I'm not building and I haven't searched this topic, but somehow I landed here and ended up watching the entire presentation. Very interesting. I am interested to see the next episode.
6:25 in older buildings whirlybirds work because the majority of the buildings leak air like sieves, nothing is sealed. In newer buildings with insulation in the walls and roof and even floors with every little air gap plugged or calked the whirlybird can only let hot air escape until the pressure is equalised, then when things cool down cold damp air can be sucked in. Always install vents in the eaves along with whirlybirds.
I had three whirlybirds installed in my Penrith (zone 6) 1972 brick veneer cement tile roof prior to having the roof painted, which in itself was in preparation for the installation of my solar system only 7 years ago. They spin like crazy on hot days. The tiles themselves are laid directly in the rafters with no material underneath. Believe me, there is plenty of access for air to enter the ceiling space without having to add vents is the eaves. I have corner ceiling vents in all four corners of my kitchen, bathroom, and laundry (as was the building standard in 1972), and exhaust fans in each of those rooms, and air can (and does) enter the ceiling cavity above the guttering around my entire house. When in my ceiling, I see daylight entering around the entire gutter/roofline, and from in between the individual tiles.
I have two whirlybirds on a four bedroom house (tin roof), and one eave vent from when I had the first wb installed before extensions. I notice there is a constant draft into the exhaust fans in each bathroom. I leave the bathroom windows cracked so I expect this is a work around that may be useful. Otherwise, interesting stuff. Jeff
I’m a builder in the trade for about 40 years. You are correct, they are part of an air circulation system and there needs to be air inflow for them to do their job.
I have had a whirlybird installed for over 20 years and it makes a big difference to the interior comfort of my home over summer BECAUSE I have made two very important improvements. One, I have a piece of core flex that I slip under the whirlybird over winter so the heat does not escape, and two, the eave vents I have used are central heating floor vents that I can open in summer and close in winter using the end of a broom. As soon as I make it operational at the beginning of summer the need to use air conditioners is greatly reduced and as I live right on the coast I can normally just use the cool breeze I get after 4pm to cool down the home.
Its not the spinning that is helping but your the implementation of the stack effect. You could have a chimney to achieve the same result without the rattle as it spins.
Any roofer that's cut a hole in a roof mid summer knows they work. Hot air bellows out of that hole like a hot aircon right into your face, hot air rises and the whirly bird itself Is just propelled by that hot air, which then draws more air in. It's basically a turbo for your roof, 10/10 do recommend
I don't agree completely with the author above, for the whirlybird to work properly you have to install them in pairs, in different heights and far away from each other ( an instruction I read somewhere may be 30-40 years ago ). The lower whirly can also act as the air input , plus the difference between them in height will create different air pressure to suck in air or to expel air, etc....With one whirly installed then you have to worry about an air inlet, with 2 unit installed, they will automatically sort themselves out.
Omfg no, whirly birds are not (turbos for your roof) they are literally less efficient than a vent with no moving parts. The motion of the whirly bird on a still day is driven by the hot air rising through them, in order to turn the hot air loses energy as it passes through the whiy bird, this reduces the flow rate. Installing a vent with no moving parts means no pressure drop due to energy lost turning the whirly bird. All you need is a path in and a path out of the roof space
Had a heat problem in roof on my old 1979 Perth house (poor insulation). We installed whirly birds in 2014 and it lowered the house temperature by 5-10C on hot days. it lowered the attic temperature by considerably more. The reason it worked is because the air was coming in from under the back verandah (facing south, away from sun) and then up into roof, then out the whirlybird. But I was well aware of the air replacement issue (I am a physics teacher) and the roofer understood the problem. The reason I did not get insulation at the time was cost. We simply didn't have the money for new insulation at the time.
You are correct about the ventilation needed for the birds, they won't suck a vacuum so can only suck as much air as they can get in to replace it. But I don't agree they don't work for a second. The old man put whirly birds in his house around 25ish years ago and they made a HUGE difference. We got some put in here about 4 months ago and the difference to the house (badly insulated) has been phenomenal. When 40c outside, our house was 50c inside before, now the portable aircon actually works in the lounge room for a first time. In saying that we have slotted eaves most of the way around so MANY places to drag air from (including the ceiling vents I'm putting in). We also made some other changes like shade cloth across the front verandah (north facing) to stop the concrete block heating up as if it had been a 40c day, that concrete pad was STILL too hot to walk on at 1130pm at night. Now it doesn't get the chance to heat up because the sun was blocked. We also made and installed shade cloth covers for windows (not just the screen but over the entire window) and we're slowly upgrading the roof from filthy yellow bats (house had a mice issue at some point before us) to R4.0 or R4.5 earthwool bats. Where this house today at 28c would have been 32-34c, it's only about 24c so a HUGE change to liveability.
@@AlphaGeekgirl ceiling vents in the lounge room are closable so will be fine. It's never held it's heat in winter anyway and the bedrooms we're not worried about but can use cloth tape over teh vents if needed.
Yep, daft. A light roof reflects light / heat. Case in point we have a new light roof (surfmist) a neighbour has a dark grey roof. They had to install whirly birds because it got so hot upstairs. Ours is fine.
in a cooler climate, we *want* that heat to help warm the house during the longer cool periods. Yes it means hotter in the shorter summer period, so controlled ventilation is the answer. One solution does not work everywhere.
They damn well work on Queenslander houses, in order for a whirlybird to work they require an airflow so that means a ventilated eaves for airflow, that allows air to be sucked in and exit thru the whirlybird.
If you want to see a bigger difference, make a chimney stack with metal tube about 2 meters long, paint it matt black, have the bottom at the apex of the roof to suck from the highest point, mount the whirlybird on top, but any rain cover will work too. The tube allows the whirlybird to move more air, plus the black tube will heat up the air as it moves up making it move up even quicker.
They do work, even if they’re not spinning or the bearings are siezed. Mount at the highest point of the roof. As soon as I cut the hole, very hot air flowed quickly out of the hole due to convection. Eave vents are a great idea to allow cooler air to enter. Some tiled roofs have enough airflow with the thin gaps between roof tiles and a whirly bird is a waste of money
Some older houses in North Queensland have vents in all the rooms not in the eaves. I have 1 vent in each of 3 bedrooms and 2 in the living room and 1 in the kitchen and one in the toilet. I have 2 whirlybirds. The houses were built with out eaves. Very easy to put a vent into the ceiling of a room to have flow through to a vent. I did have one vent blocked off in a bedroom due to a BIR. Once I installed a new vent the difference was amazing in cooling the room. Thanks for the vid! Recommend white colour bond rooves as well. :)
I have 3 extractor fans for removing steam; laundry and bathrooms. I also have 2 whirlybirds. The extractor fans supply air to the roof attic (whether they are turned on or not) so in effect they ARE air inlets.
You should not ventilate into the roof cavity as you are putting moisture in there creating mold and wetting your ceiling insulation. If you live in a cold climate open your hatch into the ceiling one night in winter after you have showers and shine a torch in you will likely see sliver stars reflecting back at you from water droplets on the back side of your roof material or sarking.
My house has 2 whirlybirds but no eave vents. On a warm day, the whirlybirds spin like crazy, so I'm guessing the airflow is happening due to ceiling vents in bathrooms and toilets.
@iamdave84 Yes, more than likely. Though, being colder air, it should sink and displace the warmer air in the room. But not an ideal scenario. Case of house designers not thinking things through.
My dad put these on his roof when he built his house and mum didnt like them because at the time they were meant for sheds, but the method worked and the house was about 10°-20° cooler in the summer.
Older houses in Melbourne all had vents in the top of the gable, and vents to the under floor area. The heat goes out the top vent and cool air is drawn up the wall cavity from the under floor. For some reason these vents seem to have gone.
