High humidity and condensation

iphone4

I'm suffering from condensation dripping down windows and creating puddles on window sill, especially in bedroom. It's causing mouldy patches on walls, and a damp smell.

I've got a humidity meter and it tends to read about 90% in the morning (reduces to about 80% during day). I've been leaving the window open a fraction overnight, but that hasn't helped. Currently we haven't got the heating on in the house. (Even when it is on, no one is in during the day, so it would only be on in the evening).

I've read all the threads here, and I'm trying to use extractor fan in kitchen and bathroom as much as possible. I'm also opening windows when I can.

I recently topped up the insulation in loft. It was just a rather thin sprinkling of loose vermiculite, and this has been replaced with fibreglass rolls, and a partial chipboard flooring. I wonder if this is contributing to less ventilation in the house generally. I'm not sure if I should have left a gap in insulation around edge of roof, as my roof has no eaves - there is no overhang of the roof beyond the walls. Inside the loft, there is no daylight or explicit ventilation, although the loft itself does not seem to be suffering from condensation.

Also, the house was built in 1920, the exterior walls have no cavity, and the windows are all UPVC double glazed.

Any recommendations?

ariba10

This might be of help to you.

(Removed by Forum Team)

cookie_monster

Had the same problem, purchased one of these and it seems to have helped, windows now only have a slight mist on them in the morning.

http://www.comet.co.uk/shopcomet/product/582409/DELONGHI-DES-12?cm_sp=FeatureEnd-_-Dehumidifiers-_-position

Well recomended.

David_Aldred

Hi,
Excellant that you are able to measure the relative humidity yourself and you really need a thermometer to measure the room temp and surface temps too.

Naturally occurring mould will flourish from around 74%RH so you can see you are well above this level so no wonder you have mould. The temps are very important as the dew point (the temp at which condensation will occur) varies with the temp.

For example at 80%RH if your room temp was say 16 deg Celcius the dew point would be 12 deg Celcius so any surface temp you measure to walls / floors / ceilings at or below that temp will have condensation with associated mould form on it.

If the room temp is 18 deg C at still 80%RH the dew point will be higher at 15 deg C and equally if the room temp is lower say at night / when you are out and drops to say 10 deg C at 80%RH then the dew point will also drop to 7 deg C so you can see how / why tboth air and surface temperatures are so important as well as relative humidity figures.

People will say they don't see condensation but it is when they are out or at night and the temp falls such that what the air could hold as a vapour at one level of temperature it can no longer hold at a lower temp and accordingly condenses out.

Relative humidity of 80-90%RH is high and wood is wet at 85%RH so you need to get this down by all the usual means. Humidistat controlled extractor fans (not manual) of sufficient capacity set to a level below which mould will occur and to overrun at least 15 minutes fitted by NICEIC electrican to all bathrooms, utility, and kitchen. Background controllable ventilation to all rooms either through window heads and doors. Consider self closers to kitchen utility and bathroom doors - keep closed when cooking / bathing and open windows within these areas during such events. Fit PIV units if you can afford them and check any voids beneath suspended timber ground floors are not wet and evaporating up into your rooms compounding the problem. If they are this needs to be addressed by opening up / sub floor ventilation and additional works. Having a boiler thermostat that hunts for minimum temps (say 15 deg C and trips in and out to meet them rather than on a simple clock so the property does not go cold will also help.

At 90%RH at a room temp of say 16 deg C the dew point is only 14 deg C so the walls and other surfaces only have to be 2 deg C lower than the air temp in the rooms and you will have condensation but in truth 90%RH is a saturated environement in which to live and will not be doing you and your house / possessions any good at all. The products of mould growth will make you poorly.

Insulating the loft void by applying insulation on the horizontal ceiling makes the air above the insulation (i.e. on the cold side of it) colder than it used to be before you insulated the loft void. Older houses (and even some modern ones) are not designed to function for this occurence and the dew point within the loft void is lowered such that condensation / mould occurs more readily.

To make it worse if the property was old there may have been ventilation through the roof covering slates / tiles because there was a lack of roofing felt. If the roof has been stripped and re-roofed using a non breathable roofing felt this reduces ventilation through the roof void and as a result the relative humidty within the loft void may go up and the risk of condensation especially if the ceilings have been insulated consequentially goes up.

There should be at least 50mm between top of insulation to ceilings and underside of roof covering and if condensation within the roof void is confirmed steps should be taken to improve the roof void ventiation at both the eaves and high level to encourage cross ventilation of the roof space. If there is no soffit board at the eaves within which to fit vents (that should include insect protection) then under slate or under tile vents can be fitted in this area (see Redland or other tile / slate manufacturer websites) along with ridge vents all in accordance with the Building Regulations.

A small de-humidifier of the types sold in DIY and other chain stores tend to be only effective within the room they are placed. There may be some benefit in hiring an industrial sized unit for a short period as these are more up to the job to remove chronic levels of realtive humidity and dry the fabric of the building down. Remember everything wants to be in equilibrium and decorations / plaster / wood etc will all readily absorb this excess humidity until in balance with it. If this is sustained a moisture resevoir builds up within the fabric of the building that will make the situation continuous rather than transient such that the property will remain dampe ven during more favourable weather / temperatures.

