How can I prevent damp in unused rooms if I close them off during winter?

jj_43

MattMattMattUK said:

Buy some of the cheap single use dehumidifiers (Something like the below), if no one is going into the room generating moisture then there should be very little, when they are used up then replace them.

https://www.amazon.co.uk/ANSIO-Dehumidifier-Condensation-Moisture-Dehumidifiers/dp/B015AOGP1S/ref=sr_1_3?keywords=dehumidifiers+disposable&qid=1661518580&sprefix=dehumi,aps,127&sr=8-3

save you money, these are not effective. ventilation will work.

wrf12345

Last year I closed down one room, this time it will be two rooms - will move the bed into the office which is south facing. I get condensation on the north side but not the south, on the windows (crap pre-fensa doubling glazing). In the other north facing room with large bay I will be using celotex insulation against four of the five windows, glued in so they can form a seal and covered by curtains. I already have the insulation so minimal cost. I also have celotex cut to fit some of the other windows but removable rather than glued in, placed overnight to retain whatever heat comes into the house. Have not decided if I will be using spot infrared heating or the newish combi boiler (I would not have fitted it if I knew gas prices were going to more than double). If the weather gets siberian I will be down to one room plus unheated kitchen. I am fixed until March so 3kw of electric heating costs me a quid and thanks to the govn £400 freebie I have some "free" heating, so not all bad. I know gas is cheaper per kw but I am inclined to keep it turned off at the meter just to flick two fingers at the energy companies.

lindatoo

wrf12345 said:

Last year I closed down one room, this time it will be two rooms - will move the bed into the office which is south facing. I get condensation on the north side but not the south, on the windows (crap pre-fensa doubling glazing). In the other north facing room with large bay I will be using celotex insulation against four of the five windows, glued in so they can form a seal and covered by curtains. I already have the insulation so minimal cost. I also have celotex cut to fit some of the other windows but removable rather than glued in, placed overnight to retain whatever heat comes into the house. Have not decided if I will be using spot infrared heating or the newish combi boiler (I would not have fitted it if I knew gas prices were going to more than double). If the weather gets siberian I will be down to one room plus unheated kitchen. I am fixed until March so 3kw of electric heating costs me a quid and thanks to the govn £400 freebie I have some "free" heating, so not all bad. I know gas is cheaper per kw but I am inclined to keep it turned off at the meter just to flick two fingers at the energy companies.

 Is your celotex clear as I've just looked it up and can't see any clear panels. Also how much kwh does your spot heater use as it is an option i'd like to consider

chris_n

Celotex is not clear.

wrf12345

it is 50mm solid insulation with foil on each side (I have painted the outside bit black so it absorbs heat and does not look strange from outside) - the windows are huge and I usually only have one not closed off by curtains so plenty of light. The windows are almost useless as the plastic sections have no insulation and there are large gaps around the glass and the plastic frame in which they sit, and it is only 16mm thick two planes of glass. If they were smaller I would fit (double glazed) secondary glazing based on tilt and turn windows, bought direct from the factory but too expensive for the sizing I would need. I have done it on one of the smaller north facing windows, no codensation, bought from eBay for £100 pre-Brexit when there was a chap selling them from Poland.

If you have pre-Fensa double glazing, worth thinking about going for DIY tilt and turn secondary glazing (double glazed) if the windows are reasonably small as it is legal to fit them yourselves with no Fensa or Building Control needed as secondary glazing and can buy direct from the factory via the internet. It seems to be a third of the cost of getting a Fensa guy to replace the original windows (which are usually still watertight and can be cleaned up). It also gets rid of condensation and the inner windows do not seem to suffer from water build up themselves, although strictly speaking they should be fitted so they can drain off. I also use old doubled glazed doors internally to seal off the hallway from the rest of the house and turn off its radiator.