Yes they work. End of. Our neighbours either side don't have the convection fans, their air-con runs every day the temperature exceeds 25C. We have2 on our house and have used the air-con perhaps 6 times in 8 years. Granted, we've been going through a lengthy cooler period in tha time but even days 35+ we don't need to switch it on. Standard 8' ceilings, steel frame, gable roof, brick veneer.
Your comments would only apply to roof cavities that are airtight. Very few roofs would be airtight. My roof is a tile roof which means there are gaps everywhere!
Even iron sheet roofs are not airtight, if you have just one or two whirlybirds, there is ample room around a roof perimeter corrugations to allow air flow.
Also if your roof is tiled your house is probably brick. Brick houses don’t have eave vents on purpose. They have ventilation slits at the bottom of the external walls around the house to ventilate the walls as well as the roof. I hope people don’t watch this and then cut holes in their eaves. It will stop the buildings ventilating in the way that they were designed.
Well half the houses I see, especially 2 storeys, don't even have eaves. So good luck with placing the vents. We are worrying about roof ventialtion but allowing eaveless houses that need active cooling a lot more.
Yes, most concrete tile and terracotta tile roofs have gaps between the tiles. These would allow sufficient air to be drawn in to replace the rising hot air being extracted.
To get ventilation working under tiles you have a special shaped tile. Its more rounded and shaped a bit like an ice cream cone (without the pointed tip).
Get a thermal camera and some different thermometer types in a roof space. Get a whole summers worth of readings. Next summer install some whirly birds on the same roof and get the same number of days measured. That way you will be able to accurately determine the effectiveness of the whirly birds.
There is debate about whether the spinning action of the whirlybird works or not. But roof exhaust vents absolutely do work when used in conjunction with eave vents. Basic law of thermodynamics, hot air rises to be replaced by cool air.
Spinning is useless, there is a video (in foreign language) where air flow is compared with conventional ventilation. There were no improvement, whirlybird was even worse, they reduced air flow.
I installed one for 2 reasons, I cut vents in the ceiling of 2 of my bedroom inside the sliding cupboards (always leaving open gaps on the sliding doors) and the window always slightly open. The first reason is to create air flow into the 2 rooms, as they both suffer from stale air and potential mold. The second is to take all the heat out of the roof... both have been achieved or at least had an impact on the issues we have...
In my house in north brisbane, there is whirlybird but no ceiling inlet vent. But it still make a cooling job. the air inlet comes out by way from the ceiling vent fan installations. 2 in the bathroom, 1 at the laundry and 1 in the kitchen. this is better here in queensland because of hot weather since it takes away warm air inside the room while sucking the hot air at the ceiling at the same time. Also, the roof area inside the ceiling is not 100% air tight construction, therefore air can get in wherever there is a gap. Try to look inside your ceiling through a manhole and you can see light from the outside.
Remote rural off grid NSW here have uses whirly gigs for the past decade or so , solar and wind here have ventilated eves around the house am working an extension using packed earth tires atb ground level I have put in air-con ducting so the cold air gets drawn in and expelled out the roof outlets. In winter I will close them off. Before I go I invested in ecotech white paint for the roof bit pricey but on a 48 degree day the core of the main house is around 31 C , it works.
There used to be a product called Decor Vent which seems to have gone into obscurity. Decor Vent consisted of cement sheet eaves lining with a continuous run of slots usually at right angles to the building wall and approx 120 mm x 12 mm and spaced about 100 mm apart. This provided a continuous vent for the full extent of a building's eaves overhangs and was very successful. May be it will come back again although there are other companies that will perforate cement sheet in any pattern you want. I'm not sure that the congestion you refer to at the wall line is such a big problem as there is usually plenty of air space there - often more so with today's truss framing. In saying that, care is needed with the placement of ceiling insulation to ensure the airway isn't blocked - as you suggest.
Have a question... would a man hole cover exchanged for a flyscreen cover inside a garage for example, allow cool air to get into the roof space there, instead of eave vents. ?
No, we have plenty of land, but most of it are places not many people want to live. 90% of our population live on the eastern side of the Ranges and nobody wants to work on large scale water catchment for the centre and west so we can green up the place and make it nicer for people to live.
Very interesting. Seems like roof ventilation needs to be bespoke. From what I can see the whirlybird creates a vacuum to drag more air into the roof space ? But the air needs to come from somewhere cooler (eaves)… but takes a lot to inspect to see if your home eaves are ‘blocked’. In those cases, Amy even need to install a fan and ducting to drag in new cooler air?… or watch part 2….. Also, I’m loving everyone’s comments posting their knowledge…
G'day, This is an interesting topic. I cannot however agree with some of the descriptions you have used. This may be due to a poor choice of words or that you are making broad generalisations. As an example, A whirly Bird installed on an otherwise unventilated location will allow air out as the air heats up and expands during the day. Then as the air cools overnight some fresh cooler air will return to the void. Thus the device does work, just not efficiently. Various things can be done to improve this efficiency, that is what I think you are trying to get across. I look forward to seeing more on the subject.
You are quite correct. Hot air expand and will force itself out through any opening. As as air cools, it contracts and drags air back through the opening. The video is mainly aimed at the new National Construction Code that dismisses the ability of the whirlybirds (or any other ventilation system) to cool the house (living spaces). It quite rightly stipulates high R rating ceiling insulation to provide energy efficiency - instead of ventilating the roof space. The NCC is now asking for roof attic ventilation as part of the ventilation requirements for livability (to stop mould growth). Therefore, the emphasis is on the number of 'air changes' that is needed. So, fresh air in and stale air out at a certain rate is the requirement for roof ventilation. That is why the 'new' need for inlet vents is now very important. A question that needs to be asked (which I did recently at a NCC seminar) is: Do existing houses now need to comply with these new NCC ventilation requirements? - or only just houses built after 2023...
Have 2 of these on my roof. Replaced about 15 years ago and current ones have been there about a further 15 years. Seem to keep the roof space cooler than it would normally be but hey I am no expert. Looks like I am in a zone 5 area. No eaves vents though. This is my second house and has a green colorbond roof. This house is much cooler in summer than my first house which had a dark coloured tile roof and was virtually uninhabitable during hot summer days/nights!
Love your content. Keep up the great work - Tiled roofs without sarking do get a bit of passive airflow through dry valleys/etc, but honestly, whirlybirds don’t do much. Go for a SolarKing V3 instead-it’ll make a real difference.
@NullaNulla I love your engagement-keep up the great work, Are you referring to a standard wind turbine? While they do help, let’s remember it’s 2024. You’re talking about a product designed in 1929, capable of ventilating an average of 70- 90 square meters at a constant wind speed of 16-25km/h. Trust me, I’m always exploring better ways to do things, and I’d love to hear your suggestions and opinions
@@JSIUROOFING my concern with the solar/electric jobs is birds crapping on solar panels, dirty panels, hail damage to the entire unit etc. When we were organising ours we had to cross the path of electric fan units. Unfortunately in our case they weren't a good fit for reasons above and more, BUT, for sure with that extra motion they'll push more air. One of our other concerns was after dark the damn things would stop and our house after a stinker of a day (38-48c) the roof cavity would stop flowing and retain the heat. I guess these considerations need to be covered for person/per situation.
Fantastic response - I’m not paid by the company- we are an accredited installer, and we’ve installed quite a few of these units because we like the product. Regarding concerns like birds messing up the solar panels or dirt build-up, the unit will still function well. We’ve even seen roofs where the units were oversprayed during a budget roof resto, and they still worked surprisingly well As for nighttime operation, you can connect the unit to main power using a DC adaptor plugged into a GPO inside the roof cavity. This setup allows you to control the fan via remote, adjust wind speeds, and use the thermostat, which is preset at 25°C. While there are better products out there, based on my experience installing a range of options, this one offers the best balance between cost and value.
