ᐅ Comparison Tests of Various Centralized Mechanical Ventilation Systems with Heat Recovery + Additional Questions
Created on: 1 Nov 2017 17:46
4
4Motion
Hello dear forum community,
I have a few questions about controlled residential ventilation systems that my own research online and in this forum haven’t helped me with. If you don’t want to read everything, feel free to jump straight to the questions.
First, about our situation: Two builders independently advised us against controlled residential ventilation. The first said it’s not necessary. He prefers to build with clay bricks (Poroton), which are vapor-permeable and allow excess moisture to move outside. He also applies hydraulic lime plaster to the walls, which can quickly absorb and release a lot of moisture and also absorb pollutants. Both the plaster and Poroton do not provide a breeding ground for mold or bacteria. Just occasional manual ventilation (opening windows briefly) is sufficient. He is also critical of the cleaning of duct systems. Well, that’s his opinion for now.
The other builder builds entirely with wood but argues similarly. He told us about customers who installed a controlled residential ventilation system just for safety but have now completely turned it off because they didn’t need it.
So initially, we were against controlled residential ventilation. After my research, however, I still want to have one. Personally, I’m somewhat negligent when it comes to ventilation. My wife, on the other hand, is a ventilation fanatic and always needs a lot of fresh air. She also always finds the air in prefabricated house showrooms very stuffy, which made us even more opposed to controlled residential ventilation. She actually prefers to ventilate manually all the time. Some windows in our home are even left slightly open for longer periods.
1. I am still a bit skeptical. Is there a statistic on what percentage of new builds have a controlled residential ventilation system?
2. To me as a layperson, all systems sound the same. Are there any comparison tests between different brands? Since controlled residential ventilation systems are so widespread, there should be tests similar to those for vacuum cleaners or kitchen appliances.
3. Who are the market leaders and which brands are rather niche players? So I can compare the top 5 myself.
4. Is it better to use round ducts with wide radii instead of flat ducts that sometimes bend sharply at 90°, to allow better cleaning? Or have you not considered that important?
I have a few questions about controlled residential ventilation systems that my own research online and in this forum haven’t helped me with. If you don’t want to read everything, feel free to jump straight to the questions.
First, about our situation: Two builders independently advised us against controlled residential ventilation. The first said it’s not necessary. He prefers to build with clay bricks (Poroton), which are vapor-permeable and allow excess moisture to move outside. He also applies hydraulic lime plaster to the walls, which can quickly absorb and release a lot of moisture and also absorb pollutants. Both the plaster and Poroton do not provide a breeding ground for mold or bacteria. Just occasional manual ventilation (opening windows briefly) is sufficient. He is also critical of the cleaning of duct systems. Well, that’s his opinion for now.
The other builder builds entirely with wood but argues similarly. He told us about customers who installed a controlled residential ventilation system just for safety but have now completely turned it off because they didn’t need it.
So initially, we were against controlled residential ventilation. After my research, however, I still want to have one. Personally, I’m somewhat negligent when it comes to ventilation. My wife, on the other hand, is a ventilation fanatic and always needs a lot of fresh air. She also always finds the air in prefabricated house showrooms very stuffy, which made us even more opposed to controlled residential ventilation. She actually prefers to ventilate manually all the time. Some windows in our home are even left slightly open for longer periods.
1. I am still a bit skeptical. Is there a statistic on what percentage of new builds have a controlled residential ventilation system?
2. To me as a layperson, all systems sound the same. Are there any comparison tests between different brands? Since controlled residential ventilation systems are so widespread, there should be tests similar to those for vacuum cleaners or kitchen appliances.
3. Who are the market leaders and which brands are rather niche players? So I can compare the top 5 myself.
4. Is it better to use round ducts with wide radii instead of flat ducts that sometimes bend sharply at 90°, to allow better cleaning? Or have you not considered that important?
