Roofing/Ventilation Works

[chiang mai]

I'm considering very strongly buying a house that I've found, it suits in every respect except one, read on:

As with so many houses in Thailand, the builders didn't instal air vents in the roof so the hot air builds up and the upper floor of the house is several degrees hotter than the downstairs - the current owners have tried to mitigate this problem by planting tall trees to shade the property and using film on the windows, however the basic problem of no air flow in the roof void remains the major problem - it is not an insurmountable problem however and it doesn't really detract from the desirability of the property.

Has anyone come across useful products and/or a reliable company that can solve this problem? There are no gables on the house so there's no where to instal a vertical grill to vent the roof, the only two remaining options I can think of are:

(1) ridge tile vents which involves a partial re-roofing, or, (2) installation of a roof vent/turbine on the backside of the house, not attractive but very effective and could potentially be hidden to some degree.

Is there a third or fourth option?

The soffits are all solid so there's no cooler air intake under the eves, the roof is CPAC on steel and about seven years old.

Attic insulation either on the undersides of the roof or on the floor of the attic is probably not that helpful since it does nothing to solve the venting problem.

Thanks in advance for any relevant and useful ideas, tips on a local constructor to do whatever the work turns out to be, will be most gratefully received.

[ClutchClark]

Attic insulation between the roof rafters (underside of roof) is not going to help you.

Attic insulation at the ceiling joist level (floor of the attic) is beneficial in many applications.

A power exhaust vent in the attic space moves a large volume of air rapidly but it requires an intake vent on the opposite side of the space to be effective. Ofcourse, you would want both vents to be near the upper portion of the airspace.

Roof vents along the ridge are passive in nature but as you mentioned, they also require an intake and you indicate your soffits are "solid" so they would need to be modified/replaced with a breathable design.

Its difficult to provide a solid answer without seeing the actual existing structure and roofline and any penetrations will have to be placed well to mitigate risk of leaks.

Enjoy the new home. ;-)

[chiang mai]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

[kaptainrob]

Whirlybird type [rotating] roof vents are very efficient and may be installed below ridge-line so not visible from road. Building supplies on HD/CM Rd just south of airport and on the western side had a stack of them outside yesterday.

[noise]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

I would say the highest since hot air rises.

THIS MIGHT BE AN OPTION: I am thinking of installing a ceiling exhaust fan in the "trap door" attic access as the easiest and least invasive attempt to alleviate that heat build up. THEORY: It would pull hot air out of the 2nd floor while sucking in cool air from outside through the windows. And this air being pushed into the attic would push air out the soffits which, in my house, are all open.

While it may or may not create enough circulation to pull the hotest air from the roof peak(s), my assumption is it has to make a noticeable difference.

If it fails miserably, all I have to do is take in down and put up a new square piece of plywood.

[evenstevens]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

[chiang mai]

The theory sounds good, but heat rises hence trying to create positive pressure inside the roof void is not likely to force the hot air downwards and out through the soffits, dunno, this sounds like one for Herr Naam. But as you say, if it fails then reverting to the status quo is cheap and easy so you're probably right to give it a shot.

Also, am wondering if anyone has tried spray on foam to the underside of the roof, the theory being that it prevents/reduces heat transfer from the CPAC into the roof void. That's another one where the theory sounds good but at 500 baht a square metre it needs to be proven before actually doing it.

[chiang mai]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

[AnotherOneAmerican]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

I would say the highest since hot air rises.

THIS MIGHT BE AN OPTION: I am thinking of installing a ceiling exhaust fan in the "trap door" attic access as the easiest and least invasive attempt to alleviate that heat build up. THEORY: It would pull hot air out of the 2nd floor while sucking in cool air from outside through the windows. And this air being pushed into the attic would push air out the soffits which, in my house, are all open.

While it may or may not create enough circulation to pull the hotest air from the roof peak(s), my assumption is it has to make a noticeable difference.

If it fails miserably, all I have to do is take in down and put up a new square piece of plywood.

Let's hope radon gas isn't a problem in Thailand (looked for reports, 20% of tested modern houses (not wood) have elevated radon levels).

Really you should ensure clean air is brought in from a clean and safe source, giving the living area of the house a slightly positive pressure..

Edited June 13, 2014 by AnotherOneAmerican

[evenstevens]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

[Naam]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

you do need a low intake with enough open area for sufficient airflow under the eaves. a "whirly bird" with an additional electric exhaust fan (30-50 watts) on a timer (timer easily ascessible and switchable) will cost you including installation 6-8k Baht.

eaves intake cost no idea.

use search function "attic ventilation" and you will find dozens of postings.

[Naam]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

without attic ventilation mostly money wasted!

[chiang mai]

Thanks Naam, most helpful.

[ClutchClark]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

When using passive ridge vents then the draft is created by convection--hot air rising through the ridge vent and drawing cooler air in at the eave.

With a power vent, the draft is created by the power vent and it draws air through the intake vent. The hottest air is at the peak and upper portion of attic space and that is what you want to remove. If you place the intake vent low then you create a dead air space at the side of the attic above the intake vent--hot air remains in place.

