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?
D
Deliverer8 Jun 2018 09:04Tom, nobody is trying to talk you out of a gas heating system. If we had access to a gas connection here, I would have chosen one too...
But now I am quite satisfied with the air-to-water heat pump, as the heating costs have been low for the past two winters. In addition, the subsidies for almost 20 kWp photovoltaic systems will expire in the next few years. The electricity has to be used somewhere then...
But now I am quite satisfied with the air-to-water heat pump, as the heating costs have been low for the past two winters. In addition, the subsidies for almost 20 kWp photovoltaic systems will expire in the next few years. The electricity has to be used somewhere then...
Our residential development was established and sold by a subsidiary of Volksbank starting in 2013. The first houses were built around 2014. At that time, there was no question that gas connections were included in the infrastructure. However, many homeowners, especially in 2016-2017, chose to forgo gas. The gas supplier responded with a combined offer: take the connection and gas supply, and receive a 50% discount on the connection fee. Since then, the number of gas boilers has increased. Between 2017 and 2018, all new houses were equipped with boilers. Anyone doing the math would come to the same conclusion. The chimney sweep charges €96 every two years, which is negligible. Electricity prices in Schleswig-Holstein are moderately priced. My tariff with E.ON is €10 per month basic fee plus €0.32 per kWh. There are cheaper options with other providers, but currently we are tied to E.ON due to the low combined gas tariff. Here, the basic fee is €5.00 per month plus €0.048 per kWh. Karsten
Thanks for the many tips, suggestions, and ideas. I think it will now come down to KFW 55 with gas, solar thermal, underfloor heating, and ventilation. The only uncertainty I still have is with the ventilation. For me, window frame ventilation is definitely out. In your opinion, is a decentralized ventilation system only in the wet rooms sufficient? That would be the utility room, kitchen, and bathroom downstairs, and the bathroom upstairs. That might be a bit weak, right?
I’m facing the same decision as the original poster, but for us, the background is more financial:
We’re both in our late 30s or early 40s, so the house needs to be paid off within 20 years without the monthly payment causing sleepless nights.
Underfloor heating is a must for us, as well as a mechanical ventilation system with heat recovery.
Condensing gas boilers are the standard offered by the builder. An air-source heat pump adds about €10,000–12,000 (around $11,000–13,000) to the price, which I consider excessive.
Gas is available right at the property line, and the gas connection to the house costs only €399 ($430) because it’s subsidized by the utility company.
With the extra cost of the heat pump, I could buy a lot of gas instead. However, I am planning to size the underfloor heating for a possible future switch to an air-source heat pump.
My question is this: since I don’t fully understand all the KfW (German energy efficiency) requirements, can I achieve KfW 55 efficiency with just a condensing gas boiler and a mechanical ventilation system with heat recovery? Or is solar thermal heating also absolutely necessary to secure KfW 55 status?
At the same time, for comfort reasons, we’d like a circulation system. However, according to the builder, that could cause the loss of KfW 55 certification. Or, in a bungalow with 110m² (1,184 sq ft), one bathroom, and a guest WC, can we safely do without a circulation system?
I don’t fully trust the so-called “3-liter rule” shown on paper/the installation plan regarding the actual pipe routing and sizing on site...
Well, many questions remain...
We’re both in our late 30s or early 40s, so the house needs to be paid off within 20 years without the monthly payment causing sleepless nights.
Underfloor heating is a must for us, as well as a mechanical ventilation system with heat recovery.
Condensing gas boilers are the standard offered by the builder. An air-source heat pump adds about €10,000–12,000 (around $11,000–13,000) to the price, which I consider excessive.
Gas is available right at the property line, and the gas connection to the house costs only €399 ($430) because it’s subsidized by the utility company.
With the extra cost of the heat pump, I could buy a lot of gas instead. However, I am planning to size the underfloor heating for a possible future switch to an air-source heat pump.
My question is this: since I don’t fully understand all the KfW (German energy efficiency) requirements, can I achieve KfW 55 efficiency with just a condensing gas boiler and a mechanical ventilation system with heat recovery? Or is solar thermal heating also absolutely necessary to secure KfW 55 status?
At the same time, for comfort reasons, we’d like a circulation system. However, according to the builder, that could cause the loss of KfW 55 certification. Or, in a bungalow with 110m² (1,184 sq ft), one bathroom, and a guest WC, can we safely do without a circulation system?
I don’t fully trust the so-called “3-liter rule” shown on paper/the installation plan regarding the actual pipe routing and sizing on site...
Well, many questions remain...
Similar topics