Do These Roof Exhaust Fans Let In The Rain?

[chiang mai]

The vented ridge that I've seen are different from the ones in the video.

[IMHO]

Great, for everyone else, the product is made by CPAC Monier and is the Trachang brand, as said, Home Mart is the stockist..

And if I was going to use that product I would simply cement it into place, just like a normal ridge tile but obviously leaving the air gaps open.

would you think the rain would likely blow under these tiles during a windy storm Chiang Mai? the guy in Home mart told us we should buy the rubber seal too to go with the tiles, that had air holes already punched through

it was quite hard to judge from the display tiles in the shop, if the rubber would be necessary or not. i guess without the rubber, a better airflow would be achieved, but if the rain leaked in sometimes, i would be in for the chop from the Mrs

Perhaps the sales rep was showing you the "Dry Tech" system?

We now use this exclusively - no more using cement on ridges, and no more problems with cement cracks and leaks.

yes, that is teh exact system the sales rep was showing us IMHO

it seems quite expensive at 1450 B for 3 meters. is there a cheaper alternative system that you know about mate?

Yes, there is. C-CO brand Dry Tech (same product name) is also made by the same company (SCG) but does not have the ventilated center strip in the butyl rubber, and is about half the price.

We are building to a price, but trying to retain quality, so we only use the non-ventilated C-CO product on runs that don't really require any ventilation (e.g. the short hip run from a gable downwards on a Dutch hip section) - for long hip runs and ridges, we only use the Tra Chang version.

[IMHO]

The vented ridge that I've seen are different from the ones in the video.

You are talking about an actual ridge tile that's vented though right? i.e. not the waterproofing process

[chiang mai]

The vented ridge that I've seen are different from the ones in the video.

You are talking about an actual ridge tile that's vented though right? i.e. not the waterproofing process

Sorry yes, my error, I refer to a vented ridge tile only. Imagine a side view of a ridge tile where at the bottom of the tile, the centre four fifths are recessed by about half/three quarters of an inch or so, it essentially leaves the tile standing on four feet, two at each ends.

[IMHO]

The vented ridge that I've seen are different from the ones in the video.

You are talking about an actual ridge tile that's vented though right? i.e. not the waterproofing process

Sorry yes, my error, I refer to a vented ridge tile only. Imagine a side view of a ridge tile where at the bottom of the tile, the centre four fifths are recessed by about half/three quarters of an inch or so, it essentially leaves the tile standing on four feet, two at each ends.

Sounds interesting, guess it's time to go visit SCG again

[chiang mai]

I'll try to get a picture today and post it, but first, let me do a brain dump on this subject:

There's loads of really neat roof venting products on the Australian and American markets, low profile thermostatically roof fans that are unobtrusive, solar powered and include a fan. Similarly, there are roof vent tiles that are designed for that purpose as there are after market vents that can be used. The problem comes in two areas, the first is the availability of those products in Thailand which appears close to zero, the second is compatibility with roof tile sizes. CPAC appears to be the largest manufacturer of roof tiles here although MAGMA is also very popular. MAGMA makes a purpose designed roof vent tile that is ideal, they stopped making it however because nobody bought it and it cost more than a regular roof tile! MAGMA, CPAC and most Australian roof tiles are different sizes!

I think the answer might be to import or even go fetch a couple of items from say Australia, the other option dare I say it is to copy an existing roof vent (not a whirly bird which is less than useless) and have it fabricated in a machine shop!

[IMHO]

One big question I have, especially seeing as we have "Australian" brands (Monier and V-Con) is, why don't they have any of these overseas products/solutions for convection cooling as we're seeing in some of the posts here?

Either the market is backwards (I find that hard to believe - new building products always sell well here*), or they have all decided that "overseas" methods of convection cooling just isn't a good fit here, or just don't work as well as, or better than, more common Thai concepts such as vented gables, vented soffits, "roof hats" etc.

You can't say it's because the labour force wouldn't understand it - there are plenty of clued up architects, engineers and foremen in the trade.

Either way, it's an interesting discussion - if there is a genuine better way of keeping the roof space cool, I'm all for it

* New materials/techniques are fantastic differentiators/selling points to sell your house over the next developer, and we're not the only developers using them to win sales.

Edited July 7, 2014 by IMHO

[chiang mai]

I cannot begin to count the number of people I have met here who have told me they vent their roof void using vented soffits, nothing else, the rest of the roof is sealed, just vented soffits, "that's where the hot air comes out you see"! When you are faced with that mentality, along with the desire to save 700 baht per roof vent tile times six or eight, it's no wonder the market is lacking. But, there is a serious market opportunity to be had here for anyone with the stamina and the get up and go, currently that void is being filled by the spray on PU foam people at 700 baht a square metre, an expensive solution to an otherwise cheap problem.

