I can't understand this idea of "leaving a window open" to ventilate a
room, particularly at night. If you have a humidity meter outside, it
almost never fails to reach 95%+ humidity, in the early hours, whereas
inside it will usually be 60 - 70%. So by opening a window, you are
allowing damper air to enter!


If you warm up the same moisture laden air the (relative) humidity will
go down, humidity is just a measure of how much moisture the air ( at
that temperature will hold)
e.g.
15C 100% humidity air warmed to 21C will be 70% humidity.
So letting colder air in will not necessarily let in more moisture.

In message , Jeff Layman
writes

In cleaning up the air we breath, we've just exchanged one form of air
pollution for another, except this time it's fungal rather than
chemical.

I have no idea how sound the science behind that claim may be, but it
certainly makes a lot of sense. We really didn't see mould in most
ordinary houses 50-60 years ago, but these days, it is everywhere. Why?
My grandparents, like so many people then, had a room which was only
used on high days and holidays, yet it was never mouldy. No central
heating of course, and the fire lit Boxing Day.

--
Graeme

On 01/10/2017 12:10, sweetheart wrote:
On Sunday, October 1, 2017 at 11:37:06 AM UTC+1, Bob Minchin wrote:
sweetheart wrote:
On Sunday, October 1, 2017 at 9:06:57 AM UTC+1, Brian Gaff
wrote:
Small but significant leak in a pipe somewhere near a
radiator? I guess you need to run a de humidifier and see what
you end up with. If there are masses of water being removed
with few people in the house there has to be another source of
moisture somewhere. I mean you do need ventilation but not to
the extent of heating the outside! I suppose it is possible
that the surfaces concerned are much colder than the rest of
the place but unlikely I'd have thought.

Brian



There is absolutely nothing leaking. I have been through the
whole place. Its basically condensation.
--

OK No leaks then so where is the water coming from? I assume this
house is a relatively modern build standard with a damproof
membrane under the floor?

If there is a continuous DPM, then usually the answer boils down
to lifestyle. Sources are Breathing: already covered, unavoidable
but keep a small window open overnight in the bedroom to help.
Cooking: Use lids on all pans, microwave instead of boiling veg,
use extractor hood to outside from the start of cooking until 30
mins after. Laundry: never ever dry clothes in the house. Use of
high spin speed and a tumble drier is best or have a utility room
with a dehumidifier and forced air circulation. Bathing: showers
and baths create a lot of air born water vapour. A powerful
extractor when you are in the bathroom and open windows with
extractor still running for 30 minutes after leaving the bathroom.
Heating: long term heating will heat up the fabric of the house
and reduce condensation. short term heating just raises the air
temperature which enables it to hold more water which is dumped as
condensation on cooler walls.

If that lot does not improve things, and it really ought to, then
a mechanical heat recovery and ventilation system should be
considered.

The house is sound. I have had it checked, double checked and
maintenance has all been done.

I think someone before me actually over insulated this house. Its
1950's and its supposed to breathe, it was not built to be bubble
wrapped and it doesnt breathe anymore - or at least not properly.
All the surveyors and builders just laugh and tell me its " The
Cornish problem" and I am lucky because many houses are worse. But I
have a weak chest as a result of pneumonia a few years ago and the
mold is a big issue for me.

I have had it suggested I need to ventilate more. I have got
ventilators.

Exchanging warm moist air for external drier air with some sort of smart
heat exchanger might help a bit. Letting some more air in from outside
will help but getting rid of the wettest internal air will help more.

Every year I have to re pain the wall and ceiling and remove the
mold. I did it just a few weeks ago and its already coming back.

It shouldn't be that bad unless you have a lot of people in the house
all taking a shower every day and no air extraction in the bathroom.

I open windows but that really doesnt work. Its works in summer . It
works on a dry day. The hygrometer in the kitchen is currently
showing 70 ( 60 is maximum normal) . I am cooking and this does
increase the problem. However, I have lids on the pans. I have my
oven door firmly shut. I have to cook and feed my family and
myself.

Its the pans of boiling water that are the biggest source of water
vapour - do you have an extractor hood over the cooker hob?
Any other extraction in the kitchen?

A hermetically sealed house can end up with silly levels of humidity
inside if you make it completely draft proof. But I can't see that a
1950's house would be all that sensitive to being insulated. A Victorian
building with lime mortar and no damp course you have to be very careful
what you do since disturbing the moisture equilibrium in the brickwork
can cause serious trouble. Makintoshes Hill House is an example of what
can go wrong (he believed the claims of Portland cement render at the
time of building and it is now a nightmare to control humidity inside).

Bad problems once the impervious render ages and cracks water can get in
trapped against the brickwork but cannot get out except into the house.

