Positive ventilation system any help please?

sophieandemily

We have had problems with damp in our end terrace house for quite a while and have gone round in circles trying to find someone who can tell us the cause or suggest something that works to prevent the patches of mould and also where the walls actually look damp. We have work done to gutters, roof etc etc nothing has worked we have also looked at insulation etc which has not helped.
We open the windows as much as possible, no clothes are dried inside etc etc, anyway we asked our local council for help however the funds they had to help are no longer available but they recommended a company to come and look at the property. Today someone came out and recommended installing a positive ventilation system he said the damp was clearly condensation as it was causing mould where penetrating damp the water would contain salt and not allow any mould growth everything he said seemed to make sense but does anyone have any experience of these systems are they effective, are they easily installed any advice is really appreciated

shaven-monkey

It's a sort of the reverse of an extractor fan.
In theory it takes warm air from somewhere and feeds it down into the living area creating better air flow and carrying the humidity up and out of the house.

Seems most of these systems involve having a fan in your loft to pump the warm air from the loft into the living space. If the loft has higher humidity levels than the house this will be no help at all.

Is this a council property or is it your own?

David_Aldred

Hi Sophieandemily,
Dampdaveski and myself write quite a few informative posts on here regarding dampness / mould / condensation with myself as an independent specialist surveyor in these subjects and dampdaveski as a good contractor who sells quite a few of the units you are describing which makes a good balance of views between us so please have a read of previous posts by the pair of us regarding these products which may be helpful especially dampdaveski's comments regarding mould removal products etc.

Where moisture laden air is excessive and unable to be removed adequately by background ventilation of the property the units you are decribing can be a helpful supportive measure and are widely adopted by Housing Associations.

The comments within your post are however a little cause for concern. Penetrating dampness does not always produce salts and can quite easily produce chronic mould growth just as much as condensation problems can. In addition during the midst of summer as we are at present condensation problems are far less common than within the cold wet winter months so jumping to the conclusion the problem is solely condensation from somebody selling a product to reduce such needs a bit of consideration.

This being the case I would really try and find the true cause of the problem before spending money on addressing the symptoms with PIV units / extractor fans. These things may still be required if found to be justified but if you can bottom out the true cause of the problem you can target what you spend your money on most effectively. If you spend a few hundred pounds on a PIV unit and it does not resolve the problem you are not going to be best pleased I imagine.

Unfortunately although people on here who post can try and suggest causes of your problem based upon the information you give, actually properly confirming the true cause unseen via the forum is only ever going to be guesswork by a process elimination from what you describe and it would be preferable if somebody competant really had a good look into what was truly going on with a site visit.

Such a visit should include metering timbers, surfaces, undertaking dew point analysis, looking into any wall cavites with endoscopes, looking under any suspended timber ground floors, inspecting roof voids and the external fabric of the building, checking if windows / walls have background ventilation, whether fireplaces are no longer in use, whether the cavity wall insulation if fitted is wet, whether there are voids to any insulation within walls and roofs, whether there is any leakage, occupant lifestyle, heating regimes, the list goes on etc.

A list of both contractors selling treatments and alternatively independent specialist surveyors be they Freelance or Consultants is available from the Property Care Association (PCA) website for a selection of those local to you. Alternatively if dampdaveski or myself can be of any further assistance please ask on the forum or private message us and we will do our best to help. Kindest regards, David Aldred Independent damp and timber surveyor

Dry_Rot

We are outside the usual condensation 'season'.

However, the problem often leaves mould stains in a pattern which can be useful as a diagnosis. If the mould is on furniture, clothing and such, which are not in contact with the outside walls then that's a strong indicator of excessive humidity. Penetrating damp does not always cause salts, especially if it is a short term or transient issue. Long term penetrating damp almost always does lead to some salting though, as minerals are absorbed as the water passes through the building fabric. Evaporation on the internal surfaces usually leaves these behind.

I have sold some PIV's which are very useful, but I tend to do so in properties where the occupancy level is very high, or where other measures have been taken and failed. Student lets with half a dozen girls in them, washing their hair every day, spring to mind.

Older property, which has been double glazed, had the fireplaces bricked up and then filled with the modern luxury's of life; power shower, microwaves, electric kettles and such, are very prone to it. The absolute minimum I like to see in place like this, is good extraction in the bathroom, which comes on with the light or is trickle and boost operated - with timer over-run. Plus good extraction in the kitchen, which is diligently used - even boiling a kettle is a good reason to pop the fan on.

A second opinion wouldn't harm, but maybe a chat with the contractor, to get more confirmation of why he has diagnosed condensation will help you, call him.

Most contractor will have access to data loggers and such, which are usefull for measuring the humidity, temperatures and dew point, but like mine, they probably won't see the light of day until the end of September, when the 'season' starts again.

Good luck with it - please do post more as you get to know it.

Dry Rot.