Positive Input Ventilation System

[foxyferret]

My mum has been quoted a price of £597.00 including VAT for a company to install a positive input ventilation system in her bungalow. They tested the walls and said there was no rising damp. the mould on the bedroom walls was due to condensation. Is this a reasonable price? She has asked me to find out for her, she lives in Norfolk, thanks.

[The Builder]

Considering they have to install ducts and fan(s), I would guess that's about right, foxy.
The only trouble with "forced air systems" is that the air has to go somewhere. Unless the rooms are linked by vents, air will take the easiest way, possibly bypassing the "damp" rooms. Leaving doors slightly open alleviates this.

My (personal) opinion is that it over-complicates the issue. It was one of those systems that came up in the 70s...... along with electric damp-proof systems.

I much prefer the simplicity of PSV (Passive Stack Ventilation). Passive, so no fans needed. No power used.
Ducts and vents around the house encourage a flow of air through the whole house......... right up to ridge level, where damp, stale air escapes to the atmosphere.

You know when people block up old fireplaces? It's important to put a simple vent in the boarded over flue. The reason is that, that is an example of a natural Passive Stack Ventilation system.

[Buenchico]

It might be worth finding out what your mother would get for her money. Is it just the fan or is there additional provision to ensure that the bedroom ceilings are airtight (as would seem to be necessary for the system to work properly).

This page examines the evidence behind the claims for the system
http://projects.bre.co.uk/positivevent/
while this thread includes estimates for the costs
http://forums.moneysavingexpert.com/showthread.php?t=495875

Chris

[The Builder]

Helpful stuff there Chris. :o)

[foxyferret]

Thank you both for your very informative answers.