Avoiding condensation in such cold weather

David_Aldred

Hi - lots of answers bouncing about about from simple increased ventilation to improving heating to improving lifestyle / ventilation to more technical views on relative humidity / temperature calcs.

Do not get too hung up on hygrometer / room temperature readings from the type of instrument you buy at Argos etc as you are probably looking at the readings during the day when it is warmer than at night or you are out working with heating off and without knowing what the room surface temperatures are the picture is incomplete and you may only confuse yourself.

When we do dew point analysis for investigations at properties we may take snapshot readings at time of visit for room relative humidity, air temperatures and surface temperatures to see if condensation is shouting at us upon wall surfaces etc but in depth analysis needs to be done over at least a week with sensors in place that constantly monitor and record the information to be of any real use to build up a lifestyle picture.

Going back to the original post the kitchen in this case is unheated, it is fairly large with two outside walls to its boundary and it is an area where warm moisture is produced no matter how many lids you put on pans etc. The property is rented which limits structural alterations the tenant can do themselves and the tenant does not want to spend a lot of money heating walls surfaces / air temperatures.

Given the above it is not surprising condensation with associated mould will occur and at the very least / best this is going to be transient and at worst highly likely to be sufficiently prolonged for the fabric of the walls and other surfaces to accumulate that airborne moisture in order to be in balance with it. As the fabric of the building accumulates this moisture it forms a resevoir that will sustain the problem even during better weather in come cases. The thermal conductivity will increase as materials that should contain air in their pores start to contain moisture instead. When this is sustained the building becomes colder because water is less of an insulator than air and therefore this only makes the fabric of the building more prone to condensation both on the surfaces and within the depth of the wall itself which result in a downward spiral of coldness and dampness.

So where does the tenant go with this? Well they can throw the problem back at the Landlord and say the balance of insulation / heating / background and mechanical ventilation is so poor as to make the area unfit for habitation. The Landlord if they want to dig in and not spend money can claim that they are only liable for disreapir and if the property was built like that then whilst they may attempt to improve things they are not compelled to do so. The tenant may respond by either putting up with it and clean the mould down as soon as it occurs to prevent their health suffering or move to a better property.

Hopefully it will not come to that and the Landlord will see that it is in their own interest to have a happy tenant / a property free of unwanted dampness / mould and they will take measures to improve the situation.

Such measures will be by making surface temperatures a little higher, constant background heating rather than peaks and troughs of on / off heating (since condensation is temperature related) where the thermnostat trips in and out to meet minimum temperatures rather than going on / off by clock and improvements to secure background and mechanical ventilation to the area.

The best type of extractor fan for kitchens are humidistat controlled which activate automatically rather than manually and these are typically specified at 150mm diameter, 60 litre / second air exchange with minimum 15 minute overrun once activated to commense at 65%RH or above given naturally occurring airborne spores of mould will flourish at around 74%RH.

Keep doors to kitchen leading to other parts of the property closed during cooking / boiling kettles etc to allow the extractor to do its job and remove this moisture laden air before it is allowed to migrate to other parts of the flat.

Hope this helps, kindest regards David Aldred Independent damp and timber surveyor

richardc1983

neas wrote: »

Sorry to contradict what you are saying but relative humidity RH... is dependant on temperature... hence why all hydgrometers have a temperature reading.

from wikipedia:



Damp is a problem because if you have 50% RH at 20-22 ºC... but then the temperature drops to 10 ºC (i.e. in OPs kitchen) then the relative humidity there will be up to 60-70% compared with the 'hot' room... which will be a nice environment for mould. So although the water in the air is eventhroughout the building... living rooms and bedrooms (at 20ºC) will not get mould... but the cold room (at 10ºC) will.



Also the even if you have a RH of 50% at 20ºC... or even 30ºC.... because your windows/external walls are at 0ºC when the water vapour touches the window it will condense (as you put it there RH at that point will saturate i.e. go above 100% and form to water)

I think we saying similar things just in different way :P. In winter with cold windows you will always get a bit of condensation unless you get really low Relative humidity. With OP its worse because room is cold and produces lots of water vapour to start with.

I dont think you have read all the messages properly:

The OP states:

" the hyro thingy/clock/thermometer is reading 55%, 12d, 17:15 not too bad by your post, gotta work out this relative bit though."

So at 12C the user has 55% so at perhaps 20,21C this would be about 40% which is not an issue and is considered normal humidity and comfort level.

Again I dont think the user has a damp problem, just a very cold room where any moisture in the air will condense.

I will mention the glass of cold water on a summers day.

Moisture condenses on the glass because its the coldest day.

Same thing happening here, as the glass reaches ambient temperature, this affect stops.

richardc1983

Again we are going round in circles, the key to this is heating that room and keeping air circulation moving in that room, a fan heater would be good for this, dehumidifier is a more expensive option but you havent got a damp problem.

Your walls only get wet when you cook so its only the cooking.

You could speak to the landlord to see if they can put some sort of heater in, or an additional radiator and explain the problems your having, make out you are not cleaning it up and it could start to damage the walls etc.

neas

He has 55% at 12 degree C... but his walls are probably at 0-4 degrees... if they are poorly constructed... so as mentioned the RH at those points will shoot up to higher RH. For example.. windows are colder than rest of flat normally .... because they aren't as good insulators as walls and bricks etc... so its why most people see condensation in winter... as window has been at 0 to -4 degrees.... meaning RH at that point will increase.... ergo water changes to liquid.

Again we saying same things... point im making is the wall and windows... will be at a higher RH... as mentioned by David Aldred... when doing proper analysis they need to read the dew/humidity content on wall by touching a sensor to it... and it differs throughout building... similar to how they detect damp (rising or otherwise i guess)

gemmalouanna

I bought this dehumidifier today:

http://www.homebase.co.uk/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=20001&partNumber=148310&Trail=searchtext>DEHUMIDIFIER

Overall best value I think (looked at argos/B&Q etc) as it is 16L (plus an extra 10% off price today/tomorrow)
Hoping it helps with the condensation problem in our house!
It has already collected quite a bit of water in the couple of hours it has been on so it can only help - I hope

richardc1983

THe argos one for £70 is prob better value and has front air discharge so you will get the warm air blown at floor level.