Balanced Pressure Ventilation with Heat Exchanger worth it?

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tweake

2391 posts

Uber Geek

#3083865 2-Jun-2023 13:00

MikeAqua:

tweake:

a tad odd to have a separate bath system, unless it could not be plumbed into the other system. or they just wanted to sell more stuff.

one of the problems doing a separate system is that you need make up air, especially if the fan is upgraded. some ventilation systems have that option and will boost incoming airflow when the bath fan gets turned on (or stove hood). but generally its cheaper and gets better results, to just use the bath room as one of the ventilation exhausts.

sorry i may have gotten my wires crossed here. depends on if you have HRV core or ERV core. HRV keeps inside heat in and outside heat out. ERV keeps inside heat and humidity in and outdoor heat and humidity out. the downside of the ERV is because it keeps that moisture in, it can build up to danger levels. this is also why its important to know what core they sold/installed.

I wanted the bathroom system set up that way. Simpler. The house was a 1950s and 1970s build so not air-tight and easy to draw make-up air.

The core was an air-to-air heat exchanger. Cold dry air sucked in and warm wet are sucked out with transfer of most heat from outgoing to incoming air. Worked well enough to justify the investment. Humidity would stabilise at ambient or below if we were running heat pumps in cooling mode.

sounds like HRV core.

however with a non air tight house they are typically not worth it. pretty rare, tho not impossible, for older homes to be air tight enough for them to work well.

Barnholbol

2 posts

Wannabe Geek

#3160016 15-Nov-2023 23:14

Hi there. Very helpful discussion on BPS. I'm currently debating whether or not to install a BPS into our circa 2005 brick & tile Whangarei home.

We're well sited and insulated to high standard but single glazed and as yet not uniformly heated, so usual story with condensation - obviously all through winter, but most notably mid to late autumn.

I plan to upgrade the heating once I've dealt with the ventilation - the house isn't particularly cold and I'm also keen to see what effect the (theoretically) improved circulation of tempered air would have using a BPS first.

Front runner BPS at the moment is Cleanaire - I've read their various info front to back and they appear well built, well researched and logically presented. Next best is a Lossnay system, which again has the smarts applied (I also like the wall mounted systems they have available). They're also compatible with ducted HP systems I believe. Smartvent coming in pricier and not interested in HRV or DVS.

Pricing for DIY install is around the $6,000 mark for a 5 supply/4 exhaust system.

Most domestic ventilation in Northland seems to be PPS and there's depressingly little in the way of knowledge base/supply for BSP in the region.

Some might say that BPS is overkill up here, but I'd argue it still gets relatively cold and I cannot see how inflating the building envelope with untempered air, either from the roof space or directly from outside, is all that clever in the guts of winter.

I'm definitely keen to hear of any other first-hand experience with BPS.

One issue I cannot seem to find any info on is how these systems preform with full length curtains - obviously, we're encouraged to utilise them to keep the warm air in, but as I understand the physics, reduction of condensation (by a BPS) would rely to some degree on air movement across the glass and I don't see this being achived where curtains are installed(?)

andrew75

145 posts

Master Geek

ID Verified

#3160029 16-Nov-2023 06:45

Based on my experience with an early DVS unit, in actual practice any heat recovery is minimal and most is lost in the ducting anyway unless heavily insulated. $6000 would be a waste of money and better spent on a simple ventilation system and buying energy to heat.

BlargHonk

147 posts

Master Geek

#3160118 16-Nov-2023 12:11

andrew75:

Based on my experience with an early DVS unit, in actual practice any heat recovery is minimal and most is lost in the ducting anyway unless heavily insulated. $6000 would be a waste of money and better spent on a simple ventilation system and buying energy to heat.

Man I have gone around the loop so many times with this and I'm still no clearer on what I want to do. We have an old 60s single glazed weatherboard house. I have done my best to close up all the gaps but I imagine it is still very leaky compared to a modern house. I have talked to quite a few installers and read all the threads on Geekzone. The balanced system makes the most sense in my head. Using fresh air from the inside and transferring heat from the exit air. What's not to love (other than the price)?