The infrared heaters have three elements each 600W, so max is 1.8kw - they are very directional so properly placed are pretty good on the lowest setting. Dunelm have a wall mounted infrared heater with two elements 1kw each on special offer right now, at £13.75 and it is plug-in rather than wire in (as many of them are) - it is designed as a patio heater but no reason why it can't be used indoors and out of the way on the wall it can't be accidentally knocked over. Various types are available on eBay and Amazon, not talking about the little plastic things that you can get for a tenner.

pineapple

jj_43 said:

MattMattMattUK said:

Buy some of the cheap single use dehumidifiers (Something like the below), if no one is going into the room generating moisture then there should be very little, when they are used up then replace them.

https://www.amazon.co.uk/ANSIO-Dehumidifier-Condensation-Moisture-Dehumidifiers/dp/B015AOGP1S/ref=sr_1_3?keywords=dehumidifiers+disposable&qid=1661518580&sprefix=dehumi,aps,127&sr=8-3

save you money, these are not effective. ventilation will work.

I disagree. I live in an old stone cottage with flagged floors and thick walls. Dehumidifiers have been a lifesaver. I'm on E7so if I run one, it's overnight. Takes out a vast amount of water and warms the air in the process.

[Deleted User]

pineapple said:

jj_43 said:

MattMattMattUK said:

Buy some of the cheap single use dehumidifiers (Something like the below), if no one is going into the room generating moisture then there should be very little, when they are used up then replace them.

https://www.amazon.co.uk/ANSIO-Dehumidifier-Condensation-Moisture-Dehumidifiers/dp/B015AOGP1S/ref=sr_1_3?keywords=dehumidifiers+disposable&qid=1661518580&sprefix=dehumi,aps,127&sr=8-3

save you money, these are not effective. ventilation will work.

I disagree. I live in an old stone cottage with flagged floors and thick walls. Dehumidifiers have been a lifesaver. I'm on E7so if I run one, it's overnight. Takes out a vast amount of water and warms the air in the process.

To be fair to jj, I think they're referring to the single use desiccant pots rather than a 'real' dehumidifier.

TheGardener

Most of the suggestions above combined really: We closed off one of Mums bedrooms last year and the first thing I'd say is: make sure the loft space above the rooms you intend to close off is very well insulated. We then removed all the soft furnishings except the curtains (sill - not floor length) and carpet and moved any furniture that was against an outside wall forward a few inches. Emptied the wardrobes of clothes no one wore anyway. We ran the electric dehumidifier for a day or two to have a dry start. We set the radiator thermostatic thingies to frost protect only. The trickle vents on the glazing were left open. We then drew the curtains (thick heavy lining) and closed the door. Mum opened the door and hovered around/dusted once a week and opened the curtains and windows on dry, bright days. 
It was fine - her house is a 50's built and she'll do the same this year. 
In my view the soft furnishing and lots of junk in drawers and against outside walls are the things to avoid most. Also - long curtains are asking for mildew below sill length in an unheated room. 

Green_hopeful

We did this last year in three bedrooms and two reception rooms. There was a small amount of mould around a couple of windows frames but we have wooden frames and not very good double glazing. There isn’t much moisture if you are not living in those rooms and there isn’t much cold bridging where warm moist air hits a noticeably colder area. There wasn’t any mould anywhere else. 

We also had mould on the windows of the rooms we lived in. The mould on the windows was much worse in those rooms because we created more moisture and the air was warmer. We cleaned the windows with bleach quite a bit. We are thinking of some form of tertiary glazing this year and increasing our extraction. 

I think for us the problem is just our poor windows.  I would make sure that the furniture is not pushed up against the walls so there is airflow behind the furniture and then perhaps check every week if you are worried. 

Coffeekup

jj_43 said:

MattMattMattUK said:

Buy some of the cheap single use dehumidifiers (Something like the below), if no one is going into the room generating moisture then there should be very little, when they are used up then replace them.

https://www.amazon.co.uk/ANSIO-Dehumidifier-Condensation-Moisture-Dehumidifiers/dp/B015AOGP1S/ref=sr_1_3?keywords=dehumidifiers+disposable&qid=1661518580&sprefix=dehumi,aps,127&sr=8-3

save you money, these are not effective. ventilation will work.

I agree single use dehumidifiers, are a wasteful product. Use an old jam jar/s (more than one might be needed for one location) fill it 1/3 table salt and leave near the area's you get condensation, it's worked for me the last 2 years. No plastic waste, no chemical waste and saved money.

Edit: in bold