@@JSIUROOFING unfortunately the offerings we received for thought were solar only. A house a few doors down the road had serious issues with his solar units (hail damage for one) but I cannot say for hardwired units as I've not met anyone with them. Either way both when installed in-correctly are useless.
Hmm. I think he’s overlooking the fact that most Aussie houses don’t have the vents in the eaves on purpose. They are at the bottom of the brick walls, evenly distributed around the house. The whirlybird draws air from closer to the ground and ventilate the external walls as well as the roof. Installing vents in the eaves will just stop the air drawing through the walls. They just look like small slits in the brickwork around the bottom of the external walls. Could be different in a non-brick house.
This guy lost all credibility around the 5:30 mark. Roofing isn't air tight, you need eve venting to allow more air in, the fact you see a whirly bird spinning means its working.
My old house had whirlybirds and an intake vent in the middle of the house, I hardly ever used the A/C in Summer as it kept the heat out of the house (rural QLD at the time).
I had always thought of using the warm air that forms in the roof space in winter sunshine, to warm the house. Wouldn't be hard to install a reverse fan in the ceiling. Is there such a system available?
I would not recommend this. I have looked into so many roof attic spaces and the dust up there is better vented out of the house. You would not want that dust blowing back into your living space...
Got several WBs and vents in the eaves but installing the vents is a shitty job . Works well though and I can usually run without air con up to about 35 degrees. If you are really keen there is much advantage in creating air flow in the roof cavity and if you own a newer house with wall insulation even better as most of the heat transfers through the walls on those stinking hot afternoons. Keep in mind as one previous comment asked, it’s the opposite it winter.
Very interesting, I had 2 whirlybirds installed, no mention of venting but that makes sense! I have no saking in the rood, so would this provide enough or am I best putting in a few eave vents to be sure? Beyond that, I had advice my roof has "rusty nail problem" by another roofer that causes my tiles to crack, I'm replacing tile often which is annoying.. not sure what the solution is beyond reroof!
The NCC does its best to add onerous costs on to new builds with low regard to the housing crisis that's been brewing for 20+ years. Recent one supposedly added $30K to a build, and am sure they new venting requirements will add extra thousand(s) to it - probably requiring solar powered whirly birds with power backup (when sun not shining) for ventilation - they're so damned expensive and was told they're useless for cooling as marketed as you have more energy going in from the sun every hour than those solar powered extractors can remove, so for cooling it only works when the sun goes down and then it relies on mains power for them over just hot air/wind from the manual ones.
Why am I watching this excellent and informative video on roof ventilation? How about a single eaves vent with a fan powered by a solar panel actively pushing air into the space? The biggest issue with building regulations are that they proscribe a fix for a problem rather than just stating the result required.
I’ve got a double brick house, open cavity between the brick courses. Wouldn’t the numerous mandatory anti condensation brick vent gaps installed by the bricklayer allow cooler ambient air to be drawn into the attic under the negative suction of the whirlybird?
There is no negative suction, they just create a path for air to escape, convection forces do all the work. Yes air will be drawn in through the weep holes but not much, proper vents should be installed for air movement to be effective.
@BenState sounds like they are asking if weep holes are enough. If there are only weep holes (not vents) it would be slab on ground (no sub floor and vents). Weep holes are not enough, they are only placed under window openings to allow water out in the event the flashing leaks.
Are there any alternative outlet vents to whirly birds in Australia? The spinning is completely unnecessary, if anything physics suggests they would slow the airflow. I personally think they should be taken off the market and replaced with a chimney type outlet.
My glazed terracotta roof tiles have so many gaps around them the wind howls through the roof space. No rain leaks. Older brick veneer houses with underfloor areas let cool air up the inside of the uninsulated walls. No need for vents in the asbestos eaves. Modern houses built on polystyrene blocks have zero air up the walls, no eaves, and use roofing tiles/sheets that are effectively sealed.
Thank you for sharing this, it is very informative. We have concrete tiles for our roof, and because of the gaps and light that comes through at the eve, I had thought that we enough for air transfer. Would I be better off installing vents as well? It would not be hard to do, single story, new construction, so no asbestos. When I installed whirlybirds on our roof I did notice a drop in temp in the attic when I am there, but I am wondering if I am missing out on some of the air transfer by not having vents, and relying on the gap in the tiles.
My house is 70s built concrete tile, i can see so much light under tiles in the roof space that I'm certain the whirly bird will work because it would be impossible to create a vacuum up there. Replacement air will definitely make its way in. That said, I'll endeavour to get eaves vents in eventually and compare temperatures
Ventilation can get quite complex. The smart engineers have worked out that unsarked tile roofs will ventilate themselves. That is why the National Construction Code states that unsarked tile roofs do not need any inlet or outlet vents. Whirly birds can be quite ineffective in circulating the roof cavity air in unsarked roofs. It will take the lazy way out and draw the air in from the tile air gaps immediately around it - and not from the gaps on the tiles near the eaves. So, it does not create the 'front door - back door open effect'. It is just like only having one door open if you put a whirlybird on an unsarked roof - there will still be ari movement. But nothing like if when two doors on opposite ends are open...
Question ? With the air replacement for the whirly bird .. Does the gap around the bottom row of tiles not do the same thing .. Same with tin roof .. All homes ive owned have all got a gap around the bottom of the roof itself.. The tin roof house i had had actual ventilation gaps under the roof .. And i stuck a whirly bird on the top and it seemed to help a lot ..
you could argue any brick veneer house is inherently vented. The roof will be framed off the timber and the whirly birds should be able to suck air through the cavity
Yes, they all add up. That is why the new NCC requirements on ventilation does not apply to un-sarked roofs. However, as soon as the roof gets sarked none of these openings comes into the equation.
Do you think whirlybirds work to help cool down an outside deck area with a flat colourbond roof? Our west facing deck gets very very hot but the flat roof isn't high enough to install outdoor ceiling fans
I have two installed on a tin shed which has no ceiling. Eaves are open, one RSD and three louvre windows. They do keep the shed cooler but suck in airborne dirt, etc from nearby trees which covers everything inside the shed with a film of rime. Not good if you’re storing anything valuable inside the structure.
questions for the presenter; what air change per hour (ACH) do passive whirly birds provide? How many ACH do tiled and sarked roofs have without? How many ACH are required to reduce the temperature? As a guide, for energy ratings a tiled roof is considered to have 11.4 ACH, and a sarked tile roof or a metal roof is 4.2 ACH. A whirly bird is said to add only 1 ACH per 200m2. There certainly is a place for them, especially to reduce condensation forming in a roof space (which is the intent of the NCC requirements and AS3999), but cooling is not effective. You want an powered roof ventilator for cooling.
Hi Andrew, Great questions. And I am not technically qualified to answer these questions. However, Table 10.8.3 (NCC) provides guidelines to minimum openings depending on the pitch of the roof - and the length of the roof. ACH has always confused me (due to my lack of knowledge). And I also think that the writers of the NCC have no idea of EXACTLY the amount of ACH that is needed to prevent the level of condensation that is UNSATISFACTORY. That is why they just give guidelines on opening sizes and not ACH when it comes to condensation management. And since condensation management has no relationship to cooling the attic (but the two are surely related) - we must accept that the NCC does not care about cooling the attic at all... Jack
You're assuming that all roofs are airtight. My roof is definitely not airtight, you can even see sunlight poking through in some places, likely due to the 20mm gap you spoke of later.
I had a slab on the ground house and created louvre pivot windows in the gables. I could open the louvres from inside the house with a cord. This allowed the entire roof space to change air mass very quickly.... not all Australians are as dumb as you infer..... 😄😃😀🇦🇺
Yeah, those kind of louvres are perfect for Queensland weather. high ceilings with easy accessible lever windows; every house needs one. You should be working for Department of housing or whoever it is that makes up all those housing rules! I swear whoever has been doing it for the past 50 years has been totally inadequate.
