibe F 750 with supply air module SAM 40 as the heating system. The maximum building heating load is said to be 7.5 kW.
Additionally, there is underfloor heating and a 180 L (48 gallon) domestic hot water storage tank.
The house is located near Cologne/Bonn Airport (for climate reference) and is about 120 m² (1,290 sq ft) in size (excluding the basement).
I have already read a lot of negative things about exhaust air heat pumps, so I want to ask again if this system is any good, and if not, what would be an alternative and how much more would that cost?
Thank you very much!
Today I received a house offer from a prefabricated house supplier.
They list the exhaust air heat pump Nibe F 750 with supply air module SAM 40 as the heating system. The maximum building heating load is said to be 7.5 kW.
Additionally, there is underfloor heating and a 180 L (48 gallon) domestic hot water storage tank.
The house is located near Cologne/Bonn Airport (for climate reference) and is about 120 m² (1,290 sq ft) in size (excluding the basement).
I have already read a lot of negative things about exhaust air heat pumps, so I want to ask again if this system is any good, and if not, what would be an alternative and how much more would that cost?
Thank you very much!
B
boxandroof27 May 2019 09:25querys_ schrieb:
I think that with these values, a ground source heat pump would be too expensive.Yes, that's true for deep drilling. A horizontal ground collector could still be an option: Similar costs thanks to subsidies and doing the installation yourself. Slightly nicer technology and a slightly lower energy consumption.B
boxandroof27 May 2019 09:27querys_ schrieb:
This is what was listed on the homepage.You need the H't value of the house. You are missing windows, floor, and thermal bridge allowances. In the end, about 1.x kW will be added.Either way, 4 kW is enough if the controlled ventilation system is installed—and probably otherwise as well—but then not according to calculations.
Inform yourself about the planning of the underfloor heating.
querys_ schrieb:
That is what was stated on the homepage.Yes, the U-value of the walls is 0.148.The HT value according to the Crinks tool is something completely different.
For this house, it should be between 0.25 and 0.3.
Ah, okay, thanks for explaining.
But even with 0.3, everything is still acceptable. Instead of 1500 W transmission load, you then end up with about 3000 W.
Controlled ventilation is desirable because the property borders the A3 highway to the west.
A closed-loop trench collector probably won’t work for this property (No. 231), according to the "Geothermal Portal" of NRW. The brief statement on this is "too shallow."
But even with 0.3, everything is still acceptable. Instead of 1500 W transmission load, you then end up with about 3000 W.
Controlled ventilation is desirable because the property borders the A3 highway to the west.
A closed-loop trench collector probably won’t work for this property (No. 231), according to the "Geothermal Portal" of NRW. The brief statement on this is "too shallow."
Is it actually possible to calculate the electricity consumption based on the total heating load?
With an estimated 12,000 kWh of heat, the gas cost (just as a comparison) would be around 800 euros per year, and for electricity at 4,000 kWh it would be just under 1,000 euros on a heat pump tariff, and with a “regular” electricity tariff slightly more than 1,000 euros.
Or is this calculation incorrect?
With an estimated 12,000 kWh of heat, the gas cost (just as a comparison) would be around 800 euros per year, and for electricity at 4,000 kWh it would be just under 1,000 euros on a heat pump tariff, and with a “regular” electricity tariff slightly more than 1,000 euros.
Or is this calculation incorrect?
Just roughly. But KFW40 for 120m² (1300ft²) is way too much at 12,000 kWh, and with a heat pump you don’t get a factor of 3 but more like 4, so around 3,000 kWh.
Also, with gas, you still have the chimney sweep cost.
For 120m² (1300ft²), with the described house, not in an exposed location, no heavy shading, and normal heating behavior, it’s probably closer to 7,000 kWh.
So around €450 gas including the base fee + about €100 chimney sweep.
Electricity would also be around €450, but without additional costs.
Also, with gas, you still have the chimney sweep cost.
For 120m² (1300ft²), with the described house, not in an exposed location, no heavy shading, and normal heating behavior, it’s probably closer to 7,000 kWh.
So around €450 gas including the base fee + about €100 chimney sweep.
Electricity would also be around €450, but without additional costs.
Similar topics