Separate exhaust ventilation fans vs central exhaust ventilation

Question

Context: we're in the Netherlands. Here, since about 30 years, all houses are built with what they call "mechanical ventilation". Actually, what they really mean is central ventilation, with one big unit serving, via ducts, local exhaust in bathrooms, WC, kitchen.

Our house was built just before this became a commonplace, and wasn't updated in this respect. It still relies on natural ventilation. I would like to add mechanical ventilation. Central ventilation is nice, but routing ducts is hard, and would cost a lot. I am thinking: could I achieve all benefits of the central ventilation by installing standard bathroom fans in all wet rooms? It should be cheaper and will look nicer. It even has the advantage that, when one wet room gets wetter, I can increase the local exhaust without making ventilation in outher rooms noisier.

Are there any disadvantages?

Answer 1

A common but not universal feature folded into central mechanical ventilation is heat recovery or energy recovery, where the outgoing air is passed through a heat exchanger which has incoming fresh air passing in the other direction. This helps to save on heating and/or cooling energy needs while providing positive ventilation to the house (not merely blowing air out while letting fresh air make its own way in through leaks.)

That is more difficult (or less cost effective) to do on a per room basis. However, if the cost equation includes a central duct being difficult and expensive, it may work out.

Answer 2

A simple calculation will tell you if your bathroom fans will do the job.

The air calculation is a product of Air exchanges per hour.

Minimal is 3 Air exchanges and better is 5 or more.

3 means 3 room air exchanges

You need to calculate the romm size in CF (cubic feed.

L x W x H

10 x 10 X 8 = 800 cf

The fan motor is 100 cfm x 60 = 6000 cf/h

= 7.5 Room air exchanges per hour = excellent