Yet another home ventilation query

Forums › Home Workshop DIY › Yet another home ventilation query - 2024 edition

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214 posts

Master Geek

#3289875 2-Oct-2024 08:58

tweake:

btw moisture out of the ground under the house is at least 1L per 10sqm per day (i think there is a later study which shows it higher), so for 165m2 thats at least 16.5 liters of water every day thats mostly coming up through the floor (due to stack effect).

Wow that's a lot! Bit eye opening actually..

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roderickh

214 posts

Master Geek

#3289880 2-Oct-2024 09:07

Wheelbarrow01:

This is all interesting stuff. I have a 1960's brick veneer house that was hard to heat and full of condensation when I bought it, despite it already having double glazing, underfloor foil, and good ceiling insulation in the areas that don't have skillion ceilings.

I installed insulation in the skillion ceiling portion, installed a log burner, and Insulmax dry blown insulation in the walls, all of which made the house a million times warmer + fantastic heat retention, but the condensation on the windows continued (minimal in summer but terrible in winter), and I was emptying my dehumidifier of around 10 litres every few days over winter (set to 60% humidity like the OP). I was going down the road of looking at ventilation systems but the partial skillion ceiling was making things difficult.

Then at the start of last winter, I had a ground moisture/vapour barrier installed under my timber floor. I wasn't convinced at all that it would work. However the difference was dramatic and immediate. Within 48 hours every window in the house had stopped collecting condensation and it has never returned. I stopped using the dehumidifier altogether as it failed to collect more than 100mls or so over the course of several weeks following the ground sheet installation. I plug it in now and then to double check but it never collects anything significant.

It's creepy how closely my situation matches the OP so it's strange that condensation is still such a problem for them when it no longer is for us:

nearly all walls are insulated - all of mine insulated
mix of single glazed alum joinery and timber windows - all mine double glazed aluminium (but not thermally broken)
concrete tile roof with no building paper - mine is corrugated iron (with paper I think)
single heatpump in kitchen/dining that can blow through to living room (not sure why prev owners did what they did..) - mine is the exact same!!
fireplace insert in living room - freestanding ULEB log burner in the living room
damp proof membrane installed below the house (not a fun job!) - same since last year
mitsubishi dehumidier on 24/7 set to run at 60% auto mode - works dang hard during rainy days! - Delonghi used to be on 24/7 set at 60% on auto, but we haven't needed it since the damp proof membrane was installed
The only other differentiators I can think of:

Location/climate - I am in Christchurch, not sure where the OP is.

Cooking ventilation - We have a rangehood where the OP does not.

House size - Ours is around 100m2, so around 65m2 smaller (not sure that really makes a difference though)

Orientation - we get all day sun all year, with the long side of our rectangular house facing due north.

Ha! Glad there's other NZ homes to compare to 🤣🤣

I must say, the house is definitely warmer after the insulation was done - we didn't need the second blanket this year.

I am based in AKL - definitely more humid than Chch! I wonder if the overall RH % in the region is enough to topple the scale over. We'd like to think we've visited enough houses that we know what is considered 'damp' - of which ours isn't (doesn't feel that way anyway).

Really good that the interventions done on yours has made the house much better though! Out of curiosity do you keep windows partially opened also?

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tweake

2391 posts

Uber Geek

#3289970 2-Oct-2024 11:52

roderickh:

I am based in AKL - definitely more humid than Chch! I wonder if the overall RH % in the region is enough to topple the scale over. We'd like to think we've visited enough houses that we know what is considered 'damp' - of which ours isn't (doesn't feel that way anyway).

absolutely bang on. the big culprit is outside humidity coming into the house. akl is massively different to chch. you only have to drive down to Waikato to notice the difference in humidity. this is why you do not want to much ventilation or high air leakage rates.

i think this is also why auckland/northland have most of the moldy homes in the country.

Wheelbarrow01

1723 posts

Uber Geek

Trusted

Chorus

#3290164 2-Oct-2024 18:25

roderickh:

Ha! Glad there's other NZ homes to compare to 🤣🤣

I must say, the house is definitely warmer after the insulation was done - we didn't need the second blanket this year.

