Convert multi duct extraction

[spinho]

Hello,

My costumer wants to convert the existing extraction of a familiar building to be made for a unique fan on the roof (instead of independent fans in each flat). As you can see bellow, each flat has its indpendent duct to extrat air from WC. A identical system was made for kitchens. Is it recommended to install a fan to extract air from all flats (1 fan for WC and another for kitchens) with a union duct on the roof to connect to the fan.

The building has 6 floors with 2 flats/floor.

Current situation:

 

[MintJulep]

As you can see bellow

Actually, not so much.

Anyway:

Noise.
Oder.
Single point of failure that affects the entire building vs. only one flat.

 

[spinho]

Actually, not so much.

Why? Because it a bad solution? Or due to the works at site? I know this a bad solution, but my customer keeps with his ideas. In his opinion this is the only possibility to force the ventilation on each flat and reduce the humidity.

This is a sketctch of what we have at site. The idea of my customer is to install a duct collecting all the vertical ducts and connect it to a single fan.

 

[FacEngrPE]

So your customer has decided upon a solution to his humidity problem, and wants you to design it's installation?
I think there is a high risk of not correcting the humidity problem, or even making it worse.

There is some logic in placing all of the exhaust air requirements for a building into the locations where exhaust is needed, however the exhaust needs to run continuously vs the current being intermittently, which will impact make up air conditioning requirements.

Better to get your customer to change his requirement so you can solve his problem.

 

[spinho]

Yes. That is the hardest part. This is an old building. Without any thermal insulation.
Now they want to convert this natural ventilation (intakes on low level) to mechanical ventilation.

And for me it is being hard to convince the costumer to don’t do it.

 

[FacEngrPE]

If the customer wants to modernize the installation, doing the upgrade one piece at a time is the most expensive approach, with highest risk of ending up with a "Sick Building".

 

[nuuvox000]

Look at the energy code as well. If you have lots of small exhaust sources, sometimes you don't need energy recovery. If you have a large equipment that does a large amount of exhaust, energy recovery may be required ($$$).
If you end up connecting all the ducts, make sure you use pressure-independent air balancing valves for each unit or else you'll never get it balanced correctly as pressures change throughout the year.