ᐅ Please review my mechanical ventilation system design for residential buildings.

Hello everyone,

could you please review my mechanical ventilation with heat recovery (MVHR) system design?

Objectives:
1. Good air quality in all rooms
2. A system that is absolutely quiet and hardly audible in the rooms

Questions:
1. Are the airflow rates sufficient?
2. Is the system barely audible?
3. ...

Thanks in advance!!

Attached are the planning documents.

We are using the RecoVair 360/4 from Vaillant.

Supplement:

Family: 2 adults, 2 children

Rooms Ground Floor:

• Living/dining room with open kitchen = total area 58 m² (624 sq ft), of which 44 m² (474 sq ft) living/dining room Supply air: 2x 30 m³/h (in the ceiling), and 14 m² (151 sq ft) in open kitchen Extract air: 45 m³/h (in the ceiling)
• Guest room = 11 m² (118 sq ft) area, Supply air: 1x 25 m³/h (in the ceiling)
• Guest bathroom = 4.5 m² (48 sq ft) area, Extract air: 40 m³/h (in the ceiling)
• Utility room = 8 m² (86 sq ft) area, Extract air: 30 m³/h (in the ceiling)

Rooms Upper Floor:

• Child 1 = 17 m² (183 sq ft) area, supply air: 1x 25 m³/h (in the floor)
• Child 2 = 18 m² (194 sq ft) area, supply air: 1x 25 m³/h (in the floor)
• Master bedroom = 14 m² (151 sq ft) area, supply air 1x 35 m³/h (in the floor)
• Walk-in closet connected to master bedroom with door = 8 m² (86 sq ft) area, extract air 30 m³/h (in the wall below the ceiling)
• Office = 8 m² (86 sq ft), supply air: 1x 20 m³/h (in the wall below the ceiling)
• Main bathroom = 12 m² (129 sq ft), extract air: 1x 45 m³/h (in the wall below the ceiling)

Total = 190 m³/h

Just a few thoughts:
The ducts to the rooms with the highest air volume are the longest when using the same diameter.
This means that the airflow to the other rooms must be significantly throttled, resulting in high pressure losses, which leads to increased noise levels and higher power consumption.
Either the rooms with large demand are located very close to the distributor, or the duct cross-sections need to be larger, meaning two ducts.

I wouldn’t install any unit without an enthalpy exchanger.

The noise level specifications for this unit are quite concerning...

Tell me, who planned this? Did you do it yourself?
Which ventilation ducts are being used? In an extreme case (kitchen), you are running 45m³/h (26.5 cfm) through one duct.
We installed Zehnder Comfotube 75 ducts. The pipes have an inner diameter of 63mm (2.5 inches). At 45m³/h (26.5 cfm), this results in an airflow velocity of 4m/s (13 ft/s). That would already be way too high for me.
We connected almost every outlet with two ducts.

Vaillant offers similar pipes, if I’m not mistaken, although they specify the inner diameter as 62mm (2.4 inches).
So, either you go for the larger duct (92mm (3.6 inches) outer diameter / 75mm (3 inches) inner diameter), but you will most likely have trouble fitting the duct between the reinforcements of the concrete ceiling slab, or you use two ducts per outlet.
But five exhaust ducts at 190m³/h (112 cfm) would definitely be too few for me. Noise is practically guaranteed there.

Alternatively, there is also the flat duct, which is not cast into the concrete slab but laid on top of the subfloor into the insulation layer afterwards. Although the fundamental problem probably won’t change.
Vaillant only specifies this one with outer dimensions of 52 x 132mm (2 x 5.2 inches). Subtracting the 13mm (0.5 inch) difference between outer and inner dimensions of the small round duct for the wall thickness leaves inner dimensions of about 39 x 119mm (1.5 x 4.7 inches).
The free cross-sectional area of the flat duct is then similar to the small round duct.

I still maintain: there are too few supply ducts for that volume of air.

Thanks already for the initial feedback.

This was planned by Fa. PEDOTHERM.

Flat ducts will be installed on the raw ceiling slab.

Unfortunately, I do not know exactly which duct will be installed. I will ask.

Does anyone know the company PEDOTHERM and can provide some information about them?

Are there any other comments on the design I posted above?
I deliberately included the detailed planning as a document so you can have a comprehensive overview.

Is a volume of 45 m³ (about 1,590 ft³) at an "extraction nozzle" already too loud?

What about the 35 m³ (about 1,236 ft³) supply air at the floor outlet in the bedroom?

This is completely new territory for me.

Are there perhaps professionals in this forum who could help?

Many thanks,
Christian