I am based in AKL - definitely more humid than Chch! I wonder if the overall RH % in the region is enough to topple the scale over. We'd like to think we've visited enough houses that we know what is considered 'damp' - of which ours isn't (doesn't feel that way anyway).

Really good that the interventions done on yours has made the house much better though! Out of curiosity do you keep windows partially opened also?

We have the bathroom window slightly open most of the time just to assist the extractor fan, but we keep the bathroom door closed almost all the time to stop that window from cooling the rest of the house. Other than that we really only open the windows for an air out at weekends. However we do have sliding doors in the lounge that are regularly open on sunny days when I am working from home.

And yes I agree - Christchurch air is generally a lot drier than Auckland for sure.

roderickh

214 posts

Master Geek

#3295024 9-Oct-2024 13:05

Ok so we have gotten a few quotes back.. Hopefully will help others that are considering these too with the pricing.

From barebones to most expensive I guess..

For PPV systems

Bettevent - 6 vents - total $2,900 installed (no summer intake option)

appears to be barebones system no frills
uninsulated dual 150mm ducting
replacement filters cost $58 from bunnings
no information on what smarts it contain at all
wall switch is simply on/off operation

SmartVent Positive3 - 6 vents - $4,367 installed (+$1,300 for summer kit) - total $5,667

acoustic insulated 150mm ducting
temp & humidity sensing (3x sensors) - they honestly appear to be very similar to aqara temp&humidity zigbee sensor
wall switch slightly prettier with more info
replacement filters cost $95 from smartvent official, or $60 from 3rd party brand at bunnings
wifi connect & app control

DVS EC Climate Control Humidity Sensitive - 5 vents - $4,320 installed (+$1,465 for summer kit) - total $5,785

uninsulated single 200mm ducting
temp & humidity sensing (no idea how many sensors or where info is captured)
replacement filters cost $82 from DVS or $60 from 3rd party brand at bunnings
wall switch slightly prettier with infographic
no wifi connect/app control

Smartvent Positive Advance - 6 vents $4,912 installed (+$1,300 for summer kit) - total $6,212

acoustic insulated 150mm ducting
temp & humidity sensing (4x sensors) similar to above - apparently with dew point control calculations (whatever this means)
touchscreen wall panel
replacement filters cost $95 from smartvent official, or $60 from 3rd party brand at bunnings
wifi connect & app control

For BPV systems

Cleanaire CL130 - $6,599 installed (not including summer kit - which is apparently an option)

from the phone call it appears to be 6 outlets with 2 inlets
not much other info on hand

DVS EC Reclaim Plus - $6,470 installed (when added wiht summer kit ($825) and solar gain/roof intake ($795)) - total $8,090

uninsulated single 200mm ducting
temp & humidity sensing (no idea how many sensors or where info is captured)
2x fans so 2x filters (replacement filters cost $82 from DVS or $60 from 3rd party brand at bunnings)
wall switch slightly prettier with infographic
no wifi connect/app control

I then sourced how much it would cost to buy in parts (work had some trade pricing offer at a smartvent retailer) - Positive3 parts only - $3,652 (assumed labour from the original quote then becomes $2,015)

At this stage we're leaning on the smartvent positive 3 option, deciding to either DIY it and or find an installer for a reasonable cost.

The BPV system (CL130) is also up for consideration, but given the house is a 1960s build together with earlier comments might mean it is not as wortwhile?

What's even more interesting is I read up the recently published homestar design guide https://nzgbc.org.nz/homestar-design-guide .

In the document under "Controlling the interior environment" section pg 102 onwards, it suggests that PPV systems are being phased out in Britain - I wonder if this will also happen here?

aaah decisions.

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CrazyM

110 posts

Master Geek
Inactive user

#3295036 9-Oct-2024 15:00

I've got a balanced air Cleanaire and its brilliant. My 2000's house is not super sealed and its mostly constructed from ranch-sliders, but it has been fantastic. Completely silent, no condensation anywhere, anytime of the year. Previously had all of my aluminium joinery windows weeping in the winter and would comfortably filling up the Karcher window vac every morning.

