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Chicknsoup

10 posts

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#251399 23-Jun-2019 23:20
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Hi all,

I know this topic has been talked to death about but I normally see HRV/DVS etc. mentioned with their positive pressure systems. After some research, I’m thinking that a balanced pressure/heat exchanging system is best for my house. Would love to hear your thoughts and opinions on these systems -especially the Mitsubishi Lossnay and Smartvent Synergy systems. Any other suggestions are very much welcomed and appreciated!

Just a some information about our house - built in 2015, fully insulated, double glazed, heat pumps in the lounge (open plan with living, dining and kitchen) and the hallway. We are getting bad condensation and the house is quite hard to heat on the colder nights.

Thank you very much in advance!

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Aredwood
3885 posts

Uber Geek


  #2263117 23-Jun-2019 23:57

Fix your heating problems first before worrying about ventilation. Is the whole house hard to heat or just parts of it?

For comparison, I have a 1960s house with no insulation at all. And the only condensation I get is on the actual window glass, on approximately the bottom 1/2 if the night is cold enough for a frost. And much less if the night is not so cold. (original single glazed wooden windows in my bedroom)

But I have 6 heatpumps in my house. 4 of them for individual bedrooms. A large unit that was intended to be a ducted heatpump, although I have installed it so it only heats the open plan lounge (although it's return air comes from the hallway). And a garage / man cave heatpump.



I'm guessing that the bedrooms are the problem rooms. If so, then either get heatpumps installed into them. Or get a whole house ducted system.





timmmay
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  #2263150 24-Jun-2019 07:42
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I'm not sure I agree that you need to fix heating problems before ventilation. Sounds like both need to be resolved. Modern houses don't have much ventilation, the build up of moist air (ie water in the air) makes it more difficult to heat as well.

 

An integrated heating / ventilation system would probably be best, though is probably expensive. A balanced ventilation system would no doubt help, but it will make your house colder, so you really need to be adding heat as well.

 

If you don't want an integrated system I would probably add another heat pump, ideally ducted or in another area of the house. At the same time add your ventilation system.

 

The big name ventilation system providers are generally expensive and their sales teams straight out lie - I had a sales gut for one at my house but kicked them out. Check out the Lossnay and Cleanaire. You could get a decent company in who understand heating and ventilation rather than just an heat pump installer. If you say where you are someone may be able to point you to a good firm.


Chicknsoup

10 posts

Wannabe Geek


  #2263161 24-Jun-2019 08:35
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Thanks guys for your thoughts so far! I’m in Christchurch if that helps. I haven’t looked into ducted heat pumps but I’m sure it will cost a pretty penny! We’ve already been quoted $4100 for a lossnay system and $4600 for the smartvent synergy system. Both supposedly have the same function so I’m not too sure about the price difference. I have DVS around and have heard horror stories about HRVs sales so I’ve avoided them like the plague. DVS quoted me over $6000 for their balanced air system so we decided to not go down that road.....

Any other suggestions/thoughts are most welcome and very much appreciated



timmmay
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  #2263170 24-Jun-2019 08:53
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I think Cleanaire is in Christchurch.

 

All ventilation systems lose heat, even heat recovery ones. They might have a 90% efficient heat exchanger, but heat also escapes from the fairly poorly insulated ducts. So you might fix your condensation problem by adding cold, dry air to your house. Adding heat is going to be necessary.

 

Lossnay can integrate with a Mitsubishi heat pump. That might be a good option to give you some kind of central heating, and doing both at once will be cheaper than doing individually.

 

I personally don't think you need fresh air being pumped through 24/7. I have my positive pressure ventilation system going three or four hours a day around midday in winter, and it's pretty much as effective as when it was running more. We get a small amount of condensation on very cold mornings, but it's gone and the whole house is fresh by the time we get home. The heating has turned on by then as well. Weekends we don't turn heating off other when we sleep, but it comes on an hour before we get up, the house hasn't cooled down all much by then.


ratsun81
417 posts

Ultimate Geek


  #2263172 24-Jun-2019 08:57
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Have you tried running a dehumidifier or the heatpump on dry mode? Typically its a lot harder to heat a damp house...

 

 


timmmay
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  #2263176 24-Jun-2019 09:13
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A dehumidifier isn't typically a long term solution, it's more a temporary stopgap IMHO. Remove moisture at the source where possible with good powerful extractors, not those whimpy ones integrated with lights.

Aredwood
3885 posts

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  #2263225 24-Jun-2019 09:28

timmmay:

I'm not sure I agree that you need to fix heating problems before ventilation. Sounds like both need to be resolved. Modern houses don't have much ventilation, the build up of moist air (ie water in the air) makes it more difficult to heat as well.


An integrated heating / ventilation system would probably be best, though is probably expensive. A balanced ventilation system would no doubt help, but it will make your house colder, so you really need to be adding heat as well.


If you don't want an integrated system I would probably add another heat pump, ideally ducted or in another area of the house. At the same time add your ventilation system.


The big name ventilation system providers are generally expensive and their sales teams straight out lie - I had a sales gut for one at my house but kicked them out. Check out the Lossnay and Cleanaire. You could get a decent company in who understand heating and ventilation rather than just an heat pump installer. If you say where you are someone may be able to point you to a good firm.



