ᐅ Controlled ventilation for indoor air quality: useful or even necessary for us?

Hello everyone,

We will soon be building in the Bremen region. The plan is for 130 sq meters (1,400 sq feet), double-layer masonry, a 45° (45°) gable roof, with a gas central heating system, underfloor heating, a south/west orientation, flat solar thermal collectors for domestic hot water preheating with storage, and KfW 70(+) energy standard without any additional extras. These are the basic details.

We often consider whether or not to install a controlled mechanical ventilation system. We have been offered a ready-to-install recoVAIR 275 for 9,300 euros. Currently, it’s just the two of us, both working full time. Additionally, we frequently travel on weekends, so at least two weekends per month from Friday afternoon to Sunday afternoon there is no opportunity to ventilate.

What are your opinions on this?

Best regards,
Heiko

Hello Heiko,

In my opinion, a mechanical ventilation system with heat recovery is a comfort feature. It may not always be necessary, but all my acquaintances who have such a system in their homes would not want to build without it anymore...

Of course, manual ventilation can be done properly as well, but especially given your usage pattern, I think a mechanical ventilation system would be a sensible choice.

Regards,

Dirk

OHeikoZ schrieb:
....We are currently (still) two people living here, both working full-time. Additionally, we are often away on weekends, so at least two weekends per month from Friday noon to Sunday afternoon no ventilation can take place.....

On one hand, where should odors or moisture come from if no one is present? On the other hand, the “critical rooms” are mainly bedrooms, bathrooms, and kitchens. Bedrooms: Modern buildings are intentionally constructed to be nearly airtight according to current standards. For example, if the window faces a busy street, an open or tilted window is hardly a suitable solution. These rooms have the longest usage and exposure times! Here, odors and CO2 levels play the most important role. The ventilation level setting alone in demand-controlled ventilation (DCV) systems is usually not sufficient. Rain and snow conditions often prevent partial or additional window opening. In a “ballroom”-sized room volume, two people can easily sleep without any noticeable change in CO2 concentration. With a room volume of 30 m³ (1060 ft³), the situation is completely different! Bathrooms: Rooms with short usage times but high moisture loads. In windowless bathrooms, at least exhaust ventilation is generally required by national building codes or regulations. However, the supply air must come from somewhere. Whether window ventilation is sufficient here also depends on the room volume and moisture load. The limitations also apply if only DCV systems are installed! Kitchens: Here, odors and moisture are essential factors. For someone who cooks daily or constantly, conditions are completely different compared to occasional weekend cooking! “Steam kitchens” are certainly rare in single-family houses. In terms of room volume, small, closed, intensively used kitchens require a completely different air exchange than infrequently used, open kitchens with large room volumes. Occasionally, decentralized partial solutions, despite lower efficiency individually, can be effective. However, equipping an entire building with decentralized controlled residential ventilation systems seems largely unrealistic to me. Even a central controlled residential ventilation system can turn out poorly; I would not consider spending approximately 10,000 euros on it. As always, the specific needs and requirements of the building owner are decisive, so making a solid, general recommendation in advance is impossible! Best regards.

Hello,

thank you for your responses. Comfort certainly plays a role in controlled ventilation systems. I am also trying to look at it objectively from a cost perspective. The explanations provided by €uro are very helpful in this regard. I had not yet considered a partially decentralized solution. All rooms (except for hallways and the utility room) will have at least one window. Maybe a few words about odors. We are building directly opposite a farm with a cowshed. Ventilating will definitely be an experience because of the smells—perhaps yet another reason for choosing a controlled ventilation system. We cook fresh meals almost every day, though without a steam cooker. For this reason, we plan to install a powerful kitchen extractor fan, even with a controlled ventilation system.

Honestly, I have little confidence that a general contractor (“GC”) would provide reliable advice on controlled ventilation systems. Who would be the best contact for this? Independent construction consultants, energy advisors, architects?

Good luck and enjoy the rest of the weekend
Heiko

OHeikoZ schrieb:
... We are building directly opposite a farm with a cowshed. Ventilating will always come with odor issues. Perhaps for that reason alone, a controlled ventilation system would be advisable.

Correct, such project-specific particularities can have a significant impact on finding a sensible solution.

OHeikoZ schrieb:
... Honestly, I hardly trust a “general contractor” to provide thorough advice on controlled ventilation systems...

That assessment is certainly justified, because general contractors tend to prioritize sales over the actual well-being of the homeowner. On the other hand, as market participants, this cannot be held against them. Everyone wants a share of the available market. Nearly all means are used for this, as long as the client (employer) allows it.

OHeikoZ schrieb:
... Who should I turn to best? Independent building consultants, energy consultants, architects?..

Most suitable would be an independent MEP (mechanical, electrical, plumbing) planner specialized in small projects like single-family homes. They are usually needed anyway for heating and domestic hot water systems. Large MEP firms are rather unsuitable for this purpose (costs, expertise).

Best regards.

Hello,

many thanks €uro for the assessments and advice. I have now contacted an MEP planner who specializes in small residential units (mostly passive house and energy-plus) and can take over the entire planning for the single-family home. I’m curious to see the final outcome.

Thanks & regards

Heiko