Positive Pressure Ventilation Systems 2022

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#2941854 14-Jul-2022 14:48

If you're prepared for a higher up-front cost you can also get what amount to whole-house dehumidifiers that extract moisture from the air, whether it's coming from inside or outside, and blow the dried air back into the house. We've got one of those and run it every night for 3 hours during the free-power period to keep the basement dry, or at least much drier than it'd otherwise be.

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tweake

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#2941857 14-Jul-2022 14:53

mattenz:

tweake:

your missing the point.

why bother preheating it when there is as much if not more non-preheated outdoor air coming in anyway. your only preheating a small amount of total airflow. its rather expensive equipment for very small gain.

same applies to PPV on 100 year old homes that have massive amount of wind blowing through them already.

True, but that doesn't really answer my original question of why received wisdom indicates that you need to prefer PPV in an old house, you're just saying that they're both equally useless.

what system you use is dictated by how air tight the house is.

typically old house with wind blowing through it needs none (or draft stopping first).

later houses leak to much air for balanced systems to work well in so PPV works best for the price.

in air tight houses a PPV doesn't work well so is best suited to balanced system.

this is a generalization because some older homes can be very air tight, sometimes more than modern houses. our houses are not designed for air tightness so its dumb luck if it is or not. best thing to do is blower door test, find out the air leakage rate and fit the system that suits.

mattenz

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#2941859 14-Jul-2022 14:57

neb: If you're prepared for a higher up-front cost you can also get what amount to whole-house dehumidifiers that extract moisture from the air, whether it's coming from inside or outside, and blow the dried air back into the house. We've got one of those and run it every night for 3 hours during the free-power period to keep the basement dry, or at least much drier than it'd otherwise be.

Who was the supplier?

tweake

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#2941860 14-Jul-2022 14:58

neb: If you're prepared for a higher up-front cost you can also get what amount to whole-house dehumidifiers that extract moisture from the air, whether it's coming from inside or outside, and blow the dried air back into the house. We've got one of those and run it every night for 3 hours during the free-power period to keep the basement dry, or at least much drier than it'd otherwise be.

they are really suited for really air tight houses and to be used with an ERV system. otherwise your drying out the outdoors and all the ventilation air that comes in.

its the modern trend now and highly recommended, but you need to have a suitable house and mainstream builders do not build for that.

neb

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#2941878 14-Jul-2022 15:16

mattenz:
neb: If you're prepared for a higher up-front cost you can also get what amount to whole-house dehumidifiers that extract moisture from the air, whether it's coming from inside or outside, and blow the dried air back into the house. We've got one of those and run it every night for 3 hours during the free-power period to keep the basement dry, or at least much drier than it'd otherwise be.

Who was the supplier?

In our case these guys, but there's bound to be others around. One problem is that since it's, for NZ, rather exotic technology there aren't too many major suppliers around. We went with that one because they've been around for awhile, and the unit is built like a tank.

neb

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#2941880 14-Jul-2022 15:18

tweake:
they are really suited for really air tight houses and to be used with an ERV system. otherwise your drying out the outdoors and all the ventilation air that comes in.

its the modern trend now and highly recommended, but you need to have a suitable house and mainstream builders do not build for that.

Yeah, that's why we're using it for the basement, which is the new build portion and pretty airtight. So the 1970s upper half just has windows slightly open at all times and is naturally a bit leaky, the basement is airtight and gets dry air moved into it.

FineWine

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#2941886 14-Jul-2022 15:24

scuwp:

Love our Smart Vent system. Solved our condensation problem overnight. I wouldn't live in a house without some sort of system installed now. Just a small side-note, don't get sucked into the "positive pressure" sales pitch, they are just a fan in a box that blows air, with some smarts added. We went Smart Vent because it was cheaper, wasn't locked in to any service or maintenance, and could even install ourselves. Filters are $90 from Bunnings and take about 2 minutes to replace. We get about a year out of a filter depending on the fan speed.

@scuwp

Noted thanks. Did you self install or get the agent to do it ?

I have noted, from our received quote, that you can add a grand on the price for agent to install.

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rphenix

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#2942289 15-Jul-2022 16:42

Highly recommend against HRV if you do go down the fan in a box route.

I see you had considered dual glazing instead of working with the existing frames - why not see how cost compares to replace them? I would recommend homerit with Veka frames.

FineWine

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#2942344 15-Jul-2022 17:10

rphenix:

Highly recommend against HRV if you do go down the fan in a box route.

I see you had considered dual glazing instead of working with the existing frames - why not see how cost compares to replace them? I would recommend homerit with Veka frames.

Are not PPV systems all "fan in a box" with an inlet filter ?? (not balanced or summer or winter systems)

Why not HRV ??

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#2942372 15-Jul-2022 19:12

i wouldn't buy HRV just because of their long history of dodgy sale tactics and over priced products.

neb

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#2942468 15-Jul-2022 22:38

FineWine:
Why not HRV ??

