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Roof ventilation advice in Canberra?

By frg1978 31 July 2015 18

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I am just hoping for some advice from other Canberrans who have some experience with installing any of the various types of roof ventilation in their home. Basically what did you pick and why, what was the cost, and was it successful?

We have a small house in a new subdivision that was built in 2012 that currently has no roof ventilation or cross ventilation downstairs due to a lack of windows. In summer, the house is like an oven and does not cool down until very late into the night, long after the temperature has dropped outside. The ceiling is insulated so we’re not sure if the temperature inside the roof cavity would actually have much impact on the temperature inside the house.

We have done a fair bit of research and there seems to be a lot of conflicting information on whether installing some kind of roof ventilation would even assist with cooling the house, and/or which type of ventilation would work best in these conditions. Most of the reviews online for the various types seem to be from people trying to sell some kind of roof ventilation so any firsthand experience would be much appreciated.

What’s Your opinion?


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Roof ventilation advice in Canberra?
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vintage123 7:37 pm 06 Aug 15

GardeningGirl said :

tim_c said :

You need to try to find where the heat is getting in before you try to reduce it. I’d suggest if you’ve got decent insulation (ie. R4.0 batts or better, not the originally installed patch of fluff here and there) then a whirly vent is probably not likely to make any appreciable difference.
If you’ve got west facing windows or walls, I’d be trying to shade these (with shrubs or awnings).

Try shutting the place up one day when it’s going to be hot, come back in the heat of the day and see if it’s warmer inside or outside. You can also try shutting each of the rooms and finding out which ones heat up more (or if they all heat up equally) – this should help to identify where the heat is getting in.

The lack of cross ventilation is really going to hinder you getting those cool evening breezes through to cool the place down though, so short of installing windows in the opposite walls, there may not be much you can do short of installing air-con or evaporative cooling (usually if there are no windows in one side of the house there’s a reason for it though, like a shared wall).

+1

There’s no easy cheap one size fits all solution. It really does require working out where the heat is getting in and what specific solution or combination of solutions will work for that house.

What’s the story with the windows, how is there a “lack of windows”, are there any big west facing windows?

Are you serious? Just shut the blinds, turn on the reverse cycle ducted aircon and move on with life. Geeez it’s only heating and cooling, not rocket science.

GardeningGirl 6:34 pm 06 Aug 15

tim_c said :

You need to try to find where the heat is getting in before you try to reduce it. I’d suggest if you’ve got decent insulation (ie. R4.0 batts or better, not the originally installed patch of fluff here and there) then a whirly vent is probably not likely to make any appreciable difference.
If you’ve got west facing windows or walls, I’d be trying to shade these (with shrubs or awnings).

Try shutting the place up one day when it’s going to be hot, come back in the heat of the day and see if it’s warmer inside or outside. You can also try shutting each of the rooms and finding out which ones heat up more (or if they all heat up equally) – this should help to identify where the heat is getting in.

The lack of cross ventilation is really going to hinder you getting those cool evening breezes through to cool the place down though, so short of installing windows in the opposite walls, there may not be much you can do short of installing air-con or evaporative cooling (usually if there are no windows in one side of the house there’s a reason for it though, like a shared wall).

+1

There’s no easy cheap one size fits all solution. It really does require working out where the heat is getting in and what specific solution or combination of solutions will work for that house.

What’s the story with the windows, how is there a “lack of windows”, are there any big west facing windows?

tim_c 4:25 pm 06 Aug 15

You need to try to find where the heat is getting in before you try to reduce it. I’d suggest if you’ve got decent insulation (ie. R4.0 batts or better, not the originally installed patch of fluff here and there) then a whirly vent is probably not likely to make any appreciable difference.
If you’ve got west facing windows or walls, I’d be trying to shade these (with shrubs or awnings).

Try shutting the place up one day when it’s going to be hot, come back in the heat of the day and see if it’s warmer inside or outside. You can also try shutting each of the rooms and finding out which ones heat up more (or if they all heat up equally) – this should help to identify where the heat is getting in.

The lack of cross ventilation is really going to hinder you getting those cool evening breezes through to cool the place down though, so short of installing windows in the opposite walls, there may not be much you can do short of installing air-con or evaporative cooling (usually if there are no windows in one side of the house there’s a reason for it though, like a shared wall).

JC 11:18 pm 04 Aug 15

vintage123 said :

JC said :

vintage123 said :

Madam Cholet said :

We have a Ventis system in our roof space. We had it out in about three years ago. Our house is north facing, small, three bedroom. So generally not an ice box in winter or a sweat box in summer. It’s all relative of course and we still need heating (for which we have undertile and a split system if necessary), and cooling for the very odd occasion we give in – likely to be just to cool the living areas when we first come home. Outside of that we rely on opening windows to catch the breeze and wear sock and jumpers to keep warmer rather than rely too early on external sources.

