Positive pressure ventilation

I've been informed that my damp problems are caused by condensation and that a positive pressure ventilator would solve them. This seems to consist of an extractor fan (with or without a heater) working in reverse in the loft and feeding air to the landing. They seem to be a very fancy price (£300 to £570 + installation).
Has anybody done this? Any recommendations?
Another Dave
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On 07/04/13 10:02, Another Dave wrote:

It sounds like utter bollocks to me.
Condensation means either drag in cold air from outside, heat it and use it to lower the RH, or simply heat the inside more to allow the air itself to hold more moisture.
the firmer has ti be teh most expensive, especially with electric heating
heat recovery ventilation is much better
Or far cheaper, insulate the areas that are colder
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wrote:

It won't.

These single fan magic solutions simply don't work. Whilst adequate ventilation is a large part of the solution to condensation simply putting a fan in the attic and blowing air in somewhere does not guarantee any sort of air flow where it is needed. Additionally, most houses are not sealed so leaking windows, holes where pipes come in etc can create a pressure of their own which will reduce the fan ventilation effectiveness.
There are ventilation/extraction systems which do work but these have input vents in every room and extract vents in kitchens and toilets/bathrooms.
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Another Dave used his keyboard to write :

That sounds like rubbish to me. You need to extract moist air at the source of the moist air only. Other than that - insulation, especially where moisture condenses.
Drawing air in and allowing it to distribute itself randomly will not help at all, especially it will not help with your heating bills.
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On Sunday, April 7, 2013 10:02:12 AM UTC+1, Another Dave wrote:

Bollocks, but not complete bollocks; there is a grain of sense in it that i s being sexed up to make it attarctive to the ill-informed.
The recommendation was, undoubedly, made by someone offering to sell you a positive pressure ventilation unit.
The real fix, as others said, is more ventilation (lower the indoor air Rh , increases heating costs) and/or insulation (increase the surface temperat ures above the air dew-point, lowers heating costs).
Extract fan(s) will make the space negative pressure with respect to outsi de and the make-up air (cold and with entrained dirt) will be dragged in th rough any gaps (open windows, cracks around doors, under floor boards, etc. ).
Positive pressure will have a supply air fan, ideally heated and filtered, so air leaks out. It is used in clean rooms, but as ventilation systems co sting vastly more than a simple fan. They have seized on the 'positive pres sure ' buzz words to mis-sell their cheap tat.
There was a study done in 'Which?' (ISTR, decades ago, I've never seen it mentioned since) in which ventilation systems were an effective cost-savin g measure IF the costs of reduced cleaning were taken into account.
A trickle-ventilation extract fan with a humidistat sounds more like what you'd need. Or a kitchen extract hood, if the moisture originates from coo king.
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Onetap wrote:

Are you suggesting that the OP tackles the cause of the humidity at source instead of spending 500 (or more) by installing a fan in the loft?
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On Sunday, April 7, 2013 4:41:41 PM UTC+1, snipped-for-privacy@blueyonder.co.uk wrote :

e

He can give me the spare £400, so he doesn't feel like a cheapskate.
Actually the OP said the problem was damp, which he was told was caused by condensation and the solution was the £500 positive pressure gizmo.
Did the salesman have a damp meter with green and red flashing LEDs?
The condensation suggestion may have just been the link to sell the gizmo and is equally suspect.
I think I'd start by checking gutters, downpipes, roofs, flashings, air pa ths into cold lofts, etc., the usual suspects re damp.
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you could buy a good dehumidifier for that price and without the installation cost, and they really do work.
-
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I'm the OP.
Alright, already. I've got the message.
For the past two weeks I've been running a couple of de-humidifiers I borrowed from a neighbour (he's discovered two springs under his kitchen and lives next to Well Cottage!). They do seem to work and I've just this minute bought my own on e-bay.
I'll go with this for a while and see what happens.
Thanks.
Another Dave
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On Sunday, April 7, 2013 4:54:39 PM UTC+1, Another Dave wrote:

Are you in Peckham, Dave?
Has he found the well? Could be the groundwater is the cause of the problem.
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On 07/04/2013 18:42, Onetap wrote:

I think there is more than one source of the problem. The kitchen floor is tiles laid on top of the original quarry tiles (the house was built in 1928) and there is almost certainly no membrane. In addition the log stove chimney is not lined and I'm trying to get that seen to as some of the damp shows signs of smoke. The other chimney is lined but has no air bricks. The previous owners fitted double glazing (no trickle vents) and cavity wall insulation (23 air bricks blocked up) etc, etc.
I'm expecting a long campaign :(
Another Dave
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On Sunday, April 7, 2013 7:05:13 PM UTC+1, Another Dave wrote:

Damp is discussed on this forum, about old buildings;
http://www.periodproperty.com/forum/viewforum.php?f=1&sid 1db8c094bc7 633fd9a932178297ee1 Allegedly, an impervious floor covering (usually cement, but tiles could d o) will reduce the evaporation from the floor, but shifts the problem up th e walls. Similarly cement rendering will trap moisture within walls; they'r e very keen on hacking cement off old properties, French drains and similar stuff; search the archives.
If the neighbour has a spring, the water level must be high. Maybe you cou ld investigate using some of it as grey water and thereby lowering the wate r level.
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On 07/04/2013 22:46, Onetap wrote: <>

Or he is living next door to Zebedee?
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The best way to fix condensation is at source with extract fans, run when there is an activity going on. Showers, bathrooms, cookers etc.
And/or, buy yourself a dehumidifier which has the fringe benefit that it helps to warm the place up a bit.
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