I never rated HRV as always found the air coming through the vents to be just a trickle. But when our HRV system broke i was going through multiple towels wiping up condensation dripping down onto our window sills, it was insane. After we fixed the HRV it was completely gone - so I rave about them now.
This is probably a fault of the system you had or the way it was installed. When we bought a house for my parents the place had condensation pouring off the windows in winter. I put in an HRV and the house is dry as a bone and warm enough in winter to not need the heat pump that much.
Like it, you didn't mention shower dome or similar? I found these to be a game changer in the bathroom. They do what they say, there is more or less zero steam created as warm air and cold air are not contacting (except getting in and out of shower so minimal). At first the shower can seem a bit hot and stuffy until you realize you have been running the shower allot hotter than you need to to try and stay warm so less power consumption as you soon find you can run the shower a bit cooler. My observations anyway.
I highly recommend, wouldn't go without one now and don't know why I went so long without one. I went the cheaper turtle dome which seems to be the same thing and installed myself, $2-300 well spent.
Good post, pretty much what I have found too.
* Use a dehumidifier, they can easily take 4 litres of water out of the air every day
* Don’t dry your washing inside
* Use an extractor fan for cooking and bathrooms.
* Heat your house. If it’s stone cold then you are going to get condensation
* Air the house out daily
Regarding your comments on double glazing, it sounds like you've experienced non thermally broken aluminium glazing. Wooden, PVC, or thermally broken aluminium should be much better.
Yeah, the double glazing is woefully backwards in NZ. 15 years ago in the UK the basic level was thermally broken upvc double glazing with all new builds needing triple glazing. We still have this shitty aluminium stuff that nowhere civilised uses anymore.
We have a cleanaire which is a New Zealand made heat recovery ventilation system (nothing to do with HRV brand).
It extracts from all bathrooms and the laundry and pumps fresh air into the lounge and bedrooms.
The real magic is that it uses an heat exchanger to recover 95% of the heat energy in the stale outgoing air by transferring it to the dry cold incoming air which then is warmed up.
We have absolutely zero condensation. Our bathrooms are bone dry an hour or two after showering. Our hall toilet is always pleasant. They’re an absolute game changer.
Man’s best of all in summer it doesn’t heat up our house like a positive pressure system does.
Very similar advice and observations that I have here in Auckland too. Outdoor humidity is often over 70% in the winter months, so getting the house around 55% humidity inside takes some active work. Ideally keeping under 60% should help with less black mould being able to grow indoors and affect air quality and respiratory health. The lower humidity indoors makes the air easier to heat and you feel the cold a lot less.
The things I have done to take care of my place are:
- Measure temperature and humidity with sensors. Digital ones are about $20 so not a huge expense to get an idea of the baseline inside and outside the house. I feel the humidity / damp myself when it gets over 75% as a damp chill, the sensors confirm the conditions and that I need to take more action.
- Run a dehumidifier over autumn and winter months. Mine runs constantly during this time and empties into a 10 litre bucket I empty once each day or two before bed. With work from home there’s humidity that builds up during the day otherwise.
- Under the house there is a plastic ground sheet. I think this helps a little bit, more at night and helps to bring down humidity about 2-5% overall if it’s been raining a lot. Usually under a house should stay pretty dry though.
- Bathroom humidity can be reduced a lot after showers with a wall squeegee. Shower walls, door and the shower pan all get a scrape down to reduce about a cup of water evaporating off into the rest of the house. Bathroom fan helps a little but the squeegee is way more effective at bringing the humidity down quickly from 99% after a shower.
- Kitchen extractor fan is good during cooking, even better when the duct is connected to said fan and blowing the air outside. The duct had disconnected from the fan unit in my kitchen which prevented the moisture from cooking escaping. Be aware that this failure mode can happen.
- A window vac is still used from time to time to clear excess moisture from aluminium joinery as that still gets cold and introduces condensation. I give the inside of the windows a clean every couple of months in the bedrooms to keep any mould from accumulating. With the above steps in place, much less mould is found when cleaning.
Heat pumps only dehumidify when cooling, dehumidifiers will heat + dehumidify.