The Ventis helps obviously with ventilation. You can’t rely on it for heating or cooling. The times that it comes into its own is what I would refer to as the shoulder seasons….around April/May when you can capture roof space heat and put it in the house in daytime, and of course in September to do the same again. The biggest benefit is the cool night air you can get pumped in – to bedrooms especially. We find that even on the hottest night it will start using cooler air by about 10/11pm. That’s probably the latest you’d have to wait. After a few days of constant over 40 degrees it is really appreciated.

Our system cost us 5k. Obviously the value is based on what you expect to get from it and why (maybe you have an environmental or even a health reason in addition to just wanting some ventilation), and your actual property. I’d be happy for you to check ours out.

If you do go ahead, be careful about where the thermostat gets place. We had a false start with ours as they out it in an area where it gets naturally warm in winter – therefore the system was not working properly due to the false reading.

I do hope that anyone who was in a mr fluffy house didn’t have one of these systems.

Think you will find it works on a heat exchange basis, so no issues with Mr Fluffy. Besides even without that who would want roof space air recirculated?

Oh JC, if only we all had your optimism bias.

The ventis system referred is the one with the two dollar fan and filter, which apparently pulls air into the box, cleanses it, and then expels it into the house. Now call me cynical, but I wouldn’t bet my life on a single stage simplistic filer to completely remove anything remotely harmful from the roof before forcing it into the house.

Here it is mate, it’s even got a nice little video showing you how wonderful it is.
http://www.ventis.com.au/how-it-works/warm-home/

Why on earth would you pay 5k for something like this? Especially when you read the disclaimer that you still need a seperate heating and cooling system. Come in spinner.

Sorry that’s not what I thought it was, I thought it was the type where air inside air was pumped into a sealed heat exchanger. Seen it on either Grand Designs or one of those US home shows. So with you wouldn’t want one, nor would I want to be the installer in a fluffy house.

vintage123 3:12 pm 03 Aug 15

JC said :

vintage123 said :

Madam Cholet said :

We have a Ventis system in our roof space. We had it out in about three years ago. Our house is north facing, small, three bedroom. So generally not an ice box in winter or a sweat box in summer. It’s all relative of course and we still need heating (for which we have undertile and a split system if necessary), and cooling for the very odd occasion we give in – likely to be just to cool the living areas when we first come home. Outside of that we rely on opening windows to catch the breeze and wear sock and jumpers to keep warmer rather than rely too early on external sources.

The Ventis helps obviously with ventilation. You can’t rely on it for heating or cooling. The times that it comes into its own is what I would refer to as the shoulder seasons….around April/May when you can capture roof space heat and put it in the house in daytime, and of course in September to do the same again. The biggest benefit is the cool night air you can get pumped in – to bedrooms especially. We find that even on the hottest night it will start using cooler air by about 10/11pm. That’s probably the latest you’d have to wait. After a few days of constant over 40 degrees it is really appreciated.

Our system cost us 5k. Obviously the value is based on what you expect to get from it and why (maybe you have an environmental or even a health reason in addition to just wanting some ventilation), and your actual property. I’d be happy for you to check ours out.

If you do go ahead, be careful about where the thermostat gets place. We had a false start with ours as they out it in an area where it gets naturally warm in winter – therefore the system was not working properly due to the false reading.

I do hope that anyone who was in a mr fluffy house didn’t have one of these systems.

Think you will find it works on a heat exchange basis, so no issues with Mr Fluffy. Besides even without that who would want roof space air recirculated?

Oh JC, if only we all had your optimism bias.

The ventis system referred is the one with the two dollar fan and filter, which apparently pulls air into the box, cleanses it, and then expels it into the house. Now call me cynical, but I wouldn’t bet my life on a single stage simplistic filer to completely remove anything remotely harmful from the roof before forcing it into the house.

Here it is mate, it’s even got a nice little video showing you how wonderful it is.
http://www.ventis.com.au/how-it-works/warm-home/

Why on earth would you pay 5k for something like this? Especially when you read the disclaimer that you still need a seperate heating and cooling system. Come in spinner.

