Condensation issues

[no_heat]

I had an earlier thread about a potential sub-floor damp problem, which is now closed:

finally had this inspected by a specialist today (from Timberwise) - he observed that the subfloor is damp due to poor ventilation, but that hasn't yet developed into anything serious, so more airbricks is the likely way forward.

He also noted that our perception of damp in the actual room was due to excess condensation. There are a lot of cold/dead-air spots in the room where we have mould forming on wallpaper behind cabinets etc. These are typically north-facing external walls.

Companies like Nuaire were mentioned, so I've been doing a little research. PIV products like the Drimaster 2000 or 365 seem widely used, although opinion is mixed. I guess I'm looking for guidance on whether installing one of these is a worthwhile step. It's not a small house -

4 beds, 3 recept, 2 bath - and I'm slightly dubious that one of these venting into the landing could make a difference in the downstairs lounge. On the other hand, I'm not averse to the expense if it could be beneficial. Equally, are there alternative solutions that would be better?

Thanks, Gareth

[The Natural Philosopher]

Right. I would say the two problems are linked. You are getting underfloor damp that is evaporating into the room and condensing on the colder walls.

My take is that venting the underfloor, and SEALING it against draughts and moisture ingress - will remove the source. In an older cottage I once inhabited, I nailed hardboard over the old pine boards, and carpeted over. That plus some mastic at the skirtings totally stopped draughts and made the room a huge amount warmer.

Then the best thing you can do is to put some insulation on the colder walls, and possibly some moisture barrier.

If there is space to dry line the exterior walls - assuming you have solid brick walls - with say 1x1 battens and 25mm of celotex plus foil backed plasterboard over, you will then totally lose the condensation, even when the room is a bit warm and sticky and its an icy gale outside.

De humidifiers are a temporary solution at best. What you need to do is prevent excess water getting in. and heat ventilate and insulate to prevent it building up and condensing.

[Dave Fawthrop]

|I had an earlier thread about a potential sub-floor damp problem, which |is now closed:

|

one can *ever* close a thread on any usenet newsgroup. What the Hell is Google up to now.

I tried to follow up the last post on that thread from my Google.groups account and got the following error message.

Sorry... You cannot reply to this topic because it is more than 30 days old or has been closed by a manager.

[Owain]

This is normal and has been so for ages (ever?). Googlegroups don't allow replying via their system to usenet messages over 30 days old; I think the 'manager' comment applies to Google's membership (non-Usenet) groups.

Probably nothing and why should they?

IMHO it's a sensible restriction as, unlike most news servers, Google has a retention period of years, and if it didn't do this there would only be pointless replies to long-dead threads.

Owain

[Pedt]

In message , at 14:12:56 on Tue, 3 Oct 2006, Dave Fawthrop wibbled

It would have helped immensely if you had read the response message in its entirety and referenced it back to that thread before making your assumptions, getting all hot around the U-bend and turning your rant and outrage spigot on and appearing to be short of a washer or two.

[Alison Hopkins]

So is his brain.

Ali

[John Bean]

Hyphenated in the wrong place probably.

[Stuart Noble]

You could try running the heating for longer and, if necessary, having the rads moved to the furthest point in the north facing rooms.

[Lobster]

What, no recommendation of a new DPC? I'm impressed!

David

[Phil L]

> We finally had this inspected by a specialist today (from Timberwise)

Ventilation and plenty of it!! - you may need to get under the floor and check for cross flow - dwarf walls are built in a criss-cross fashion underneath the joists, these are supposed to have holes in them (half a brick missing here and there)but sometimes they are inadvertently missed and air will not travel through a solid wall. Also, you may be susceptible to flooding, I have seen underfloor voids with eight inches of fetid water in them many times, if there is standing water you may need to build a sump and install a sump pump.

Obviously these are extreme measures but if it's not very bad, just extra ventilation bricks for now may cure the problem, 9X6 airbricks, three on each elevation is minimum, the ones you already have may be slotted and have become clogged (insects!) or just blocked with debris falling down the cavity or the sleeving has fallen down or something, you may be able to cure this from underneath rather than knock them out and renew, especially on the front where asthetics may be important.

The damp you are perceiving in the rooms is probably connected with the moisture under the floorboards.

[meow2222]

> We finally had this inspected by a specialist today (from Timberwise) -

sounds good

Condensation is due to either very poor insulation (eg uninsulated 4" walls) or excess interior RH. In most cases the latter. The solution to that is to reduce the sources of dampness, just go round all the usual sources and see what can be improved.

Failing that, ventilation or dehumidification can reduce RH and stop condensation. But always try to sort the cause out before resorting to these secondary measures. If you have to use these, a humidistatic dehumidifier works out cheaper as it doesnt throw all the heat away, plus it gives better RH control.

NT

[no_heat]

Thanks for bringing this back on-topic after the outrageous thread hijack. All good advice that I will take on board. Any specific opinions on the Drimaster?

Gareth

[Cicero]

==================== The advice given by your specialist seems to coincide pretty well with the suggestions I made in your earlier thread.

I don't know anything specific about the 'Drimaster' system but basically it appears to be just a system for procuring good ventilation.

I would suggest that you experiment with a couple of domestic fans used locally near your cold spots / mould areas. Direct the fan(s) towards the offending walls for a few days to see what effect they have. You should see a quick improvement in the damp although the mould is unlikely to disappear. I think that this method of localised ventilation is likely to produce better results than a general ventilation programme since you're problem is more a question of 'dead' areas than general ventilation.

Cic.

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[meow2222]

I wonder why youre asking this. The drimaster brings outdoor air in, which inevitably causes interior heated air to be pushed out of the house. It does nothing to tackle the cause of the problem, so is a fallback approach only, and its continual outpouring of heat would be a significant ongoing cost. Not a system I would consider.

NT

[The Natural Philosopher]

Agreed. Dehumidifiers are not a solution to damp, they are a way of stopping museum pieces rotting in old houses that are listed.

Or drying out houses that have been flooded.

No house that is fit for purpose needs one.

Its a bit like saying that the way to sort a cold house with unglazed windows is to stick a 100KW boiler in it.