Vapor Pressure Difference Between the Interior and Exterior of the House
The denser and colder a building material is, the more water vapor from the indoor air condenses on it as liquid moisture. Persistent dampness can cause structural damage. Materials that initially absorb moisture and gradually release it again help regulate the indoor climate – they are said to be permeable to vapor diffusion.
Residents cook, shower, and sweat: in a household of four people, 10 to 12 liters (2.6 to 3.2 gallons) of water vapor fill the indoor air daily. The gaseous molecules spread evenly throughout the space, creating a certain vapor pressure known as relative humidity. Vapor pressure can also be measured outdoors. When it matches the relative humidity inside the house, a balance exists. If the vapor pressure inside is higher or lower than the relative humidity outside, this is called a vapor pressure difference. Vapor moves toward the area of lower pressure within the building component, diffusing through it. This creates an equalizing flow called diffusion.
Resistance to Vapor Pressure
Building materials offer varying levels of resistance to vapor. The strength of this resistance compared to a 100 cm (39 inch) thick layer of air is indicated by the vapor diffusion resistance factor µ (mu) – the lower the value, the easier water vapor passes through. Dense materials with a vapor diffusion resistance factor above 100 µ are considered vapor barriers, such as bitumen membranes. Vapor retarders are materials that slow vapor diffusion but do not completely prevent it.
Moisture Buffer
Building materials or assemblies that offer little resistance to vapor pressure are called vapor-permeable. Homeowners aiming for “healthy” living appreciate the benefits of walls, ceilings, and roofs that allow water vapor to pass through: when the indoor air is humid, these surfaces store water molecules; conversely, they release moisture back into the air when it becomes too dry. This buffering effect works slowly, over hours or even days, and only about 2% of the indoor moisture actually passes through the building element.
Vapor-Permeable Components, Airtight Building Envelope
Moisture from cooking or bathing cannot be removed by diffusion alone, since vapor molecules do not move through building elements via airflow – there are no “breathing” walls. If drafts occur, the building has open joints and loses excessive heating energy unnecessarily. Therefore, a tightly sealed building envelope is now standard practice. Energy saving regulations (such as energy performance standards or codes) require this for new constructions. This approach has benefits but also risks, making proper ventilation especially important.
The denser and colder a building material is, the more water vapor from the indoor air condenses on it as liquid moisture. Persistent dampness can cause structural damage. Materials that initially absorb moisture and gradually release it again help regulate the indoor climate – they are said to be permeable to vapor diffusion.
Residents cook, shower, and sweat: in a household of four people, 10 to 12 liters (2.6 to 3.2 gallons) of water vapor fill the indoor air daily. The gaseous molecules spread evenly throughout the space, creating a certain vapor pressure known as relative humidity. Vapor pressure can also be measured outdoors. When it matches the relative humidity inside the house, a balance exists. If the vapor pressure inside is higher or lower than the relative humidity outside, this is called a vapor pressure difference. Vapor moves toward the area of lower pressure within the building component, diffusing through it. This creates an equalizing flow called diffusion.
Resistance to Vapor Pressure
Building materials offer varying levels of resistance to vapor. The strength of this resistance compared to a 100 cm (39 inch) thick layer of air is indicated by the vapor diffusion resistance factor µ (mu) – the lower the value, the easier water vapor passes through. Dense materials with a vapor diffusion resistance factor above 100 µ are considered vapor barriers, such as bitumen membranes. Vapor retarders are materials that slow vapor diffusion but do not completely prevent it.
Moisture Buffer
Building materials or assemblies that offer little resistance to vapor pressure are called vapor-permeable. Homeowners aiming for “healthy” living appreciate the benefits of walls, ceilings, and roofs that allow water vapor to pass through: when the indoor air is humid, these surfaces store water molecules; conversely, they release moisture back into the air when it becomes too dry. This buffering effect works slowly, over hours or even days, and only about 2% of the indoor moisture actually passes through the building element.
