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5 posts

Wannabe Geek

# 223813 18-Oct-2017 13:32
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Hi all,


After reading through some interesting/useful comments about different types of vent systems and passive ways warm your house, I am now trying to decide whether to go for a balanced ventilation or a positive ventilation system.


I have always been sceptical about the positive ventilation system and wanted to get a balanced system for various reasons as below


1. It provides no active way for the supplied/stale air to be extracted out.


2. Supplied air being cold in winter(whereas balanced vent comes with heat exchange system)






But recently come across an interesting article by Beacon Pathway about how PPV can be better suited for older/draughty homes that are not as air tight as new homes. 


 'They(Balanced systems with a heat exchanger) don't work in older houses because they require very airtight homes (more airtight than most new construction in New Zealand) combined with a severe climate (think Central Otago) before you save more energy than you spend in the running costs.'


I suspect this is because for an older house the air would get pushed out though bottom-of-wall areas such as under skirtings or where timber windows whereas for the balanced system, the return air will be extracted out through the grill in a ceiling before there is enought build up of time/pressure to sufficiently reach the floor level.




My home is a 50m2 two bedroom unit in 1970's brick and block located in Auckland. Timber joinery with no double glazing.




For the system, I would look at the one with humidity and temperature sensor that draws air directly from outside as the roof cavity's full of filthy stuff.


I got a quote from HRV without the above features which was $3500.


For the balanced system I got a quote for a Mitsubishi 350m3/hour air volume unit for $4400.




On a side note, the house only has ceiling insulation and no floor insulation as there's no cavity below ground.


Got a quote from Insulmax  $6000 for wall insulation. 


Been told that a 6kw high wall heat pump would cost me $3000.


And a Panasonic ducted heat pump with 4 vents would set me back $6400.




If money wasn't a concern I would start by doing up the insulation first, followed by the vent and the heat pump but I am struggling to establish as to how much I should spend to retrofit this small 1970's house.




The main reasons why I am considering some sort of upgrade are


- the whole family including my 2 year old been getting chesty coughs for a year ever since we moved in to the house from an apartment.


- we frantically open our windows and ventilate, clean up the rooms every on the regular basis but continue to get sore throats. There's no visible signs of mould. The wall has not been painted over since we moved in and it was previously a rental unit.


- got a granny flat downstairs which we let out that is also 50m2 with two bed rooms. It had mould problem over the winter and I suspect the mould had grown trough the mid floor ceiling and behind our gib wall.


- thought about getting a dehumidifier but felt like it is only going to be temporary measure.




Thanks for taking time to read through the rather lengthy post.


I would greatly appreciate any opinion from anyone who's been in a similar situation please. 



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15565 posts

Uber Geek


  # 1885710 18-Oct-2017 13:44
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I think ventilation is worthwhile given your situation. If you can afford it then positive pressure is better, check out Cleanaire. I suspect if your house isn't too drafty the combination of fans that blow fresh air in and take old air out would still have an advantage. If you want positive pressure then you don't need HRV / DVS, go for a cheaper company - there are plenty. I run my cheap PPV system on a timer to prevent too much cold air coming in over winter and hot air coming in over summer. Not even sure what brand it is - maybe smartvent? It's a really simple system, a fan and ducts. I don't use ceiling cavity air, it smells, I use fresh air from the eaves.


Without proper heating like a heat pump there's possibly not much point putting in heat recovery units.


You might get a better system overall if you get heating and ventilation in the same system. Mitsubishi Lossnay is worth considering. Though at 50 sq m it might not be worth the bother.


You're right, a dehumidifier isn't worthwhile. Where's the moisture coming from? You need to remove it at source. Decent bathroom fan, extractor over stove, etc.


I didn't find wall insulation very helpful, in my very very old weatherboard house, but there was a thread in the past few months about someone in your situation who did it and found it useful.

3244 posts

Uber Geek

  # 1885730 18-Oct-2017 14:25
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PPV is snake oil, don't be fooled by the sales hype, it's simply a fan that blows air, nothing more.  That said IME they do a brilliant job of dealing with moisture and condensation problems.  



  1. Deal with the source of any moisture (extractor fans in bathrooms, kitchen etc)
  2. Install a SmartVent/DVS/HRV ventilation system (we went with Smartvent because they don't lock you into servicing, and can do it yourself).  If taking air from outside consider an in-line heater so you can still use it during the colder months when you need it most (otherwise you are just pumping in cold air)
  3. Insulate what you can
  4. Once the air is clean/dry you will find heating more efficient - install a heat pump. 



Always be yourself, unless you can be Batman, then always be the Batman


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Uber Geek


  # 1885734 18-Oct-2017 14:33
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Agree that most PPV salespeople are basically outright liars. It's just a fan with ducting and outlets. It's similar to opening a window on a day with a gentle breeze, but it's reliable. It will reduce condensation a bit, but the main thing is fresh air is good.


A $10 timer from a hardware store set to run say 11am to 4pm in winter will reduce the cold air problems, and if you like run it a bit evening and night. I think I run 15 minutes a few times in the night to help get a bit of fresh air in without making it cold. In summer I run 6am to 9am and 8pm to midnight, or something like that.