JC 2:29 pm 03 Aug 15

vintage123 said :

Madam Cholet said :

We have a Ventis system in our roof space. We had it out in about three years ago. Our house is north facing, small, three bedroom. So generally not an ice box in winter or a sweat box in summer. It’s all relative of course and we still need heating (for which we have undertile and a split system if necessary), and cooling for the very odd occasion we give in – likely to be just to cool the living areas when we first come home. Outside of that we rely on opening windows to catch the breeze and wear sock and jumpers to keep warmer rather than rely too early on external sources.

The Ventis helps obviously with ventilation. You can’t rely on it for heating or cooling. The times that it comes into its own is what I would refer to as the shoulder seasons….around April/May when you can capture roof space heat and put it in the house in daytime, and of course in September to do the same again. The biggest benefit is the cool night air you can get pumped in – to bedrooms especially. We find that even on the hottest night it will start using cooler air by about 10/11pm. That’s probably the latest you’d have to wait. After a few days of constant over 40 degrees it is really appreciated.

Our system cost us 5k. Obviously the value is based on what you expect to get from it and why (maybe you have an environmental or even a health reason in addition to just wanting some ventilation), and your actual property. I’d be happy for you to check ours out.

If you do go ahead, be careful about where the thermostat gets place. We had a false start with ours as they out it in an area where it gets naturally warm in winter – therefore the system was not working properly due to the false reading.

I do hope that anyone who was in a mr fluffy house didn’t have one of these systems.

Think you will find it works on a heat exchange basis, so no issues with Mr Fluffy. Besides even without that who would want roof space air recirculated?

vintage123 1:52 pm 03 Aug 15

Madam Cholet said :

We have a Ventis system in our roof space. We had it out in about three years ago. Our house is north facing, small, three bedroom. So generally not an ice box in winter or a sweat box in summer. It’s all relative of course and we still need heating (for which we have undertile and a split system if necessary), and cooling for the very odd occasion we give in – likely to be just to cool the living areas when we first come home. Outside of that we rely on opening windows to catch the breeze and wear sock and jumpers to keep warmer rather than rely too early on external sources.

The Ventis helps obviously with ventilation. You can’t rely on it for heating or cooling. The times that it comes into its own is what I would refer to as the shoulder seasons….around April/May when you can capture roof space heat and put it in the house in daytime, and of course in September to do the same again. The biggest benefit is the cool night air you can get pumped in – to bedrooms especially. We find that even on the hottest night it will start using cooler air by about 10/11pm. That’s probably the latest you’d have to wait. After a few days of constant over 40 degrees it is really appreciated.

Our system cost us 5k. Obviously the value is based on what you expect to get from it and why (maybe you have an environmental or even a health reason in addition to just wanting some ventilation), and your actual property. I’d be happy for you to check ours out.

If you do go ahead, be careful about where the thermostat gets place. We had a false start with ours as they out it in an area where it gets naturally warm in winter – therefore the system was not working properly due to the false reading.

I do hope that anyone who was in a mr fluffy house didn’t have one of these systems.

vintage123 1:01 pm 03 Aug 15

Madam Cholet said :

vintage123 said :

Ok here we go.

Roof ventilation is just that. Its ventilating the roof space. Moving air through the roof. Best way is to draw air from vents in the eaves into the roof and then expel it out of a vent on the roof. This can be a whirlybird or powered vent etc. Roof ventilation moves air to prevent moisture and mould. It can reduce air temperature in the roof cavity but not to the degree that you will reduce the temperature in the house.

Ok. So we have ventilated the roof, next, cooling the house.

Ducted aircon. 9k purchase plus 7k install. 16k and you now have a cool house.

Anyone can put a whirlybird on their roof.

The purpose of the ventilation systems the OP is asking about is to provide ventilation and clean air to the house using ducts, such as you would install with an AC system. It allows the system to push warm or cool air from the roof space into the house. If you stand under the ducts that we have in our house you can indeed feel the warm or cool air.

You are correct in saying that they are beneficial in reducing mould and moisture and also that it is not a heating or cooling system as such, but that can be an added benefit. The reality is it’s dependent on the property as to what you are going to achieve.

I read the OP as asking about two seperate things. Firstly how to ventilate the roof cavity and secondly how to cool the house. That’s why I gave him a specific answer to the two questions. Eave vents and roof vent for ventilation. That will cost hume about $200 and reverse cycle inverter ducted aircon (ceiling or floor vent) to cool and heat the home. For heating and cooling you just can match a multi zoned ducted inverter reverse cycle air con.

What I did not think the OP was asking for, was for a magical cheap solution of removing the hot air in the roof and magically having a cool house as a result. But I may have been wrong. If they expect a $200 whirlybird to do this then they are kidding themselves.

Anyway if the house has floor access best way is to duct from the floor for both heating and cooling.