I like that it is set and forget with no temperature control, just fresh air coming in all the time. Yes there are some heat losses with the insulated ducts running through the un-insulated crawl space, but I just have the fans running slower at times of the year when there is a large heat differential between the inside and outside.

Biggest issue is when the neighbour has a smoky fire and the intake sucks up the fumes and pumps it into the house. My fix was to put the Cleanaire on a TP-Link wifi smart plug so if I smell smoke I just open the app and turn it off. The app lets me set timers and moniter energy consumption too which is nice.

tweake

2391 posts

Uber Geek

#3295090 9-Oct-2024 17:07

BPV system, don't bother even looking. the house is just to air leaky for it to be effective. its 7k that does the same as a 2k system. they also tend to be missing a proper air filter (the 2x filters are not meant for air cleaning) so there is more expense.

also HomeStar is irrelevant, as is passive house. your house is a completely different ball game. uk might be changing but that will be because more people are building air tight houses.

its not actually a summer kit, its a fixed external air intake. so its cheaper than a summer kit. you just have to have a filter that you can fit ducting to the inlet. however the system cannot reclaim heat out of your ceiling, not that there is any heat in there in winter.

the other thing is heat transfer system due to you having a fireplace. a more basic system with heat transfer would be better. but you have to fit returns from the rooms, something many installers will skimp on to cut costs, but it could kill you.

you can get different grades of filters and also carbon filters to filter out the neighbors smoke.

use insulated ducting. anything to help keep the summer heat out of the air flow and fan. otherwise the fan turns off because the air is to hot and you get no ventilation.

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tweake

2391 posts

Uber Geek

#3295092 9-Oct-2024 17:17

CrazyM:

I've got a balanced air Cleanaire and its brilliant. My 2000's house is not super sealed and its mostly constructed from ranch-sliders, but it has been fantastic. Completely silent, no condensation anywhere, anytime of the year. Previously had all of my aluminium joinery windows weeping in the winter and would comfortably filling up the Karcher window vac every morning.

I like that it is set and forget with no temperature control, just fresh air coming in all the time. Yes there are some heat losses with the insulated ducts running through the un-insulated crawl space, but I just have the fans running slower at times of the year when there is a large heat differential between the inside and outside.

Biggest issue is when the neighbour has a smoky fire and the intake sucks up the fumes and pumps it into the house. My fix was to put the Cleanaire on a TP-Link wifi smart plug so if I smell smoke I just open the app and turn it off. The app lets me set timers and moniter energy consumption too which is nice.

not to be rude but a bathroom fan would also work just as well. BPV are meant for homes where you HAVE to use a balanced system, otherwise its a waste of money. one of the cheaper system will do just as well for a lot less.

easy way to fix the smoke issue is to fit a charcoal filter. however check IF you even have a filter. many companies cheat and rely on the core filters. the core filters are just there to stop big stuff from blocking up the core. your meant to fit a suitable filter on the inlet side to actually clean the air.

Kickinbac

427 posts

Ultimate Geek

#3295288 9-Oct-2024 23:27

Lots of people say that you shouldn’t or don’t need to put MVHR in a not so airtight house but this is based on outdated information or wives tales. If you are after a healthy home, which to be brief is properly heated, efficient and has good ventilation for good indoor air quality then MVHR is essential.
CO2 monitors are getting more affordable and relative humidity monitors are dirt cheap so no reason you can’t test for yourself.
If interested, this link to ‘The case for MVHR’ is worth a read.

https://www.passivhaustrust.org.uk/UserFiles/File/research%20papers/MVHR/2020.04.27-The%20Case%20for%20MVHR-v7.pdf

Handle9

11386 posts

Uber Geek

Trusted

Lifetime subscriber

#3295296 10-Oct-2024 01:26

Kickinbac: If you are after a healthy home, which to be brief is properly heated, efficient and has good ventilation for good indoor air quality then MVHR is essential.

Statements like this drive me nuts. It is far from true and often makes no sense financially or has minimal impact on IAQ. The study you linked to was purely focused on CO2 emissions and didn't look at ROI or IAQ.

There are a lot of variables to consider and selecting how you ventilate depends on each individual building and how it is used.