If you place both power and intake vents high then the lower air in the attic space will eventually become the warmest remaining air and will rise to the peak.

Clear as mud ? ;-)

[chiang mai]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

When using passive ridge vents then the draft is created by convection--hot air rising through the ridge vent and drawing cooler air in at the eave.

With a power vent, the draft is created by the power vent and it draws air through the intake vent. The hottest air is at the peak and upper portion of attic space and that is what you want to remove. If you place the intake vent low then you create a dead air space at the side of the attic above the intake vent--hot air remains in place.

If you place both power and intake vents high then the lower air in the attic space will eventually become the warmest remaining air and will rise to the peak.

Clear as mud ? ;-)

Quite logical, now that you've described it, many thanks, again!

[Naam]

The theory sounds good, but heat rises hence trying to create positive pressure inside the roof void is not likely to force the hot air downwards and out through the soffits, dunno, this sounds like one for Herr Naam. But as you say, if it fails then reverting to the status quo is cheap and easy so you're probably right to give it a shot.

Also, am wondering if anyone has tried spray on foam to the underside of the roof, the theory being that it prevents/reduces heat transfer from the CPAC into the roof void. That's another one where the theory sounds good but at 500 baht a square metre it needs to be proven before actually doing it.

spraying expensive foam under the roof tiles is only done by thermo-physic ignorants (companies which advise and customers who pay money for nothing and no chicks free). the same applies to aluminium foil under the roof tiles dipped in a mixture of snake oil and holy water.

shade trees: the OP talked about a double story home. to shade his roof i suggest he gets seeds of Australian Mammoth trees or American Sequoias and his roof will be shaded in not more than two or perhaps three rebirths (assuming he is a Buddhist or a Hindu).

the foam only slows down the built-up of heat in the attic. foam insulation should be only used on ceilings and is in combination with a ventilated attic the optimal insulation solution.

[evenstevens]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

without attic ventilation mostly money wasted!

^^^^^^^^^^^^^^^uhhh????and stainless steel stacks are not a attic ventilation, are u for real

[Lancelot]

I had a house in the US with soffit vents for air to enter and a ridge vent along the entire peak of the roof, for the hot air to escape. Worked well and reduced the attic temperatures, which in turn reduced the load on the air conditioner

The old timers knew about passive air ventilation in traditional Thai houses

[Naam]

If you place both power and intake vents high then the lower air in the attic space will eventually become the warmest remaining air and will rise to the peak.

please dear Sir, i beg of you! stop torturing me

[eyecatcher]

We are so used to building roofs in the west with roof vent tiles,ridge vents and soffit vents and crossflow is a given because its always windy.

Here these type of vents are not as effective because there generally is no airflow.

So as others have suggested,a mechanical vent is your number one option.

I haven't seen vent tiles on roofs,though I bet they sell them but you can create some soffit ventilation by hole cutting and inserting a plastic vent disc every 600mm.

Combine with ridge vent tiles and your mechanical whirlygig and that's as good as you will get.

You could really go to town and turn your roof into a Thai style roof with a super ridge vent like mine

[Naam]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

without attic ventilation mostly money wasted!

^^^^^^^^^^^^^^^uhhh????and stainless steel stacks are not a attic ventilation, are u for real

what part of "without attic ventilation money is wasted" is it you don't understand? did i somewhere mention stainless steel stacks?

[Naam]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

without attic ventilation mostly money wasted!

^^^^^^^^^^^^^^^uhhh????and stainless steel stacks are not a attic ventilation, are u for real

what part of "without attic ventilation money is wasted" is it you don't understand? did i mention stainless steel stacks in the above post?

but yes, they don't work if intake and outlet are placed as you suggested in your other post (the warmest air from down...).

for the record: thermo-physics is a science which quite often defies logical thinking. and that no matter how logical it might appear for a layman.

[chiang mai]

Let me summarize, for my benefit:

Ventilation is key, power ventilation is optimal here.

Closed soffits for air intake are not a major problem since they can be drilled/vented.

Air intake (where ever it might be located) must exceed exhaust capacity.

Sprayed foam is probably not worthwhile nor good value for money.

Attic rafter insulation has benefits.

Under roof panels/insulation are not optimal.

Whirly birds (powered and thermostated) are inexpensive, lower profile, solar powered, US style vents are optimal - anybody seen them for sale here?

All those things being true, it's now a case of trying to find the exhaust unit and a contractor.

Thanks to all, it's been useful and I've got my way forward on this..

[ClutchClark]

Thanks for that.

If I were to use a power exhaust vent, wouldn't the intake need to be at the lowest point rather than in the upper portion of the airspace, similar in concept to vented soffits, or do I misunderstand the design concept?

I would say the highest since hot air rises.

