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

[danlightbulb]

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?

yes correct and that is exactly what condensation is - moisture coming out of the air near a cold surface because the air has more moisture in it than it can hold at its new suddenly lower temperature.

What paragraph are you referring to?

Ha - yes your first one was completely correct.

 

[dlockers]

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?

You're asking if you can create a microclimate/rain cloud in your house? I am also interested in this

 

[Mason-]

You're asking if you can create a microclimate/rain cloud in your house? I am also interested in this

You effectively do at your cold spots i.e. the windows. You have warm air at e.g. 60-70% RH, rapidly cooling at a window (and the RH therefore increasing) causing condensation.

 

[Sinbad2000]

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?

You can experience this if you ever do a chamber dive.

When they start releasing the pressure you get the entire inside of the chamber turning into a cloud (both because decreasing pressure and decreasing temperature increase RH)

 

[dlockers]

Seems some are mindlessly chasing numbers reported on their thermostats than any actual benefit.

This is my current situation -

(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.

^

So as per latest discussion; I don't actually have an issue then? I'm at the top end of recommended but within the tolerance of the sensors probably fine?

 

[Richie]

I would say so.

 

[danlightbulb]

You're asking if you can create a microclimate/rain cloud in your house? I am also interested in this

Take a hot shower with no windows open and extractor off. You'll be inside a cloud of near 100% humidity water vapour.

 

[danlightbulb]

^

So as per latest discussion; I don't actually have an issue then? I'm at the top end of recommended but within the tolerance of the sensors probably fine?

Yeah you're lower than me. Solid wall older house will always be worse than new cavity wall house (assuming new house is ventilated).

Any mould spots in corners or behind furniture, especially on external walls?

 

[dlockers]

Yeah you're lower than me. Solid wall older house will always be worse than new cavity wall house (assuming new house is ventilated).

Any mould spots in corners or behind furniture, especially on external walls?

Tiny bit on skirting board by the french doors - nothing anywhere else as far as I can tell.

 

[danlightbulb]

Tiny bit on skirting board by the french doors - nothing anywhere else as far as I can tell.

For me, similar, odd spot of mould in the colder areas near doors but nothing major.

And we get condensation on the windows when its cold out.

Its a big improvement on when we moved in, there was a very musty smell to the downstairs. If I go away for a few days and the rooms are closed up, then this comes back in my living room but its better than it was when I moved in.

Just have to keep an eye on it until I can get under the floors properly and see whether I have any water pooling.

 

[jpaul]

I'd maybe be checking calibration on some of these humidity measures ..... (earlier post somewhere) had done that on one I picked up for parents ... you put them in a sealed bag with a brine solution.

 

[dlockers]

I'd maybe be checking calibration on some of these humidity measures ..... (earlier post somewhere) had done that on one I picked up for parents ... you put them in a sealed bag with a brine solution.

Only practical thing to do is check them against each other tbh

 

[Mysterae_]

yes correct and that is exactly what condensation is - moisture coming out of the air near a cold surface because the air has more moisture in it than it can hold at its new suddenly lower temperature.

What the hell is going on in my loft then?!

I've not been up there to check on the upstairs swimming pool that is the loft going by the 99% humidity....

Not long back from work, I'll put my trunks on tomorrow and check it.

 

[danlightbulb]

What the hell is going on in my loft then?!

I've not been up there to check on the upstairs swimming pool that is the loft going by the 99% humidity....

Not long back from work, I'll put my trunks on tomorrow and check it.

Nothing is wrong there. The temperature dropped to near zero, so the moisture carrying capacity of the air fell too which is why the relative humidity rose. There won't be much absolute moisture in the air at such low temperatures and it won't be condensing onto colder objects either.

 

[Mysterae_]

Nothing is wrong there. The temperature dropped to near zero, so the moisture carrying capacity of the air fell too which is why the relative humidity rose. There won't be much absolute moisture in the air at such low temperatures and it won't be condensing onto colder objects either.

Thanks for the reassurance. There's nothing up there at the moment bar a few tools as I'm not quite finished flooring it. I'm half expecting the new loft flooring to be soaking up any moisture like a sponge.

I placed the humidity sensors at either end of the loft near the apex of the roof, so that may be the worst (or best) place for them to be, dunno. If only the sensors were rated for outdoor use, that would have a useful comparison.

 

[Grim5]

Nothing is wrong there. The temperature dropped to near zero, so the moisture carrying capacity of the air fell too which is why the relative humidity rose. There won't be much absolute moisture in the air at such low temperatures and it won't be condensing onto colder objects either.

I was gonna say I thought temp dropping = less moisture in the air, and higher temp = higher moisture carrying potential. If he goes into his loft I wouldn't expect he can feel moisture on his skin

 

[Kol]

Ever since watching Charlie DIYte and his journey into the humidity rabbit hole I became obsessive about it. In my old Victorian terrace winter was a challenge but our Meaco’s did great.

In our current place, I’ve almost the opposite issue during the cold weather, it’s between 41-45% relative humidity. The dehumidifier clicks on to measure and then clicks straight back off as it’s not needed.

 

[krooton]

I got a PIV and it didn't really help, I think they might be BS.

Conversely, ours has worked wonders.

Master bedroom now sits in the 50-55% range, whereas before it would hover around 70%.

New build, Drimaster set to 4, trickle vent in en-suite, cat flap, and extractor fans are the only escape routes and it has cured condensation on en-suite and master bedroom windows completely. No more mould in the en-suite as well.

Landing can feel a wee bit draughty, but heating drier air is easier so out actual heating bills haven't changed at all. Running a dehumidifier would have pushed leccy bills up a fair bit.

 

[squerble]

Ever since watching Charlie DIYte and his journey into the humidity rabbit hole I became obsessive about it. In my old Victorian terrace winter was a challenge but our Meaco’s did great.

In our current place, I’ve almost the opposite issue during the cold weather, it’s between 41-45% relative humidity. The dehumidifier clicks on to measure and then clicks straight back off as it’s not needed.

Yep I regularly see 40-45% RH around our house during the cold weather.

I've even filled our trickle vents with foam to reduce the noise and cold air they were letting in, though I've left the one in the en-suite alone. We don't have to do much other than have the window open briefly after showers and leave the trickle vent for a little bit longer too. RH drops very quickly and then we can close the window/vent and let the heating drop the RH even further.

 

[danlightbulb]

What do people make of this:

Downstairs in my house. There is a front living room, a back dining room (not connected, separated by hallway), and a narrow long kitchen also at the rear.

Temperature is 18 degrees in my house today, heating set to this and it's not that cold outside so no real chills to deal with. It's been a stable 18 inside all day, so plenty of time for house to stabilise.

There's no washing drying in my house today, only me and dog here and I'm not doing anything particularly demanding.

Humidity sensor in both living room and dining room. Living room 18 degrees, 75% humidity. Dining room 18 degrees 60% humidity.

That's a 15% difference between two rooms getting identical use at the same temperature, separated only by a corridor and about 3m in distance.