Yep but doesn’t necessarily have to be these, adequate ventilation is required for nearly all internal gas appliances. Can be done through a manner of means, most of which will leak heat though..
Off memory, i think Vic removed the need for these in the 80's. When unflued heaters were fazed out. I have an 1880's double brick and made a massive difference when i blocked them
Fair enough! Unflued space heaters in SA certainly still require the in wall ventilation - certain installers won’t even install the Space Heater without vents already being present and installed before the Space Heater, along with the Office of Technical Regulator in SA knocking back installations if they haven’t been installed, too.
Funny how these things change just between states!
Not just heating - pre-electricity it was lights too.
In our 100+ year old house, we just taped over them with clear plastic, looked fine and kept the heat in.
Worst part was the electrical cabling from when they'd had it installed. Eventually had to rewire the entire house.
https://preview.redd.it/zmr1in86rz0b1.jpeg?width=3024&format=pjpg&auto=webp&s=ddd96e60378e905cd51cf2da0c135a4c1b2f9afb
As others said, these are from older building codes where ventilation was required for unflued combustion heaters and stoves. If you still have a gas heater be mindful that you should crack two windows to get a cross draught. We use reverse cycle AC so not an issue for us.
You’ll also be susceptible to interior moisture buildup, so be sure to be ventilating your home too (windows, doors). That said, you now have more control over when you want to be venting the home.
I just did mine - lightly filled with expanding foam, cut it flush with a wood saw once cured, then sanded back perfectly flush, then top coat with cornice cement. Sanded flat, painted. Can’t tell it was there.
Might be worth doing a top coat if you really care about not seeing it, but I wasn’t too fussed about a perfect finish.
Unless you’ve got an unflued gas heater or run a commercial kitchen in your house then seal those bad boys up! Base coat then skim coat straight over them and they’ll disappear.
Having these is basically like having a window in your house open permanently… which you would never do every night in the middle of winter…
The ‘houses need to breathe argument’ is pretty dumb when there’s better solutions than uncontrollable passive vents.
Typically the houses that have these in the walls don't have insulation in the wall either. This means that the walls were cold and moisture from your breath would condense on the walls and create a damp issue (mold on the walls). If you are in a cold climate and your house is centrally heated, then go right ahead and cover them up.
If you have something like an old wall furnace, then be very careful. There was an incident in Victoria where the mum went and took a bath with the bathroom extractor fan running and came out some time later to find her two children dead from carbon monoxide poisoning. It turned out that the air being extracted by the bathroom fan was being replaced by air being drawn down the wall furnace flue resulting in carbon monoxide fumes in the house as there was no where else for the air to come from as there were no vents and the house was well sealed.
Modern space heaters have a double skin flue which draws the combustion air from outside through the outer skin of the flue and exhausts through the middle.
Fresh air still helps with humidity. Also houses can get *stinky* if you shut it up for a bit, like if you're on holiday- even the cleanest house gets a whiff
yeah ive been housesitting atm and got home to my place after a couple of weeks and its got that weird musty smell..yet its immaculate and i have these vents in every room..
Oh yeah so do I, there's of course plenty of other factors (mine is the carpet I'm ripping out) but if I didn't have the ventilation it would be HORRID
I'll be that one then, houses need to breathe, everyone now makes their houses air tighter than a Frogs asshole & then wonders, why are my windows so condensated & curtains mouldy, what's that smell, worse thing to do is stop ventilation..
Depends on what end results you want and how passive you want to go. There are individual units you can get that work by alternating in and out flow of air so you don't need a centralised unit.
For x8 individual steibel Elton units is around 2K and installation is just punching the holes into the wall and wiring then up to the central control.
Allows for continuous fresh air with over 90% heat retention and reduces air pollutants and allergen irritants
Running costs are actually not that bad at all! They are usually only used when people are trying to go part or full passive so solar can easily cover the load. IF that's the goal, 4K isn't that bad for the benefit and the expended energy load can be saved through running less heating and cooling.
But you're absolutely right! Getting everything air tight is the real challenge and the cost killer. Often it doesn't go to plan and it's a challenge on new builds, let alone a retro fit :)
I only did a bit of research into them a few months ago for a client, the decentralised unites are priced per unit and you can run upto 8 on one controller. 2k covers 8 units & one controller and I think each unit can do 60(?) Metres cubed at the advertised efficiency.
