Humidity in the House....Talk to me!

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b0rn2sk8 said:
You could also just run the de-humidifier overnight on the cheap rate power and you'd hardly notice it on your energy bill
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Yes but again no scheduling capability on the meaco.

I think a PIV would do the whole house better than s dehumidifier. Its only really good for doing one room at a time.
 
PIV is meant for those who have condensation issues, I’d avoid it otherwise.

If you just want to lower the general humidity, use a dehumidifier on a timer plug or smart plug. It will be easier and cheaper.

The warm moist air will naturally rise so put the dehumidifier upstairs somewhere and it will do the job.
 
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CaptainRAVE said:
Smart plug/timer.
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Not supposed to on the meaco, it specifically says not to power on/off the unit without using the power button. I don't know why, and obviously I could ignore this but if it does somehow cause damage then obviously don't want to.

b0rn2sk8 said:
The warm moist air will naturally rise so put the dehumidifier upstairs somewhere and it will do the job.
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My front living room downstairs is my worst room so the dehumidifier mostly lives in there.
 
Is condensation on windows an inevitability this time of year no matter what? Most of our windows are getting on a bit (probably 20+ years old) and we're thinking of replacing them anyway - would changing them for newer, more efficient double, or even triple, glazing help? None of the windows in the house have trickle vents either which I believe would help ventilation.

It's mainly the bedrooms that suffer, but we also have condensation downstairs on a morning too. On window downstairs does have trickle vents and when they're left open the two top openers are relatively condensation free, but the large pane underneath still suffers condensation.

I don't think we have anything especially moisture generating, especially downstairs. Bathroom extractor fan and window left open after showers, extractor fan on when cooking, heat pump tumble dryer if we can't dry out side but thats about it as far as I can think.

I assume it's simply the temperature differential between inside and outside.
 
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b0rn2sk8 said:
Not sure I’d ever bother with the heated versions. use your central heating, it will be cheaper.

Likewise, I would t get one unless you actually have issues with condensation.




Frost protection is fine.

The humidity itself isn’t a problem, it’s when very warm and moist air (like say from your breath) condenses on cool surfaces, that’s when you get mould.

If nothing is in the house producing moisture, you aren’t going to get damp.
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OK cool so I will leave my heater off?
 
Sinbad2000 said:
The humidity number you're quoting there is relative humidity.

The warmer the air is, the more physical water it can contain - RH is the percentage "saturation" of the air with water vapour at that particular temperature.

So air that's the same "wetness" will have say a RH of 47% at 25 degrees and a RH of nearly 100% at 12 degrees (ie, if you took some outside air at 12 degrees 98% humidity, brought it inside (through a door/window/vent etc) and heated it up to 25 degrees (without adding or removing any moisture) the RH will be 47%.

With your high RH at relatively high temperatures, I'd say you need a bit more ventilation.
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You could air the house every so often. Just heat the place up, then open all the upper/lower windows. The humid hot air rises out of the house with new hair drawn in and the warmer walls/surfaces will evaporate humidity. Only needs to be 10-15minutes. Yes it's cold and yes it's lost heat but it's not wasted as it's driving out humidity.

Originally this house used to have no cooker hood or bathroom extractor fan. Cooking and showers left the place dank and the humidity condensed on the cooler gable wall. The bathroom has an axial flow extractor and the kitchen has a 150mm sized hood vent both vent to the outside. The cooker hood in turbo mode vents enough to suck open the French doors to the kitchen. The cooker hood also acts like a slow incoming vent (there's flaps on the outside) when it's windy but overall it's not an issue. Since then we've not had a big issue although we still will open all the windows periodically. What is really annoying is the house has one window that has a little wooden 3-sides with a window that acts to provide a nice light source - it also acts like a condenser for the main bedroom so needs maintenance to prevent it from turning into a mold breeding ground - so that gets treatment just as we open the windows.. An alternative would be for us to simply put a dehumidifier into the room once in a while but the return on that approach is low as it also makes it uncomfortable to sleep in a dry atmosphere.
 
