Hello,
we would like to build a one-and-a-half-story single-family house with about 125 sqm (1,345 sq ft) plus additional development space in the attic. Without a basement but with a 9 m (30 ft) garage.
We have a plot of land in sight, which we hope to reserve by May. We have already had several appointments with construction companies, including TaC, a developer from Krefeld, and one from Sonsbeck. I feel increasingly uncertain. Both developers offer roughly the same concept, but their prices differ significantly. One says that a ventilation system is not necessary for a KfW 55 solid construction house, while the other says it is very important. I am completely confused. Intuitively, the developer from Sonsbeck was our favorite—until we saw the cost estimate.
It is just too expensive! With TaC, the costs are within our budget, but opinions about the company are mixed.
Does anyone have experience in the NRW area?
Best regards
we would like to build a one-and-a-half-story single-family house with about 125 sqm (1,345 sq ft) plus additional development space in the attic. Without a basement but with a 9 m (30 ft) garage.
We have a plot of land in sight, which we hope to reserve by May. We have already had several appointments with construction companies, including TaC, a developer from Krefeld, and one from Sonsbeck. I feel increasingly uncertain. Both developers offer roughly the same concept, but their prices differ significantly. One says that a ventilation system is not necessary for a KfW 55 solid construction house, while the other says it is very important. I am completely confused. Intuitively, the developer from Sonsbeck was our favorite—until we saw the cost estimate.
It is just too expensive! With TaC, the costs are within our budget, but opinions about the company are mixed.
Does anyone have experience in the NRW area?
Best regards
Primary energy is completely irrelevant since you don’t pay for it.
The correct calculation is as follows. If you use 1 kWh of electricity and save 20 kWh of thermal energy, but the air-source heat pump has a seasonal performance factor (SPF) of 3.5, then you actually save only (!!!) 5.7 kWh of electricity per each kWh of electricity consumed by the mechanical ventilation system.
Links, sources, etc. are not allowed here. On Visionair’s website, a ratio of 1 to 25 is stated, and Manfred Lusch says the following: approximately 1 to 25 up to 1 to 40.
Ratios of 1 to 15 to 1 to 20 are more realistic experience values, which are also used for calculations in the pink forum, among others.
The correct calculation is as follows. If you use 1 kWh of electricity and save 20 kWh of thermal energy, but the air-source heat pump has a seasonal performance factor (SPF) of 3.5, then you actually save only (!!!) 5.7 kWh of electricity per each kWh of electricity consumed by the mechanical ventilation system.
Links, sources, etc. are not allowed here. On Visionair’s website, a ratio of 1 to 25 is stated, and Manfred Lusch says the following: approximately 1 to 25 up to 1 to 40.
Ratios of 1 to 15 to 1 to 20 are more realistic experience values, which are also used for calculations in the pink forum, among others.
B
bierkuh833 May 2017 22:23Grym schrieb:
In a typical existing house with double glazing and poor window frames, uninsulated walls, poorly insulated roof, etc., the 20% figure is accurate. In a modern house built to the 2016 energy saving regulation standard with maximum insulation but still relying on normal window ventilation, you can expect at least 30%, and more likely up to 50%.I like that because I enjoy numbers like these. I also have a few. I could save a bazillion quark-crystals by ignoring the specific heat capacities of air compared to screed, masonry, and plaster, switching off the warp drive in the Delta Quadrant, and instead getting hypertranscided by the controlled mechanical ventilation inverter. By the way, KFW0 is free for that.
T
toxicmolotof3 May 2017 22:30This is exactly where it gets interesting.
So, we stick with 17.5 kWh of thermal energy and instead of an air-to-water heat pump, we use a ground-source heat pump with an annual performance factor of 4.5... This way, we are slowly approaching parity. Now add a house that already requires little heating energy (insulation), and the mechanical ventilation system will soon use more energy than the heating itself.
So, we stick with 17.5 kWh of thermal energy and instead of an air-to-water heat pump, we use a ground-source heat pump with an annual performance factor of 4.5... This way, we are slowly approaching parity. Now add a house that already requires little heating energy (insulation), and the mechanical ventilation system will soon use more energy than the heating itself.
toxicmolotow schrieb:
This is exactly where it gets interesting.
So, let's stick with 17.5 kWh (6,300 BTU) of thermal energy and instead of an air-to-water heat pump, consider a ground-source (geothermal) heat pump with a seasonal performance factor (SPF) of 4.5... We are slowly approaching break-even. Now, if the house requires very little heating energy anyway (due to insulation), the mechanical ventilation with heat recovery will soon use more energy than the heating system. 17.5 / 4.5 = 3.9 and not break-even.
How good or bad the insulation is would be completely and 100% irrelevant. Insulation changes 0.0 (exactly 0.0 — not just rhetoric) of the heat loss due to ventilation.
And even if it were a passive house with triple or quadruple glazing, 100 cm (39 inches) of EPS insulation, etc. — at best the ratio remains 1 to 3.9.
By the way, in my calculation above, I implicitly assumed a seasonal performance factor of 5.5 for the heat generator. Our current prices are 26.54 cents per kWh electricity and 4.82 cents per kWh gas. With a ground-source heat pump achieving an SPF of 4.5, the price for thermal energy would increase to 5.90 cents instead of 4.82 cents — 22.4% higher.
It gets really interesting when the light bulb goes on: the mechanical ventilation with heat recovery just covers its own costs — including financing, maintenance, and auxiliary energy — though only barely. The added comfort features and mold protection come free on top.
If energy prices rise in the future, or if the mechanical ventilation is used as a base load for photovoltaic self-consumption, the economic case shifts further in favor of mechanical ventilation with heat recovery. The comfort features and mold protection — yes, those remain free extras.
T
toxicmolotof3 May 2017 23:353.9 - 1 = 2.9... another step closer to break-even. And now add costs for maintenance and filters... let’s skip that. The calculation is getting tight (additional investment costs not considered).
We’ve already discussed comfort. It doesn’t exist.
Dust filters... fine, if you insist. But allergies seem to be increasing rather than decreasing. Need some disinfectant?
Also, a house without controlled mechanical ventilation doesn’t necessarily develop mold. So mold protection... fine, if you want. I have that without controlled mechanical ventilation as well. So it’s not a definitive argument either.
This is getting too detailed now. But self-consumption doesn’t make a photovoltaic system profitable for the owner. It only just balances out and doesn’t save a single cent. Controlled mechanical ventilation or not. I have a pool in the garden... I’m not saving any money from the photovoltaic system. If the system lasts 10 years, I’ll finally reach the point where savings begin.
We’ve already discussed comfort. It doesn’t exist.
Dust filters... fine, if you insist. But allergies seem to be increasing rather than decreasing. Need some disinfectant?
Also, a house without controlled mechanical ventilation doesn’t necessarily develop mold. So mold protection... fine, if you want. I have that without controlled mechanical ventilation as well. So it’s not a definitive argument either.
This is getting too detailed now. But self-consumption doesn’t make a photovoltaic system profitable for the owner. It only just balances out and doesn’t save a single cent. Controlled mechanical ventilation or not. I have a pool in the garden... I’m not saving any money from the photovoltaic system. If the system lasts 10 years, I’ll finally reach the point where savings begin.
B
bierkuh833 May 2017 23:45Come on, your discussion is just getting started... Please recalculate the potential savings for fixed glazing compared to the old windows with RC2 security rating... Opening windows is obsolete anyway... Then please consider sticking the insulation to the inside of the walls, so at least you don’t get hurt by the air gaps despite all the money saved...
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