Then there are the Positive Pressure ones which seemed to range from simply a filter, fan and one outlet in the middle of the house to designs with multiple outlets in each room with options for heat transfer and summer kits. The controllers also seemed to range in smarts too.

Pulling air from the roofspace seems like a poor idea most of the time. During summer it is stinking hot up there so it would be better to source air from outside (i.e. summer kit). Plus the air quality can't be great, even with a filter.

I'm still on the fence whether I spend $5k (installed) on a Lossnay VL250 or if I just get a cheap PPV system with a summer kit. Any advice welcome! Especially things to look out for when going for the el cheapo version.

tweake

2391 posts

Uber Geek

#3160197 16-Nov-2023 15:48

Barnholbol:

Hi there. Very helpful discussion on BPS. I'm currently debating whether or not to install a BPS into our circa 2005 brick & tile Whangarei home.

We're well sited and insulated to high standard but single glazed and as yet not uniformly heated, so usual story with condensation - obviously all through winter, but most notably mid to late autumn.

I plan to upgrade the heating once I've dealt with the ventilation - the house isn't particularly cold and I'm also keen to see what effect the (theoretically) improved circulation of tempered air would have using a BPS first.

Front runner BPS at the moment is Cleanaire - I've read their various info front to back and they appear well built, well researched and logically presented. Next best is a Lossnay system, which again has the smarts applied (I also like the wall mounted systems they have available). They're also compatible with ducted HP systems I believe. Smartvent coming in pricier and not interested in HRV or DVS.

Pricing for DIY install is around the $6,000 mark for a 5 supply/4 exhaust system.

Most domestic ventilation in Northland seems to be PPS and there's depressingly little in the way of knowledge base/supply for BSP in the region.

Some might say that BPS is overkill up here, but I'd argue it still gets relatively cold and I cannot see how inflating the building envelope with untempered air, either from the roof space or directly from outside, is all that clever in the guts of winter.

I'm definitely keen to hear of any other first-hand experience with BPS.

One issue I cannot seem to find any info on is how these systems preform with full length curtains - obviously, we're encouraged to utilise them to keep the warm air in, but as I understand the physics, reduction of condensation (by a BPS) would rely to some degree on air movement across the glass and I don't see this being achived where curtains are installed(?)

waste of time and money with BPS (balanced hrv) simply due to the homes air leakage. simply use a PPS. for BPS to be effective you need a very very air tight house, and it has to be made air tight on purpose. kiwis construction practices means they are rarely ever air tight. btw afaik cleanaire use aluminum heat exchangers which are really only good for really cold areas.

untempered air, you need to remember your already leaking large amounts of hot air out (and sucking cold air in) anyway. you just don't notice it because its not in one place (ie vent). its really a non issue, its simply a perception thing.

air flow stopping condensation works because the air flows across the ceiling then down the wall behind the curtain. if you have pelmets that can stop the airflow. of course air getting around the curtains takes away some of the insulation value of the curtain. personally i don't care about condensation. your always going to get some with single glazing and our humidity levels. thats normal. its bad condensation then the house may have issues. much better to use a temp/humidity guage to tell if you have a house issue.

their is very little knowledge of bps in nz because so there is so few homes can use them effectively.

tweake

2391 posts

Uber Geek

#3160204 16-Nov-2023 15:59

BlargHonk:

andrew75:

Based on my experience with an early DVS unit, in actual practice any heat recovery is minimal and most is lost in the ducting anyway unless heavily insulated. $6000 would be a waste of money and better spent on a simple ventilation system and buying energy to heat.

Man I have gone around the loop so many times with this and I'm still no clearer on what I want to do. We have an old 60s single glazed weatherboard house. I have done my best to close up all the gaps but I imagine it is still very leaky compared to a modern house. I have talked to quite a few installers and read all the threads on Geekzone. The balanced system makes the most sense in my head. Using fresh air from the inside and transferring heat from the exit air. What's not to love (other than the price)?

