Positive Pressure Ventilation Systems 2022

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#2942858 16-Jul-2022 14:21

FineWine:
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

If they're anything like under-bench water filters then you should be able to get third-party ones every bit as good if not better than the branded ones at a fraction of the price, I change water filters for various family & neighbours and the cost is anything from 1/2 to 1/4 the brand-name price that someone's trying to sell them. So another consideration would be "which ones have the best third-party support?".

tweake

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#2942860 16-Jul-2022 14:25

FineWine:

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.

its BS like that, that turns me off these companies. its adding something fancy sounding to promote even tho it does nothing.

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.

they do not bring cooler air into the roof space (the standard roof vents is already doing that) , it simply diverts the air intake to the outside you the ventilation air comes from outside.

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.

its should not be 3 air changes per hour (3ach) which is a gale blowing through the house. it should be 0.3ach.

once every 90 minutes ? i would have to look that up. typically two main ways of providing air flow. a small amount constantly, my preferred method but requires variable speed fan that you can adjust. or a large amount every so often, which uses a high speed fixed speed fan and a timer. trouble is DVS should be a variable speed fan so i'm not sure why they would advertise that. it also makes NO difference in bringing cold air into the house. it sounds like BS marketing.

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.

no need for it to be central tho technically its better. put it somewhere where you can change the filter easy enough.

hope that helps.

neb

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#2942864 16-Jul-2022 14:40

FineWine:
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.

That was another consideration for the Casa, pull cooler air from the basement up into the living room in summer, so the reverse of the usual cycle, but at the moment it looks like it'll be solar panels driving the heat pump since more or less by definition there'll be a ton of sun when you need cooling the most.

For the tin roof, next time you repaint it consider a high-albedo paint colour. For new builds the manufacturers list reflectance values, e.g. for Coloursteel so you can pick one that maximises the amount of solar power that goes back up into the sky. Be aware that the small patches tend to look a lot lighter than the whole roof once it's done, we went with Titania, close to 70% reflectance, which looks quite white but actually works really well when it's over an entire roof.

Compare that to the popular Karaka in terms of how much that'll bounce back...

tweake

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#2942928 16-Jul-2022 15:24

That was another consideration for the Casa, pull cooler air from the basement up into the living room in summer, so the reverse of the usual cycle,

thats typically a bad idea. apart from that the natural cycle is actually up, stack effect means all the air wants to go up through the building, the problem is it can drag moisture from the basement into your living room. a lot of places have poor moisture management in basements with the false idea that the upstairs is separate from it.

neb

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#2942933 16-Jul-2022 15:41

tweake:
thats typically a bad idea. apart from that the natural cycle is actually up, stack effect means all the air wants to go up through the building, the problem is it can drag moisture from the basement into your living room. a lot of places have poor moisture management in basements with the false idea that the upstairs is separate from it.

We typically have all the north-facing doors and windows in the basement open in the summer to allow air flow through it. Any bit of moisture that somehow manages to find its way inside will get zapped by the baking heat in the floor above... it really depends on the house layout, in this case it'd be moving dry air that's maybe 5-10 degrees cooler from downstairs to upstairs.

Some of this will admittedly be resolved when we get the massive black heatpipes masquerading as French doors replaced with Homerit uPVC ones.

tweake

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#2942943 16-Jul-2022 16:10

neb:
tweake:

thats typically a bad idea. apart from that the natural cycle is actually up, stack effect means all the air wants to go up through the building, the problem is it can drag moisture from the basement into your living room. a lot of places have poor moisture management in basements with the false idea that the upstairs is separate from it.