Thanks for this video. I have a very old house with a corrugated iron roof in Tasmania. We don't have a moisture problem, but I was going to have whirlybirds installed to remove heat. We also don't have eaves of any substance. What would you suggest for a lower level vent in such a roof? Would a whirlybird installed low on the roof work for the intake in conjunction with one installed high for the outflow? Or some form of other vent that is weatherproof?
They generally don't work well enough to justify their purchase & installation cost. Typically a disaster during the winter because they suck the warm air out of the condutioned space inside the house. Much better investment to cover the roof in solar panels, Or have a pale coloured roof, or shade parts of the roof with trees. Furthermore, they tend to shade solar panels if they are installed as well.
This where the misunderstanding arises. The NCC does not care whether the whirlybird works or not in the energy efficiency of the house. This is because it knows that roof cavity ventilation does very little in keeping the house warm or cool. It demands insulation batts on ceilings to do this job. As long as you have good ceiling insulation, the heating requirements of the house in winter is not impacted by the roof ventilation.
If the structure is on fire, these things make it spread super fast, then they eventually spin so fast they can actually separate from the roof. They’re great when the place is not on fire.
@ Clearly. 😂. My point being that while they’re great when everything is ok, if there’s a fire you can almost certainly kiss the entire structure goodbye. Without them, fires spread far less quickly and there is a chance of containing damage to one area. (I’m a former firefighter btw so I am not talking out of my blowhole 👍).
Hot air expands - it takes up more volume than cold. And then it goes out the vent. You do NOT need an air intake for these to work. It can help, but that is not how physics works. The heated and expanded air remaining within the roof cavity has less mass, density and conductivity - less thermal energy - less ability to make the house hot. I am trying to explain in layman's terms. Alternatively, just look at all the whirlybird installations that WORK WITHOUT INLET VENTS. Measure the difference. You can do that easily by stopping the birds spinning for a day.
The problem with Whirlybirds is the create negative draw and can draw the air-conditioned air from your home working your air conditioning overtime. Making incredibly inefficient..
Whirly birds need to turn over the roof space volume 3 times in 10 minutes to make a small cooling effect. They can't do 10% of that. They do turn a bit of air to reduce mould but are a "cooling" scam.
Passive whirlybirds dont replace air fast enough (assuming adequate intake ventilation). Roof design needs to progress past these outdated ideas and adopt ventilation above the membrane and below the roofing material, as is common to Passive Houses.
That would be for a roof with silver sarking which is mot permeabke and mot a vapour permeable membrane. Yhis is because the conensayion gorm on the underside of yhe silversatking unlike a vapour permeable membeane where irs on th e bottom of yge tole which then goes into the gutter when it falls on the membrane. The heat in the toof cavity is radiant heat you cant ventilate radiant heat. Best yo go outside in the evening a spray water on your roofing material to remove the heat energy.
This is a very complicated - yet insightful answer. The confusion lies in what we are trying to achieve by ventilating the roof cavity. The National Construction Code on roof cavity ventilation is only concerned with removing moisture from the cavity. NOT HEAT. The code stipulates other means (insulation) to make the house heat efficient. Traditionally (before the NCC ventilation requirements), home owners just wanted to make the house heat efficient - and were sold on the myth that whirlybirds were the answer. Moving forward into the future, we must look at these two issues separately. 1) How to make the house more energy efficient and livable? 2) How to reduce the likelihood of mould growth in the house - caused by lack of adequate ventilation? Homeowners have been more concerned about heat efficiency because they can feel temperature differences easily. They are less likely to feel the presence of mould and lack of ventilation. We think the updated National Construction Code is trying to tackle the issues that most homeowners are not aware of...
@@roofingportal I should not type on my phone without glasses on. Best way to keep heat out of a roof is to have a white roof (or roof which higher solar reluctance) and low solar absorbance (less heat absorbed and radiated later). The insulation above your ceiling plaster is the means of resisting heat transfer from one side to another. This layer needs to be continuous and thick wihout gaps. The alternative to this is to have a conditioned attic which means all the insulation is immediately adjacent to the roof material. The approach to manage moisture below the ceiling is to use a heat recovery ventilation (HRV) system - there are ones that are centralized and not centralized. These are made by Laros and STIEBEL ELTRON's. These are required for homes with ACH (airchanges per hour of less than 5 - not common in Australia). Really old houses in Australia have slits and vents on the walls of plasterboard. These were installed to allow fireplace and oil burners that ran inside your home to not kill you from carbon monoxide. The simple reality is that most home owners, builders, and trades do not know much about the building science today, or why homes were built they way they were in the past. The Energy Smart Housing Manual produced by Sustainability Victoria is a really good guide for homeowners to understand and make sensible changes to their homes (or when buying new ones). In addition you should also source the The YourHome website of the Australian government.
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
I'm not building and I haven't searched this topic, but somehow I landed here and ended up watching the entire presentation.
Very interesting. I am interested to see the next episode.
Really well explained wasn't it
6:25 in older buildings whirlybirds work because the majority of the buildings leak air like sieves, nothing is sealed.
In newer buildings with insulation in the walls and roof and even floors with every little air gap plugged or calked the whirlybird can only let hot air escape until the pressure is equalised, then when things cool down cold damp air can be sucked in.
Always install vents in the eaves along with whirlybirds.
Therefore the first 6:00 of this video was a waste of my time.
I had three whirlybirds installed in my Penrith (zone 6) 1972 brick veneer cement tile roof prior to having the roof painted, which in itself was in preparation for the installation of my solar system only 7 years ago. They spin like crazy on hot days. The tiles themselves are laid directly in the rafters with no material underneath. Believe me, there is plenty of access for air to enter the ceiling space without having to add vents is the eaves. I have corner ceiling vents in all four corners of my kitchen, bathroom, and laundry (as was the building standard in 1972), and exhaust fans in each of those rooms, and air can (and does) enter the ceiling cavity above the guttering around my entire house. When in my ceiling, I see daylight entering around the entire gutter/roofline, and from in between the individual tiles.
I have two whirlybirds on a four bedroom house (tin roof), and one eave vent from when I had the first wb installed before extensions. I notice there is a constant draft into the exhaust fans in each bathroom. I leave the bathroom windows cracked so I expect this is a work around that may be useful. Otherwise, interesting stuff. Jeff
I’m a builder in the trade for about 40 years. You are correct, they are part of an air circulation system and there needs to be air inflow for them to do their job.
I have had a whirlybird installed for over 20 years and it makes a big difference to the interior comfort of my home over summer BECAUSE I have made two very important improvements. One, I have a piece of core flex that I slip under the whirlybird over winter so the heat does not escape, and two, the eave vents I have used are central heating floor vents that I can open in summer and close in winter using the end of a broom. As soon as I make it operational at the beginning of summer the need to use air conditioners is greatly reduced and as I live right on the coast I can normally just use the cool breeze I get after 4pm to cool down the home.
Its not the spinning that is helping but your the implementation of the stack effect. You could have a chimney to achieve the same result without the rattle as it spins.
Any roofer that's cut a hole in a roof mid summer knows they work. Hot air bellows out of that hole like a hot aircon right into your face, hot air rises and the whirly bird itself Is just propelled by that hot air, which then draws more air in.