Check this out and even watch the short video, it's brilliantly simple and inexpensive, AUD 75 each plus shipping and duty, trouble is, they wont work with CPAC tiles.http://www.universaltileventilators.com.au/

[IMHO]

I cannot begin to count the number of people I have met here who have told me they vent their roof void using vented soffits, nothing else, the rest of the roof is sealed, just vented soffits, "that's where the hot air comes out you see"! When you are faced with that mentality, along with the desire to save 700 baht per roof vent tile times six or eight, it's no wonder the market is lacking. But, there is a serious market opportunity to be had here for anyone with the stamina and the get up and go, currently that void is being filled by the spray on PU foam people at 700 baht a square metre, an expensive solution to an otherwise cheap problem.

Check this out and even watch the short video, it's brilliantly simple and inexpensive, AUD 75 each plus shipping and duty, trouble is, they wont work with CPAC tiles.http://www.universaltileventilators.com.au/

Not sure what "that" kind of mentality is, but guess I've got some of it

Get into the roof space of a house will only ventilated soffits, and you will notice air moving (close the man hole though to be sure). If you're unlucky there's no wind at the time you're up there, just have a look at the spider webs that were able to be constructed

[chiang mai]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

[Tywais]

These are two of our buildings with different venting methods. The 3rd building is two stories with the middle completely open and offices surrounding the center and 5 vents but my camera couldn't get a shot of that one due to high contrast. The 1st shot below is the storage shed I mentioned and has 4 vents, two visible in this shot. Obviously can't see it but the vents are spinning now. Both buildings with vents are slopped and the vents mounted on the slopped part.

[IMHO]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

I don't know what to say... except get up in a roof and see for yourself. Not talking about passive ventilation at all, this is active, thanks to the wind.

Oh crap, sorry, you're in Chiangmai! No wind up there unless it's raining.

[chiang mai]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

I don't know what to say... except get up in a roof and see for yourself. Not talking about passive ventilation at all, this is active, thanks to the wind.

Oh crap, sorry, you're in Chiangmai! No wind up there unless it's raining.

I don't want to unnecessarily belabor the point but I also want to be certain that you don't think I'm just making this up:

"How Soffit Vents Work

Soffit vents are intake vents installed in the eaves to draw in cool air from the outside and allow warm air to escape out of the exhaust vents. Soffit vents are never installed without other types of vents installed at a higher location to draw air and moisture out of the attic".

http://www.doityourself.com/stry/how-does-soffit-venting-work

"Function

Outside air enters the attic through the soffit vents, which are installed on the underside of the eaves--the part of the roof that overhangs the sides of the house. Other vents farther up on the roof then allow attic air to escape to the outside".

http://www.ehow.com/facts_6915482_purpose-soffit-vents-houses_.html

[IMHO]

Vented soffits were designed as an air intake and not as a method of venting, the idea being that hot air rises and if allowed to escape near the ridge, cooler air will be drawn into the roof void from below, via the vented soffits.

The idea that hot air will vent from the soffits in an otherwise sealed roof is nonsense, especially since the soffits are often lower than upstairs ceiling height, the hot air from the void therefore permeates the upstairs ceiling and makes the bedrooms hot before the hotter air has any chance of partial escape via the soffits - if only hot air didn't rise, it could be a decent solution.

I don't know what to say... except get up in a roof and see for yourself. Not talking about passive ventilation at all, this is active, thanks to the wind.

Oh crap, sorry, you're in Chiangmai! No wind up there unless it's raining.

I don't want to unnecessarily belabor the point but I also want to be certain that you don't think I'm just making this up:

"How Soffit Vents Work

Soffit vents are intake vents installed in the eaves to draw in cool air from the outside and allow warm air to escape out of the exhaust vents. Soffit vents are never installed without other types of vents installed at a higher location to draw air and moisture out of the attic".

http://www.doityourself.com/stry/how-does-soffit-venting-work

"Function

Outside air enters the attic through the soffit vents, which are installed on the underside of the eaves--the part of the roof that overhangs the sides of the house. Other vents farther up on the roof then allow attic air to escape to the outside".

http://www.ehow.com/facts_6915482_purpose-soffit-vents-houses_.html

Next time you have some wind in CNX, find a house with soffit vents only, and ask if you can take a trip into their ceiling - no amount of theory will then convince you it doesn't work

[chiang mai]

OK, I think we're all done on this point.