Vapor-Permeable Components, Airtight Building Envelope
Moisture from cooking or bathing cannot be removed by diffusion alone, since vapor molecules do not move through building elements via airflow – there are no “breathing” walls. If drafts occur, the building has open joints and loses excessive heating energy unnecessarily. Therefore, a tightly sealed building envelope is now standard practice. Energy saving regulations (such as energy performance standards or codes) require this for new constructions. This approach has benefits but also risks, making proper ventilation especially important.
A short story from the neighborhood: A neighbor built a house with a ventilation system but decided to skip it in the basement. Now he is having ventilation retrofitted in the basement at a high cost. Apparently, seeing the direct comparison convinced him that spending a lot of money on ventilation is worthwhile.
I always find the idea of a vapor-permeable wooden house amusing. We are building a solid construction house with a 25 sqm (270 sq ft) wooden stud-frame extension. So, the area that is clearly the least vapor-permeable is the wooden stud-frame extension: OSB panels, sealing tapes, adhesive tapes, waterproofing layers, insulation between two vapor barriers, and drywall on the inside. Pure nature, right?
In contrast, the solid construction house uses thin-walled, hollow bricks, with lime-plaster and gypsum plaster on the inside and silicate paint, and only plaster and silicate paint on the outside as well. No adhesives—no membranes.
I could still consider a log house ecologically acceptable, but as soon as insulation materials are involved, vapor barriers are also necessary.
Back to the topic: Just with the screed, you can already notice that it takes a long time to ventilate moisture out of a tightly sealed house. Currently, we would not want to build without ventilation, especially since the costs here are about 2.5% of the total project costs — manageable and much cheaper than retrofitting.
In contrast, the solid construction house uses thin-walled, hollow bricks, with lime-plaster and gypsum plaster on the inside and silicate paint, and only plaster and silicate paint on the outside as well. No adhesives—no membranes.
I could still consider a log house ecologically acceptable, but as soon as insulation materials are involved, vapor barriers are also necessary.
Back to the topic: Just with the screed, you can already notice that it takes a long time to ventilate moisture out of a tightly sealed house. Currently, we would not want to build without ventilation, especially since the costs here are about 2.5% of the total project costs — manageable and much cheaper than retrofitting.
4Motion schrieb:
So yesterday I visited another builder. He also uses a breathable construction method. Since I definitely want that, I only go to builders who offer it. Maybe that’s where the problem lies. In real life, everyone advises me against mechanical ventilation systems with heat recovery. But here in the virtual world, everyone definitely recommends such a system.
You can guess what the builder said. He only installs a mechanical ventilation system in 10% of his projects. According to him, it’s not necessary with his breathable construction method using wood.
I’m very grateful for your feedback. But maybe you could also mention whether you have a vapor barrier in your walls or, as my builders always say: Are you living in a plastic bag or a Gore-Tex jacket?We are building completely breathable with wood, without any plastic vapor barriers. Our general contractor clearly recommended a mechanical ventilation system with heat recovery, even though that was clear to us from the start. The added quality of life is something you can never retrofit later! I’m really looking forward to finally living in well-ventilated but warm and non-stuffy rooms during winter! And I’m not worried about power consumption for now—the photovoltaic system with battery storage will take care of that.
Tentakel schrieb:
I always find the idea of a diffusion-open wooden house amusing. We are building a solid house with a 25sqm (270 sq ft) wooden stud extension. So the area that is clearly the least diffusion-open is probably the wooden stud extension, with OSB boards, sealing tapes, adhesive tapes, waterproofing, insulation between two vapor barriers, and drywall inside. Pure nature Then that is not a diffusion-open wall construction! Our wooden stud wall build-up from inside to outside: clay plasterboards - OSB - stud frame with mineral wool - wood fiber insulation - plaster... absolutely no vapor barrier or any plastic materials. Considered a very good wall construction by an independent building inspector from the Homeowners Protection Association.
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