Yet another home ventilation query

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

roderickh

214 posts

Master Geek

#316261 30-Sep-2024 12:40

Fellow GZ,

So much experience abound here! Hoping someone could direct us to the right option and or things we haven't considered yet..

We have a 165m2 1960s built home:

nearly all walls are insulated
mix of single glazed alum joinery and timber windows
concrete tile roof with no building paper
single heatpump in kitchen/dining that can blow through to living room (not sure why prev owners did what they did..)
fireplace insert in living room
damp proof membrane installed below the house (not a fun job!)
mitsubishi dehumidier on 24/7 set to run at 60% auto mode - works dang hard during rainy days!

We're looking at getting a ventilation system to assist with air quality in the house and also crying windows.

95% of the time all alum windows are partially opened (through the two option window stay) - in colder months we do close the bedroom set and sometimes due to noise supression from outside.

I have found a few threads (from 2022 etc) that were relevant, just wondering if they're still relevant in 2024?
If I read correctly, general consensus is that Smartvent is well rated, with HRV not so much?
Any other options worth considering to get a quote etc from? (DVS, unovent, etc?)

We also have 3 beds, 2 living areas and a kitchen / dining - should we proceed, is it advisable to get a 6 outlet sytem?

I also read that balanced pressure system is better than positive pressure systems - will this make much difference in a house like ours?

Thanks for the knowledge and guidance.

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#3288175 30-Sep-2024 13:28

Previous house we had DVS installed - didn't know about Smartvent back then.

This current house, got quote from DVS and Smartvent, went with Smartvent because cheaper.

We have 5 outlets, and get some heat transferred from fireplace into the other rooms (set to run on a time to coincide when the fire is going) - doesn't make a huge difference (e.g. not toasty warm like the lounge is) but you can feel something.

Happy with both DVS and Smartvent in that the wet windows disappeared, and air is being circulated.

We do open windows often during day for fresh air.

I like how with DVS and Smartvent we can change the filter ourselves.

Avoid HRV at all costs. More expensive, and pushy salespeople.

Good luck!

wellygary

8321 posts

Uber Geek

#3288179 30-Sep-2024 13:40

"Mitsubishi dehumidier on 24/7 set to run at 60% auto mode - works dang hard during rainy days!

We're looking at getting a ventilation system to assist with air quality in the house and also crying windows.

95% of the time all alum windows are partially opened"

What's the daily output of the Dehumidifier?, its usually easier to stop the water getting in, than getting it out...

But, with underfloor waterproofing already installed. there has to be reasonable water ingress occurring somewhere?

roderickh

214 posts

Master Geek

#3288190 30-Sep-2024 14:12

wellygary:

"Mitsubishi dehumidier on 24/7 set to run at 60% auto mode - works dang hard during rainy days!

We're looking at getting a ventilation system to assist with air quality in the house and also crying windows.

95% of the time all alum windows are partially opened"

What's the daily output of the Dehumidifier?, its usually easier to stop the water getting in, than getting it out...

But, with underfloor waterproofing already installed. there has to be reasonable water ingress occurring somewhere?

Thanks for the response, provides a different view point! Dehumidifier is a mj-e22vx (I assume 22L daily capacity?) Tank is 4L, on a very heavy rainy week, usually it is emptied once a day.

No obvious water ingress anywhere.. 3/4 of the home was renovated in the last 2 years, we added wall insulation and there wasn't any obvious water damage anywhere when the walls were opened up.

Current dehumifidier location is between the kitchen/dining/living room - crying windows observed in our bedroom (further away spot from this) - we have thought about getting a second dehumifidier unit, but thought if it was better to get a whole-house system thus this query :)

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tweake

2391 posts

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#3288350 30-Sep-2024 18:32

roderickh:

I also read that balanced pressure system is better than positive pressure systems - will this make much difference in a house like ours?

the only thing a balanced system will do is empty your wallet. your house will be far to air leaky for it to be worth buying. they are meant for air tight houses.

the reason your dehumidifier collects so much is simply because of air leakage. all the moisture is just coming in with the air. most likely you will have have slat flooring or T&G and it all leaks air unless its been sealed with polyurethane etc. what you will might notice is the gaps opening up more as your house dries.

a positive pressure ventilation system will work ok, but try not to have to much ventilation. to much ventilation will bring in more moisture. it will certainly work far far better than opening windows.

don't get to hung up on getting moisture free windows. your always going to get some condensation and the better the curtains the worse it gets. the trick ventilation companies do is blow air along the ceiling and down behind the curtains. that stops moisture condensation but also cools your house more.

brands, there is also i think its simx which does a DIY kit (mitre10??). DVS if you want all the bells and whistles.

if you have a fire place a few brands have a combo ventilation/ heat transfer system. however if you install a heat transfer system make sure they install the return(s).

dimsim

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#3288401 1-Oct-2024 07:12

not sure where you are but this may be of interest?

https://www.reddit.com/r/diynz/comments/1ft1nz5/anyone_want_an_hrv_install/

roderickh

214 posts

Master Geek

#3288407 1-Oct-2024 07:47

tweake:

the only thing a balanced system will do is empty your wallet. your house will be far to air leaky for it to be worth buying. they are meant for air tight houses.

the reason your dehumidifier collects so much is simply because of air leakage. all the moisture is just coming in with the air. most likely you will have have slat flooring or T&G and it all leaks air unless its been sealed with polyurethane etc. what you will might notice is the gaps opening up more as your house dries.

a positive pressure ventilation system will work ok, but try not to have to much ventilation. to much ventilation will bring in more moisture. it will certainly work far far better than opening windows.

don't get to hung up on getting moisture free windows. your always going to get some condensation and the better the curtains the worse it gets. the trick ventilation companies do is blow air along the ceiling and down behind the curtains. that stops moisture condensation but also cools your house more.

brands, there is also i think its simx which does a DIY kit (mitre10??). DVS if you want all the bells and whistles.

if you have a fire place a few brands have a combo ventilation/ heat transfer system. however if you install a heat transfer system make sure they install the return(s).