It's basically a turbo for your roof, 10/10 do recommend
I don't agree completely with the author above, for the whirlybird to work properly you have to install them in pairs, in different heights and far away from each other ( an instruction I read somewhere may be 30-40 years ago ). The lower whirly can also act as the air input , plus the difference between them in height will create different air pressure to suck in air or to expel air, etc....With one whirly installed then you have to worry about an air inlet, with 2 unit installed, they will automatically sort themselves out.
stu stu stu stuuu
Omfg no, whirly birds are not (turbos for your roof) they are literally less efficient than a vent with no moving parts. The motion of the whirly bird on a still day is driven by the hot air rising through them, in order to turn the hot air loses energy as it passes through the whiy bird, this reduces the flow rate. Installing a vent with no moving parts means no pressure drop due to energy lost turning the whirly bird. All you need is a path in and a path out of the roof space
@@ryanclarke2161 you really don't understand this
the best thing since sliced bread we always had mold in our house for 20 years not any more
I’ve got a few whirly birds and intake vents and it’s a huge difference. Still gets warm up there but it’s nowhere near the hell furnace without them
Had a heat problem in roof on my old 1979 Perth house (poor insulation). We installed whirly birds in 2014 and it lowered the house temperature by 5-10C on hot days. it lowered the attic temperature by considerably more. The reason it worked is because the air was coming in from under the back verandah (facing south, away from sun) and then up into roof, then out the whirlybird.
But I was well aware of the air replacement issue (I am a physics teacher) and the roofer understood the problem.
The reason I did not get insulation at the time was cost. We simply didn't have the money for new insulation at the time.
You are correct about the ventilation needed for the birds, they won't suck a vacuum so can only suck as much air as they can get in to replace it. But I don't agree they don't work for a second.
The old man put whirly birds in his house around 25ish years ago and they made a HUGE difference. We got some put in here about 4 months ago and the difference to the house (badly insulated) has been phenomenal. When 40c outside, our house was 50c inside before, now the portable aircon actually works in the lounge room for a first time. In saying that we have slotted eaves most of the way around so MANY places to drag air from (including the ceiling vents I'm putting in).
We also made some other changes like shade cloth across the front verandah (north facing) to stop the concrete block heating up as if it had been a 40c day, that concrete pad was STILL too hot to walk on at 1130pm at night. Now it doesn't get the chance to heat up because the sun was blocked. We also made and installed shade cloth covers for windows (not just the screen but over the entire window) and we're slowly upgrading the roof from filthy yellow bats (house had a mice issue at some point before us) to R4.0 or R4.5 earthwool bats.
Where this house today at 28c would have been 32-34c, it's only about 24c so a HUGE change to liveability.
How is the house in winter now?
@@AlphaGeekgirl ceiling vents in the lounge room are closable so will be fine. It's never held it's heat in winter anyway and the bedrooms we're not worried about but can use cloth tape over teh vents if needed.
you do not understand the air density changes with temperature. or any physics.
@@davidstephenson3615 you're making a VERY arrogant and incorrect assumption there!
How about people stop have dark coloured roofs that cause the excessive heat in the roof mmm
Light colors show mould and grime
Yep, daft. A light roof reflects light / heat. Case in point we have a new light roof (surfmist) a neighbour has a dark grey roof. They had to install whirly birds because it got so hot upstairs. Ours is fine.
in a cooler climate, we *want* that heat to help warm the house during the longer cool periods. Yes it means hotter in the shorter summer period, so controlled ventilation is the answer. One solution does not work everywhere.
All the above plus there are rules to follow regarding colour. Stupid isn't it 😅
@@Andrew-kz8qp In hot cities of Australia, light roofs are great
They damn well work on Queenslander houses, in order for a whirlybird to work they require an airflow so that means a ventilated eaves for airflow, that allows air to be sucked in and exit thru the whirlybird.
I have a picture of a ghost on a tv.
A cone on a cone could do as good.
That's what he said in the video..
If you want to see a bigger difference, make a chimney stack with metal tube about 2 meters long, paint it matt black, have the bottom at the apex of the roof to suck from the highest point, mount the whirlybird on top, but any rain cover will work too.
The tube allows the whirlybird to move more air, plus the black tube will heat up the air as it moves up making it move up even quicker.
They do work, even if they’re not spinning or the bearings are siezed. Mount at the highest point of the roof. As soon as I cut the hole, very hot air flowed quickly out of the hole due to convection. Eave vents are a great idea to allow cooler air to enter. Some tiled roofs have enough airflow with the thin gaps between roof tiles and a whirly bird is a waste of money
Some older houses in North Queensland have vents in all the rooms not in the eaves. I have 1 vent in each of 3 bedrooms and 2 in the living room and 1 in the kitchen and one in the toilet. I have 2 whirlybirds. The houses were built with out eaves. Very easy to put a vent into the ceiling of a room to have flow through to a vent. I did have one vent blocked off in a bedroom due to a BIR. Once I installed a new vent the difference was amazing in cooling the room. Thanks for the vid! Recommend white colour bond rooves as well. :)
I have 3 extractor fans for removing steam; laundry and bathrooms.
I also have 2 whirlybirds.
The extractor fans supply air to the roof attic (whether they are turned on or not) so in effect they ARE air inlets.
You should not ventilate into the roof cavity as you are putting moisture in there creating mold and wetting your ceiling insulation. If you live in a cold climate open your hatch into the ceiling one night in winter after you have showers and shine a torch in you will likely see sliver stars reflecting back at you from water droplets on the back side of your roof material or sarking.
My house has 2 whirlybirds but no eave vents.
On a warm day, the whirlybirds spin like crazy, so I'm guessing the airflow is happening due to ceiling vents in bathrooms and toilets.
Does that mean they're sucking the cool (air conditioned?) air from inside your house?
@iamdave84
Yes, more than likely.
Though, being colder air, it should sink and displace the warmer air in the room. But not an ideal scenario.
Case of house designers not thinking things through.
My dad put these on his roof when he built his house and mum didnt like them because at the time they were meant for sheds, but the method worked and the house was about 10°-20° cooler in the summer.
They do work!
Nearly everyone calls them whirlybirds but in actual fact it’s called a Spinaway vent!
Older houses in Melbourne all had vents in the top of the gable, and vents to the under floor area. The heat goes out the top vent and cool air is drawn up the wall cavity from the under floor. For some reason these vents seem to have gone.
Yes they work. End of. Our neighbours either side don't have the convection fans, their air-con runs every day the temperature exceeds 25C. We have2 on our house and have used the air-con perhaps 6 times in 8 years. Granted, we've been going through a lengthy cooler period in tha time but even days 35+ we don't need to switch it on. Standard 8' ceilings, steel frame, gable roof, brick veneer.
Your comments would only apply to roof cavities that are airtight. Very few roofs would be airtight. My roof is a tile roof which means there are gaps everywhere!
Even iron sheet roofs are not airtight, if you have just one or two whirlybirds, there is ample room around a roof perimeter corrugations to allow air flow.
Also if your roof is tiled your house is probably brick. Brick houses don’t have eave vents on purpose. They have ventilation slits at the bottom of the external walls around the house to ventilate the walls as well as the roof. I hope people don’t watch this and then cut holes in their eaves. It will stop the buildings ventilating in the way that they were designed.
@@lesskinner8588those corrugations fill up with the insulation blanket mass.
Whirly birds are intended for metal roofs, not tile roofs. They serve little real function on a tile roof.
@@aussie8114 nonsense.
Wow. Something regular home owners don’t think about hey. Thanks 🙏 so much for all of that info.
Well half the houses I see, especially 2 storeys, don't even have eaves. So good luck with placing the vents. We are worrying about roof ventialtion but allowing eaveless houses that need active cooling a lot more.
on older homes, when inside the roof, you can see light between the tiles, i see inlets everywhere!
Yes, most concrete tile and terracotta tile roofs have gaps between the tiles. These would allow sufficient air to be drawn in to replace the rising hot air being extracted.
To get ventilation working under tiles you have a special shaped tile. Its more rounded and shaped a bit like an ice cream cone (without the pointed tip).
