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Post 2 - Humidity indoors - doesn't have to be a problem 60+ % (lemmy.nz)
submitted 1 year ago by sylverstream@lemmy.nz to c/newzealand@lemmy.nz
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A couple of weeks ago I've posted here regarding humidity in our house as I noticed it went up to ~75% indoors. I've bought a dehumidifier, but noticed that the humidity went up again after dehumidifying a room to eg 60%. Then, I installed a temp/humidity sensor outdoor and also calculated the absolute humidity to be able to compare easily. And... then I noticed when it's moist, like now, the outdoor humidity would be close to 100%. Thus, it would almost be impossible to get it <60% indoors, unless you would heat it to 25c +

Right now, it's 99% humidity @ 11c outside, which comes to 9.9g / m3 absolute humidity:

In the bedrooms it's 16.4 @ 65% which is as expected. In the living room it's 21c @ 55% which is almost the same absolute humidity as outside:

Still, it's important to heat your rooms to ensure RH doesn't reach 100% as that may cause dampness/mould. I've installed temp sensors & panel heaters in all rooms and set the min temp to 16c.

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[-] Alfiegerner@lemmy.nz 5 points 1 year ago

Nice to see homeassistant out in the wild! I'm into 3d printing and the humidity causes havoc with my filaments.

[-] SamC@lemmy.nz 4 points 1 year ago

Yeah, I've basically come to the conclusion that in many cases it's just not possible to keep humidity under 60% in NZ all the time. It's partly how homes are built, but it's also just that NZ is just a pretty bloody humid place, at least in a lot of regions. All you can do is upgrade your home as best you can (good insulation and double glazing can help, but won't fix it on its own), and heat and extract moisture as best as you can.

We've upgrade our insulation, got some double glazing, a good heat pump, oil heaters in some rooms, 2x desiccant dehumidifiers and temperature/humidity sensors. We're a bit stingy with our electricity usage, so generally only heat rooms we're using. We manage to keep humidity to around 55-65% most of the time without blowing out our power bill. Not really any problems with mould (which we did before we developed this strategy - even 70% is enough for mould to form). I'm not sure there's a lot more we can do, short of running heating/dehumidifiers 24/7 which would probably triple our power bill.

[-] ArthurStevensNZ@lemmy.nz 3 points 1 year ago

The real issue is our building regulations are an absolute joke. It should be mandatory to include ducting to each room and then at least include a balanced pressure ventilation system. That alone massively reduces errant humidity from sources like cooking / showering etc (no, an asthmatic range hood or pathetic fan wired to the light switch is NOT sufficient).

I live in a crappy 80s house with single glazing and poor insulation. I’ve got to run 3 dehumidifiers 24/7 at 60% here or else it’s mould city. In winter it’s massively helpful if I heat the place - have heat pumps in every room just about and as the house is pretty open plan I run them on a timer to maintain a minimum of 21 in the living areas during the day and 18ish when sleeping. In summer I cool as well which removes the humidity from the air.

But you’re right, NZ, and specifically Auckland is hella humid as it’s a thin piece of land in the oceans. I’ll be moving to central NI soon, bit further from the coast. The weather seems way more stable compared to living so close to the coast, and the slightly more sane property market doesn’t hurt either.

[-] aerir@lemmy.aerir.xyz 2 points 1 year ago

Which sensors are you using? I'm have a couple of Xiaomi sensors but they seem to be draining battery pretty fast.

[-] sylverstream@lemmy.nz 3 points 1 year ago

Sonoff Zigbee ones. Batteries should last a year.

[-] Psythik@lemm.ee 2 points 1 year ago* (last edited 1 year ago)

That sucks.

Meanwhile I have to run a humidifier year round to keep my skin from drying out where I live (not in NZ), especially during the summer. Which is irritating cause I have to run the A/C too, and it works harder when both are running. But it's either pay a higher electric bill or suffer.

[-] 2tapry@lemmy.nz 2 points 1 year ago

You probably know this?

Ensure you "flush" you house with cold fresh air once a day if possible. As this cold air is reheated it becomes much drier (relative humidity).

Living in the South of the South with a very soggy winter we are able to maintain around 50% RH with just a heat pump for heating and no dehumidifier.

[-] sylverstream@lemmy.nz 2 points 1 year ago

Yes, I know, that's why I'm comparing absolute humidity. It's almost the same inside & outside.

[-] 2tapry@lemmy.nz 1 points 1 year ago

I haven't read your previous post - perhaps that's the problem, but I'm a bit confused by this post.

You say:

when it’s moist, like now, the outdoor humidity would be close to 100%. Thus, it would almost be impossible to get it <60% indoors, unless you would heat it to 25c +

But then say:

In the living room it’s 21c @ 55% which is almost the same absolute humidity as outside:

These two statements conflict?

Side Note: Less than 60%RH is the recommended acceptable indoor air quality.

If you flushed your house when the temperature outside was 11C outside @ 98.9%RH and then warmed that air up to 21C you should have a RH of around 54% as you have said you do. If you flush your house when it's 9C outside @ 100%RH then warmed that air up to 21C you should have a RH of 48%. So a little temperature difference can make all the difference.

Sorry, I've probably missed something, and it sounds like you know all this. Just comparing our experience where we typically run the heat pump at 18-19C at night when we are awake and let it idle down to 15C when asleep. Typically, (but not always) flush the house during the day and maintain around 48%RH. Perhaps, overall, the air is a little "drier" down in the South?

[-] sylverstream@lemmy.nz 2 points 1 year ago

Thanks for your reply! Yes, you're right, my message conflicts. What I meant to say was that in bed rooms it can be 60+% and that's fine. The recommended temp for bed rooms is 16c and if it's 100%@11c outside it's almost impossible to get it below 60% @ 16c.

this post was submitted on 30 Jul 2023
21 points (100.0% liked)

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