CrazyM

110 posts

Master Geek
Inactive user

#3295297 10-Oct-2024 06:41

tweake:

CrazyM:

I've got a balanced air Cleanaire and its brilliant. My 2000's house is not super sealed and its mostly constructed from ranch-sliders, but it has been fantastic. Completely silent, no condensation anywhere, anytime of the year. Previously had all of my aluminium joinery windows weeping in the winter and would comfortably filling up the Karcher window vac every morning.

I like that it is set and forget with no temperature control, just fresh air coming in all the time. Yes there are some heat losses with the insulated ducts running through the un-insulated crawl space, but I just have the fans running slower at times of the year when there is a large heat differential between the inside and outside.

Biggest issue is when the neighbour has a smoky fire and the intake sucks up the fumes and pumps it into the house. My fix was to put the Cleanaire on a TP-Link wifi smart plug so if I smell smoke I just open the app and turn it off. The app lets me set timers and moniter energy consumption too which is nice.

not to be rude but a bathroom fan would also work just as well. BPV are meant for homes where you HAVE to use a balanced system, otherwise its a waste of money. one of the cheaper system will do just as well for a lot less.

easy way to fix the smoke issue is to fit a charcoal filter. however check IF you even have a filter. many companies cheat and rely on the core filters. the core filters are just there to stop big stuff from blocking up the core. your meant to fit a suitable filter on the inlet side to actually clean the air.

Nah I dont agree. The fresh air temperature coming in from a BPV is always close to your exhausted air temperature so you can have it running all the time. A summer intake kit for PPV's helps to get around this but then remember to have insulated ducting otherwise you still are getting a lot of preheat through the ductwork in the roof space. And on a winter night you still need to turn off the airflow unless you want to cool your house down.

Another advantage of the BPV is you get to choose where the extract is taken from, you dont have to rely on where its leaking out. This ensures you get airflow where you want it and no dead spots. After installing my BPV and running it for a month the increase in air quality made me realise that our master wardrobe and linen cupboard were comparitively musty and stale, so I put in additional airflow there. I now have fresh air supply at the outside edge of every room and extracts from the kitchen, both bathrooms, and the linen cupboard. I also have a separate intake filter box with pre-filtration and a carbon filter, and use bathroom extract fans.

The only advantage (price excepted) of a PPV is the possibility for them to heat or cool your house, but that is dependant that you want to change the temperature of your home in the direction of the roof space (or summer intake temp if you have the option)

Given that the BPV is within $1000 of the PPV systems I would go that direction.

tweake

2391 posts

Uber Geek

#3295559 10-Oct-2024 14:37

Kickinbac: Lots of people say that you shouldn’t or don’t need to put MVHR in a not so airtight house but this is based on outdated information or wives tales. If you are after a healthy home, which to be brief is properly heated, efficient and has good ventilation for good indoor air quality then MVHR is essential.
CO2 monitors are getting more affordable and relative humidity monitors are dirt cheap so no reason you can’t test for yourself.
If interested, this link to ‘The case for MVHR’ is worth a read.

https://www.passivhaustrust.org.uk/UserFiles/File/research%20papers/MVHR/2020.04.27-The%20Case%20for%20MVHR-v7.pdf

table 1 shows its flawed if not down right fake.

they are making the assumption that the house is air tight, which in this case most certainly is not and will be rather high air leakage rates.

tweake

2391 posts

Uber Geek

#3295570 10-Oct-2024 14:58

CrazyM:

Nah I dont agree. The fresh air temperature coming in from a BPV is always close to your exhausted air temperature so you can have it running all the time.

while thats true its only part of the story. what your not factoring in is the heat loss/effects etc from the air leakage. in a typical nz house you will be leaking as much, or quite easily up to double, the ventilation airflow. so the air thats going into the house and being filtered etc by the bpv is actually less than 50%. with a PPV your filtering a whole lot more of it because your using the house leakage as the exhaust instead of an inlet. yes there is no real heat recovery with ppv but the amount of energy it takes to heat air is pretty minimal and a bpv is only recovering from 50% or less of the airflow. so the difference between the systems is very little.

if you have an air tight house thats got very little air leakage then the bpv is handling 90% or more of the air going into the house and then its very effective.

the other interesting thing is that bathroom fans don't really work in air tight homes because they can flow more air out than the air leakage rate lets air in (also range hoods). this is why you use the bpv as the bathroom fans. conversely if you have bathroom fans, you may not have a house air tight enough to make a bpv worth while.

a house (especially kiwi homes) need to be build specially to be air tight. its fairly rare for standard kiwi homes to be air tight enough that a bpv is required.

