this post was submitted on 21 Jun 2023
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We've got an insulated house, heat it properly, ventilate it, but still see humidity levels of 70%+ in bed rooms. How to fix that? (self.newzealand)
submitted 1 year ago by sylverstream to c/newzealand
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We built a house 7 years ago and it's insulated and has double glazing. I've installed Home Assistant with temp sensors in the bed rooms and seeing 70%+ humidity levels. Temperature is always above 16c

We ventilate it, but still it's 70% in the bedrooms. WHO recommends 40-60%, so we're a bit worried.

Living room is around 55% during the day when we have the heat pump set at 21c.

As it's pretty humid outside I think it's almost impossible to get it lower, but are there any other tips? I don't want to run dehumidifiers. Would an HRV like system help?

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[–] sylverstream 3 points 1 year ago (1 children)

I'm seeing some odd behaviour. I've set the heat pump to dry twice, for about 30 minutes. Both temp and RH drop, which is good. However, as soon as I turn it back to heat, the RH jumps up about 6% within 5-10 minutes. The sensor is a couple of meters away from the heat pump, so that's odd.

Also outside it's 14.5c @ 72% so I have no idea how to get it 16c and below 60%. That seems only possible if I shut all windows and have dehumidifiers running 24/7. I see articles where they recommend 30-50% in winter, how the heck is that possible when it's damp outside.

[–] Dave 2 points 1 year ago (2 children)

I’m seeing some odd behaviour. I’ve set the heat pump to dry twice, for about 30 minutes. Both temp and RH drop, which is good. However, as soon as I turn it back to heat, the RH jumps up about 6% within 5-10 minutes. The sensor is a couple of meters away from the heat pump, so that’s odd.

Could this be as simple as the heat pump is blowing out dry air, but hasn't turned over much air total. Then when you stop it, the dry air mixes with other air around the house and the humidity comes back up?

Also outside it’s 14.5c @ 72% so I have no idea how to get it 16c and below 60%. That seems only possible if I shut all windows and have dehumidifiers running 24/7. I see articles where they recommend 30-50% in winter, how the heck is that possible when it’s damp outside.

I dunno man. I tend to think I live in a warm, dry house. We only heat rooms we are using but otherwise we don't hesitate to turn on a heat pump. We have never had an issue with mould or dampness. But I just have this feeling when I get some sensors they are gonna say 70% like yours and I'm gonna have to go down a rabbit hole trying to work out why!

We do have a DVS, but ours is an older home. I think they help more with heat recovery (all they do is pump air from your ceiling cavity into your house - which is often warmer because heat rises). They do slightly pressurise the house because they are pumping air in, which can help stop outside air getting in cracks, but I can't imagine a fairly new house like yours would have the same issue with that as our 50's house. Maybe throw a sensor in the ceiling and see if the air is warm and dry up there?

[–] TagMeInSkipIGotThis 3 points 1 year ago

I think your assessment is likely correct, 30 minutes isn't long for a dehumidifier to do much work, and unless there's a unit in each room, or its central then for the total volume of air it won't have pulled much more than was in the general area its located.

[–] sylverstream 2 points 1 year ago (1 children)

Yeah we assumed our house wouldn't have moisture issues being so new. But... If I hadn't measured I wouldn't know as we don't have massive moisture issues. Main issue is condensation on the window frames as they are not thermally broken. Well it is what it is.

I've ordered a 10L dehumidifier, we'll ventilate more, and let's see how it goes then.

It's not so easy to get onto the ceiling but it's indeed worthwhile.

[–] Dave 2 points 1 year ago

Good luck!

It’s not so easy to get onto the ceiling but it’s indeed worthwhile.

You don't have a man-hole in the ceiling in a wardrobe/laundry or other out of the way place where you can just poke a sensor up into the ceiling?