We typically have all the north-facing doors and windows in the basement open in the summer to allow air flow through it. Any bit of moisture that somehow manages to find its way inside will get zapped by the baking heat in the floor above... it really depends on the house layout, in this case it'd be moving dry air that's maybe 5-10 degrees cooler from downstairs to upstairs. Some of this will admittedly be resolved when we get the massive black heatpipes masquerading as French doors replaced with Homerit uPVC ones.

while every house is different to give some idea, something like 80-90% of moisture in a home comes in from under the home.

considering a lot of basements are block/concrete with mediocre moisture control, a lot of moisture comes through it. sometimes its brought in by a car (assuming there is a garage in the basement). even the outside air itself can easily be 80-90% humidity. point here is that "moisture that somehow manages to find its way inside" is not true. its already in even if you do not notice it.

ideally you want is the basement vented separately to upstairs. so moisture from the basement gets vented out so it cannot get pulled up into the floor above. but every home is different and there is a few different ways to manage moisture.

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FineWine

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#2942957 16-Jul-2022 18:00

tweake:

FineWine:

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.

its BS like that, that turns me off these companies. its adding something fancy sounding to promote even tho it does nothing.

FineWine reply: agree

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.

they do not bring cooler air into the roof space (the standard roof vents is already doing that) , it simply diverts the air intake to the outside you the ventilation air comes from outside.

FineWine reply: apologies I meant it brings cooler air directly into the system therefore into the living spaces. Not the roof space.

its should not be 3 air changes per hour (3ach) which is a gale blowing through the house. it should be 0.3ach.

FineWine reply: correct - HRV is 0.3ach and SV is 0.35 whilst DVS 1 change per 90 min I read in the small print some where

no need for it to be central tho technically its better. put it somewhere where you can change the filter easy enough.

FineWine reply: agree

hope that helps.

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

mattwnz

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#2942958 16-Jul-2022 18:08

mattenz:

I've never read a convincing argument that PPV roofspace air is better than a heat exchanger for older homes.

Agree regarding the outside humidity being too high, 70% is pretty much universally considered unhealthy, realistically you should be down under 60%, and around 50%. To get my outside air (in Waitākere) to that right now only via heating, I'd need to get it to 26°, which doesn't seem very realistic for the whole house (and of course, I'd have to prevent other sources of water from evaporating).

From my experience roof air is nearly as cold as outside air. We have had a PPV system in a house and it made no noticeable difference to condensation.

But YMMV. Our house was a typical 60s house that had a 90s extension and no double glazing. But on piles with foil underneath.

tweake

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#2942973 16-Jul-2022 19:32

FineWine:

FineWine reply: correct - HRV is 0.3ach and SV is 0.35 whilst DVS 10.5 changes I read in the small print

it won't be 10.5. that would cause damage to any half decent house.

any link to the small print?

tweake

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#2942974 16-Jul-2022 19:39

mattwnz:

mattenz:

I've never read a convincing argument that PPV roofspace air is better than a heat exchanger for older homes.

Agree regarding the outside humidity being too high, 70% is pretty much universally considered unhealthy, realistically you should be down under 60%, and around 50%. To get my outside air (in Waitākere) to that right now only via heating, I'd need to get it to 26°, which doesn't seem very realistic for the whole house (and of course, I'd have to prevent other sources of water from evaporating).

From my experience roof air is nearly as cold as outside air. We have had a PPV system in a house and it made no noticeable difference to condensation.

But YMMV. Our house was a typical 60s house that had a 90s extension and no double glazing. But on piles with foil underneath.

roof air temp depends on a lot of things. if your measuring in winter its typically much the same. however good sunny day with the right sized roof it can be a very hot. a mates roof space went from 1c and 3 hours later it was 30c.

window condensation also depends on house humidity and how well the curtains work. better the curtains the more condensation you get, especially if you have old school pelmets (which stops the PPV from blowing over the glass). also with a house on piles and no moisture barrier, that ground moisture will be going up into the house.

neb

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#2943017 16-Jul-2022 22:07

tweake:
considering a lot of basements are block/concrete with mediocre moisture control, a lot of moisture comes through it. sometimes its brought in by a car (assuming there is a garage in the basement). even the outside air itself can easily be 80-90% humidity. point here is that "moisture that somehow manages to find its way inside" is not true. its already in even if you do not notice it.