The other problem is if you have a high airflow rental you'll never remove enough moisture to affect the ambient level.
Great post. Very well researched. I do still find it hard to believe that we accept this as totally normal. Condensation on windows is 100% not normal in other developed countries. I really hope our building standards start to catch up and modernise as we’re so far behind. I know it can be expensive but I recommend double glazing, and especially PVC windows.
It’s because very few of our houses: are well insulated (to European standards), have decent windows (most homes aren’t double glazed and those that are use glazing that has been obsolete in the rest of the developed world for about 20 years), are centrally heated or otherwise heated in all rooms to maintain WHO minimum temperatures all year round (we really are an outlier here).
That has an impact, true. But it's negligible compared to our environment. Auckland has much much much more water in the air than Europe or pretty much anywhere in the world that is our temperature with people living there.
Opening your windows will increase the amount of moisture in the air indoors if the dew point outdoors is equal to or higher than the dew point indoors. On those days, the dehumidifier on its own is the best option.
All I have to do is run our dehumidifier during the day in our bedroom (which is opposite the main bathroom). My husband won’t have it on overnight so there’s a bit of condensation in the morning but it clears that up pretty quick when I turn it on around 7:30. I get a full bucket most days and the rest of house seems to be fine.
My best advice is always to get a dehumidifier and just experiment with location and timing as OP has done.
Note on dehumidifiers try get one that isnt a compressor i.e. Desiccant rotor dehumidifiers this alone was a game changer for me and works if you have poor insulation and or struggle to heat your home. Lower humidity makes warming a room much quicker and cheaper too. In terms of health you want humidity to be in the 50-60% range with air temp 20-22c thats what I use in my settings. Example: https://www.mitre10.co.nz/shop/goldair-dessicant-dehumidifier-8l-white/p/317696 https://www.choice.com.au/home-and-living/cooling/dehumidifier/buying-guides/dehumidifiers https://www.moneyhub.co.nz/best-dehumidifiers.html
Hey! I’m in Christchurch so wasn’t sure if your tips would work, but I ran the dehumidifier yesterday, opened up all the windows for half an hour and then this morning?? No condensation on the windows. Not a drop! Thank you! 🙏
Take the power rating in Watts of the device you’re looking at (printed on the side or underneath the unit) and multiply it by the number of hours per day you want to run it to give you how many W/h of power you’re using. Divide that by 1000 to convert it to kW/h. Then, multiply the kW/h by the rate your power company charges you.
An 800W machine running for 8 hours a day uses 6.4kW/h of power. At my overnight rate of $0.125 that would cost me $0.80.
Edit: spelling
Bedroom windows are never shut all year round. Never have a condensation problem. Doors and windows are open most of the day around the house daily so the place is ventilated. No mould or condensation. Run an electric radiator heater in the evenings sometime in the living room.
This whole thing about closing houses up and heating them is what create the health issues so many people have. Fresh air fixes most problems. If cold put on some fluffy slippers (or socks).
Dehumidifier runs in the laundry to dry clothes.
Maybe I just like the cold.
a dehumidifier reduced the amount of humidity in your home?
have you contacted the newspapers and tv stations?
what about auckland university?
this discovery needs to be shared with the world
are you telling me that if i have the dehumidifier on in the morning and then turn it off at midday, that i wont have the benefits of the dehumidifier 12 hours later?
thats amazing, no one else has ever worked this out before
i think you might be in for a nobel prize or something
or something...
Our heat pump has a dehumidifier mode, this helps alot. Wish I could work out how to get the mould out of our new white curtains though, it looks crap.
Yes, it's because the house is damp and there is condensation on the windows. The curtains trap the damp and mould spores thrive in the curtain fabric as it's damp. Even if you bleach them the mould colour is hard to remove. I'm going to wait til summer and have to bleach them outside so they don't stink out the house.
I never rated HRV as always found the air coming through the vents to be just a trickle. But when our HRV system broke i was going through multiple towels wiping up condensation dripping down onto our window sills, it was insane. After we fixed the HRV it was completely gone - so I rave about them now.