[IMHO]

Theory is all well and good - that's how we get new ideas... but all ideas need to be tested in practice before we truly understand what works and what doesn't...

What I see in these types of threads are lots of good intentions by people who've never built a house in this climate (or at all) who are just trying to to make their best effort to get it right, first time (and I suppose for many, last time too). I think that's great, and the kind of thing more intelligent people do.

But to dismiss off-hand the documented, heavily researched and physically tested work of respected manufacturers, and the hands-on knowledge those in the trade that have "been there, done that, do it every day" based on some theoretical research on the internet, especially coming from a source dealing with a completely different climate, seems a bit short sighted to me.

No amount of theory will ever beat testing.

[lopburi3]

In the days of wood frame roofs soffit vents did serve a purpose without higher vent. Hot air expands so indeed it will vent down under pressure.outside the actual house. And it keeps the temp high enough in attic to prevent termites.

[chiang mai]

Theory is all well and good - that's how we get new ideas... but all ideas need to be tested in practice before we truly understand what works and what doesn't...

What I see in these types of threads are lots of good intentions by people who've never built a house in this climate (or at all) who are just trying to to make their best effort to get it right, first time (and I suppose for many, last time too). I think that's great, and the kind of thing more intelligent people do.

But to dismiss off-hand the documented, heavily researched and physically tested work of respected manufacturers, and the hands-on knowledge those in the trade that have "been there, done that, do it every day" based on some theoretical research on the internet, especially coming from a source dealing with a completely different climate, seems a bit short sighted to me.

No amount of theory will ever beat testing.

OK, I'm always happy to learn, can you post supportive evidence from a reasonably reliable source confirming that the physics you describe actually works in practice, in still air? Since Tywais teaches Physics at CMU, feel free to enlist his support.

[IMHO]

Theory is all well and good - that's how we get new ideas... but all ideas need to be tested in practice before we truly understand what works and what doesn't...

What I see in these types of threads are lots of good intentions by people who've never built a house in this climate (or at all) who are just trying to to make their best effort to get it right, first time (and I suppose for many, last time too). I think that's great, and the kind of thing more intelligent people do.

But to dismiss off-hand the documented, heavily researched and physically tested work of respected manufacturers, and the hands-on knowledge those in the trade that have "been there, done that, do it every day" based on some theoretical research on the internet, especially coming from a source dealing with a completely different climate, seems a bit short sighted to me.

No amount of theory will ever beat testing.

OK, I'm always happy to learn, can you post supportive evidence from a reasonably reliable source confirming that the physics you describe actually works in practice, in still air? Since Tywais teaches Physics at CMU, feel free to enlist his support.

When did I ever say still air?

Hint: never

It was you that started saying that soffit vents were one part of a convection cooling system (which indeed could be the case). All i said is that they still work all by themselves when wind is present.

Edited July 7, 2014 by IMHO

[chiang mai]

Theory is all well and good - that's how we get new ideas... but all ideas need to be tested in practice before we truly understand what works and what doesn't...

What I see in these types of threads are lots of good intentions by people who've never built a house in this climate (or at all) who are just trying to to make their best effort to get it right, first time (and I suppose for many, last time too). I think that's great, and the kind of thing more intelligent people do.

But to dismiss off-hand the documented, heavily researched and physically tested work of respected manufacturers, and the hands-on knowledge those in the trade that have "been there, done that, do it every day" based on some theoretical research on the internet, especially coming from a source dealing with a completely different climate, seems a bit short sighted to me.

No amount of theory will ever beat testing.

OK, I'm always happy to learn, can you post supportive evidence from a reasonably reliable source confirming that the physics you describe actually works in practice, in still air? Since Tywais teaches Physics at CMU, feel free to enlist his support.

When did I ever say still air?

Hint: never.

I'll give you a break here, provide the proof that it works in a tropical environment instead.

[IMHO]

Theory is all well and good - that's how we get new ideas... but all ideas need to be tested in practice before we truly understand what works and what doesn't...

What I see in these types of threads are lots of good intentions by people who've never built a house in this climate (or at all) who are just trying to to make their best effort to get it right, first time (and I suppose for many, last time too). I think that's great, and the kind of thing more intelligent people do.

But to dismiss off-hand the documented, heavily researched and physically tested work of respected manufacturers, and the hands-on knowledge those in the trade that have "been there, done that, do it every day" based on some theoretical research on the internet, especially coming from a source dealing with a completely different climate, seems a bit short sighted to me.