--
Regards,
Martin Brown

Graeme wrote
Jeff Layman wrote

In cleaning up the air we breath, we've just exchanged one form of air
pollution for another, except this time it's fungal rather than chemical.

I have no idea how sound the science behind that claim may be,

It isnt.

but it certainly makes a lot of sense.

No it doesn't.

We really didn't see mould in most ordinary houses
50-60 years ago, but these days, it is everywhere.

No it isnt, particularly in the super insulated houses in scandinavia etc.

Why? My grandparents, like so many people then, had
a room which was only used on high days and holidays,

Odd way to do things, particularly with the real
standard of living so much lower for most people.
We never operated like that and I am older than you.

yet it was never mouldy.

No mould in my place, even in the room where the shower is.

No central heating of course, and the fire lit Boxing Day.

And draughty as all hell presumably.

But the scandinavians prove that superinsulated can be done
properly and you don't end up with mould everywhere.

Robert wrote:


I can't understand this idea of "leaving a window open" to ventilate a
room, particularly at night. If you have a humidity meter outside, it
almost never fails to reach 95%+ humidity, in the early hours, whereas
inside it will usually be 60 - 70%. So by opening a window, you are
allowing damper air to enter!


If you warm up the same moisture laden air the (relative) humidity will
go down, humidity is just a measure of how much moisture the air ( at
that temperature will hold)
e.g.
15C 100% humidity air warmed to 21C will be 70% humidity.
So letting colder air in will not necessarily let in more moisture.

Why not just knock the place down and start again?

On Sunday, 1 October 2017 08:54:41 UTC+1, sweetheart wrote:
Some will understand this problem and others will not. You have to know about wet and damp weather and condensation in old ( and over insulated maybe?) houses.

So, winter is coming on and now I have to close the windows ( its colder) or heat the rain and the wind outside. My condensation and mold problems are returning and they are spreading. What was a problem in the kitchen has now it the whole house. Its musty, stinking and black mold is growing in a lot of corners.

I have cleaned, painted and sorted all the maintenance problems. This is not leaking roof, guttering or anything else. I have cut back trees and checked under the floor. This is a condensation issue - beyond stopping breathing. I am at a loss.

I have been told to put more insulation in, new windows double glazed and all manner of energy efficiency - and I did - problem made worse! Its still biggest in the kitchen ( where I have both a de humidifier and a heater now)

So, I seem to be down to two solutions. I either

(a) I have to turn up the heat ( most rooms are sitting at 20 degrees C - with the kitchen at around 15 C). I have even had one heater on all summer .....

b) try for one of those ventilation things that go in the roof ( Nu air?) which promises to sort it out ( but, hey, promises, promises?)

Can anyone who has really had this problem and who has sorted it advise now?

Dehumidifier really is the way to go. Ventilation achieves less RH reduction, and in winter at much higher price. HRV beats bare ventilaion but still DH is better.

Options:
A 2nd dehumidifier
Adding a 400w building type type - but as they're more noisy and use a big fan you may want to just run that when you're out.
And is the current dehumidifier working correctly?

For paint there are various additives you can put in, eg copper sulphate, zinc sulphate, aspirin. Cleaning existing moudy areas with bleach can help.

http://wiki.diyfaq.org.uk/index.php/Dehumidifier
http://wiki.diyfaq.org.uk/index.php/...esistant_Paint


NT

On 01/10/2017 09:26, sweetheart wrote:
On Sunday, October 1, 2017 at 9:06:57 AM UTC+1, Brian Gaff wrote:
Small but significant leak in a pipe somewhere near a radiator?
I guess you need to run a de humidifier and see what you end up with. If
there are masses of water being removed with few people in the house there
has to be another source of moisture somewhere. I mean you do need
ventilation but not to the extent of heating the outside!
I suppose it is possible that the surfaces concerned are much colder than
the rest of the place but unlikely I'd have thought.

Brian



There is absolutely nothing leaking. I have been through the whole place. Its basically condensation.
--

That's easy enough to isolate - run the duhumdifier, get the humidity
down to whatever it is outside, and go out for the day. If the
humidity's significantly higher than outside when you get back, you have
water coming in. Mentioned without wishing to wind you up further :-)

I'm sure you've checked - but the obvious might be bridged DPC (rubbish
against the outside walls), brdiged cavity, poorly sealed or blocked
chimney, failed DPM/poor underfloor ventilation, poorly functioning
gutters.

And things like uninsulated walls combined with walls with no solar gain
are always going to be against it even with normal use. That can be a
quick and cheapish fix - I've put 25/50mm of celotex into alcoves and a
south facing wall - made a huge difference to the comfort and measurements.

Then again, as you suggest, it could be environmental, and you're just
in what is in effect a swamp bed. Do your neighbours have similar problems?


--
Cheers, Rob