Then there are the Positive Pressure ones which seemed to range from simply a filter, fan and one outlet in the middle of the house to designs with multiple outlets in each room with options for heat transfer and summer kits. The controllers also seemed to range in smarts too.

Pulling air from the roofspace seems like a poor idea most of the time. During summer it is stinking hot up there so it would be better to source air from outside (i.e. summer kit). Plus the air quality can't be great, even with a filter.

I'm still on the fence whether I spend $5k (installed) on a Lossnay VL250 or if I just get a cheap PPV system with a summer kit. Any advice welcome! Especially things to look out for when going for the el cheapo version.

60's house, complete and utter waste of money to use a BPS. far to air leaky.

you do not need much for ventilation. a lot of the features are gimmicks to get you to buy. a simple efficient fan, good filters and i much prefer a "summer kit". most systems turn off in high temps so you don't get any ventilation until the roof cools down. having a "summer kit" means it can run a lot longer before the heat overwhelms the system and it turns off. you can make your own with a y branch damper, thermostat and 24v power supply.

have a look at weiss eco home ventilation system, they sell them at mitre 10.

andrew75

145 posts

Master Geek

ID Verified

#3160233 16-Nov-2023 18:15

Or go to MingFans they were good to deal with when I set up my DYI head transfer system.

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dzh

50 posts

Geek

Trusted

#3169496 7-Dec-2023 23:48

I'm researching HRV + ducted heating install too. Having lived in HRV'd house the CO2 it removes is 100% worth it.

With standalone HRV install you'd extract stale air from bathrooms and supply into bedrooms.

My question where would you place your return ducts where integrating with ducted heater?
One of my goals is to reduce humidity in bathrooms, but from looking at diagram below, there'd be still some air thats not simply not captured by HRV and returned back into furnace back into your bedrooms... Yikes!

Edit: nevermind - I've looked into second diagram of the article where I pulled this image and it has much better solution - https://www.finehomebuilding.com/project-guides/energy-retrofit/ducting-hrvs-and-ervs

MikeAqua

7773 posts

Uber Geek

#3169734 8-Dec-2023 13:03

tweake:

#sounds like HRV core.

however with a non air tight house they are typically not worth it. pretty rare, tho not impossible, for older homes to be air tight enough for them to work well.

Not HRV the brand but yes HRV the technology. And made an absolutely transformational difference to the liveability and comfort of the house. For example, reduced our power bill, reduced severity of respiratory symptoms and made the whole house feel warmer.

When we moved to a house without the system, everything felt damp to me.

Mike

tweake

2391 posts

Uber Geek

#3169816 8-Dec-2023 15:21

dzh:

I'm researching HRV + ducted heating install too. Having lived in HRV'd house the CO2 it removes is 100% worth it.

With standalone HRV install you'd extract stale air from bathrooms and supply into bedrooms.

My question where would you place your return ducts where integrating with ducted heater?
One of my goals is to reduce humidity in bathrooms, but from looking at diagram below, there'd be still some air thats not simply not captured by HRV and returned back into furnace back into your bedrooms... Yikes!

Edit: nevermind - I've looked into second diagram of the article where I pulled this image and it has much better solution - https://www.finehomebuilding.com/project-guides/energy-retrofit/ducting-hrvs-and-ervs

one of the issues with using the hvac system as ventilation ducting, is you need the hvac fan to run. which typically means the fan runs constantly. so you really need one system to be able to talk to the other so the hvac turns on when ventilation is on.

as per the other pic, the ventilation return is kept separate and goes straight to the HRV and goes outside. one thing that pic gets wrong is they have a return in the kitchen. unfortunately people like to do the complete hack job of using the ventilation system as a range hood. duct fouling is a real problem which is why they do not go in the kitchen. install a proper range hood and boost the supply or have a make up air supply for the range hood.

also need to factor in if you go ERV core.

tweake

2391 posts

Uber Geek

#3169818 8-Dec-2023 15:24

MikeAqua:

tweake:

#sounds like HRV core.

however with a non air tight house they are typically not worth it. pretty rare, tho not impossible, for older homes to be air tight enough for them to work well.