You could connect the vents under the eaves to large ducts which are then place in the roof cavity
Get a thermal camera and some different thermometer types in a roof space.
Get a whole summers worth of readings.
Next summer install some whirly birds on the same roof and get the same number of days measured.
That way you will be able to accurately determine the effectiveness of the whirly birds.
you could do this is a day, the youtuber is an idiot
Whirlybirds made a HUGE difference to my 1980's home.
There is debate about whether the spinning action of the whirlybird works or not. But roof exhaust vents absolutely do work when used in conjunction with eave vents. Basic law of thermodynamics, hot air rises to be replaced by cool air.
Spinning is useless, there is a video (in foreign language) where air flow is compared with conventional ventilation. There were no improvement, whirlybird was even worse, they reduced air flow.
I installed one for 2 reasons, I cut vents in the ceiling of 2 of my bedroom inside the sliding cupboards (always leaving open gaps on the sliding doors) and the window always slightly open. The first reason is to create air flow into the 2 rooms, as they both suffer from stale air and potential mold. The second is to take all the heat out of the roof... both have been achieved or at least had an impact on the issues we have...
In my house in north brisbane, there is whirlybird but no ceiling inlet vent. But it still make a cooling job. the air inlet comes out by way from the ceiling vent fan installations. 2 in the bathroom, 1 at the laundry and 1 in the kitchen. this is better here in queensland because of hot weather since it takes away warm air inside the room while sucking the hot air at the ceiling at the same time. Also, the roof area inside the ceiling is not 100% air tight construction, therefore air can get in wherever there is a gap. Try to look inside your ceiling through a manhole and you can see light from the outside.
Remote rural off grid NSW here have uses whirly gigs for the past decade or so , solar and wind here have ventilated eves around the house am working an extension using packed earth tires atb ground level I have put in air-con ducting so the cold air gets drawn in and expelled out the roof outlets. In winter I will close them off. Before I go I invested in ecotech white paint for the roof bit pricey but on a 48 degree day the core of the main house is around 31 C , it works.
Beats me. Served a carpenter & joiner apprenticeship in the 70’s.
Vents in the soffits were standard in Queensland
What do you do with all the newer houses that do not have eves?
There used to be a product called Decor Vent which seems to have gone into obscurity. Decor Vent consisted of cement sheet eaves lining with a continuous run of slots usually at right angles to the building wall and approx 120 mm x 12 mm and spaced about 100 mm apart. This provided a continuous vent for the full extent of a building's eaves overhangs and was very successful. May be it will come back again although there are other companies that will perforate cement sheet in any pattern you want. I'm not sure that the congestion you refer to at the wall line is such a big problem as there is usually plenty of air space there - often more so with today's truss framing. In saying that, care is needed with the placement of ceiling insulation to ensure the airway isn't blocked - as you suggest.
Have a question... would a man hole cover exchanged for a flyscreen cover inside a garage for example, allow cool air to get into the roof space there, instead of eave vents. ?
If Australia, of all places, has a limited supply of land, then my eyes are sloped.
No, we have plenty of land, but most of it are places not many people want to live. 90% of our population live on the eastern side of the Ranges and nobody wants to work on large scale water catchment for the centre and west so we can green up the place and make it nicer for people to live.
Very interesting. Seems like roof ventilation needs to be bespoke. From what I can see the whirlybird creates a vacuum to drag more air into the roof space ? But the air needs to come from somewhere cooler (eaves)… but takes a lot to inspect to see if your home eaves are ‘blocked’. In those cases, Amy even need to install a fan and ducting to drag in new cooler air?… or watch part 2…..
Also, I’m loving everyone’s comments posting their knowledge…
G'day, This is an interesting topic. I cannot however agree with some of the descriptions you have used. This may be due to a poor choice of words or that you are making broad generalisations. As an example, A whirly Bird installed on an otherwise unventilated location will allow air out as the air heats up and expands during the day. Then as the air cools overnight some fresh cooler air will return to the void. Thus the device does work, just not efficiently. Various things can be done to improve this efficiency, that is what I think you are trying to get across. I look forward to seeing more on the subject.
You are quite correct.
Hot air expand and will force itself out through any opening. As as air cools, it contracts and drags air back through the opening.
The video is mainly aimed at the new National Construction Code that dismisses the ability of the whirlybirds (or any other ventilation system) to cool the house (living spaces). It quite rightly stipulates high R rating ceiling insulation to provide energy efficiency - instead of ventilating the roof space.
The NCC is now asking for roof attic ventilation as part of the ventilation requirements for livability (to stop mould growth). Therefore, the emphasis is on the number of 'air changes' that is needed. So, fresh air in and stale air out at a certain rate is the requirement for roof ventilation.
That is why the 'new' need for inlet vents is now very important.
A question that needs to be asked (which I did recently at a NCC seminar) is: Do existing houses now need to comply with these new NCC ventilation requirements? - or only just houses built after 2023...
The question I have is, having been in quite a few roof spaces, there are so many air gaps that wouldn't this be sufficient to allow cooler air in?
Have 2 of these on my roof. Replaced about 15 years ago and current ones have been there about a further 15 years. Seem to keep the roof space cooler than it would normally be but hey I am no expert. Looks like I am in a zone 5 area. No eaves vents though. This is my second house and has a green colorbond roof. This house is much cooler in summer than my first house which had a dark coloured tile roof and was virtually uninhabitable during hot summer days/nights!
Love your content. Keep up the great work - Tiled roofs without sarking do get a bit of passive airflow through dry valleys/etc, but honestly, whirlybirds don’t do much. Go for a SolarKing V3 instead-it’ll make a real difference.
I've seen a few houses, including our own where they made all the difference.
@NullaNulla I love your engagement-keep up the great work, Are you referring to a standard wind turbine? While they do help, let’s remember it’s 2024. You’re talking about a product designed in 1929, capable of ventilating an average of 70- 90 square meters at a constant wind speed of 16-25km/h. Trust me, I’m always exploring better ways to do things, and I’d love to hear your suggestions and opinions
@@JSIUROOFING my concern with the solar/electric jobs is birds crapping on solar panels, dirty panels, hail damage to the entire unit etc.
When we were organising ours we had to cross the path of electric fan units. Unfortunately in our case they weren't a good fit for reasons above and more, BUT, for sure with that extra motion they'll push more air.
One of our other concerns was after dark the damn things would stop and our house after a stinker of a day (38-48c) the roof cavity would stop flowing and retain the heat.
I guess these considerations need to be covered for person/per situation.
Fantastic response - I’m not paid by the company- we are an accredited installer, and we’ve installed quite a few of these units because we like the product. Regarding concerns like birds messing up the solar panels or dirt build-up, the unit will still function well. We’ve even seen roofs where the units were oversprayed during a budget roof resto, and they still worked surprisingly well
As for nighttime operation, you can connect the unit to main power using a DC adaptor plugged into a GPO inside the roof cavity. This setup allows you to control the fan via remote, adjust wind speeds, and use the thermostat, which is preset at 25°C. While there are better products out there, based on my experience installing a range of options, this one offers the best balance between cost and value.
@@JSIUROOFING unfortunately the offerings we received for thought were solar only. A house a few doors down the road had serious issues with his solar units (hail damage for one) but I cannot say for hardwired units as I've not met anyone with them. Either way both when installed in-correctly are useless.
Hmm. I think he’s overlooking the fact that most Aussie houses don’t have the vents in the eaves on purpose. They are at the bottom of the brick walls, evenly distributed around the house. The whirlybird draws air from closer to the ground and ventilate the external walls as well as the roof. Installing vents in the eaves will just stop the air drawing through the walls. They just look like small slits in the brickwork around the bottom of the external walls. Could be different in a non-brick house.
Those vents near the foundation don't bring cold air into the house, that's not what they are there for...