As for anyone being able to put a whirlybird in the roof, yep, you are correct. Yet how many of this people fit the eave vents……..mmmm

vintage123 12:51 pm 03 Aug 15

Maya123 said :

vintage123 said :

Ok here we go.

Roof ventilation is just that. Its ventilating the roof space. Moving air through the roof. Best way is to draw air from vents in the eaves into the roof and then expel it out of a vent on the roof. This can be a whirlybird or powered vent etc. Roof ventilation moves air to prevent moisture and mould. It can reduce air temperature in the roof cavity but not to the degree that you will reduce the temperature in the house.

Ok. So we have ventilated the roof, next, cooling the house.

Ducted aircon. 9k purchase plus 7k install. 16k and you now have a cool house.

I gave the examples of my two solar/thermal chimneys. They ventilate the house, not the roof space. I don’t even have roof space. The solar/thermal chimneys are VERY effective, if used in combination, at night, with open windows to draw the air through. This method is very old and have been in use for hundreds of years, possibly thousands.

Yes absolutely. When I submitted my post, which was a general explanation, your post wasn’t active as yet. There has been a bit of a delay this weekend with posts appearing. Your method sounds good.

Madam Cholet 11:40 am 03 Aug 15

vintage123 said :

Ok here we go.

Roof ventilation is just that. Its ventilating the roof space. Moving air through the roof. Best way is to draw air from vents in the eaves into the roof and then expel it out of a vent on the roof. This can be a whirlybird or powered vent etc. Roof ventilation moves air to prevent moisture and mould. It can reduce air temperature in the roof cavity but not to the degree that you will reduce the temperature in the house.

Ok. So we have ventilated the roof, next, cooling the house.

Ducted aircon. 9k purchase plus 7k install. 16k and you now have a cool house.

Anyone can put a whirlybird on their roof.

The purpose of the ventilation systems the OP is asking about is to provide ventilation and clean air to the house using ducts, such as you would install with an AC system. It allows the system to push warm or cool air from the roof space into the house. If you stand under the ducts that we have in our house you can indeed feel the warm or cool air.

You are correct in saying that they are beneficial in reducing mould and moisture and also that it is not a heating or cooling system as such, but that can be an added benefit. The reality is it’s dependent on the property as to what you are going to achieve.

Maya123 10:51 am 03 Aug 15

vintage123 said :

Ok here we go.

Roof ventilation is just that. Its ventilating the roof space. Moving air through the roof. Best way is to draw air from vents in the eaves into the roof and then expel it out of a vent on the roof. This can be a whirlybird or powered vent etc. Roof ventilation moves air to prevent moisture and mould. It can reduce air temperature in the roof cavity but not to the degree that you will reduce the temperature in the house.

Ok. So we have ventilated the roof, next, cooling the house.

Ducted aircon. 9k purchase plus 7k install. 16k and you now have a cool house.

I gave the examples of my two solar/thermal chimneys. They ventilate the house, not the roof space. I don’t even have roof space. The solar/thermal chimneys are VERY effective, if used in combination, at night, with open windows to draw the air through. This method is very old and have been in use for hundreds of years, possibly thousands.

Madam Cholet 10:40 am 01 Aug 15

We have a Ventis system in our roof space. We had it out in about three years ago. Our house is north facing, small, three bedroom. So generally not an ice box in winter or a sweat box in summer. It’s all relative of course and we still need heating (for which we have undertile and a split system if necessary), and cooling for the very odd occasion we give in – likely to be just to cool the living areas when we first come home. Outside of that we rely on opening windows to catch the breeze and wear sock and jumpers to keep warmer rather than rely too early on external sources.

The Ventis helps obviously with ventilation. You can’t rely on it for heating or cooling. The times that it comes into its own is what I would refer to as the shoulder seasons….around April/May when you can capture roof space heat and put it in the house in daytime, and of course in September to do the same again. The biggest benefit is the cool night air you can get pumped in – to bedrooms especially. We find that even on the hottest night it will start using cooler air by about 10/11pm. That’s probably the latest you’d have to wait. After a few days of constant over 40 degrees it is really appreciated.

Our system cost us 5k. Obviously the value is based on what you expect to get from it and why (maybe you have an environmental or even a health reason in addition to just wanting some ventilation), and your actual property. I’d be happy for you to check ours out.

If you do go ahead, be careful about where the thermostat gets place. We had a false start with ours as they out it in an area where it gets naturally warm in winter – therefore the system was not working properly due to the false reading.

vintage123 9:16 pm 31 Jul 15

Ok here we go.