When you increase the air temperature, the relative humidity of a given volume of air decreases. Even though you haven't added or removed any moisture. And the larger the temp difference between inside and outside temperatures, the more air leakage you get due to convection currents. These 2 things are why fixing heating problems often also fix ventilation problems. It would be very unlikely that the OPs house would be anywhere near compliant with the Passive House air sealing rules. Especially if they have non LED down lights, or downliights that were retrofitted with LED lamps.

Since a ventilation system is not going to fix a heating problem, they are going to have to spend money on fixing their heating problems regardless. So it makes sense to do the “must be done” things first.







bfginger
1229 posts

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  #2263727 25-Jun-2019 08:28
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Where are you seeing condensation? On the window frames? The glass? The walls?

 

 

Do you have large areas of glazing? Low e glass?

 

 

Do you have a rangehood and shower extractor fan?

 

 

Air tightness on some newer houses can be good although not up to passivehouse standards. Good if you have ventilation, bad if you don't. Do you have a humidistat or a dehumidifier to tell you the relative humidity?

 

 

Have you looked up into the ceiling cavity and checked the insulation is all there? Under the house? Is there R2.2 in the walls?

 

 

What room temperatures are you experiencing versus outside without heating? What size and model is the heat pump or heat pumps, are you sure it isn't undersized? How big is the living area?

Chicknsoup

10 posts

Wannabe Geek


  #2263828 25-Jun-2019 10:49
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bfginger: Where are you seeing condensation? On the window frames? The glass? The walls?

Do you have large areas of glazing? Low e glass?

Do you have a rangehood and shower extractor fan?

Air tightness on some newer houses can be good although not up to passivehouse standards. Good if you have ventilation, bad if you don't. Do you have a humidistat or a dehumidifier to tell you the relative humidity?

Have you looked up into the ceiling cavity and checked the insulation is all there? Under the house? Is there R2.2 in the walls?

What room temperatures are you experiencing versus outside without heating? What size and model is the heat pump or heat pumps, are you sure it isn't undersized? How big is the living area?






Hi Bfginger

Condensation is on the bottom of the windows as well as the frames themselves. In the living/dining/kitchen area we have full length windows all around so you can definitely see the condensation at the bottom and middle as there is aluminium framing there. No condensation on the walls thankfully.

Yes we do have a range hood in the kitchen and extractor fan in both bathrooms

We don’t have a humidistat and we don’t use a dehumidifier - I have a good collection of indoor plants which would suffer quite quickly with a dehumidifier. On a side note, I thought it was my plants causing the condensation but according to the ventilation guys, they contribute slightly only - not sure how true this is!

Insulation is all there according to the building records

The heat pump in the hallway is most probably a bit smaller than required but we were limited by the size of the hallway itself. The heat pump in the living area seems to be doing it job most of the time but it can get quite cold at night sometimes. I’m not sure of the exact size of the living area but it is quite large as it’s sort of an open plan living/dining/kitchen/second living area. Getting a bigger heat pump in there would probably help a lot with the heating but my main concern is the condensation we are seeing. Should I focus on the heating - would that help with the condensation? I know ventilation doesn’t heat but I was of the understanding that a dryer home is easier to heat?

Thanks again all!


bfginger
1229 posts

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  #2264702 25-Jun-2019 23:47
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My preference would be to deal with humidity over temperature because high humidity is miserable at any temperature. Increasing temperatures reduces relative humidity but if there is low ventilation relative to moisture production the increased heating may not solve the problem as relative humidity could continue to build up and suddenly condensate heavily once heating is withdrawn.

 

 

I don't think you'd see condensation on double glazing unless the indoors relative humidity is very high. Unless you get a humidistat to tell you what the RH is it's hard to say how bad the problem is. Indoors relative humidity should ideally be no higher than 60% or 65% at the maximum. Good humidifiers come with a humidistat to target a relative humidity to prevent overdrying. It'd be hard to make humidity go low enough in New Zealand to harm a pot plant.

 

 

You could get one of those home weather station units that tells you the indoors and outdoors temperatures and relative humidities. For a cool room dehumidifier you could try the Goldair GD330 / GD350 which you can get for $349 or $298 when on sale.

 

 

Aluminium without a thermal break is always going to have condensation on it but the amount shouldn't be too bad if the humidity inside the room is acceptable.

 

 

A good double glazed window loses a similar amount of heat to an uninsulated wall. The heat loss for full length plain glass windows with thermally unbroken window frames would be immense in Chch and over twice that of an uninsulated wall. Was there any mention of low e glass in the building records?

 

 

The heat pump will have a sticker under it that shows the model name which will tell us the size. You shouldn't be having low room temperature problems with two heat pumps running but the requirements of the New Zealand building code are too low for Christchurch.

 

 

Insulation is all there according to the building records
It's always going to say that but you need to check as it may have been forgotten around corners from the manhole.

timmmay
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  #2264753 26-Jun-2019 08:10
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We get a little bit of condensation on the glass of our double glazing glass (not the PVC) on very cold mornings, but the door to the room is closed and we only have the ventilation system running during the day to avoid pushing heaps of cold air in. Before we had double glazing we had to wipe the window with a large towel every morning and it was completely saturated.


bfginger
1229 posts

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  #2265401 26-Jun-2019 22:29
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Sorry I meant to say dehumidifiers not humidifiers.

 

 

Although good double glazing is less prone to condensation it doesn't always mean the relative humidity in the room ends up lower for it. Condensation is what people notice first but mould and dust mite are always going to appear when relative humidity is too high.

acetone
132 posts

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  #2281856 23-Jul-2019 00:35
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How did you get on, what solution did you go with or are you still investigating?


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