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?
From a strictly economic perspective, only the minimum standard of the Energy Saving Ordinance (EnEV) makes sense. For example, our house was built with 163mm (6.4 inches) 30 Ytong blocks, plus Weber lightweight plaster and a silicone resin paint finish. It has triple-glazed windows and underfloor heating. This means it only meets the minimum standard of the Energy Saving Ordinance. Now, we are upgrading it to KfW 55 standard. That means 365mm (14.4 inches) Ytong blocks, resulting in a larger foundation or smaller rooms. We are replacing the gas heating system with an air-to-water heat pump. Blower door test included.
The additional cost is around 20,000 euros. Heating cost savings are about 100 euros per year, [emoji3] do the math yourself.
The additional cost is around 20,000 euros. Heating cost savings are about 100 euros per year, [emoji3] do the math yourself.
Hm, okay. It’s a pity that it’s not worthwhile. I like the idea of becoming somewhat more independent from price developments like electricity, gas, etc. I think I get more upset about annually rising costs, sometimes significantly, than about investing a bit more once. Since I can’t just throw money around, the investment shouldn’t unnecessarily be several thousand euros. Especially if I hardly get that back. As a starting point, covering about two-thirds of the costs would actually be enough for me if I could get that back.
Maybe someone has information on which systems work particularly well together, or especially which don’t. For example: Does it even make sense to have photovoltaics and/or solar thermal with a heat pump? Unfortunately, I don’t trust offers very much, since they usually end up with a lot of technology for a lot of money.
How much more do air source heat pumps cost compared to gas heating? Is gas even suitable for underfloor heating (which is fixed)?
Maybe someone has information on which systems work particularly well together, or especially which don’t. For example: Does it even make sense to have photovoltaics and/or solar thermal with a heat pump? Unfortunately, I don’t trust offers very much, since they usually end up with a lot of technology for a lot of money.
How much more do air source heat pumps cost compared to gas heating? Is gas even suitable for underfloor heating (which is fixed)?
Gas condensing boilers work very well with underfloor heating. As a rule of thumb, if I need a lot of electricity, for example with a heat pump, installing photovoltaic panels makes sense. If I need little electricity, with a gas heating system, solar thermal panels are worthwhile. In my opinion, a mechanical ventilation system with heat recovery is an optional comfort feature, but trickle ventilation in window frames is necessary.
All other building services technology is mainly designed to drain your money.
The most ecological heating method would be district heating from renewable energy or combined heat and power (CHP). Unfortunately, these options are rarely available.
All other building services technology is mainly designed to drain your money.
The most ecological heating method would be district heating from renewable energy or combined heat and power (CHP). Unfortunately, these options are rarely available.
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Deliverer6 Jun 2018 13:04Please take some time to read through the forum. The topic of heating has been discussed here countless times...
Additional note: Even with the minimum standard, you can expect very low energy costs. Also, air-to-air heat pumps do not heat underfloor heating systems; what you need is an air-to-water heat pump. But you probably meant that.
Solar thermal systems are rarely cost-effective, photovoltaic systems often are, and some form of mechanical ventilation is mandatory.
Additional note: Even with the minimum standard, you can expect very low energy costs. Also, air-to-air heat pumps do not heat underfloor heating systems; what you need is an air-to-water heat pump. But you probably meant that.
Solar thermal systems are rarely cost-effective, photovoltaic systems often are, and some form of mechanical ventilation is mandatory.
Okay, I didn’t expect to end up considering gas, but it seems that’s where I’m heading. Is a ventilation system mandatory for new builds with a certain level of insulation?
Trickle vents in window frames are not really an option for us. I find that “technology” quite outdated. Sure, it’s inexpensive, but it doesn’t provide optimal ventilation, nor does it offer any other benefits, right? With that option, I’d still have to ventilate manually anyway.
So, does that mean I really need to consider a ventilation system after all?
Trickle vents in window frames are not really an option for us. I find that “technology” quite outdated. Sure, it’s inexpensive, but it doesn’t provide optimal ventilation, nor does it offer any other benefits, right? With that option, I’d still have to ventilate manually anyway.
So, does that mean I really need to consider a ventilation system after all?
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