THIS MIGHT BE AN OPTION: I am thinking of installing a ceiling exhaust fan in the "trap door" attic access as the easiest and least invasive attempt to alleviate that heat build up. THEORY: It would pull hot air out of the 2nd floor while sucking in cool air from outside through the windows. And this air being pushed into the attic would push air out the soffits which, in my house, are all open.

While it may or may not create enough circulation to pull the hotest air from the roof peak(s), my assumption is it has to make a noticeable difference.

If it fails miserably, all I have to do is take in down and put up a new square piece of plywood.

In order for a system as you describe to work, you would need a very powerful fan because you are attempting to use it to "push" air and these fans are designed to "draw" air. Essentially, you are going to have a fan running that is not doing anything because it lacks the force to push the attic space air out the vents and so cannot draw out the air from the living space.

You may as well just use a window fan in one of the 2nd floor windows facing outward so it is exhausting air from the living space and drawing it in from the other window. In either of the above scenarios, the attic space air is a moot point I am afraid.

As another poster has suggested, stapling reflective foil on the underside of the rafters has been proven to work. A suggestion would be to use tack strips rather than staples.

Best wishes.

[evenstevens]

naam .nice to see that you finally got on to my swing

my posts are simply answering the o/p requests,he may take or come what may from them

[ClutchClark]

Let me summarize, for my benefit:

Ventilation is key, power ventilation is optimal here.

Closed soffits for air intake are not a major problem since they can be drilled/vented.

Air intake (where ever it might be located) must exceed exhaust capacity.

Sprayed foam is probably not worthwhile nor good value for money.

Attic rafter insulation has benefits.

Under roof panels/insulation are not optimal.

Whirly birds (powered and thermostated) are inexpensive, lower profile, solar powered, US style vents are optimal - anybody seen them for sale here?

All those things being true, it's now a case of trying to find the exhaust unit and a contractor.

Thanks to all, it's been useful and I've got my way forward on this..

IF soffits are drilled vented--they must be screened to prevent unwanted insects and critters AND ceiling insulation must be kept 24"-36" away from outside wall so it does not block soffit ventholes.

Attic rafter (framing from outside wall to ridge) insulation is not good.

Ceiling joist (on top of living space ceiling) insulation is good.

Best to find an electrician to do the wiring and a roofer to install the vents. Roofers understand the Zen of water but not electrical current and Sparkies just the opposite ;-)

Edited June 13, 2014 by ClutchClark

[ClutchClark]

If you place both power and intake vents high then the lower air in the attic space will eventually become the warmest remaining air and will rise to the peak.

please dear Sir, i beg of you! stop torturing me

Naam, I have probably forgotten more than you have ever learned about sound construction practices so try to breathe deep and think happy thoughts ;-)

[chiang mai]

Yes agreed, I got my rafter/joist terminology confused, the flat bits are good for insulation, the angled bits not so

Just for clarity: unsure where you live etc but nearly all roof frames here are made from welded steel,

Thanks yet again.

[masuk]

u have indicated that your roof is CPAC tiles

the sucessful inexpensive route which i took is as follows

bought cpac cut out tiles for ventilation stacks to be made and fitted

went to a local engineering shop and had small stainless steel ventilation stacks made (they have a little cap that fits on top to stop anything from entering)

they are in no way a ugly sight, in fact fit snugly into the pitch of the roof, those hopeless ugly whirly birds etc etc are for factory bldings etc etc

u are always welcome to drop in,to have a bow peep just p.m

That's another possibility although like the "whirly birds" they are largely passive devices. I've seen one type of ridge tile that does similar to what you've described, it has a plastic vent built into the tile but again, it's passive. The problem also is with sealed soffits there is no cooler air being brought in to replace the expelled hot air, the risk when using a power fan for hot air evacuation is that it pulls in cooler air from the living space which in turn increases air con. costs.

honestly u can talk about this until the cows come home,

from my experience in building rather a large home, and overseeing a few other housing projects

and based on , u buying a second hand house

lay aluminium foil to the underside of your tiles

lay insulation bats on your ceiling floor

and install s/s stacks as i have already given

the best way, which beats all possible soluotions are trees, but rather a long process to get the necessary results, have done that about 6 yrs ago, and are reaping the benefits in now bigtime

as for the spray on foam suggestion by you,

it all comes down to the contractor,if carried out correctly in applying and foam made of the right stuff, it works very well

BUT

if not, you will be whistling sweet dixie as i have seen jobs rot away in very short space of time

all have a nice day

Sounds good to me. I've lived in the tropics in northern Australia, and it's the ceiling radiating heat into the rooms that's the killer.

Reduce the ceiling cavity heat from 70C, and life below is much easier. "Even Stevens" knows what he's talking about.

A common sight in places like Townsville was the whole family moving their bedrooms to the ground level in the hot season. (the houses were almost always raised by 8ft.)

The introduction of ceiling insulation made a huge difference, and all new homes seem to have aluminium sarking under the roofing material.

[Naam]

Sprayed foam is probably not worthwhile nor good value for money.

wrong assumption CM. sprayed foam on ceilings which "border" the attic is the Rolls Royce of insulation.