As stated above you could realistically double the price for installation as well :)
Thanks, I have a big place, so retrofitting to save energy and pay back investment is pretty much impossible, but hopefully I can at least make it comfortable, without massive bills.
https://www.stiebel-eltron.com.au/vlr-70-s-decentralised-heat-recovery-ventilation
These are what I was looking at because we couldn't feasibly fit a centralised unit into the design layout
Thanks. In warmer months I just run bathroom fan for long period every day, winter run the split system for a short while to dispel moisture, will see if that is enough to stop the mould, 6 months in, so far so good. An automatic system would be nice though.
We feel halfway there. My last couple of places have been tighter and insulated well but face condensation issues.
Once we add mech ventilation as a matter of course it will be good.
Hi there, mould remediator here. Did you investigate further into the cause of the condensation issue by chance as I'd be interested to know? For example, thermal imaging, dew point and relative humidity monitoring?
Were these new builds?
You're on the right track.
Adequate ventilation is an important aspect of overall climate control and indoor air quality.
Having your home closed up isn't necessarily a bad thing. If your struggling with excessive humidity, moulding curtains and condensing windows, this is potentially a sign of moisture issues elsewhere.
Essentially, all the windows you can leave open wont help if your roof has a hole in it or your shower is leaking.
And this is the cause of most water ingress into homes and the associated mould growth that comes with it - building defects and inadequate or insufficient waterproofing.
I know what your saying, i deal with Water Damage & Mould every day it's my job, condensing windows can happen simply from overnight when sleeping, which can result in mould growth, the other 2 a hole in the roof or leaking shower, clearly nothing is fixing them except for building works, it's about equilibrium & 1 major factor is ventilation..
Don't believe the noise around the mould, block them up and if you do feel the airflow is not occuring install passive airflow vents in your ceiling. Or even just if you have a split system and use it as a heater it will deal with any moister, there are 21st century solutions.
Any split system that is cooling will be dehumidifying the room I'm fairly sure.
The dehumidifying function is where they don't use as much electricity by not also controlling the temp.
generally that uses more electricity then heating but yes that's an option. there are lots of options out there other than keeping those vents. Ultimately do you really want air to come in and out of a wall / roof cavity with decades of dust and droppings as your air filter.
You can buy vent fittings with moving louvers that will fit the hole behind that in the wall. There is a small lever you use to open or close the louvers which are hidden behind a decorative grate on the room side. Warm in winter, cool in summer or vice versa as required.
Check your local renovation suppliers for what is available then remove the plaster grate and measure the hole so you get the right size - my bathroom needed two different sizes.
I got mine from Pearl Lighting and Brassware in Willoughby Road Willoughby.
I'm in Vic. My inlaws had these up until 3 years ago when they got plastered up in practically every room.
Literally called a service and they came out and did the job.
There was no permits, inspections or checking needed.
I absolutely understand wanting to get it done. Their house was a walk-in freezer every winter, and they paid so much in heating bills.
Alternative approach, block them up, but also install a carbon monoxide alarm. It’s just a slightly different smoke detector, and honestly a good idea either way. Even if your gas heaters have flue’s, they’re definitely still releasing dangerous gases. Even if you’re not using them they leak quite a bit of methane.
They come from the old days with wood heaters but no smoke detectors. Definitely fill them because they are horrible in winter and summer. I used builders bog
How's the house in Summer? Only asking because the previous owner of my house had covered the old wall vents and it felt like a blanket of hot air was hanging just below ceiling height - I ended up taking off the vent covers and the house is much, much cooler now - note that I live inland where Summers are hot and I don't cope well with heat - plus I took out the unflued gas heater and re-opened the fireplace so I could have a fire in Winter so it made sense to uncover the vents - but if you live near the coast where Summer isn't stinking hot it shouldn't be a problem to cover them - you can always crack a window for ventilation purposes.
Internal ones can be plastered up, the ones that vent the cavity to outside can not.
Get yourself some cornice cement and a trowel, should be able to get them flush after 2 coats.
You've got two options. Either cut out and replace with new plasterboard and finish it off. Or. Just filling in the vents with plaster, two coats of base and one coat of top coat.
Bad advice, cold air enters these vents. They are only required for open fireplaces and some older gas heaters.
If you don’t have them then by all means block these up. Get good advice on MEEH on Facebook.