So many houses barely even have eaves these days.
metal frames they insulate everything , good for winter not for summer ha ha ha
This guy lost all credibility around the 5:30 mark. Roofing isn't air tight, you need eve venting to allow more air in, the fact you see a whirly bird spinning means its working.
My old house had whirlybirds and an intake vent in the middle of the house, I hardly ever used the A/C in Summer as it kept the heat out of the house (rural QLD at the time).
As in, just in the ceiling or wall?
Or from the subfloor?
@@willhooke in the ceiling in the middle of the house.
@ thank you 👍🏻
I had always thought of using the warm air that forms in the roof space in winter sunshine, to warm the house. Wouldn't be hard to install a reverse fan in the ceiling. Is there such a system available?
I would not recommend this.
I have looked into so many roof attic spaces and the dust up there is better vented out of the house.
You would not want that dust blowing back into your living space...
How about in winter when you would prefer to have warm air retained inside the roof space how is there a way to close the vents?
Got several WBs and vents in the eaves but installing the vents is a shitty job . Works well though and I can usually run without air con up to about 35 degrees. If you are really keen there is much advantage in creating air flow in the roof cavity and if you own a newer house with wall insulation even better as most of the heat transfers through the walls on those stinking hot afternoons. Keep in mind as one previous comment asked, it’s the opposite it winter.
Very interesting, I had 2 whirlybirds installed, no mention of venting but that makes sense! I have no saking in the rood, so would this provide enough or am I best putting in a few eave vents to be sure?
Beyond that, I had advice my roof has "rusty nail problem" by another roofer that causes my tiles to crack, I'm replacing tile often which is annoying.. not sure what the solution is beyond reroof!
The NCC does its best to add onerous costs on to new builds with low regard to the housing crisis that's been brewing for 20+ years. Recent one supposedly added $30K to a build, and am sure they new venting requirements will add extra thousand(s) to it - probably requiring solar powered whirly birds with power backup (when sun not shining) for ventilation - they're so damned expensive and was told they're useless for cooling as marketed as you have more energy going in from the sun every hour than those solar powered extractors can remove, so for cooling it only works when the sun goes down and then it relies on mains power for them over just hot air/wind from the manual ones.
Why am I watching this excellent and informative video on roof ventilation?
How about a single eaves vent with a fan powered by a solar panel actively pushing air into the space?
The biggest issue with building regulations are that they proscribe a fix for a problem rather than just stating the result required.
I’ve got a double brick house, open cavity between the brick courses.
Wouldn’t the numerous mandatory anti condensation brick vent gaps installed by the bricklayer allow cooler ambient air to be drawn into the attic under the negative suction of the whirlybird?
There is no negative suction, they just create a path for air to escape, convection forces do all the work. Yes air will be drawn in through the weep holes but not much, proper vents should be installed for air movement to be effective.
@@stevegus2845 Do you mean proper vents with fans on them?
@@lesleyhiddins2067 no. As explained in the video. A path for cooler air to enter the cavity/roof space.
@@stevegus2845 But the path is there, via the cavity in the walls to the attic space.
@BenState sounds like they are asking if weep holes are enough. If there are only weep holes (not vents) it would be slab on ground (no sub floor and vents). Weep holes are not enough, they are only placed under window openings to allow water out in the event the flashing leaks.
Are there any alternative outlet vents to whirly birds in Australia?
The spinning is completely unnecessary, if anything physics suggests they would slow the airflow.
I personally think they should be taken off the market and replaced with a chimney type outlet.
My glazed terracotta roof tiles have so many gaps around them the wind howls through the roof space. No rain leaks. Older brick veneer houses with underfloor areas let cool air up the inside of the uninsulated walls. No need for vents in the asbestos eaves. Modern houses built on polystyrene blocks have zero air up the walls, no eaves, and use roofing tiles/sheets that are effectively sealed.
Thank you for sharing this, it is very informative. We have concrete tiles for our roof, and because of the gaps and light that comes through at the eve, I had thought that we enough for air transfer. Would I be better off installing vents as well? It would not be hard to do, single story, new construction, so no asbestos.
When I installed whirlybirds on our roof I did notice a drop in temp in the attic when I am there, but I am wondering if I am missing out on some of the air transfer by not having vents, and relying on the gap in the tiles.
There is no sarking on our house, just straight tiles on the purlins.
My house is 70s built concrete tile, i can see so much light under tiles in the roof space that I'm certain the whirly bird will work because it would be impossible to create a vacuum up there. Replacement air will definitely make its way in. That said, I'll endeavour to get eaves vents in eventually and compare temperatures
Ventilation can get quite complex. The smart engineers have worked out that unsarked tile roofs will ventilate themselves.
That is why the National Construction Code states that unsarked tile roofs do not need any inlet or outlet vents.
Whirly birds can be quite ineffective in circulating the roof cavity air in unsarked roofs. It will take the lazy way out and draw the air in from the tile air gaps immediately around it - and not from the gaps on the tiles near the eaves. So, it does not create the 'front door - back door open effect'.
It is just like only having one door open if you put a whirlybird on an unsarked roof - there will still be ari movement. But nothing like if when two doors on opposite ends are open...
Depends on what your roof is. If it is metal well, you have ample air flow and do not need eve vents.
Yes, Very Informative !
Now, Speaking of Replacement -Please Replace those Crapy Whiteboard Markers with New Ones 😁
Question ? With the air replacement for the whirly bird .. Does the gap around the bottom row of tiles not do the same thing .. Same with tin roof .. All homes ive owned have all got a gap around the bottom of the roof itself.. The tin roof house i had had actual ventilation gaps under the roof .. And i stuck a whirly bird on the top and it seemed to help a lot ..
There are so many gaps in a tiled roof, do you really need a vent?
you could argue any brick veneer house is inherently vented. The roof will be framed off the timber and the whirly birds should be able to suck air through the cavity
I was thinking the same thing, especially if the house isn’t on a slab.
It’s not just about heat, it’s about condensation laws as well
I remember all housing commission in the fifties had vents in their eaves and internal walls
What about the vents for the extractors in the bathrooms? It’s not as if the attic space is airtight.
What about advantageous air openings around the roof and between the tiles? They all add up?
Yes, they all add up. That is why the new NCC requirements on ventilation does not apply to un-sarked roofs.
However, as soon as the roof gets sarked none of these openings comes into the equation.
@roofingportal ahh thanks mate... Good information.
Do you think whirlybirds work to help cool down an outside deck area with a flat colourbond roof? Our west facing deck gets very very hot but the flat roof isn't high enough to install outdoor ceiling fans
Might be a bit of work but you could try XPS insulation.
Universal tile ventilators are a good alternative to bothe whirlybirds and under-eave inlets.
I have two installed on a tin shed which has no ceiling. Eaves are open, one RSD and three louvre windows. They do keep the shed cooler but suck in airborne dirt, etc from nearby trees which covers everything inside the shed with a film of rime. Not good if you’re storing anything valuable inside the structure.
10:00 why not have some whirlybirds extracting and other units so allow air in... even force air in. There are designs out there
The cold air doesn't push the hot air up, the hot air rising creates a vacuum and sucks the cooler air up.
What's the reccomendation to get around asbestos eaves? Replace or can you put Eeave somewhere else
It is way easier to leave asbestos alone and install alternative inlets like the roof tile ventilators.
questions for the presenter; what air change per hour (ACH) do passive whirly birds provide? How many ACH do tiled and sarked roofs have without? How many ACH are required to reduce the temperature?
As a guide, for energy ratings a tiled roof is considered to have 11.4 ACH, and a sarked tile roof or a metal roof is 4.2 ACH. A whirly bird is said to add only 1 ACH per 200m2.