Not HRV the brand but yes HRV the technology. And made an absolutely transformational difference to the liveability and comfort of the house. For example, reduced our power bill, reduced severity of respiratory symptoms and made the whole house feel warmer.

When we moved to a house without the system, everything felt damp to me.

yes they are great, but you need an fairly air tight house for it work well in. trouble is kiwi homes are not made with any thought to air tightness. so they can go from extremely tight, to massively air leaky. roll the dice if you get a good one or not.

dzh

50 posts

Geek

Trusted

#3169832 8-Dec-2023 17:19

tweake:

yes they are great, but you need an fairly air tight house for it work well in. trouble is kiwi homes are not made with any thought to air tightness. so they can go from extremely tight, to massively air leaky. roll the dice if you get a good one or not.

How so? I know A+++ grade houses absolutely need one. You can't even install traditional rangehood extractor - only filter one. All to save energy.

But my 90s bedroom gets stuffy with CO2 within an hour. Parents 1880s house (triple glazed in northern europe) is same and HRV barely keeps up.

Yes I can open the window, get dehumidifier and pay extra for heating vs expensive tradie install, but that aint the point.

tweake

2391 posts

Uber Geek

#3169837 8-Dec-2023 17:50

dzh:

tweake:

yes they are great, but you need an fairly air tight house for it work well in. trouble is kiwi homes are not made with any thought to air tightness. so they can go from extremely tight, to massively air leaky. roll the dice if you get a good one or not.

How so? I know A+++ grade houses absolutely need one. You can't even install traditional rangehood extractor - only filter one. All to save energy.

But my 90s bedroom gets stuffy with CO2 within an hour. Parents 1880s house (triple glazed in northern europe) is same and HRV barely keeps up.

Yes I can open the window, get dehumidifier and pay extra for heating vs expensive tradie install, but that aint the point.

no, you do not need one. you can ventilate with out one easy enough. as long as fan in = fan out. its simply that using an hrv/erv core is energy efficient.

plus what is a A+++ grade house? is that just looks or performance? very few homes here are blower door tested. how do you know what the air leakage is without testing?

you most certainly can install traditional rangehood. many do and its highly recommended. filter ones are so bad they should be banned. the only extra requirement is you need to account for the extra air a traditional hood flows, ie need to install make up air. not difficult, can be done a few different ways. filter hoods are used to cut corners, to cut costs at the expense of causing major problems down the road. very few kiwi homes install good range hoods, most are simply the minimum to pass the rules, and hide it so no one can see it approach. seen it done in passive homes. got the big expensive flashy cool looking bling, but used a cheapy undersized filter hood to cut costs.

euro homes are often very air tight due to their building methods and that they try to make it air tight. big difference in mentality.

if ventilation system is not keeping up, then flow rate is probably a bit low. one of the big advantages of hrv/erv is being able to run high ventilation rates without high heat loss. if its only one room it can be lack of a return system out of that room. many people put in ducted systems and forget to install returns out of each room (or installers don't put them in to cut costs).

MikeAqua

7773 posts

Uber Geek

#3170542 11-Dec-2023 10:09

tweake:

yes they are great, but you need an fairly air tight house for it work well in. trouble is kiwi homes are not made with any thought to air tightness. so they can go from extremely tight, to massively air leaky. roll the dice if you get a good one or not.

Ours was quite a leaky house in some areas, but we still experienced all those benefits.

Mike

tweake

2391 posts

Uber Geek

#3170780 11-Dec-2023 16:56

MikeAqua:

tweake:

yes they are great, but you need an fairly air tight house for it work well in. trouble is kiwi homes are not made with any thought to air tightness. so they can go from extremely tight, to massively air leaky. roll the dice if you get a good one or not.

Ours was quite a leaky house in some areas, but we still experienced all those benefits.

i have my doubts. with reasonably air leaky houses you have just as much (up to double is common) air leakage as you have air going through the balanced system. with those sort of air leakage rates a positive pressure system will work just as well for a whole lot less $$.

rule of thumb is you want to have less air leakage than your ventilation rate, thats the situations the balanced systems work really well in.

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