ᐅ Mechanical ventilation with heat recovery and swirl diffuser – Passive House

Physically, it doesn’t make sense because the air is colder than the room air – so the mixing will never be optimal. I’m not surprised you hardly notice it – what would you even notice? It should work somehow and is better than nothing.

And honestly, I don’t really see the advantages – first, installing it on the raw concrete slab is more difficult and requires good coordination among the trades plus an appropriate floor construction. And then you have exhaust air running through large slots in the walls?

Additionally, I always see the risk that something might fall into the duct... children tend to be quite curious.

Yes, that's right, my coworker also mentioned that they found some of the kids' things there again.

For the ground floor, doesn't everything have to go through the floor or the ceiling?

In the attic, you can still run pipes through the loft.

Or am I mistaken, but aren't there flat or oval pipes that would easily fit into a concrete ceiling? I think my coworker also has similar pipes in his Pluggit system.

Flat ducts are installed on the raw subfloor, while round pipes are placed in the ceiling.

So if you are fast enough—and with today's precast concrete ceilings, this becomes possible—do you then install round pipes inside?

Flat ducts would be more commonly used when there are no precast concrete ceilings, making it impossible to install flat ducts.

Bieber0815 schrieb:
We have floor outlets on the upper floor, and so far I don’t see any disadvantages. The main advantage, in my opinion, is that the duct system is very simple: two stories, installation on the raw ceiling slab, core drilling downward, with supply and exhaust air near the ceiling there, and supply air in the floor with exhaust air high up on the wall above.

Everything is correct.

- To avoid expensive core drilling, holes can be punched through the precast concrete slab or ordered with openings in advance. Be careful with too many penetrations regarding the slab’s span direction, and consult the structural engineer if needed. (Image 1)
- Installation is not a problem. However, pipe dimensions must be known quite early to adjust the insulation thickness below the screed or to specify the finished floor height for trades like window installers, entrance door fitters, and stair builders. (Image 2)
- To keep pipe lengths as short as possible (to reduce pressure loss), it’s common for supply and exhaust outlets in the basement to be located in the ceiling. Again, to avoid core drilling, simply attach a polystyrene block to the precast slab, as is common for other penetrations like drain pipes. (Image 3 and 4)
- On upper floors, supply air is at the bottom and exhaust air at the top. Used air normally rises, and circulation is slightly improved since the air is forced to move in three dimensions. (Image 5 and 6)

Some homeowners prefer to have supply air outlets directly in front of windows, for example due to space constraints. Then you have no choice but to place the connection in the floor. Advantage: more room for furniture. Disadvantage: dirt can enter since the filter discs are only at the outlets, and if curtains are planned, they will constantly be moving.

Installing ventilation ducts in the ceiling requires coordination with the structural engineer because this creates cavities with undefined runs in the intermediate ceiling. The engineer decides whether reinforcing the reinforcement bars in certain areas is sufficient or if the entire intermediate ceiling needs to be made more solid. You should then strictly follow the exact installation plan.

Depending on the contamination level of the system, there is an option to clean the ventilation ducts later. To my knowledge, this is done by blowing a foam ball through the individual ducts. With round ducts, the chance of the ball getting stuck is lower.

Sebastian79 schrieb:
because the air is colder than the room air – therefore the mixing will never be optimal.

When air is heated at floor level during the heating season and then rises, fresh air supplied there should also rise and mix with the room air. The exhaust vents installed at the top additionally create crossflow.

Sebastian79 schrieb:
And then you have exhaust air in large slots in the walls?

Correct. We have two exhaust vents upstairs. One is in the walk-in closet, installed in a drywall partition (the only one upstairs), which is practical and straightforward. The second exhaust vent is in the bathroom, where a boxed-in section was needed. The result turned out very well and neither looks bad nor takes up much space. It only extends by a few centimeters (centimeters) (inches). Alternatively, the wall would have had to be thicker (here 11 cm (4 inches) calcium silicate brick), which would have needed to be planned in advance, but the builder did not consider this. (The floor build-up and ceiling height were taken into account, so everything fits!)

Sebastian79 schrieb:
I also always see the risk that something could fall into the duct

There are so-called design covers on the floor outlets, rectangular stainless steel plates with many small round holes (perforated sheet). Children would have to make a real effort to insert anything there. And even if they do, you just remove it occasionally. Our children certainly don’t bother with it. Nothing falls in by itself.

The supply air openings are basically maintenance-free; the exhaust air covers need to be cleaned of dust occasionally, and the filters installed inside must be cleaned or replaced.