Hello everyone. My partner and I are planning to build a house. About 140-150 square meters (1507-1615 square feet), 1.5 stories. After initially considering building a KfW 40 house, I quickly moved away from that idea. The general opinion seems to be that it’s not cost-effective (considering only the costs). So now we want to build according to KfW 55 standards.
Underfloor heating is planned throughout the entire house. However, despite extensive research, we are still uncertain about other details. For the standard KfW 55, a heat pump or a gas connection (then with a share of renewable energy) is mandatory, right?
What do you think is the best combination for KfW 55? I had originally planned on a ground source heat pump / geothermal system. But this seems somewhat oversized for a new build, doesn’t it? What technology would you recommend for an air-source heat pump?
Does it make sense to install a photovoltaic system (because of the additional electricity costs of the heat pump and generally) or solar thermal collectors? Would solar thermal still be mandatory if using a heat pump? With gas, solar thermal would be mandatory, right?
I’m also interested in your opinions on a controlled mechanical ventilation system. If yes, with or without heat recovery? I know the cost of the system does not pay off financially. But it’s a gain in comfort (no need to ventilate manually and you have fresh air). Does it offer any additional benefits? The filters would also reduce dirt like pollen, dust, etc. inside the house, right? Maybe someone has current experiences with these systems. I have read a lot, but mostly reports from 3-4 years ago.
Am I forgetting any important systems or options?
Underfloor heating is planned throughout the entire house. However, despite extensive research, we are still uncertain about other details. For the standard KfW 55, a heat pump or a gas connection (then with a share of renewable energy) is mandatory, right?
What do you think is the best combination for KfW 55? I had originally planned on a ground source heat pump / geothermal system. But this seems somewhat oversized for a new build, doesn’t it? What technology would you recommend for an air-source heat pump?
Does it make sense to install a photovoltaic system (because of the additional electricity costs of the heat pump and generally) or solar thermal collectors? Would solar thermal still be mandatory if using a heat pump? With gas, solar thermal would be mandatory, right?
I’m also interested in your opinions on a controlled mechanical ventilation system. If yes, with or without heat recovery? I know the cost of the system does not pay off financially. But it’s a gain in comfort (no need to ventilate manually and you have fresh air). Does it offer any additional benefits? The filters would also reduce dirt like pollen, dust, etc. inside the house, right? Maybe someone has current experiences with these systems. I have read a lot, but mostly reports from 3-4 years ago.
Am I forgetting any important systems or options?
The DIN standards and ventilation concepts: the fact is, a building completely without any mechanical ventilation is legal and is always accompanied by a building inspector’s note advising regular ventilation! For example, we received a kind of manual for the house that clearly states and explains this in the case of opting out of mechanical ventilation, including instructions on how to ventilate properly. This places the responsibility on the customer.
I want to emphasize again that I am not against controlled residential ventilation systems for comfort reasons. However, when it comes to saving money or needing to save money, the standard window-frame ventilation combined with an exhaust fan in the bathroom works sufficiently well at low cost. That’s just how it is. We have zero mold and good air quality in the house.
Regarding the geothermal heat pump versus gas heating:
The former may be technically advanced, but in practice these devices tend to be prone to faults. I see this firsthand in our residential area. Our children already needed factory customer service because the unit consumed electricity excessively yet didn’t provide sufficient heat. Our neighbor across the street has also had technicians come twice within a year because the water was too cold. In winter, the house wasn’t warm. I could continue with three more new builds, while all the old-fashioned, building-services-resistant gas heating owners just keep heating. “Keep it simple, rugged, reliable,” as the British rightly say.
About all the KfW stuff: The KfW scheme focuses only on energy saving to reduce CO2 emissions. The production of all those insulation boards, plastic films, and foam sleeves is not taken into account. Neither is human scale considered. The higher the KfW standard, the more extreme the plastic wrapping of the house. For passive houses, you’re practically not even allowed to open the windows anymore. Anyone who has spent a few days, like I have, in a meeting facility designed like this, where only artificial climate exists indoors, will agree with me: no, that’s not comfort.