Hey, thanks for the response. Correct on the T&G flooring. SIMX's products is smartvent - we're getting quotes from a few shops to get a rough better idea on pricing. DVS came back around $5k installed - everything's going up in price!

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roderickh

214 posts

Master Geek

#3288408 1-Oct-2024 07:47

dimsim:

not sure where you are but this may be of interest?

https://www.reddit.com/r/diynz/comments/1ft1nz5/anyone_want_an_hrv_install/

Ah! interesting. I have dropped them a message.

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tweake

2391 posts

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#3288693 1-Oct-2024 16:21

roderickh:

Hey, thanks for the response. Correct on the T&G flooring. SIMX's products is smartvent - we're getting quotes from a few shops to get a rough better idea on pricing. DVS came back around $5k installed - everything's going up in price!

my bad, it was weiss weiss eco ventilation

sealing the floor will help, as will flooring insulation.

btw what cladding does the house have? is any of it brick? if so you will need to get an external air intake for the ventilation. tho i would get a summer kit regardless (so it switches over to external air intake when the ceiling space gets to hot.) not hard to DIY one.

roderickh

214 posts

Master Geek

#3288710 1-Oct-2024 17:32

tweake:

my bad, it was weiss weiss eco ventilation

sealing the floor will help, as will flooring insulation.

btw what cladding does the house have? is any of it brick? if so you will need to get an external air intake for the ventilation. tho i would get a summer kit regardless (so it switches over to external air intake when the ceiling space gets to hot.) not hard to DIY one.

Oh nice, another option to consider!

House is brick veneer, mostly insulated bar 2 walls (no plans to do kitchen reno at this stage).
Definitely considering the summer kit, really just pricing up at this stage and hopefully getting the right option.

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Handle9

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#3288786 1-Oct-2024 19:44

roderickh:

Thanks for the response, provides a different view point! Dehumidifier is a mj-e22vx (I assume 22L daily capacity?) Tank is 4L, on a very heavy rainy week, usually it is emptied once a day.

Do you have proper kitchen and bathroom extraction? If you do make sure your bathroom extractor is on a timer to run on for at least 15 minutes after you finish showering.

PDL648TM works great for this.

roderickh

214 posts

Master Geek

#3288787 1-Oct-2024 19:46

Handle9:
roderickh:

Thanks for the response, provides a different view point! Dehumidifier is a mj-e22vx (I assume 22L daily capacity?) Tank is 4L, on a very heavy rainy week, usually it is emptied once a day.

Do you have proper kitchen and bathroom extraction? If you do make sure your bathroom extractor is on a timer to run on for at least 15 minutes after you finish showering.

PDL648TM works great for this.

This is probably the biggest issue.
Our bathroom and laundry (recently renovated) runs mint.

Kitchen on the other hand, sits directly infront of a window and has no range hood, we have been opening the window everytime we cook - there appears no easy/aesthetic way to get a system in?

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tweake

2391 posts

Uber Geek

#3288793 1-Oct-2024 20:30

roderickh:

House is brick veneer,

that makes it simple, you must have an outdoor air intake rather than a on/off "summer kit".

the reason here is the cavity between the brick and timber wall is connected to the underfloor space and ceiling space. moisture from under the floor goes up the cavity and into the ceiling space. a ceiling space intake would suck all the damp air in and put all that moisture into the house. it will be a mold fest in weeks.

tweake

2391 posts

Uber Geek

#3288795 1-Oct-2024 20:41

roderickh:

This is probably the biggest issue.
Our bathroom and laundry (recently renovated) runs mint.

Kitchen on the other hand, sits directly infront of a window and has no range hood, we have been opening the window everytime we cook - there appears no easy/aesthetic way to get a system in?

its not that big a deal. moisture from kitchen is not much. pollutants, yes terribly so a rangehood is recommended if you can. bathroom is a bit but not that bad. ditto with drying clothes inside. that sounds like i'm saying the opposite of what we get told via media, but they really overplay the small stuff while ignoring the big factors. moisture from under the floor is a huge factor, which you have fixed with a moisture barrier (and why i say to seal the floor). the next biggest is often outdoor air (climate depending), to much air leakage or to much ventilation. then its how many people live in the house compared to the size of the house. then how well the house is heated.

when i put the ground moisture barrier down, window condensation drop in half overnight and i have sheet flooring not air leaky t&g. added ventilation system and it dropped i half again.

tweake

2391 posts

Uber Geek

#3288796 1-Oct-2024 20:45

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).

Wheelbarrow01

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#3288815 1-Oct-2024 22:35

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.

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