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For the people wondering about condensation in the bedrooms on cold days - I live in a very modern home with brand new windows and condensation forms on the bedroom windows that are used overnight.... There are trickle vents but they are kept closed. I just wipe them down in the morning and open them up for 10-15 mins.

I guess my point is - brand new homes suffer from condensation, so older homes will too. it's just inevitable.


It's to be cold all week so I will do a little test tonight and have the trickle vents open to see how much of a difference it makes.
 
Seems some are mindlessly chasing numbers reported on their thermostats than any actual benefit.

This is my current situation -

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(the (S) sensors are the Hue motion detectors, miles off accuracy).

Looks like the house is "fine" at ~65% but the attic still high. I think I have a hole in the roof from the old F&E tank --- I might stick a dehumidifier up there. It'll all get fixed when we extend/get the loft converted.
 
The attic isn't high because the temperature is way lower, it will be mirroring what's outside to a large extent. Like the shed is.

Your garden room is high - perhaps the wood/plastering is still drying out internally. This should be a fairly well sealed room so shouldn't be this high when unoccupied and heated.

Your bathroom is a bit high but maybe someone's had a shower this morning and its still slightly damp, towels etc.


I agree chasing a specific number is pointless, but what's important is persistent high values that are higher than they should be. In my case currently as at 13:30:

Outside: 6.8 oC, 85%
Downstairs living room: 18.5 oC, 74%
Upstairs main bedroom: 19.8 oC, 68%

I would prefer to be under 60% as above that is considered too wet. There's a definite issue in my living room, I need to get under the floor when Im able to and see what's going on. Will be a while though before I can do this.
 
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danlightbulb said:
The attic isn't high because the temperature is way lower, it will be mirroring what's outside to a large extent. Like the shed is.
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What do you mean it isn't high? It is 80 odd percent. Or are you saying because that's relative humidity because it's cold, it isn't an issue?

Are people chasing "absolute" humidity or relative humidity figures? I thought it was the latter?

danlightbulb said:
Your garden room is high - perhaps the wood/plastering is still drying out internally. This should be a fairly well sealed room so shouldn't be this high when unoccupied and heated.
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I've no idea why it is so high. It falls off a cliff when the heating comes on (80% down to ~70%). This is with AC/heating on, it must just be "me" being inside here.
 
The recommended humidity levels don’t apply to the attic, that’s effectively the outside unless you have a warm roof.

The main issue with attic spaces is condensation which is usually down to a lack of ventilation or wherever there is very low wind for extended periods of times.
 
dlockers said:
What do you mean it isn't high? It is 80 odd percent. Or are you saying because that's relative humidity because it's cold, it isn't an issue?

Are people chasing "absolute" humidity or relative humidity figures? I thought it was the latter?
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If air is heated the absolute amount of moisture in the air doesn't change but the amount of moisture the air is capable of storing goes up, so the percentage of maximum capacity goes down. That's what relative humidity is.

If heated air is at high relative humidity then it has a lot more absolute humidity too. That becomes a problem when the air rapidly cools by hitting cold surfaces as the moisture comes out of the air causing condensation.

So yes, 80+% in the loft is fine because its cold in there and its (meant to be) vented to the outside.Because its already cold, the air won't rapidly condense on colder surfaces and it will have a lower absolute humidity as well so its not so much of an issue.

Whereas if air in the house is warm and has high relative humidity then it will condense on surfaces easier and also feel more damp inside.
 
I would imagine, if your attic temp and humidity is very close to external, that it would indicate both a well ventilated attic and your attic insulation is working well to stop heat from rooms escaping into loft (if your house temp is a lot more that is)

Mebbe I am looking at it wrongly though
 
Richie said:
I would imagine, if your attic temp and humidity is very close to external, that it would indicate both a well ventilated attic and your attic insulation is working well to stop heat from rooms escaping into loft (if your house temp is a lot more that is)

Mebbe I am looking at it wrongly though
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Yep definitely.
 
Quickie (and possibly theoretical) - If RH reaches 100%, does that mean that the air cannot hold any more moisture and will start dumping it out as water if it gets any higher?
 
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