Indoor humidity 25% but condensation on windows

ahmjt

Hi all
We live in a rented two bed flat. I can't make the storage heaters to work properly, so using extra convection heaters. Every morning I get condensation on the windows. We open windows everyday for half hour, more is not possible as we have a 5 yr and 7 months old at home. Due to this condensation (and some other signs like some damp patches on bathroom for which we keep the small window open most of the time) I thought of investing on a de-humidifer (it is on its way). Today I bought a clock which also gives temp and humidity. Don't know how accurate they are, but room temperature is showing around 20C and humidity 25-28%! Now I don't know what the ideal temp and humidity shoould be but from different online source I guess they should be 20-24C and 40-50%. My humidity is way low according to these data. Temp is close. We are kind of desperate as our 5-yr one has had 4 occassions of fever/stuffy nose/cough since August. All other family members had fever at least once since then. I am just trying to eliminate the factors and I think this low humidity could be one of those.

I have a humidifier. I am running it from tonight. Question is - with 25% I get condensation in the morning (its a nightmare trying to sponge all those water from all windows every morning), and 25% is low. For healthy living I need 40-50%. How can I cope with condensation. Will I have more condensation due to higher humidity. If 25% humidity gives window condesation what can I do to prevent this condensation building up. Is my temperature of 20C OK or shoudl this be increased?
(BTW, I never understood the physics behind temperature/humidity/air-pressure, so no physics please

ahmjt

grahamc2003

It's hard to answer without resorting to physics!

But anyhow - I'd get another humidistat since a reading of 25% relative humidity seems exceptionally low to me, and probably not healthy. 45-50% is the high dehumidifications setting on my dehumidifiers, and 55-60 the normal target. Usually, our house varies around 65-75% which am trying to lower.

Now the physics and your condensation on windows (which are probably single glazed or failed double glazed?). Say you have 50% RH at 22C, then lowering the temperature will increase the RH. The temperature lowers near the windows on cold nights. When it lowers to the extent that the RH rises to 100%, then the water condenses out of the air. So put simply, the internal glass temperature is below the dew point (being the point at which the RH is 100%).(rh=relative humidity, being the ratio of how much water the air holds compared to the maximum it can hold at that temperature).

I'd say most people get some condensation - we have some new double glazed units, and even get condensation around the edges of those.

I've just bought a Karcher window Vac which is really excellent at getting the condensation off windows (we have loads of condensation due to high rh and secondary double glazing).

Edit

Oh, forgot to answer the question! Yes, if you use a humidifier you'll get more condensation on your windows (all other things being equal).

robotrobo

I've just bought a Karcher window Vac which is really excellent at getting the condensation off windows (we have loads of condensation due to high rh and secondary double glazing).

i advise you to buy one of these !!, it will not cure your problem , but :)it makes life easier & it does what it says on the tin

ahmjt

The idea of Winodw Vac is a nice one. How frequent do you wipe your windows? I find it very hard to do it in the morning (with work, getting myself and kids ready for work, school).

When I ordered the dehumidifier from Amazon I included a digital hygrometer as well. So I think I will be able to get a second reading now. and I may have to return the dehumidifier.

Many thanks for your suggestions.

HappyMJ

The ideal temperature for a bedroom is actually supposed to be low at around 16 degrees. The blanket on your bed will keep you warm.

macman

A tad off-topic maybe, but since the convectors will be costing you 3-4 times as much to run, why not get the storage heaters set up and working properly?

grahamc2003

HappyMJ wrote: »

The ideal temperature for a bedroom is actually supposed to be low at around 16 degrees. The blanket on your bed will keep you warm.

We don't mind our bedroom cooler than that, and anything approaching 20C (and you get much hotter than that in most hotels I've been to) and I get very unconfortable. One problem with a bedroom at 10 or less is the initial getting in a cold bed - but that is easily solved, as I think you do, with an electric blanket. Crisp outside the bed, warm inside the bed suits us.

As to general about the house when actually doing things, 16C is fine. It's only when I flop in front of the TV or read a book or otherwise inactive that a room temp of 20/21 is necessary for us, but most visitors feel cold at that temp - I think it's something you get used to. Many people have their homes too warm for our comfort.

macman

Cold at 21C? Yikes! I find 19C is fine for living rooms.

ahmjt

I also feel comfortable at around 19C. Anything more than that I start to get headache, stuffy nose etc.

macman, thanks for mentioning about the storage heaters. That was on my list as well. Unfortunately they are not working, and so far I am still waiting to get a response from my estate agent for this. But this is definitely on my to-do list.

ahmjt

Surprise surprise....the 2nd set of hygrometer was showing humidity of 55% when the first one was showing 37%. This morning (after some humidifier run) the first thermo showing 43% and the 2nd one 66%, so always a 20 point difference! Now I am confused.

C_Mababejive

I wonder what sort of gap there is in the panes of your double glazing? The real issue here seems to be the condensation due to the interface temps between the warm air in the room and the internal glass pane.