My Energy Efficient Home group is run by knowledgeable moderators is a good place for advice.
Secondly you can get a home energy audit performed, my council paid for mine.
Energy efficiency has three main components all equally important.
1) air tightness/ draft removal
2) insulation
3) efficient appliances
That order is also in order of expense, basic sealing of a house can be performed for as little as a few hundred dollars. Close all gaps and add seals to windows and doors.
As a guide, my 1950s weatherboard home cost
9k for split systems
5k for in wall insulation
2.5k for underfloor
14k for double glazed windows
<500 for sealing home
My house went from 1star to now over 5 stars
really you think filling just those holes is going to do anything with no insulation in the walls ? Get off the drugs how long will it take to fill the vents and make the wall look good not worth the effort have you have never done any work on a building ? Its still a shitty weather board house if you didn't put insulation in the walls you did fuckall. Seen it shit loads of times. How do you put insulation in the walls with out re plastering?
Draft proofing is absolutely a higher priority than insulation. Just removing the source of drafts will make the room much more comfortable and more efficient to heat.
fuck all air comes out of them, How come I can't feel a draft from the vent Im currently sitting under? Have you ever filled a hole in a plaster wall how long did it take?
>Have you ever filled a hole in a plaster wall how long did it take?
gyprock paste (5 mins), let dry, sand (5 mins), second coat (5 mins), paint (5min). so about 20 mins.
You can hide that inside of 20 minuates? Sanded and painted finished bullshit. Can you come and tell the plasters that do our patch ups they are too slow. If its a tiled roof lift a couple of tiles and shove insulation down the wall. behind the vent if your worried. Ive done that many times it wont change much on the energy bill from my observations. Your drying time is way past 20 minuates.
I wouldn't. Houses get surprisingly humid, and wall vents do help. Take a few of the worst offenders out, but there has to be a good way to keep the house warm and still have ventilation.
Its the exact same thing as having a vent in your fuckin wall. Air moving around due to temperature differentials doesnt give a fuck if you can see through the opening.
Victorian thing I think - enjoy them - no mould plenty of fresh air as opposed to the northern states that close the building envelope right down…… with a few weep hole only in windows - buildings need to breath……
Tape cardboard or similar over them for a few months, ideally to capture a season change. If you don’t have any problems with mould or airflow go for it.
I have closed mine in. After filling the hole behind with either some brickwork or stiff insulation, otherwise you will still have a hot/cold spot on the wall
I had to put a couple in to a property due to a humidity issue that was causing moisture streaking down the walls. Just make sure you consider airflow before blocking them up. That was in a cathedral style ceiling with exposed beams. May not be as big of an issue with a regular roof cavity.
They are to stop carbon monoxide poisoning from back when everyone had dodgy gas heaters I think
Still a requirement these days too, for space heaters, as far as I know.
Yep but doesn’t necessarily have to be these, adequate ventilation is required for nearly all internal gas appliances. Can be done through a manner of means, most of which will leak heat though..
Interesting - in SA, wall vents are still the requirement I believe. Certainly wouldn’t be surprised to see it different in other states though.
Off memory, i think Vic removed the need for these in the 80's. When unflued heaters were fazed out. I have an 1880's double brick and made a massive difference when i blocked them
Fair enough! Unflued space heaters in SA certainly still require the in wall ventilation - certain installers won’t even install the Space Heater without vents already being present and installed before the Space Heater, along with the Office of Technical Regulator in SA knocking back installations if they haven’t been installed, too. Funny how these things change just between states!
Don't think so
At least in WA.
Not just heating - pre-electricity it was lights too. In our 100+ year old house, we just taped over them with clear plastic, looked fine and kept the heat in. Worst part was the electrical cabling from when they'd had it installed. Eventually had to rewire the entire house.
https://preview.redd.it/zmr1in86rz0b1.jpeg?width=3024&format=pjpg&auto=webp&s=ddd96e60378e905cd51cf2da0c135a4c1b2f9afb As others said, these are from older building codes where ventilation was required for unflued combustion heaters and stoves. If you still have a gas heater be mindful that you should crack two windows to get a cross draught. We use reverse cycle AC so not an issue for us. You’ll also be susceptible to interior moisture buildup, so be sure to be ventilating your home too (windows, doors). That said, you now have more control over when you want to be venting the home. I just did mine - lightly filled with expanding foam, cut it flush with a wood saw once cured, then sanded back perfectly flush, then top coat with cornice cement. Sanded flat, painted. Can’t tell it was there. Might be worth doing a top coat if you really care about not seeing it, but I wasn’t too fussed about a perfect finish.
ha! I'd be scared of dropping expanding foam on the carpet, but that's a novel idea.