There certainly is a place for them, especially to reduce condensation forming in a roof space (which is the intent of the NCC requirements and AS3999), but cooling is not effective. You want an powered roof ventilator for cooling.
Hi Andrew,
Great questions.
And I am not technically qualified to answer these questions.
However, Table 10.8.3 (NCC) provides guidelines to minimum openings depending on the pitch of the roof - and the length of the roof.
ACH has always confused me (due to my lack of knowledge). And I also think that the writers of the NCC have no idea of EXACTLY the amount of ACH that is needed to prevent the level of condensation that is UNSATISFACTORY.
That is why they just give guidelines on opening sizes and not ACH when it comes to condensation management.
And since condensation management has no relationship to cooling the attic (but the two are surely related) - we must accept that the NCC does not care about cooling the attic at all...
Jack
You're assuming that all roofs are airtight. My roof is definitely not airtight, you can even see sunlight poking through in some places, likely due to the 20mm gap you spoke of later.
Great video
I had a slab on the ground house and created louvre pivot windows in the gables. I could open the louvres from inside the house with a cord. This allowed the entire roof space to change air mass very quickly.... not all Australians are as dumb as you infer..... 😄😃😀🇦🇺
Yeah, those kind of louvres are perfect for Queensland weather. high ceilings with easy accessible lever windows; every house needs one. You should be working for Department of housing or whoever it is that makes up all those housing rules! I swear whoever has been doing it for the past 50 years has been totally inadequate.
How many eaves vents per whirlybird do you recommend?
Thanks for this video.
I have a very old house with a corrugated iron roof in Tasmania. We don't have a moisture problem, but I was going to have whirlybirds installed to remove heat. We also don't have eaves of any substance. What would you suggest for a lower level vent in such a roof? Would a whirlybird installed low on the roof work for the intake in conjunction with one installed high for the outflow? Or some form of other vent that is weatherproof?
Hi, you could consider a gable vent.
That device should be an electrica generator as well, when it spins should charge the house power bank together
You should do this presentation to ABCB . They may learn something😂
Solar panels make a massive difference to the absorption of heat, of the section of roof that they cover.
They work well have 2 in my roof , noticeably cooler in the summertime .
They generally don't work well enough to justify their purchase & installation cost.
Typically a disaster during the winter because they suck the warm air out of the condutioned space inside the house.
Much better investment to cover the roof in solar panels, Or have a pale coloured roof, or shade parts of the roof with trees.
Furthermore, they tend to shade solar panels if they are installed as well.
If you had a whirly bird installed properly with vent. Wont it make your house harder/more expensive to heat in winter?
This where the misunderstanding arises.
The NCC does not care whether the whirlybird works or not in the energy efficiency of the house.
This is because it knows that roof cavity ventilation does very little in keeping the house warm or cool. It demands insulation batts on ceilings to do this job.
As long as you have good ceiling insulation, the heating requirements of the house in winter is not impacted by the roof ventilation.
A vent with a cowl will work better that a whirly bird (with a inlet vent too of course).
We never stopped using them in Adelaide, still use them today
And QLD .
Where are you getting the cool air from?
@@MatthewBayard Eave vents .
@stewatparkpark2933 so in winter you are bringing in cold air to cool your room and insulation? 🤢
@@MatthewBayard There is no winter in Queensland .
Interesting.
Wondering if this is actually tested? It could be not good if all just theory of it's not working but turn out to be working by not testing it
If the structure is on fire, these things make it spread super fast, then they eventually spin so fast they can actually separate from the roof. They’re great when the place is not on fire.
I find most things work better when not on fire.....😄😃😀🇦🇺
@ Clearly. 😂. My point being that while they’re great when everything is ok, if there’s a fire you can almost certainly kiss the entire structure goodbye. Without them, fires spread far less quickly and there is a chance of containing damage to one area. (I’m a former firefighter btw so I am not talking out of my blowhole 👍).
So wild to hear Australia and limited supply of land in the same sentence haha. But I guess it's true in some instances.
Compared to what?
Hot air expands - it takes up more volume than cold. And then it goes out the vent. You do NOT need an air intake for these to work. It can help, but that is not how physics works. The heated and expanded air remaining within the roof cavity has less mass, density and conductivity - less thermal energy - less ability to make the house hot. I am trying to explain in layman's terms. Alternatively, just look at all the whirlybird installations that WORK WITHOUT INLET VENTS. Measure the difference. You can do that easily by stopping the birds spinning for a day.
Those vents in the eve should be part of building a house in the first place.
It seems my 100yo vented lattice gables are not so bad after all!?
The problem with Whirlybirds is the create negative draw and can draw the air-conditioned air from your home working your air conditioning overtime. Making incredibly inefficient..
Only if you have air conditioning, which I don’t. My 1972 brick veneer, concrete tile roof vents itself with my three whirlybirds.
I put in solar powered roof exhaust system , it was so much better than the whirlybirds
I'm in a 100+ year old house. The roof is poorly sealed. I think a whirly might work 😂
Whirly birds need to turn over the roof space volume 3 times in 10 minutes to make a small cooling effect. They can't do 10% of that. They do turn a bit of air to reduce mould but are a "cooling" scam.
Passive whirlybirds dont replace air fast enough (assuming adequate intake ventilation). Roof design needs to progress past these outdated ideas and adopt ventilation above the membrane and below the roofing material, as is common to Passive Houses.
That would be for a roof with silver sarking which is mot permeabke and mot a vapour permeable membrane.
Yhis is because the conensayion gorm on the underside of yhe silversatking unlike a vapour permeable membeane where irs on th e bottom of yge tole which then goes into the gutter when it falls on the membrane.
The heat in the toof cavity is radiant heat you cant ventilate radiant heat. Best yo go outside in the evening a spray water on your roofing material to remove the heat energy.
This is a very complicated - yet insightful answer.
The confusion lies in what we are trying to achieve by ventilating the roof cavity.
The National Construction Code on roof cavity ventilation is only concerned with removing moisture from the cavity. NOT HEAT. The code stipulates other means (insulation) to make the house heat efficient.
Traditionally (before the NCC ventilation requirements), home owners just wanted to make the house heat efficient - and were sold on the myth that whirlybirds were the answer.
Moving forward into the future, we must look at these two issues separately.
1) How to make the house more energy efficient and livable?
2) How to reduce the likelihood of mould growth in the house - caused by lack of adequate ventilation?
Homeowners have been more concerned about heat efficiency because they can feel temperature differences easily. They are less likely to feel the presence of mould and lack of ventilation.
We think the updated National Construction Code is trying to tackle the issues that most homeowners are not aware of...
@@roofingportal I should not type on my phone without glasses on. Best way to keep heat out of a roof is to have a white roof (or roof which higher solar reluctance) and low solar absorbance (less heat absorbed and radiated later). The insulation above your ceiling plaster is the means of resisting heat transfer from one side to another. This layer needs to be continuous and thick wihout gaps. The alternative to this is to have a conditioned attic which means all the insulation is immediately adjacent to the roof material.
The approach to manage moisture below the ceiling is to use a heat recovery ventilation (HRV) system - there are ones that are centralized and not centralized. These are made by Laros and STIEBEL ELTRON's. These are required for homes with ACH (airchanges per hour of less than 5 - not common in Australia).
Really old houses in Australia have slits and vents on the walls of plasterboard. These were installed to allow fireplace and oil burners that ran inside your home to not kill you from carbon monoxide.
The simple reality is that most home owners, builders, and trades do not know much about the building science today, or why homes were built they way they were in the past.
The Energy Smart Housing Manual produced by Sustainability Victoria is a really good guide for homeowners to understand and make sensible changes to their homes (or when buying new ones). In addition you should also source the The YourHome website of the Australian government.
I found that whirlybirds don't work when I built a new home 12 years ago. Thanks for this video