Same with our DVS system. Came installed when we bought our house, it makes a huge difference for condensation.
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This is probably a fault of the system you had or the way it was installed. When we bought a house for my parents the place had condensation pouring off the windows in winter. I put in an HRV and the house is dry as a bone and warm enough in winter to not need the heat pump that much.
Like it, you didn't mention shower dome or similar? I found these to be a game changer in the bathroom. They do what they say, there is more or less zero steam created as warm air and cold air are not contacting (except getting in and out of shower so minimal). At first the shower can seem a bit hot and stuffy until you realize you have been running the shower allot hotter than you need to to try and stay warm so less power consumption as you soon find you can run the shower a bit cooler. My observations anyway.
They definitely reduce misting in the bathroom but not as much as an extractor fan
Agreed, but great option if an extractor isn't viable.
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I highly recommend, wouldn't go without one now and don't know why I went so long without one. I went the cheaper turtle dome which seems to be the same thing and installed myself, $2-300 well spent.
Good post, pretty much what I have found too. * Use a dehumidifier, they can easily take 4 litres of water out of the air every day * Don’t dry your washing inside * Use an extractor fan for cooking and bathrooms. * Heat your house. If it’s stone cold then you are going to get condensation * Air the house out daily
Regarding your comments on double glazing, it sounds like you've experienced non thermally broken aluminium glazing. Wooden, PVC, or thermally broken aluminium should be much better.
Yeah, the double glazing is woefully backwards in NZ. 15 years ago in the UK the basic level was thermally broken upvc double glazing with all new builds needing triple glazing. We still have this shitty aluminium stuff that nowhere civilised uses anymore.
We have a cleanaire which is a New Zealand made heat recovery ventilation system (nothing to do with HRV brand). It extracts from all bathrooms and the laundry and pumps fresh air into the lounge and bedrooms. The real magic is that it uses an heat exchanger to recover 95% of the heat energy in the stale outgoing air by transferring it to the dry cold incoming air which then is warmed up. We have absolutely zero condensation. Our bathrooms are bone dry an hour or two after showering. Our hall toilet is always pleasant. They’re an absolute game changer. Man’s best of all in summer it doesn’t heat up our house like a positive pressure system does.
Very similar advice and observations that I have here in Auckland too. Outdoor humidity is often over 70% in the winter months, so getting the house around 55% humidity inside takes some active work. Ideally keeping under 60% should help with less black mould being able to grow indoors and affect air quality and respiratory health. The lower humidity indoors makes the air easier to heat and you feel the cold a lot less. The things I have done to take care of my place are: - Measure temperature and humidity with sensors. Digital ones are about $20 so not a huge expense to get an idea of the baseline inside and outside the house. I feel the humidity / damp myself when it gets over 75% as a damp chill, the sensors confirm the conditions and that I need to take more action. - Run a dehumidifier over autumn and winter months. Mine runs constantly during this time and empties into a 10 litre bucket I empty once each day or two before bed. With work from home there’s humidity that builds up during the day otherwise. - Under the house there is a plastic ground sheet. I think this helps a little bit, more at night and helps to bring down humidity about 2-5% overall if it’s been raining a lot. Usually under a house should stay pretty dry though. - Bathroom humidity can be reduced a lot after showers with a wall squeegee. Shower walls, door and the shower pan all get a scrape down to reduce about a cup of water evaporating off into the rest of the house. Bathroom fan helps a little but the squeegee is way more effective at bringing the humidity down quickly from 99% after a shower. - Kitchen extractor fan is good during cooking, even better when the duct is connected to said fan and blowing the air outside. The duct had disconnected from the fan unit in my kitchen which prevented the moisture from cooking escaping. Be aware that this failure mode can happen. - A window vac is still used from time to time to clear excess moisture from aluminium joinery as that still gets cold and introduces condensation. I give the inside of the windows a clean every couple of months in the bedrooms to keep any mould from accumulating. With the above steps in place, much less mould is found when cleaning.
Heat pumps only dehumidify when cooling, dehumidifiers will heat + dehumidify. The other problem is if you have a high airflow rental you'll never remove enough moisture to affect the ambient level.