Keep observing the relative humidity and room / loft and surface temps especially when the property is at its coldest and adjust ventilation / heating and insulation until an appropriate balance is achieved that takes you out of the dew point ranges for all temps within the property though minor transient condensation will always tend to be an issue such as when you take an ice cold beer or bottle of wine out of the fridge

I hope these general comments help. Kindest regards David Aldred independent dampness and timber surveyor.

dampdaveski

Hi iphone4,
The following is copied and pasted from a post on this forum, hope it helps

Hi Fender, everyone,
condensation is a major part of my business
I've answered this quesiotion on this forum a few times
Salt / Washing up liquid / Aunty Gerties socks etc
Salt is hygroscopic i.e. it has the ability to absorb moiture from the air, washing up liquid / shaving foam all they are doing is creating a 'slippery' surface to resist the condensation forming on the glass - None are treating the cause of the condensation
Dehumidifiers
These do work, however they do indeed cost 2-3 pence an hour to run some are a bit more some a bit less, they have to run pretty much all the time, are noisy etc and again they are reacting to a symptom of the condensation problem AFTER it has occurred
Extractor Fans
Helps to have these (obviously) however if you don't use them they are only a piece of plastic sat in the wall
Trickle Vents
These can help but controlling a condensation problem is all about getting the right amount of air changes inside your house / flat, think about how much air is in each room and then think how much air can pass through a trickle vent!
What Do I recommend
Check out the nuaire drimaster, envirovent loft unit, lofty condensation control units (PIV - positive input ventilation )
http://nuaire.co.uk/Product/Residential_Products
www.envirovent.com
Can't find the lofty manufacturers website, but a typical supplier is http://www.breathingspace.co.uk/more...=8&product=176
Expelair also have one of these units but envirovent make it for them!

I regularly use www.condensationproducts.co.uk and yes I have mentioned them before on here and yes I've told them and had a bit of discount for doing so, but i regularly get good service, prices etc so what the hey!

Check these peoples websites out there is a raft of information out there and it saves me typing it
I fit these units on a daily basis at the mo and have never taken one out
hope this helps
DD
Update - just realised this post is from 2007 wish i'd saved my fingers- hey ho!

iphone4

Thanks for the responses. I checked the temperatures. It was 15 C at night, and 89% RH. It was 12 C in the morning and 91% RH.

Is leaving the window open overnight a good thing? With no heating, it means the temperature drops a few degrees, and so the relative humidity is higher.

If I want to get an expert in for advice, who can I trust? It seems there's a lot of different opinions on the causes and cures.

myhooose

Sorry to hijack the thread, but i think i may have condensation problems in my loft. Where does the condenstaion usually form?

converse

This thread of interest too! We have (what I thought are) good quality uPVC double glazed windows, all the glazing units are fine (about 8 years old, we had them fitted, to replace wooden units, none have broken down).

During the winter (this started about 2 weeks ago when the outside temp dropped) the windows are soaked from top to bottom every morning, it takes about half a roll of kitchen roll to mop it all up and it's obviously a ideal condition for mould, although I clean the window with an anti-mould spray every few months.

It only happens in our bedroom or in other bedrooms where people are sleeping, (it always happens in our en-suite window too), and only if it's cold outside, never happens in warmer weather obviously.

The windows don't have any trickle vents, but you can open them about 1cm on a locked setting, however in the winter it's just too cold to do this!

We keep our bedroom about 18 to 20 degrees before going to bed.

I did think perhaps the glass units aren't a high enough quality and was considering getting them tested (can this be done) and having the glass replaced. I've never experienced this in any other houses we've lived in, this is a modern house, but does lose temp quickly during the night, suggesting there is no cavity wall insulation. The loft has a very good layer of insulation (and in very cold and still conditions that gets condensation in.)

I did think good windows would prevent this...

We do use a black outblind at night, and I did think this made matters worse, so we've not used it for a while, but there is little difference just with the curtains shut and/or the blind used.

All other windows, on very cold nights, get a tiny bit of condensation on the bottom edge, but this evaporates in an hour or so in the morning.

Viper_7

Rather than tacking the condensation - look at why there is so much moisture in your home - usually because people dry clothes inside over radiators inside airing cupboards etc.

The moisture from the clothes ends up in the air - than as previously posted when the air cools on an evening when usually heating is off or turned down it condenses.

Same for showers/baths - look at opening a window when taking either and close the bathroom door until all the steam has gone.

The problem is made worse in modern houses as there is less natural ventilation.


so either keep the property warm all the time - or get rid of the source.

converse

As per Viper_7s advice, yes we do all that, we do sometimes dry clothes on the radiators, but only downstairs and have windows on vents when we do this.

Whenever we shower, we have the extractor and the window open, and providing we aren't going straight out, usually leave it open for 30 to 60 minutes afterwards too.

I also open the bedroom windows for a good period in the morning upstairs (regardless of how cold it is) as we like some fresh air in the house.

I think it's true as Viper_7 says, about it a problem in newer houses, we used to live in a house around 40 years old, but virtually as big, it stayed much warmer, and never got condensation anywhere.

We do live in a very exposed country area, so I suspect this doesn't help.

I wish we could fix it easily, it feels very unhealthy to wake up to streaming soaking windows.

dampdaveski

Hi converse,
Check out the links in my reply above, a PIV system will control your condensation problem with ease i'm sure. my sparks is fitting 2-4 a day at the mo, we don't overcharge, we install in social housing upto v expensive properties. I have one in my house, my sis's house, parents have one too (though i get them at cost of ocurse).
They simply work.
HOpe this helps
DD