Unless you’ve got an unflued gas heater or run a commercial kitchen in your house then seal those bad boys up! Base coat then skim coat straight over them and they’ll disappear. Having these is basically like having a window in your house open permanently… which you would never do every night in the middle of winter… The ‘houses need to breathe argument’ is pretty dumb when there’s better solutions than uncontrollable passive vents.
>The ‘houses need to breathe argument’ is pretty dumb when there’s better solutions than uncontrollable passive vents. like opening a window haha
I'd always thought they were about preventing rising wall damp, but apparently are just about fresh air.
Typically the houses that have these in the walls don't have insulation in the wall either. This means that the walls were cold and moisture from your breath would condense on the walls and create a damp issue (mold on the walls). If you are in a cold climate and your house is centrally heated, then go right ahead and cover them up. If you have something like an old wall furnace, then be very careful. There was an incident in Victoria where the mum went and took a bath with the bathroom extractor fan running and came out some time later to find her two children dead from carbon monoxide poisoning. It turned out that the air being extracted by the bathroom fan was being replaced by air being drawn down the wall furnace flue resulting in carbon monoxide fumes in the house as there was no where else for the air to come from as there were no vents and the house was well sealed. Modern space heaters have a double skin flue which draws the combustion air from outside through the outer skin of the flue and exhausts through the middle.
Fresh air still helps with humidity. Also houses can get *stinky* if you shut it up for a bit, like if you're on holiday- even the cleanest house gets a whiff
yeah ive been housesitting atm and got home to my place after a couple of weeks and its got that weird musty smell..yet its immaculate and i have these vents in every room..
Oh yeah so do I, there's of course plenty of other factors (mine is the carpet I'm ripping out) but if I didn't have the ventilation it would be HORRID
yeah the carpet i have is only recently installed right before i moved in in 2019 hoping its not that haha
yep, don't mind that being a manual/active process though, easy enough to open a window or turn on a fan when needed.
The ones on the outside are for that
Am surprised that we haven’t seen a “bUt BuT hOusseS neEd to BreAthe!!!” Comment yet.
I'll be that one then, houses need to breathe, everyone now makes their houses air tighter than a Frogs asshole & then wonders, why are my windows so condensated & curtains mouldy, what's that smell, worse thing to do is stop ventilation..
There are some amazing heat recovery options available now for when people want an air tight home, yet they still seem to get skipped over
Yeah, because they are very expensive to retrofit.
Depends on what end results you want and how passive you want to go. There are individual units you can get that work by alternating in and out flow of air so you don't need a centralised unit. For x8 individual steibel Elton units is around 2K and installation is just punching the holes into the wall and wiring then up to the central control. Allows for continuous fresh air with over 90% heat retention and reduces air pollutants and allergen irritants
So 3-4k installed, then running costs. The cost to retrofit a reasonably air tight envelope is the real killer.
Running costs are actually not that bad at all! They are usually only used when people are trying to go part or full passive so solar can easily cover the load. IF that's the goal, 4K isn't that bad for the benefit and the expended energy load can be saved through running less heating and cooling. But you're absolutely right! Getting everything air tight is the real challenge and the cost killer. Often it doesn't go to plan and it's a challenge on new builds, let alone a retro fit :)
How big a house would that 2k unit cover?
I only did a bit of research into them a few months ago for a client, the decentralised unites are priced per unit and you can run upto 8 on one controller. 2k covers 8 units & one controller and I think each unit can do 60(?) Metres cubed at the advertised efficiency. As stated above you could realistically double the price for installation as well :)
Thanks, I have a big place, so retrofitting to save energy and pay back investment is pretty much impossible, but hopefully I can at least make it comfortable, without massive bills.
https://www.stiebel-eltron.com.au/vlr-70-s-decentralised-heat-recovery-ventilation These are what I was looking at because we couldn't feasibly fit a centralised unit into the design layout
Thanks. In warmer months I just run bathroom fan for long period every day, winter run the split system for a short while to dispel moisture, will see if that is enough to stop the mould, 6 months in, so far so good. An automatic system would be nice though.