Roof ventilation is just that. Its ventilating the roof space. Moving air through the roof. Best way is to draw air from vents in the eaves into the roof and then expel it out of a vent on the roof. This can be a whirlybird or powered vent etc. Roof ventilation moves air to prevent moisture and mould. It can reduce air temperature in the roof cavity but not to the degree that you will reduce the temperature in the house.

Ok. So we have ventilated the roof, next, cooling the house.

Ducted aircon. 9k purchase plus 7k install. 16k and you now have a cool house.

Hosinator 3:41 pm 31 Jul 15

In short, your house is probably poorly constructed, even if it is new and as Maya stated you’ve probably got dark roof tiles and eaves that are either too short or nonexistent. If you have brick veneer walls this acts as a thermal mass and will heat up and hold the heat for days on end and transfer it into the house.

I wouldn’t bother with the whirlybirds; you would need about 40 of them just to keep up with extracting the heat out of the roof, let alone make a difference.

Your best bet is external awnings over windows; internal curtains are ok but cannot beat an external awning. Basically you want to keep the sun from touching the glass in summer. If you can plant deciduous trees (although you’re probably on a block barely the size of a postage stamp) that will shade the same windows or any northern/western walls/windows in summer.

darkmilk 3:02 pm 31 Jul 15

arescarti42 said :

… Evaporative cooling is certainly something to consider as well. I had it in a previous house and found when run simply as a fan, it was extremely effective at flushing all of the hot air out of the house of an evening when the outdoor temperature was much lower.

Agree about evaporative cooling, in Canberra most evenings the air is cool enough by bedtime to just run it on fan only. We do that, then after running the fan on low all night it’s cooled the thermal mass so closing up in the morning keeps the temperature tolerable all day most days, and this is in a 1950’s house with only some insulation added. I can see how vents/chimneys could do something similar with no power draw.

I reckon if you were looking for a cheap solution in a house with no cross-ventilation then get some of the ducted ceiling exhaust fans but install them backwards to blow cool air from under the eaves or the south side of the house into bedrooms. They have flap valves so in winter they’d automatically stay closed.

I’ve always wondered what the roof vents do in winter in Canberra, if they actually cool the house you’re trying to heat?

arescarti42 11:29 am 31 Jul 15

It’s a little hard to say what the best solution would be without knowing the specifics of your house.

My first port of call would be keeping direct sunlight out of the house during summer. A square meter of sunlight puts out about 1000 watts of heat, so having one or two unshaded windows can be the equivalent of running a couple of electric heaters on full blast all day.

Evaporative cooling is certainly something to consider as well. I had it in a previous house and found when run simply as a fan, it was extremely effective at flushing all of the hot air out of the house of an evening when the outdoor temperature was much lower.

Maya123 10:29 am 31 Jul 15

I have two solar/thermal chimneys. They are brilliant. I keep them closed during the hot days (and winter) to stop hot air coming in, but open them up at night, along with windows. I have a couple of windows and a doors with security screens I feel safe to leave open, to allow flow through ventilation.
Hopefully the insulation you have in the ceiling is enough and you don’t have a dark roof, which would make the house hotter. They should be outlawed. I got the palest roof that I could when I had my house built. The normal routines to keep the house cool in the hottest weather apply too. Close all windows and doors during the daytime and close most curtains (curtains with insulated backing and pelmets) or insulating blinds, such as honeycomb. Only leave enough blinds/curtains open on the shady side of the house, so you don’t need to turn on a light. All others closed. Open windows and blinds at night to let in cool air, once the outside temperature is lower than the inside temperature of course. You might know all this and be practising this, but it’s amazing how many people don’t, opening windows on hot days to let in the even hotter outside air, because they are “hot”. Well, they certainly will be, if 40 degree air comes in to replace 30 degree air inside.
https://en.wikipedia.org/wiki/Solar_chimney

https://www.google.com.au/search?q=thermal+chimney&source=lnms&tbm=isch&sa=X&ved=0CAcQ_AUoAWoVChMIytSQ-IuExwIVpxOmCh08RARs&biw=1598&bih=968#imgrc=eX4RwOoftz00nM%3A

Rollersk8r 9:51 am 31 Jul 15

Our house faces West – and is absolutely blasted by the afternoon summer sun. It got so hot that chocolate used to melt in the pantry.

We installed evap cooling, awnings and a whirlybird thingo on the roof. Personally I think the awnings made a huge difference. Very hard to know if the roof spinner did/does anything. Others have told me my roof spinner is incorrectly installed – that it needs a vent in the eaves to draw cool air in. I don’t know if this is true or not – but find it hard to believe seeing as it was professionally installed.

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