ᐅ Ground-source heat pump with or without controlled mechanical ventilation
Created on: 22 Dec 2016 22:19
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nautilus
Hello everyone,
we have received a cost estimate from the architect for a KfW 70 house, including a mechanical ventilation system with heat recovery. When I asked about KfW 55, the architect said that if you go with a ventilation system without heat recovery and add about €8000 (approximately $8,700) extra, then you could have a geothermal heat pump (deep probe). That would probably make KfW 55 achievable. Walls and everything else are planned according to the KfW 55 standard. He said it doesn’t make sense to use heat recovery with geothermal energy because supposedly there are no savings from it. The ventilation would then be €6000 (about $6,500) cheaper. I have to say I’m confused and don’t understand what he means. Can someone explain what he means?
we have received a cost estimate from the architect for a KfW 70 house, including a mechanical ventilation system with heat recovery. When I asked about KfW 55, the architect said that if you go with a ventilation system without heat recovery and add about €8000 (approximately $8,700) extra, then you could have a geothermal heat pump (deep probe). That would probably make KfW 55 achievable. Walls and everything else are planned according to the KfW 55 standard. He said it doesn’t make sense to use heat recovery with geothermal energy because supposedly there are no savings from it. The ventilation would then be €6000 (about $6,500) cheaper. I have to say I’m confused and don’t understand what he means. Can someone explain what he means?
There are two different main functions (ground source heat pump and controlled residential ventilation) and technologies involved, which, if properly designed, are only minimally interconnected. Controlled residential ventilation is implemented to provide constant “fresh” air and adequate air exchange in today’s airtight houses without the need for window ventilation. It is mainly intended to prevent sweating and mold growth and to improve the occupants’ comfort. However, the controlled residential ventilation system should be equipped with heat recovery, so that about 90% of the heat can be transferred back to the supply air. Trying to compensate for the cold air with a more efficient heating system is, in my opinion, a permanently incorrect approach from both an ecological and economical perspective.
nautilus schrieb:
That’s exactly the point. I understand that such behavior isn’t environmentally conscious. However, I wouldn’t classify this aspect under comfort. Let me try to put it differently: Are there any other benefits of a ventilation system with heat recovery besides reclaiming heat, compared to a system without heat recovery?By comfort, I didn’t mean the ecological aspect but actual differences in comfort. What I mean is, with a controlled ventilation system with heat recovery, fresh supply air is blown into your home already preheated. With a basic ventilation system, the outside air is supplied as it is outside. So, at -5°C (23°F), the heating obviously has to work harder to bring the incoming cold outside air up to room temperature. But the question is: do you really want -5°C (23°F) cold air blowing directly on you when you’re sitting on the sofa? Of course, the heating balances the temperature out over time, but a cold draft is still a cold draft.
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Bieber081529 Dec 2016 22:28When planning a mechanical ventilation system with heat recovery, the additional energy savings from heat recovery alone will likely pay off very quickly. That means mechanical ventilation should always be installed with heat recovery.
Alex85 schrieb:
By comfort, I didn’t mean the ecological aspect, but actually differences in comfort. That means with a mechanical ventilation system with heat recovery, you get fresh supply air noticeably preheated into your home. With a simple ventilation system, the outside air is supplied as it is outside. So, at -5°C (23°F), the heating has to work harder to bring the incoming cold outside air up to room temperature. But the question is: do you really want -5°C (23°F) cold air blown on the back of your neck while sitting on the sofa? Of course, the heating will even out the temperature again, but a cold draft is still a cold draft.Are there actually mechanical ventilation systems without heat recovery? Given how straightforward that works, I can’t imagine anyone still building those.
markus270330 Dec 2016 15:07That’s not correct; a decentralized ventilation system with heat recovery does exist. We installed one (Lunos e2).
Decentralized simply means that the exhaust and supply air are exchanged through individual fans, rather than centrally via a system in the basement or utility room.
You are right about exhaust-only systems — they don’t have heat recovery.
Decentralized simply means that the exhaust and supply air are exchanged through individual fans, rather than centrally via a system in the basement or utility room.
You are right about exhaust-only systems — they don’t have heat recovery.
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