No amount of theory will ever beat testing.

OK, I'm always happy to learn, can you post supportive evidence from a reasonably reliable source confirming that the physics you describe actually works in practice, in still air? Since Tywais teaches Physics at CMU, feel free to enlist his support.

When did I ever say still air?

Hint: never.

I'll give you a break here, provide the proof that it works in a tropical environment instead.

I do believe that in this type of situation, where you are challenging what I'm saying, the burden of proof actually lies with yourself

I have given you guidance on how to test for yourself, and I like you, so I'll ignore you said that until you've actually conducted a test for yourself, and can share your own findings.

Peace

[chiang mai]

Have a nice day.

[Tywais]

This site gives a pretty good overview of the concept of negative pressure.

http://brooksideroofing.ca/ridgevent.htm

[chiang mai]

The question is whether it could work without the vented ridge?

[IMHO]

OK, I'll succumb to providing internet links, instead of 1st hand experience, just for you guys though

http://oikos.com/esb/30/atticvent.html

"If a roof had only one type of vent device, I would choose soffit vents," he says, "because they work well as inlets and outlets."

Edited July 7, 2014 by IMHO

[Evilbaz]

With one whirlybird roof vent and two "soffit vents in each eave there is sufficient air flow on a still day to suck up an A4 sheet of paper against the soffit vent grill.

i.e air goes in through the soffits and out through any higher vent.

Well, at least in the hot climate of Western Australia.

[chiang mai]

OK, I'll succumb to providing internet links, instead of 1st hand experience, just for you guys though

http://oikos.com/esb/30/atticvent.html

"If a roof had only one type of vent device, I would choose soffit vents," he says, "because they work well as inlets and outlets."

Nice try, but, in the following para the author says:

"Soffit vents should always be installed whenever there are high vents. High vents, on ridges or gables, will pull air out of the attic. Without soffit vents, make-up air would be drawn through the ceiling, which increases heat loss and adds moisture to the attic". And in his diagram he shows the soffit in/out process but it's easy to overlook the teeny weeny arrow at the peak where the ridge vents".

And just to let you know that I haven't been idle, I did pop down the street where a house has soffit vents and no ridge vent. I did as suggested and knocked on the door and asked if I could have a look in the roof void, the owner told me to sod off and set the dog on me!

[IMHO]

OK, I'll succumb to providing internet links, instead of 1st hand experience, just for you guys though

http://oikos.com/esb/30/atticvent.html

"If a roof had only one type of vent device, I would choose soffit vents," he says, "because they work well as inlets and outlets."

Nice try, but, in the following para the author says:

"Soffit vents should always be installed whenever there are high vents. High vents, on ridges or gables, will pull air out of the attic. Without soffit vents, make-up air would be drawn through the ceiling, which increases heat loss and adds moisture to the attic". And in his diagram he shows the soffit in/out process but it's easy to overlook the teeny weeny arrow at the peak where the ridge vents".

And just to let you know that I haven't been idle, I did pop down the street where a house has soffit vents and no ridge vent. I did as suggested and knocked on the door and asked if I could have a look in the roof void, the owner told me to sod off and set the dog on me!

Just to be clear, I have never said that ridge ventilation was in any way ineffective, all I have ever said is that soffit ventilation only still works. You are the one seeking evidence to support that assertion, which is fine with me - I can only try to pass on my experience - up to you what you do with it after that.

Stop imagining I'm arguing against ridge vents, because I'm not. You're acting the same as that poster the other day who imagined I was arguing against foil under battens when I mentioned that foil on top of battens still works, LOL

I'm pretty sure I'm using clear enough English here. If I'm not though, please do let me know.

Anyways, I think your latest question has been answered by Wiliiam Rose (linked above)

The question is whether it could work without the vented ridge?

Edited July 7, 2014 by IMHO

[chiang mai]

To be even more clear:

You are arguing that ventilated soffits alone work, I'm asking you to supply proof because I don't believe they do.

The link you've supplied doesn't provide that proof, it actually supports the opposite that a ridge vent is mandatory.

I never thought for one moment you were arguing against the concept of ridge vents, it's just that you are not providing the evidence needed to support your claim that ventilated soffits alone are fully functional.

When you say the "question has been answered by Wiliiam Rose (linked above)", presumably you refer to the oikos link? That being the case, the link doesn't support your case.

[IMHO]

Sorry, I think I need an adjudicator here.

Either my comprehension of English isn't as good as a I thought, or Mr Chiang Mai is messing with my head.

Anyone?