ᐅ Offer for KfW 70 house – KfW 55 with additional controlled residential ventilation – is a KfW 70 too airtight?
Created on: 30 Aug 2016 14:34
K
Kaspatoo
Hello,
I received the attached offer from a developer.
It is a KfW 70 house with a gas boiler.
To achieve KfW 55, it is sufficient to install either a controlled residential ventilation system for an additional €12,400 (about USD equivalent) instead of the gas boiler, or even just a decentralized ventilation system with heat recovery for only the kitchen/living room and bathroom for €6,500 (about USD equivalent) — meaning the bedrooms would have no ventilation.
Now I am wondering: wouldn’t the KfW 70 offer be too airtight or sealed to operate properly without any ventilation?
If KfW 70 is enough for me, where can I save costs or where can I reduce insulation?
We want to use brick cladding and not polystyrene panels, but mineral wool instead.
Can the hollow bricks be made thinner? Can simple bricks be used instead of hollow bricks?
Can thinner mineral wool be used?
Thank you very much for your answers.
I received the attached offer from a developer.
It is a KfW 70 house with a gas boiler.
To achieve KfW 55, it is sufficient to install either a controlled residential ventilation system for an additional €12,400 (about USD equivalent) instead of the gas boiler, or even just a decentralized ventilation system with heat recovery for only the kitchen/living room and bathroom for €6,500 (about USD equivalent) — meaning the bedrooms would have no ventilation.
Now I am wondering: wouldn’t the KfW 70 offer be too airtight or sealed to operate properly without any ventilation?
If KfW 70 is enough for me, where can I save costs or where can I reduce insulation?
We want to use brick cladding and not polystyrene panels, but mineral wool instead.
Can the hollow bricks be made thinner? Can simple bricks be used instead of hollow bricks?
Can thinner mineral wool be used?
Thank you very much for your answers.
Our Blower Door test as well. However, we have a mechanical ventilation system with heat recovery. When I turn it off for a few hours (which I have tested), the air quality noticeably worsens. I think it’s mostly a matter of getting used to it—once you get accustomed to good air quality, you only notice when it’s gone. Whether mold develops without mechanical ventilation depends on consistently ventilating the home daily, especially bathrooms after showering, and on how much moisture is brought into the house (two working adults without pets is very different from a family with young children, pets, an aquarium, and a passion for houseplants…). So, this can’t be generalized and really depends on how the home is used. For my part, I’m glad to save the time spent on ventilation—though it’s only 5–10 minutes a day, it adds up over the years.
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