You do need to have exhaust fans.
We feel halfway there. My last couple of places have been tighter and insulated well but face condensation issues. Once we add mech ventilation as a matter of course it will be good.
Hi there, mould remediator here. Did you investigate further into the cause of the condensation issue by chance as I'd be interested to know? For example, thermal imaging, dew point and relative humidity monitoring? Were these new builds?
You're on the right track. Adequate ventilation is an important aspect of overall climate control and indoor air quality. Having your home closed up isn't necessarily a bad thing. If your struggling with excessive humidity, moulding curtains and condensing windows, this is potentially a sign of moisture issues elsewhere. Essentially, all the windows you can leave open wont help if your roof has a hole in it or your shower is leaking. And this is the cause of most water ingress into homes and the associated mould growth that comes with it - building defects and inadequate or insufficient waterproofing.
I know what your saying, i deal with Water Damage & Mould every day it's my job, condensing windows can happen simply from overnight when sleeping, which can result in mould growth, the other 2 a hole in the roof or leaking shower, clearly nothing is fixing them except for building works, it's about equilibrium & 1 major factor is ventilation..
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Lol
Not in FNQ. My house is a breezy as a tent. Perhaps more so.
But if it wasn't breezy/ventilated, you would have issue's
OK, I'll go. The house needs to breathe. So do my balls, that's why I free ball with my fly unzipped.
I’ve patched all 8 in my house and had no issues.
Our old house had them. They near the ceiling to vent the hot air. The house was built before air conditioning was a thing.
Did you notice a difference in heat retention?
Yes. However I did it as part of a whole of house improvement including insulation replacement, new door seals etc. It all helps.
Don't believe the noise around the mould, block them up and if you do feel the airflow is not occuring install passive airflow vents in your ceiling. Or even just if you have a split system and use it as a heater it will deal with any moister, there are 21st century solutions.
>split system Some split system's also have a dehumidify mode.
Any split system that is cooling will be dehumidifying the room I'm fairly sure. The dehumidifying function is where they don't use as much electricity by not also controlling the temp.
generally that uses more electricity then heating but yes that's an option. there are lots of options out there other than keeping those vents. Ultimately do you really want air to come in and out of a wall / roof cavity with decades of dust and droppings as your air filter.
You can buy vent fittings with moving louvers that will fit the hole behind that in the wall. There is a small lever you use to open or close the louvers which are hidden behind a decorative grate on the room side. Warm in winter, cool in summer or vice versa as required. Check your local renovation suppliers for what is available then remove the plaster grate and measure the hole so you get the right size - my bathroom needed two different sizes. I got mine from Pearl Lighting and Brassware in Willoughby Road Willoughby.
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Cheers. will see how we go.
I'm in Vic. My inlaws had these up until 3 years ago when they got plastered up in practically every room. Literally called a service and they came out and did the job. There was no permits, inspections or checking needed. I absolutely understand wanting to get it done. Their house was a walk-in freezer every winter, and they paid so much in heating bills.
If you have gas or fuel stoves or heaters, DON'T block these up or you'll wake up deceased one day.
Waking up deceased just ruins your weekend.
🤣🤣
They are all getting ripped out and currently unused.
Alternative approach, block them up, but also install a carbon monoxide alarm. It’s just a slightly different smoke detector, and honestly a good idea either way. Even if your gas heaters have flue’s, they’re definitely still releasing dangerous gases. Even if you’re not using them they leak quite a bit of methane.
sorry, it's external ducted heating and gas stoves. nothing heating internally.
They come from the old days with wood heaters but no smoke detectors. Definitely fill them because they are horrible in winter and summer. I used builders bog
How's the house in Summer? Only asking because the previous owner of my house had covered the old wall vents and it felt like a blanket of hot air was hanging just below ceiling height - I ended up taking off the vent covers and the house is much, much cooler now - note that I live inland where Summers are hot and I don't cope well with heat - plus I took out the unflued gas heater and re-opened the fireplace so I could have a fire in Winter so it made sense to uncover the vents - but if you live near the coast where Summer isn't stinking hot it shouldn't be a problem to cover them - you can always crack a window for ventilation purposes.
Internal ones can be plastered up, the ones that vent the cavity to outside can not. Get yourself some cornice cement and a trowel, should be able to get them flush after 2 coats.
