ᐅ Ventilation system: number of supply and exhaust air units

Hello,
our ventilation system for our house is currently being planned. Is it necessary to plan the same number of supply air vents as exhaust air vents?
Is there a guideline for how many supply air vents are needed, for example one supply vent per 30 cubic meters of room volume?
What about the walk-in closet and the hallway downstairs and upstairs?

Best regards
Sabine

Curly schrieb:
Do you need to plan as many supply air vents as exhaust air vents?

No, but the overall balance between the supplied and extracted airflow must be correct.

Curly schrieb:
Is there a guideline on how many supply air vents are needed, for example, one supply vent per 30 cubic meters of room volume?

I’m not sure, but in any case, each vent has a maximum airflow rate. The required airflow is based on the desired air exchange rate (house volume in m³ divided by time, e.g., a full exchange every two hours = m³/h, or normalized to 1/h as the air change rate). Generally, you’ll need at least one supply vent in each supply air room and one exhaust vent in each exhaust air room.

Depending on the vent type, no more than about 30 to 35 m³/h (up to 40 m³/h) of air should flow through a single vent at nominal load. Higher airflow means greater pressure drop, more noise, and possibly drafts around the vent.

Curly schrieb:
What about the walk-in closet and the hallways upstairs and downstairs?

Hallways are usually overflow areas (for example: supply air in the children’s room, exhaust air in the bathroom, the hallway is passively ventilated). For a walk-in closet, an example would be supply air in the bedroom and exhaust air in the adjacent walk-in closet.

Who is designing your system?

Our homebuilder first created a plan for us. According to it, the living area will have 2 supply air vents, and the open kitchen will have 1 exhaust air vent. The room is a total of 60m² (645ft²), and I’m not sure if 2 supply air vents are sufficient. The hallway on the upper floor has 1 exhaust air vent, but the hallway downstairs has no supply air vent. To ensure there is enough fresh air in the downstairs hallway, I think there should also be a supply air vent there. Would that be possible? Upstairs, we have 4 exhaust air vents (bathroom, dressing room, children’s bathroom, and hallway) but only 3 supply air vents (bedroom and one supply air vent each in the two children’s rooms).

Best regards
Sabine

Our hallways have no vents. I'm puzzled that you have exhaust air in the hallway on the upper floor, which makes me wonder how fresh air is supposed to enter the bathroom (and children's bathroom). Is there another toilet on the ground floor?

It would be best to upload floor plans and a list of the planned vents including their nominal airflow rates. Then we can discuss it.

In the upper floor, there is supply air in the children's rooms and in the master bedroom. There is also a toilet on the ground floor. I don't have a plan with the nominal air volume flow rates; I would need to ask about that. How many supply air vents do you have in the living area? Our living-dining room has a volume of 127 cubic meters (4,485 cubic feet); is two supply air vents enough there?

Best regards
Sabine

Curly schrieb:
I don’t have a plan with nominal volume flows; I would need to ask about that.

When the planning is complete, this information must be available; otherwise, the planning is not finished (You mentioned above that the planning is still in progress, so everything is still fine...).

Curly schrieb:
How many supply air openings do you have in the living area?

For our open plan living-dining-kitchen area, there are two supply air vents and one exhaust vent.