ᐅ Planning a Controlled Residential Ventilation System through a Local Heating and Plumbing Company

Hello, after a long back and forth, I’ve almost convinced my wife that we need a mechanical ventilation system with heat recovery. Her main concerns are the dry air in winter and noise levels. Today, we had a conversation with the local heating/plumbing company that works with our general contractor. Unfortunately, the plumber reinforced my wife’s worries, saying that dry air is indeed a bigger issue and, in response to my question about the possibility of an enthalpy heat exchanger, he said it would barely make a difference and would just be an unnecessary expense.

My biggest fear is actually a poorly planned mechanical ventilation system (noise, drafts, etc.), and I feel there is a real chance of that happening with this company. They offered us a Helios EC 370w ventilation system. From what I’ve found about this unit, it seems to be an older model and probably undersized for our house (202m² (2174 sq ft) over 2 full floors). When I asked, the plumber said there is enough capacity and that we definitely wouldn’t hear any noise. The design of the exhaust and supply air ducts will be done by the local company. According to the plumber, they have a lot of experience with mechanical ventilation systems and have never had issues with noise so far. I had understood that the planning is usually done by major companies (Zehnder, Helios, etc.) and only the installation is handled by the heating/plumbing company, which I would prefer much more.

How was it handled in your cases? Who planned the system? Does anyone know the Helios unit, and is it adequately sized for our house if you want to avoid noise?

Last house with centralized mechanical ventilation – designed by the heating engineer (for whatever reason – doesn’t really matter). On a property with centralized mechanical ventilation, you don’t experience any noise or drafts. So no worries there.

You can get dry air in winter, but that happens even without mechanical ventilation when using just heating – only with a few percent higher humidity. Enthalpy exchangers already help with this. Plants and similar also contribute.

I can’t share personal experience with Helios. But in my opinion, it’s not a problem if the unit is older. In simple terms, a central fan blows air in or extracts it. That’s far from high-tech.

Currently, I have a decentralized ventilation system installed in my new house. It is more noticeable (in terms of noise), but even here, you don’t feel any drafts (unless it’s running at full power).

My conclusion: never again without mechanical ventilation. Always fresh and pollen-free air in the house.

Thanks for the reply! The dry air issue is actually the only relevant point that speaks against a mechanical ventilation system for me. So far, I thought that the dryness problem could be well solved with an enthalpy heat exchanger. What does such a heat exchanger actually achieve? Most of our family tend to have problems with the upper respiratory tract, so I definitely want to avoid dry air.

Does anyone know the Helios 370, and isn’t the unit actually too small for our house?

An enthalpy heat exchangers do not drain condensate; instead, they return all the condensate produced (several liters per day) back into the supply air. This works so effectively that even after two winters, I still struggle to keep my building dry and often rely on manual window ventilation.

If you do not want dry air, a controlled mechanical ventilation system with an enthalpy heat exchanger (EWT) is a good option. All other types of ventilation tend to dry the air out much more significantly. The alternative to controlled mechanical ventilation is not to avoid ventilation, but rather to ventilate through windows, which results in a much higher loss of moisture. There is likely a calculation somewhere where someone knowledgeable has already worked this out.

If your heating technician says that an EWT is pointless, I would recommend finding a different heating technician and another supplier for the ventilation system.

You will not experience any noise if the system is properly designed. This includes, for example, having two rather than one air outlet in the bedroom, a slightly oversized ventilation unit, silencers, and appropriately streamlined valves.

I have no experience with Helios, but personally, I would recommend Zehnder.

Hey, my building has been completely dry since winter (CM screed measurement & air humidity with a hygrometer). You always hear that a new build takes about a year to dry out. Where does this discrepancy come from? I’m now worried that some moisture is trapped somewhere and can’t escape, potentially causing unnoticed damage over time. Until I suddenly die from mold exposure or dry rot grows. Could that happen?

Tolentino schrieb:

Say, my building has been completely dry since winter (measured screed moisture & air humidity with a hygrometer). You always hear that a new build won’t be dry for a year. Where does this difference come from? Now I’m worried that moisture might be trapped somewhere and not escaping, causing hidden damage over time. Until suddenly I get sick from mold exposure or discover dry rot. Is that possible?

I’m not an expert, but I think that’s unlikely.
The interior plaster has strong capillary action. As soon as it comes into contact with moisture, it draws it over a large area into the plaster and releases it to the indoor air. There are certainly differences between gypsum and lime plaster, but I find it unlikely that it “traps” moisture. Did you use a mineral-based paint for the interior finish?

At my place, it rained heavily during the shell construction, and the brick wall was standing in water. According to the manufacturer, this isn’t a problem as long as it doesn’t freeze or rain directly onto the bricks at the top. This water certainly takes some time before it’s released back into the indoor air.