Since there are temperature/humidity sensors at multiple locations inside and outside the basement I have a pretty good idea what the levels are. Ventilation is arranged such that outside air only comes in when it's as dry as or drier than the inside air.

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tweake

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#2943164 17-Jul-2022 14:16

FineWine:

Thanks folks for your reply's.

At the moment we are leaning towards DVS.

........

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 'the system' during our warmer summer months as we have a tin roof.

i had a look at the DVS manuals, which seam to be different from the last one i saw, and it looks like their automatic "summer kit" is a bit bogus.

it seams that they are running it off room temp, ie using the ventilation system as a cooling system, room gets to hot it switches to outside air. of course thats flawed and misses the main requirement of the summer kit. for an auto summer kit to work properly it needs a temp sensor in the ceiling space (not the one on the fan) to measure ceiling temp and switches the air inlet according to that temp. the goal here is to keep the ventilation system running and not turn off due to high ceiling temps.

however its easy enough to make your own. i've made one thats in testing at the mo. just a basic thermostat connected to the electric damper, very simple.

FineWine

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#2943178 17-Jul-2022 15:26

tweake:

FineWine:

Thanks folks for your reply's.

At the moment we are leaning towards DVS.

........

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 'the system' during our warmer summer months as we have a tin roof.

i had a look at the DVS manuals, which seam to be different from the last one i saw, and it looks like their automatic "summer kit" is a bit bogus.

it seams that they are running it off room temp, ie using the ventilation system as a cooling system, room gets to hot it switches to outside air. of course thats flawed and misses the main requirement of the summer kit. for an auto summer kit to work properly it needs a temp sensor in the ceiling space (not the one on the fan) to measure ceiling temp and switches the air inlet according to that temp. the goal here is to keep the ventilation system running and not turn off due to high ceiling temps.

however its easy enough to make your own. i've made one thats in testing at the mo. just a basic thermostat connected to the electric damper, very simple.

And apparently that is how this system is designed to work: DVS® Premium Connect - Summer Ventilation system

3 temperature sensors: main control panel, roof space & at the outside vent.

2 humidity sensors: main control panel & roof space

1 CO2 (moveable) power point plug-in wireless (through home network) can have a max 4 with average taken.

Whilst the difficult we can do immediately, the impossible takes a bit longer. However, miracles you will have to wait for.

tweake

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#2943185 17-Jul-2022 16:10

FineWine:

And apparently that is how this system is designed to work: DVS® Premium Connect - Summer Ventilation system

3 temperature sensors: main control panel, roof space & at the outside vent.

2 humidity sensors: main control panel & roof space

1 CO2 (moveable) power point plug-in wireless (through home network) can have a max 4 with average taken.

"Note: Feature operates on the main system ‘Set
Temperature’. It will use outside air to try and maintain the
Set Temperature if the outside air is cooler."

https://dvs.co.nz/wp-content/uploads/2020/07/DVS-Premium-Connect-User-Guide-Inhouse-21-July-2020.pdf

the sensor at the outside vent seams to indicate they are measuring outdoor temp not in ceiling temp. ie using it to cool the house rather then trying to provide ventilation.

keep in mind roof space can, and often does get hotter faster than the house. so the ventilation actually turns off before the house is to hot. when really you want it to switch over the outside air when roof space gets to hot, that way you keep the ventilation going.

tweake

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#2943187 17-Jul-2022 16:13

FineWine:

3 temperature sensors: main control panel, roof space & at the outside vent.

2 humidity sensors: main control panel & roof space

1 CO2 (moveable) power point plug-in wireless (through home network) can have a max 4 with average taken.

to add, i suspect what they mean by "sensor in the roof space" is actually sensor in the fan measuring whats going through the fan, not the roof space.

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