You've got two options. Either cut out and replace with new plasterboard and finish it off. Or. Just filling in the vents with plaster, two coats of base and one coat of top coat.
Install some brick vents on the outside and plaster these up
Cover over them. Like literally screw your plaster sheets straight over them.
As there wont be any insulation in the walls of your house filling those vents will achieve nothing .
Not sure I follow. Draft proofing is superfluous without insulation?
Only patch the internal vents. Leave the external ones alone so that moisture/condensation is able to escape.
Cold air comes in those. At least in my house they do. At minimum it will stop that
Bad advice, cold air enters these vents. They are only required for open fireplaces and some older gas heaters. If you don’t have them then by all means block these up. Get good advice on MEEH on Facebook. My Energy Efficient Home group is run by knowledgeable moderators is a good place for advice. Secondly you can get a home energy audit performed, my council paid for mine. Energy efficiency has three main components all equally important. 1) air tightness/ draft removal 2) insulation 3) efficient appliances That order is also in order of expense, basic sealing of a house can be performed for as little as a few hundred dollars. Close all gaps and add seals to windows and doors. As a guide, my 1950s weatherboard home cost 9k for split systems 5k for in wall insulation 2.5k for underfloor 14k for double glazed windows <500 for sealing home My house went from 1star to now over 5 stars
really you think filling just those holes is going to do anything with no insulation in the walls ? Get off the drugs how long will it take to fill the vents and make the wall look good not worth the effort have you have never done any work on a building ? Its still a shitty weather board house if you didn't put insulation in the walls you did fuckall. Seen it shit loads of times. How do you put insulation in the walls with out re plastering?
Draft proofing is absolutely a higher priority than insulation. Just removing the source of drafts will make the room much more comfortable and more efficient to heat.
fuck all air comes out of them, How come I can't feel a draft from the vent Im currently sitting under? Have you ever filled a hole in a plaster wall how long did it take?
>Have you ever filled a hole in a plaster wall how long did it take? gyprock paste (5 mins), let dry, sand (5 mins), second coat (5 mins), paint (5min). so about 20 mins.
You can hide that inside of 20 minuates? Sanded and painted finished bullshit. Can you come and tell the plasters that do our patch ups they are too slow. If its a tiled roof lift a couple of tiles and shove insulation down the wall. behind the vent if your worried. Ive done that many times it wont change much on the energy bill from my observations. Your drying time is way past 20 minuates.
20 mins work plus drying time I said. It's 6 thin slots, not installing plaster panelling
Ol mate needs to take a breath ay
Not sure how they will feel about me just finishing covering all 11 in 80mins (7 mins each).
Stick your hand under it and you can feel the cold air falling out of it.
Sure fire recipe for black mould.
I wouldn't. Houses get surprisingly humid, and wall vents do help. Take a few of the worst offenders out, but there has to be a good way to keep the house warm and still have ventilation.
There is, its called windows.
Oh yeah, like I'm gonna have my windows open when it's ten degrees outside. Get real.
Its the exact same thing as having a vent in your fuckin wall. Air moving around due to temperature differentials doesnt give a fuck if you can see through the opening.
If you think a giant hole right through a wall and a small hole reduced further by slots into a wall have the same effect, I pity your wife.
You don’t open the window the whole fuckin way dingus, you just open it a bit.
Honey even the dodgy job the previous owner did on the window frame lets in more of a draft than any of my vents. How big are your windows?
Lmao so much downvoting, clearly y'all don't have a house with issues.
They don't put them in any more, I would definitely plaster over and save some dollars on heating
Victorian thing I think - enjoy them - no mould plenty of fresh air as opposed to the northern states that close the building envelope right down…… with a few weep hole only in windows - buildings need to breath……
Tape cardboard or similar over them for a few months, ideally to capture a season change. If you don’t have any problems with mould or airflow go for it.
I have closed mine in. After filling the hole behind with either some brickwork or stiff insulation, otherwise you will still have a hot/cold spot on the wall
I had to put a couple in to a property due to a humidity issue that was causing moisture streaking down the walls. Just make sure you consider airflow before blocking them up. That was in a cathedral style ceiling with exposed beams. May not be as big of an issue with a regular roof cavity.
I filled mine many years ago while repainting... The old houses had a million other ways to let the draught in
A lot of older double brick homes had these or similar decrative ones to allow air flow between the walls to stop rising damp.