ᐅ Fewer operable windows with mechanical ventilation with heat recovery

How many windows are there? What is the total area? Windows on all sides? Even when there is no wind and the indoor and outdoor temperatures are the same? Many factors come into play here. A lot of theory.

If all these conditions don’t align, ventilation won’t be any faster. However, it tends to feel fresher since the air is usually cooler.

When the factors are right, cross-ventilation is naturally quicker.

In living spaces, an air exchange rate of 0.5 is required.

We have operable windows only where cross-ventilation is needed; the rest are fixed glazing. There is no mechanical ventilation system, and the house is a bungalow. For aesthetic reasons, I prefer fixed glazing. That’s why, unfortunately, even in one of the floor-to-ceiling fixed-glass corner windows, there is a narrow operable window. We live near the sea, and the wind blows from the west (sea) starting around 4 p.m. for about two hours. We ventilate in a north-south and west-east direction. When I am home, the house is never completely closed—except in winter or when it’s above 35°C (95°F); the terrace door is always open, and the risk of burglary is low.

Yes, the roller shutters are dirty on the inside; however, we only have them in the bedrooms, and I cannot clean them from the inside. That’s not the worst problem.

Yes, Rick, I have to disagree there. Opening windows for ventilation is a completely different matter than using a mechanical ventilation system with heat recovery. Perfect air quality can be achieved within 5 minutes by window ventilation, whereas the mechanical ventilation system requires at least 1 hour at full capacity to reach the same level.

Well, as I said, if I can ventilate crosswise. I remember with dread my husband’s old apartment: all the windows on the west side – that meant it was stiflingly hot in the evening and no real ventilation at all… even though almost the entire wall was windows and all of them could be opened.

In my opinion, controlled mechanical ventilation is never a good reason for fixed glazing – I still want to be able to open the windows (though I won’t have to as often).
Reasons for fixed glazing are
- Aesthetics
- Cost savings (but not that much)
- If I know the window won’t be opened anyway

The counterargument is always cleaning! If I can’t reach the windows any other way, I have to be able to open them.
Dirty blinds don’t bother me at all – that wouldn’t be a reason for me. But having permanently dirty windows? I wouldn’t want that at all.

@rick2018 is considering active humidification for your large mechanical ventilation system with heat recovery. With the mechanical ventilation, the indoor air in winter is very dry (sometimes below 30% relative humidity). This can be uncomfortable for the mucous membranes, especially if you already have a slight cold.
We will retrofit the hydrobox later, but the effort to install it directly would have been significantly less.

We also bought a humidifier and are now considering installing an enthalpy exchanger (we are currently checking whether this is possible with our mechanical ventilation with heat recovery system).

It’s definitely worth thinking about, rick! On the other hand, I’ve also heard some horror stories about these systems getting contaminated, so I’m really not sure whether it’s a good idea or not. The fact is: our humidity level is well below 30%, and my devices don’t like that at all (neither do we, but we’re not at home 24 hours a day).