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, the ventilation concepts. The fact is, a building without any mechanical ventilation is legal and is always accompanied by the building inspector with a note to ventilate regularly! For example, we received a kind of manual for the house that clearly states and describes this in case mechanical ventilation is omitted, including instructions on how to ventilate properly. This places the responsibility on the customer. The fact is that this is unfortunately not entirely correct.
“In Germany, it has since been required to prove whether sufficient moisture removal can be ensured without active window ventilation. If a ventilation concept is developed, the resident has a legal obligation to follow it. If the architect or planner does not point out a missing ventilation concept or non-compliance with DIN 1946-6, they can be held liable for mold damage.
[...]
This cannot be avoided by a corresponding clause in the general terms and conditions. In such cases, very detailed ventilation instructions would have to be clearly part of the contract. Even then, legal experts consider it highly doubtful whether this would not violate the generally accepted rules of technology. Those who want to be on the safe side plan their projects so that, based on a realistic assessment of occupants’ ventilation behavior, a hygienic air exchange is ensured. The ventilation concept provides solutions for this.”
Source as above.
In summary: simply saying “we are building without mechanical ventilation, you just have to ventilate twice daily” is quite controversial, especially since moisture protection must work independently of the occupant.
That some construction managers (general contractors, architects, structural engineers...) do not comply with what they should do is unfortunately nothing new in the construction sector. But to legitimize this negligence simply because it is common practice strikes me as rather odd.
By the way, the standard does not require the installation of a controlled residential ventilation system; it only requires that the air volume flow is sufficient—which can also be achieved through window trickle vents. Whether one wants that or not is another question (personally, I would find it completely outdated and penny-wise but pound-foolish for new builds. But that’s just my subjective opinion).
Deliverer schrieb:
Yes, definitely. Nowadays, you really have to search to find a better deal without basic fees.Well, I pay 25 cents, and I have a basic fee anyway.D
Deliverer7 Jun 2018 20:45Lumpi_LE schrieb:
Well, I pay 25 cents, and I have a fixed basic fee anyway. Please divide your basic fee by your kWh (both per year) and then add 0.25. Then share the result with us!