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Ultimate Geek

  # 1885775 18-Oct-2017 15:56
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They are ok I have a renovated 70s house just kitted house out in sunblinds to reduce heat in summer as don't have double glazing with blinds down which also keep cold out and thermal curtains we now get condensation as the air can't flow around the blinds , advice from DVS leave curtains has dried out the house .I would do installation first does you local council have any schemes going?

3885 posts

Uber Geek


  # 1886053 19-Oct-2017 09:11
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Do you actually have a moisture problem upstairs? Or do you simply have poor heating? As for downstairs do the tenants keep it heated? As no heating and you almost always get damp problems. If you get plenty of sun. You then have free heating. As the Sun increases the internal temp higher than outside, It gives the whole house a daily drying cycle.

No heating either from the Sun or heaters - the internal air temperature is always lower than outside. Moisture then builds up. And ventilation won't fix the problem As Auckland normally has high humidity.

In a lot of cases running a dehumidifier is far cheaper than running a heater. And if you have higher internal air temperature. You will get a lot more natural ventilation anyway due to the thermosiphon effect.

So far, it seems that you need better heating instead of a ventilation system.

5 posts

Wannabe Geek

  # 1886056 19-Oct-2017 09:12
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 Thank you all for your replies and helpful suggestions.


Totally agree with having to remove/reduce the source of the problem but it has been tricky for me as the house is well equipped with good sized extractor fans in both downstairs and upstairs baths and rangehood in both kitchens. 2no. x 300m3/hr and 2no. x 600m3/hr


One of the downstairs rooms has no window to outside but what's called borrowed light(an internal window to the lounge) that greatly restricts proper ventilation in the room.


As it is for all rental units, I am having to rely on the tenants to regularly vent the rooms. I guess this would have been hard as they could not obviously leave all the windows open throughout the day in winter for both security reasons and wet weather. And opening windows at night after early dusk attracts too many bugs in the unit which wasn't ideal. Plus opening up windows on a rainy day won't technically reduce the indoor humidity down anyway in Auckland.


There is a good chance that the main source of humidity and mould would be from the underground water movement under/surrounding the half basement granny flat.  An external side of the underground wall had been exposed to be properly tanked/waterproofed with drainage coils as per the code. Although it stopped water leaking and ponding though the side of the wall we noticed before having the tenants inn, I guess there's still some moisture arising from below the floor slab where there's probably no damp proof membrane anyway. Our bedroom that we feel sick inside sleeping is directly above this downstairs room btw.




So given that the house is reasonably well equipped with extractor fans and gets regularly ventilated by all the occupants, my best guess is that it is down to the poor design of the house back in the day that is allowing the underground moisture through the wall/floors downstairs.  However, the downstairs carpets, when flipped back, were surprisingly clean with no signs of mould. I have said we had mould issue downstairs in my original post,  the damage was only done to the tenants clothes in stored in boxes and wardrobes, leather bags and couches. There were no visible moulds on internal gib linings and this is now leaving me thinking maybe the mould could have been prevented with a dehumidifier?


In a case like this I guess the only long term solution would be for me to look at getting either of the vent system rather than just a stand alone dehumidifier? But again, I am getting a feeling that due to the small size of the house and seeing no visible mould growth on any walls or ceilings, we could probably get away with a descent sized humidifier for each floor and move them around each room to get rid of the stuffiness time to time?


If I was to get a vent system, like your suggestions, I would get Smartvent. A 2 vents + 1 fan  unit per floor so that the tenants can have the control of turning it on and off as required. But if the dehumidifiers were to be sufficient enough in our situation, we would rather not get these due to the cost and having to throw away bit of room in our 2 x wardrobes for the vertical ducts that will run from our attic to downstairs unit. 






-more convenient and likely to fix and prevent mould


-takes up wardrobe space. potential noise issue.


-more expensive to install but could be cheaper run






-less expensive to buy but could be more expensive to run. No need to install.


-l might not resolve the mould issue.


-covers only one room as we will not have one for every room. takes up floor space.




The best and but a lot more expensive solution would be for us to get the Mitsubish 'Lossnay' balanced ventilation with ducts running both upstairs and downstairs and the Panasonic ducted heap pump that gets attached to the same duct. However this won't allow the downstairs tenants to have control over the vent unit which could create some issues for the future 


Based on what the sales person was saying, I got the impression that the ducted heatpump can be installed over the Smartvent system and still be compatible. So I could just go with 2no x Smartvent unit and maybe look at getting a either a ducted or highwall heatpump depending on whether I want the whole house to be warm at the same time or just some areas..




Again, apologies for the rather lengthy post and greatly thank you 'Timmmay' and 'scuwp' for promptly taking your time out leaving helpful thoughts, opinions and suggestions. Means a lot tome as this is health related for the whole family.











5 posts

Wannabe Geek

  # 1886098 19-Oct-2017 09:48
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Hey Aredwood


Thanks for another helpful insight and suggestions.


The upstairs lounge and kitchen is north-facing so gets heaps of sun light through the window. A bit draughty but bearable as we have those thick curtains around the house touching the floor.


