I had an earlier thread about a potential sub-floor damp problem, which
is now closed:
We 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
Right. I would say the two problems are linked. You are getting
underfloor damp that is evaporating into the room and condensing on the
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.
|I had an earlier thread about a potential sub-floor damp problem, which
|is now closed:
No 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.
You cannot reply to this topic because it is more than 30 days old or has
been closed by a manager.
What is the Committee and Control going to do about this?
Posted from my news.individual.net account.
Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.
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)
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.
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.
First of all you need to recognise that the message returned by Google
is a generic one and is one returned if the last post is more than 30
days old /or/ if the thread one of their own, non-Usenet groups, has
been closed by the owner of the group.
Secondly, having recognised point one, and that uk.d-i-y is not one of
their own groups, it is perfectly obvious it's the "30 days" that is
being applied as the last article previously in that thread was posted
on the 2006-08-31.
So what they have done is say that they have set a local policy that
they don't allow further posts to threads to be made via their news
server in cases where the last article previously posted was more than
30 days ago.
I really can't see how you think the Committee or Control are going to
tell a news server what their local posting policies should be...
... It would the same as you asking the Committee and Control to tell
news.individual.net that they should change their local policy of not
accepting articles over 100KB in size.
>Dave Fawthrop <dave hyphenologist co uk> <snip>
And your SigSep is broken :(
uk.announce ~ moderated group to announce news / events of specific interest to
You could try running the heating for longer and, if necessary, having
the rads moved to the furthest point in the north facing rooms.
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.
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.
===================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.
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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.
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.
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