Kickinbac

427 posts

Ultimate Geek

#3295595 10-Oct-2024 16:03

tweake:

Kickinbac: Lots of people say that you shouldn’t or don’t need to put MVHR in a not so airtight house but this is based on outdated information or wives tales. If you are after a healthy home, which to be brief is properly heated, efficient and has good ventilation for good indoor air quality then MVHR is essential.
CO2 monitors are getting more affordable and relative humidity monitors are dirt cheap so no reason you can’t test for yourself.
If interested, this link to ‘The case for MVHR’ is worth a read.

https://www.passivhaustrust.org.uk/UserFiles/File/research%20papers/MVHR/2020.04.27-The%20Case%20for%20MVHR-v7.pdf

table 1 shows its flawed if not down right fake.

they are making the assumption that the house is air tight, which in this case most certainly is not and will be rather high air leakage rates.

Tweake - You need to read it properly, Table 1 is just the characteristics of some different ventilation strategies. The whole point of the paper is that most houses are not air tight but can still benefit from installing MVHR.

It clearly states in the paragraph above Table 1. "An MVHR system will run continuously and thus should always achieve the required air change rate. In addition, because it is a balanced system, all the air entering the building (other than unwanted infiltration or when the occupant chooses to open windows) passes through the MVHR system and through a filter."

Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks and gaps in the building envelope and through use. There is usually much more infiltration when windy/stormy weather than on still days.

PPV forces roof air into your house and relies on air leakage through cracks and gaps in the envelope. It should run when the roof is hotter than the house. It doesn't comply with the NZ Building Code, even though the NZ Building Code is essentially a joke and 30-40 years behind the modern world.

tweake

2391 posts

Uber Geek

#3295656 10-Oct-2024 16:39

Kickinbac:

Tweake - You need to read it properly, Table 1 is just the characteristics of some different ventilation strategies. The whole point of the paper is that most houses are not air tight but can still benefit from installing MVHR.

It clearly states in the paragraph above Table 1. "An MVHR system will run continuously and thus should always achieve the required air change rate. In addition, because it is a balanced system, all the air entering the building (other than unwanted infiltration or when the occupant chooses to open windows) passes through the MVHR system and through a filter."

Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks and gaps in the building envelope and through use. There is usually much more infiltration when windy/stormy weather than on still days.

PPV forces roof air into your house and relies on air leakage through cracks and gaps in the envelope. It should run when the roof is hotter than the house. It doesn't comply with the NZ Building Code, even though the NZ Building Code is essentially a joke and 30-40 years behind the modern world.

the table claims balanced ventilating filters ALL air entering a building, which is simply not true because of air leakage. also note that its being compared to exhaust ventilation not ppv, clearly not nz or comparable country.

"A modern MVHR system will result in significantly lower CO2 emissions at any reasonable level of air
permeability." which i think is true, because your increasing ventilation airflow. eg roughly speaking, if you have 0.5ach air leakage and you also have 0.5ach balanced ventilation you effectively have 1.0ach airflow through the house (0.5ach +0.5ach =1.0 ach). that will always reduce co2 levels compared to a ppv. a ppv effectively counters some of the air leakage because your using the inlet as exhaust. so the 0.5ach + (0.5ach - 0.5ach) = 0.5 ach airflow. so its going to remove less co2.

bpv is basically parrallel with air leakage while ppv is in series with air leakage, not quite the right wording but i hope you get the idea.

when it comes to heat recovery from the core, the more air leakage the house has the less effective it becomes. then its down to pricing if that small gain is worth the extra in cost especially given that air doesn't hold a whole lot of heat.

to add to that nz homes are typically about 0.5ach or worse (1-1.5) for older homes. so even on a new build a balanced system is going to double the ventilation and only recover heating etc on half of it (roughly speaking because of variables).

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