The bedroom we sleep in gets a bit of late afternoon sun light but that hasn't really been the case over the winter as it was either cloudy or rainy all throughout.


To answer your questions, no I am certain if we have moisture problem upstairs other than condensation around windows which my wife had hard time removing everyday.


As far as heat source goes we have been using 2 x thermostat oil heaters and one of those dyson cool + heat to distribute heat around the house but didn't help much with getting completely rid of the sore throats. Both me and my wife have been waking up with sore throats with phlegm regardless of whether we leave the heater on or off during the night. Changed duvets and covers a few times, vacummed them and dusted the curtains but it made only marginal or no difference.  The sore throat goes away during the day but starts creeping back in the night and through the next morning.  


At first I thought this was just to do with flu and my immune system but the fact that the same symptoms have been on going for the whole family started to concern me.  My lungs feel as if I have gone back to smoking which I have quit 10 years ago. 


Based on your suggestion, I guess it could be sensible as the most cost efficient approach to get a highwall heatpump in our upstairs bed room and a descent sized dehumidifier downstairs..




15565 posts

Uber Geek


  # 1886115 19-Oct-2017 10:06
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It's been a terrible winter for cold / flu type symptoms that go on and on. My wife had it for 6 weeks, me for 4, my 1 year old for about 8 weeks and counting. We live in a warm, dry, well ventilated home. Lots of bugs from daycare.


Window moisture is normal. It's caused by moisture inside hitting cold windows. Even with ventilation you'll still get that. Double glazing solves the problem of it condensing on the windows, but it's still in the air, so you need to ventilate to get it out.


I did proper PVC double glazing recently, for an average home the windows were around $14K fitted, plus painting. Years before that I spent around $4K doing a cheaper version, basically 3m thick perspex sheets that are attached to the windows inside, a kind of plastic double glazing. It was I guess 70% as effective as the proper double glazing at 25% the cost, and looked not too bad. I actually still have all the perspex in my shed, but attaching it would be a bugger of a job. The company (ThermalFrame) have a decent way of attaching it. Their Wellington branch was awful because of the cowboy who ran it then closed it down without warning, but my understanding is they have independent companies around the country that do it and most are good. Plenty of companies will do it. Reduces noise too. If you have thick wooden frames fitting is relatively easy.



5 posts

Wannabe Geek

  # 1905208 21-Nov-2017 12:30
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Hi again,


Thought you all deserve to know where I got to with all my quarries.


To cut to the chase,  I have found that Fujitsu's ducted heat pump system that does all of the Panasonic one I got quoted can be installed with an additional fresh air intake that draws air directly from outside through a vent on the soffit. 


The heat pump was about the same price at $6k  and the fresh intake at $600.


Wifi can be done at an extra cost but was gona cost more than $500.




With this Fujitsu unit, whether true or not, been told that the amount of fresh air equates to 15% of the indoor air volume hence the house remains slightly positive pressured as the inflow of air has no proper mechanical way to be drawn out other than through the little gaps under main door and gaps at the bottom of walls. 


If the house was a new build and fairly air-tight this wouldn't have been ideal as the sterile air won't get out as efficiently, but being an old house with small openings, this will just work as if I have a positive ventilation system on top of ducted heat pump.


The fresh air intake cannot be run on its own as a separate ventilation system as it is an additional feature to the heatpump. It only draws fresh air when the heat pump is operating. ie. either heating or cooling.






For the downstairs room, I have found a DIY ventilation system called 'Unovent' which basically is a vent with an attached fan right on top of it that is designed to bring in air from attic.  


Because obviously the downstairs have no attic space directly above, I am considering installing it on a plaster wall where there is the block wall vent to outside right behind that wall.  


This won't mean the enclosed room will be getting dryer air from attic, but will still provide some means of semi-passive ventilation to the room.  


One vent + fan with the sensor costs about $700 on their website.


Even cheaper without the sensor but this will mean the fan will start everytime the light is on in that room with the way the circuit has to be run..









15565 posts

Uber Geek


  # 1905335 21-Nov-2017 15:43
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I had a ventilation system that bought in air from the ceiling cavity. I changed the ducting to bring in fresh air. Sure you get a bit more heat, which is nice in winter, but ceiling spaces have all kinds of allergens and you probably don't want that in your house, even though a filter.

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Ultimate Geek

  # 1905346 21-Nov-2017 16:05
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We have run a dehumidifier in the hallway (where all 4 bedrooms come off) continuously over the past 6 winters. This costs around $60 per month. This solved all of our condensation and cold issues. Just make sure the filter is cleaned weekly so you don't burn the house down.

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Uber Geek


  # 1905352 21-Nov-2017 16:25
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We have run a dehumidifier in the hallway (where all 4 bedrooms come off) continuously over the past 6 winters. This costs around $60 per month. This solved all of our condensation and cold issues. Just make sure the filter is cleaned weekly so you don't burn the house down.



That's $1800 in power. A DVS costs more to put in, but running costs are smaller.


Have you tried to work out where your moisture is coming from? I did things like extraction, ground sheets, etc, that fixed the problem. Having a DVS that runs some of the time helps too.

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