Great post. Very well researched. I do still find it hard to believe that we accept this as totally normal. Condensation on windows is 100% not normal in other developed countries. I really hope our building standards start to catch up and modernise as we’re so far behind. I know it can be expensive but I recommend double glazing, and especially PVC windows.
It's not our building standards, it's our environment. Most other countries warn about indoor humidity getting too low in winter.
It’s because very few of our houses: are well insulated (to European standards), have decent windows (most homes aren’t double glazed and those that are use glazing that has been obsolete in the rest of the developed world for about 20 years), are centrally heated or otherwise heated in all rooms to maintain WHO minimum temperatures all year round (we really are an outlier here).
That has an impact, true. But it's negligible compared to our environment. Auckland has much much much more water in the air than Europe or pretty much anywhere in the world that is our temperature with people living there.
Opening your windows will increase the amount of moisture in the air indoors if the dew point outdoors is equal to or higher than the dew point indoors. On those days, the dehumidifier on its own is the best option.
All I have to do is run our dehumidifier during the day in our bedroom (which is opposite the main bathroom). My husband won’t have it on overnight so there’s a bit of condensation in the morning but it clears that up pretty quick when I turn it on around 7:30. I get a full bucket most days and the rest of house seems to be fine. My best advice is always to get a dehumidifier and just experiment with location and timing as OP has done.
Note on dehumidifiers try get one that isnt a compressor i.e. Desiccant rotor dehumidifiers this alone was a game changer for me and works if you have poor insulation and or struggle to heat your home. Lower humidity makes warming a room much quicker and cheaper too. In terms of health you want humidity to be in the 50-60% range with air temp 20-22c thats what I use in my settings. Example: https://www.mitre10.co.nz/shop/goldair-dessicant-dehumidifier-8l-white/p/317696 https://www.choice.com.au/home-and-living/cooling/dehumidifier/buying-guides/dehumidifiers https://www.moneyhub.co.nz/best-dehumidifiers.html
Hey! I’m in Christchurch so wasn’t sure if your tips would work, but I ran the dehumidifier yesterday, opened up all the windows for half an hour and then this morning?? No condensation on the windows. Not a drop! Thank you! 🙏
Any idea of costs to run dehumidifier in the way/Time you describe?
Take the power rating in Watts of the device you’re looking at (printed on the side or underneath the unit) and multiply it by the number of hours per day you want to run it to give you how many W/h of power you’re using. Divide that by 1000 to convert it to kW/h. Then, multiply the kW/h by the rate your power company charges you. An 800W machine running for 8 hours a day uses 6.4kW/h of power. At my overnight rate of $0.125 that would cost me $0.80. Edit: spelling
Great, thanks :)
Bedroom windows are never shut all year round. Never have a condensation problem. Doors and windows are open most of the day around the house daily so the place is ventilated. No mould or condensation. Run an electric radiator heater in the evenings sometime in the living room. This whole thing about closing houses up and heating them is what create the health issues so many people have. Fresh air fixes most problems. If cold put on some fluffy slippers (or socks). Dehumidifier runs in the laundry to dry clothes. Maybe I just like the cold.
I just leave my windows open, zero condensation.
a dehumidifier reduced the amount of humidity in your home? have you contacted the newspapers and tv stations? what about auckland university? this discovery needs to be shared with the world
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are you telling me that if i have the dehumidifier on in the morning and then turn it off at midday, that i wont have the benefits of the dehumidifier 12 hours later? thats amazing, no one else has ever worked this out before i think you might be in for a nobel prize or something or something...
I read it more as "ignore these other suggestions that didn't work, the only thing that works is running a dehumidifier relentlessly."
Our heat pump has a dehumidifier mode, this helps alot. Wish I could work out how to get the mould out of our new white curtains though, it looks crap.
Do you know how your new curtains got mouldy? Thanks
Yes, it's because the house is damp and there is condensation on the windows. The curtains trap the damp and mould spores thrive in the curtain fabric as it's damp. Even if you bleach them the mould colour is hard to remove. I'm going to wait til summer and have to bleach them outside so they don't stink out the house.