ᐅ But should you install a controlled residential ventilation system?
Created on: 25 May 2015 00:14
U
Uwe82
Hello everyone,
We are in the final stages of planning our house; the floor plan is set, and the detailed construction planning will take place soon. It is a prefabricated house built with a timber frame construction and a prefabricated basement on a slope, meaning the front part of the basement is fully exposed above the slope.
So far, we have excluded the topic of mechanical ventilation with heat recovery, partly due to planning concerns (we are doing everything ourselves from the rough plumbing and electrical installation stages) and partly for cost reasons. However, in recent weeks, we have started to reconsider this, mainly for comfort reasons.
Long story short: Our question mainly concerns the routing of the ductwork, which would partially be installed within the floor structure. So far, we have planned for a floor buildup of 15cm (6 inches) on the ground floor. However, if we were to increase this to 18cm (7 inches) as our house manufacturer suggests, the clear floor height would decrease from 245cm (8 ft) to 242cm (7 ft 11 in) on the ground floor. This would bother me a bit. We cannot change the floor-to-ceiling height due to the zoning plan restrictions (maximum eave height fully utilized).
Now the question is: Is it really necessary to plan for 18cm (7 inches) because of duct crossings, or are there alternatives? For a suitable floor plan (here is our current one: https://www.hausbau-forum.de/threads/efh-in-Hanglage.12265/page-3#post-90366), could the ducts be routed only within the walls? And which mechanical ventilation system with heat recovery would you recommend for a living area of 180m² (1,938 sq ft)?
Thanks in advance for all the information!
Uwe
We are in the final stages of planning our house; the floor plan is set, and the detailed construction planning will take place soon. It is a prefabricated house built with a timber frame construction and a prefabricated basement on a slope, meaning the front part of the basement is fully exposed above the slope.
So far, we have excluded the topic of mechanical ventilation with heat recovery, partly due to planning concerns (we are doing everything ourselves from the rough plumbing and electrical installation stages) and partly for cost reasons. However, in recent weeks, we have started to reconsider this, mainly for comfort reasons.
Long story short: Our question mainly concerns the routing of the ductwork, which would partially be installed within the floor structure. So far, we have planned for a floor buildup of 15cm (6 inches) on the ground floor. However, if we were to increase this to 18cm (7 inches) as our house manufacturer suggests, the clear floor height would decrease from 245cm (8 ft) to 242cm (7 ft 11 in) on the ground floor. This would bother me a bit. We cannot change the floor-to-ceiling height due to the zoning plan restrictions (maximum eave height fully utilized).
Now the question is: Is it really necessary to plan for 18cm (7 inches) because of duct crossings, or are there alternatives? For a suitable floor plan (here is our current one: https://www.hausbau-forum.de/threads/efh-in-Hanglage.12265/page-3#post-90366), could the ducts be routed only within the walls? And which mechanical ventilation system with heat recovery would you recommend for a living area of 180m² (1,938 sq ft)?
Thanks in advance for all the information!
Uwe
I turned off the central mechanical ventilation system in my new build for two hours and was surprised at how poor the air quality felt—I actually started to feel uncomfortable. Then I quickly switched it back on and now hope it doesn't fail. I don’t think I could manage adequate ventilation on my own. The house is, of course, tightly sealed, but that is basically expected for any new build.
Due to my job, I often visit clients where I have installed decentralized ventilation systems. I can usually notice the before-and-after difference quite clearly after a short time (1–2 months) during a follow-up visit. You can also often feel that the humidity has decreased.
The improved air quality that develops over time is really easy to smell. Clients often say, "If we had known this earlier, we would have chosen it much sooner!"
The improved air quality that develops over time is really easy to smell. Clients often say, "If we had known this earlier, we would have chosen it much sooner!"
Thank you for all the feedback. I have now received a response from my building surveyor: The structural engineer says that for installing the system in the concrete ceiling, it needs to be thicker, and there is definitely a risk that the pipes could be accidentally drilled into later. So, in any case, the floor construction would have to be raised.
For this reason, and due to time constraints, we will forgo the ventilation system. The building surveyor also mentioned that he generally builds very few houses with ventilation systems and has not had any negative experiences with them so far. Some acquaintances have built with him without mechanical ventilation systems and have had no issues, also reporting only positive feedback regarding air quality. Of course, they haven’t had problems yet, so that is likely a difference. But up to now, neither have we.
For this reason, and due to time constraints, we will forgo the ventilation system. The building surveyor also mentioned that he generally builds very few houses with ventilation systems and has not had any negative experiences with them so far. Some acquaintances have built with him without mechanical ventilation systems and have had no issues, also reporting only positive feedback regarding air quality. Of course, they haven’t had problems yet, so that is likely a difference. But up to now, neither have we.
BeHaElJa schrieb:
Hello Uwe,
Statements from the past can be misleading... back then, houses had more gaps.
On the other hand, if it does get too stuffy for you later, you could still install decentralized units...
Best regards Do you mean the one of my acquaintance? He moved into his house last year, same manufacturer, same wall structure.
I’m also not sure if giving up on mechanical ventilation is a good solution, even though I am generally against mechanical ventilation for various reasons.
In 2008, we built a prefabricated house with mechanical ventilation. For certain reasons, we turned it off in 2013/2014, and the air quality almost immediately got worse. Within a short time, mold appeared on the window frames in our guest toilet, bathroom, and skylight windows.
If we had built another prefabricated house the second time around, we would have chosen a decentralized ventilation system. However, we built a solid house and installed decentralized ventilation only in the bathrooms and the utility room. The air quality in our solid house (without insulation) is noticeably better without ventilation than it was in the prefabricated house after the ventilation system was turned off.
If I were in your position, I might consider whether a decentralized system could be an option. This way, you don’t need to lay complex ductwork in the floor.
In 2008, we built a prefabricated house with mechanical ventilation. For certain reasons, we turned it off in 2013/2014, and the air quality almost immediately got worse. Within a short time, mold appeared on the window frames in our guest toilet, bathroom, and skylight windows.
If we had built another prefabricated house the second time around, we would have chosen a decentralized ventilation system. However, we built a solid house and installed decentralized ventilation only in the bathrooms and the utility room. The air quality in our solid house (without insulation) is noticeably better without ventilation than it was in the prefabricated house after the ventilation system was turned off.
If I were in your position, I might consider whether a decentralized system could be an option. This way, you don’t need to lay complex ductwork in the floor.
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