Karsten
I want to emphasize again that I am not against controlled residential ventilation systems for comfort reasons. However, when it comes to saving money or needing to save money, the standard window-frame ventilation combined with an exhaust fan in the bathroom works sufficiently well at low cost. That’s just how it is. We have zero mold and good air quality in the house.
Regarding the geothermal heat pump versus gas heating:
The former may be technically advanced, but in practice these devices tend to be prone to faults. I see this firsthand in our residential area. Our children already needed factory customer service because the unit consumed electricity excessively yet didn’t provide sufficient heat. Our neighbor across the street has also had technicians come twice within a year because the water was too cold. In winter, the house wasn’t warm. I could continue with three more new builds, while all the old-fashioned, building-services-resistant gas heating owners just keep heating. “Keep it simple, rugged, reliable,” as the British rightly say.
About all the KfW stuff: The KfW scheme focuses only on energy saving to reduce CO2 emissions. The production of all those insulation boards, plastic films, and foam sleeves is not taken into account. Neither is human scale considered. The higher the KfW standard, the more extreme the plastic wrapping of the house. For passive houses, you’re practically not even allowed to open the windows anymore. Anyone who has spent a few days, like I have, in a meeting facility designed like this, where only artificial climate exists indoors, will agree with me: no, that’s not comfort.
Karsten
Tom1607 schrieb:
I didn’t say it was bad. It’s just more expensive than gas because 1 kW of heat from electricity costs around 30 cents and 1 kW of heat from gas costs about 6 cents. Since air-to-water heat pumps are also more expensive to install, you should keep that in mind. That’s all I wanted to say, no more or less.That statement is quite misleading.
Depending on the air-to-water heat pump and electricity tariff, a kWh costs between 5 and 10 cents.
You don’t even pay 30 cents for a kWh of electricity alone...
D
Deliverer7 Jun 2018 15:12Lumpi_LE schrieb:
You don’t even pay 30 cents for a single kilowatt-hour of electricity...Actually, you do. Nowadays, you really have to search hard to find a cheaper rate once you include basic fees.
Tom1607 schrieb:
I never said it was bad. It’s just more expensive than gas because 1 kWh of heat from electricity costs around 30 cents, while 1 kWh of heat from gas costs about 6 cents. Since an air-to-water heat pump is also more expensive to purchase, this should be taken into account. That’s all I wanted to say, no more and no less. This does not consider that the air-to-water heat pump upgrades 1 kWh of electricity to produce 3-4 kWh of heat. It’s not just an electric heater; it’s a heat pump! However, it should be clear to everyone that very little heat can be extracted from air at -20°C (−4°F), which causes the seasonal performance factor (SPF) to drop to very poor values. Still, SPF values around 2-3 should be expected.
Tom1607 schrieb:
I didn’t say it was bad. It’s just more expensive than gas because 1 kW of heat from electricity costs about 30 cents, while 1 kW of heat from gas costs about 6 cents. Since air-to-water heat pumps are also more expensive to buy, you should keep that in mind. That’s all I wanted to say, nothing more and nothing less.I see. So your claim is that in winter, the air-to-water heat pump basically runs continuously on the electric heating element? That would of course be nonsense and has nothing to do with reality.
It is often claimed that you will end up using a lot of electricity to heat in winter, blaming the so-called “demon” electric heating element. It is true that the heating element comes into play at temperatures between -10 and -16 degrees Celsius (14 and 3 degrees Fahrenheit). However, please also consider how often this actually occurred in recent winters. The instances of continuous heating with the electric element are negligible. Winters tend to be getting milder overall, so the likelihood of having to rely on the inefficient heating element (which it is, indeed) is also decreasing.
Yes, gas is cheaper and has proven, reliable technology, and there is nothing wrong with that. It is one possible solution, but certainly not the only one. Demonizing heat pumps (air-to-water heat pumps) is not a valid approach.
Yes, gas is cheaper and has proven, reliable technology, and there is nothing wrong with that. It is one possible solution, but certainly not the only one. Demonizing heat pumps (air-to-water heat pumps) is not a valid approach.
Similar topics