They're the Uber of home ventilation when it comes to sharp business practices. Avoid them like the plague.

scuwp

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#2942568 16-Jul-2022 10:05

FineWine:

scuwp:

Love our Smart Vent system. Solved our condensation problem overnight. I wouldn't live in a house without some sort of system installed now. Just a small side-note, don't get sucked into the "positive pressure" sales pitch, they are just a fan in a box that blows air, with some smarts added. We went Smart Vent because it was cheaper, wasn't locked in to any service or maintenance, and could even install ourselves. Filters are $90 from Bunnings and take about 2 minutes to replace. We get about a year out of a filter depending on the fan speed.

@scuwp

Noted thanks. Did you self install or get the agent to do it ?

I have noted, from our received quote, that you can add a grand on the price for agent to install.

We got a full initial install. Couple of years ago now but larger home and 6 outlets was around $5K. They set it up so I could add the summer kit later myself (I haven't got around to this). Seeing now how basic things are, I would just do the donkey work myself next time, and just get the sparky in to join the power up. From what I have learnt however, the outlet position can be quite important (i.e. opposite doors and not in bathrooms), so a bit of research on that would be valuable if doing DIY. Also do a bit of thinking about teh best place to put the motor, both for sound, and to try and get equal distances to the outlets for the best balance, although this can be managed using the adjustable outlet vents.

We also got a silencer box around ours (basically a big chilly bin). I am sensitive to noise and found the quiet humming at night irritating. Something to consider when thinking about placement of the main motor - not above bedrooms.

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tweake

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#2942634 16-Jul-2022 11:08

scuwp:

We got a full initial install. Couple of years ago now but larger home and 6 outlets was around $5K. They set it up so I could add the summer kit later myself (I haven't got around to this). Seeing now how basic things are, I would just do the donkey work myself next time, and just get the sparky in to join the power up. From what I have learnt however, the outlet position can be quite important (i.e. opposite doors and not in bathrooms), so a bit of research on that would be valuable if doing DIY. Also do a bit of thinking about teh best place to put the motor, both for sound, and to try and get equal distances to the outlets for the best balance, although this can be managed using the adjustable outlet vents.

We also got a silencer box around ours (basically a big chilly bin). I am sensitive to noise and found the quiet humming at night irritating. Something to consider when thinking about placement of the main motor - not above bedrooms.

$5k, ouch 🤬

the chilly box is probably the biggest expense. fan and controller is a fair bit. outlets are cheap. its probably max 2k worth of gear (retail).

outlets is interesting. with smaller rooms you tend to put them in door ways because its one of the few places no one sits. they typically specify to put the outlets within a certain distance of the windows. this is because they are actually setup to blow air over the windows. the airflow tends to hug the ceiling and then flow down the wall behind the curtains. moving air can stop condensation from forming. hence it "removes condensation". not great for the insulation quality of the curtains tho. ie it makes the room a tad colder.

tweake

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#2942637 16-Jul-2022 11:14

scuwp:

From what I have learnt however, the outlet position can be quite important (i.e. opposite doors and not in bathrooms),

just a note. HVAC (ducted heat pump, heat transfer systems) have vents opposite doors. that because door ways are often the air return.

i left out balanced ventilation systems because there is a few more things you can do (like vents in bathrooms).

FineWine

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#2942793 16-Jul-2022 13:17

Thanks folks for your reply's.

At the moment we are leaning towards DVS.

Not really all that enamoured with the SmartVent agent, from a contracted electrical firm. He just followed a well worn script. The quoted price did not include GST and they do not do Gold Card.

HRV is our 2nd choice, though some comments here are ensuring doubts. They really really push their Kiwi technical innovations. The greatest Kiwi designed Manuka infused filters on the planet.

As the climate is only going to get warmer we are now also looking at a auto-controlled summer add-on to bring cooler air into roof space during our warmer summer months as we have a tin roof.

Interesting that HRV & SV all say 3 air changes per hour and DVS says once every 90mins (approx). DVS logic being that, during colder winter months, you are NOT bringing more colder air in from the roof space therefore not waking up to a cold room but just enough FRESH dryer air to keep the moisture at bay.

As well HRV & SV wants to install the fan unit etc more centrally in the roof space. Whilst DVS said they always install closest practical to ceiling hatch. If I'm to change the filter, I'm not particularly keen on crawling around up there when I can not see the beams due to 6 inches of insulation.

The one thing we are looking at is ongoing costs, mainly filters:

1st price is DIY & 2nd technician

HRV
Filters 2yr $140 or $240
SmartVent
Filters 1yr $112 or $240
DVS
Filters 1yr $72 or $148

We shall see and wait for the new quotes with the summer vent system add-on included. So next week. Watch this space.

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