Roof Heat Extractors

[55Jay]

Anyone have experience with these spinning rooftop heat extractors? Specifically after-the-fact as our place is already built. Cautious about damage during installation, and any leaks during rain afterward.

Tx,

J

Edited January 22, 2013 by 55Jay

[lopburi3]

Had two installed (three counting later over cooking stove) and yes had leaks on the first two (as could not inspect) but was easily corrected and no further problems (and that was about a decade ago).

[Cloggie]

Installed them on the roof of my house - waste of money....

[rucus7]

Contrary to the above post, they are proven to be efficient. Installation, depending on the pitch and composition of your roof can be problematic. leaks are common, and not always easily remedied.

[55Jay]

Thanks all.

Spent the last hours reading in another popular LOS form on these, quite the fireworks between engineering types vs. those who have them and report good results.

I just want to remove the hot air from my roof attic space as it builds and migrates down through the 2nd floor ceiling material.

Seems the spinners are as effective as installing a non-moving ridge vent at the high apex of the roof. Contention is that the natural rise of hot air through said hole makes the vanes spin and thus creates more suction. I have to agree with the engineers, who say if the air is already moving out the hole, why have a fan in the way robbing energy of the moving air?

However, if there is some exterior wind to move the vanes, then the extraction of the hot air might be assisted further.

I'll probably look into roof tile vent attachments (CPAC) and let nature and physics do its thing without putting any moving parts in the way. I have eave vents to allow new air in to replace the extracted or rather evacuated, volume of air (thanks, Naam!).

J

[rakman]

Using a roof peak vent system, you can enhance the movement of air by putting insulated material on the inside of the roof joists. This makes an air chamber to channel the airflow towards the peak vent, while reducing the amount of heat transmitted into the empty air attic area. Especially, since you have soffit vents, the airflow will draw cooler air in, and the hot roof will drive the heat up and away from the attic area.

Also, a roof peak vent is also aided by any wind flow over the roof, pushing air in at the soffit vent and drawing air out the peak.

It's a bit tedious to install, but it can help.

[Cloggie]

Put insulation on top of your ceiling is in my opinion a better solution.

[55Jay]

Put insulation on top of your ceiling is in my opinion a better solution.

Yep, but expensive (I think) and the house/attic area is really big.

Thank you rakman.

There is a roughly 2" sq attic man access point in the 2nd floor hong nam ceiling which has been popped up/open, presume for the purpose of allowing cool air in or someone had a need to get up there and never closed it afterward. Going to get up there today and check it out.

The bathroom entry door is actually outside on the 2nd floor balconey, on a non-sun side of the house. Eyeball guesstimate, leaving this 2x2 attic access opening would probably suffice for cool air introduction if I had ridge vents working up top.

I'll give it a go as is, any improvement is better than current state as the wet/hot season is on the way.

Cheers,

J

Edited January 23, 2013 by 55Jay

[Khun Jean]

It is also the favorite way for thieves to enter a house.

We rented a small shop and we made going through the ceiling a little bit more daunting by introducing barbed wire and a aluminum frame that has only small gaps.

For insulation we used a thin foam with on one side a reflective layer. We fitted that close to the roof, about 10cm under it. That by itself already lowered the temperature from 70c to about 50c (measured close to the roof).

Then we put the fiber glass 'wool' with on both sides a reflective layer. This lowered the temperature in the room from around 40c to 35c.

This was measured on days with full sunshine and no ventilation in the room as everything was closed.

Then we put in a fan between the roof and ceiling and extracted that air. The temperature dropped another 2c to 33c.

We did not have an electricity bill before and after, but the airconditioning's compressor is only on a few times per hour, before the insulation that was considerable longer.

In hindsight it was better to make more measurements to see the effects of each part. The thin layer under the roof lowered the air temperature between roof and ceiling considerable as the hottest air is now between the roof and the thin layer. There is a unforced (convection) flow of air between this layer and the roof.

[terryp]

had 2 put on my place ..an absolute waste of time, money and effort

[55Jay]

It is also the favorite way for thieves to enter a house.

We rented a small shop and we made going through the ceiling a little bit more daunting by introducing barbed wire and a aluminum frame that has only small gaps.

For insulation we used a thin foam with on one side a reflective layer. We fitted that close to the roof, about 10cm under it. That by itself already lowered the temperature from 70c to about 50c (measured close to the roof).

Then we put the fiber glass 'wool' with on both sides a reflective layer. This lowered the temperature in the room from around 40c to 35c.

This was measured on days with full sunshine and no ventilation in the room as everything was closed.

Then we put in a fan between the roof and ceiling and extracted that air. The temperature dropped another 2c to 33c.

We did not have an electricity bill before and after, but the airconditioning's compressor is only on a few times per hour, before the insulation that was considerable longer.

In hindsight it was better to make more measurements to see the effects of each part. The thin layer under the roof lowered the air temperature between roof and ceiling considerable as the hottest air is now between the roof and the thin layer. There is a unforced (convection) flow of air between this layer and the roof.

Yes, I've seen that insulation void application in the past days reading up on this, very effective, ideally the void being able to dump the heat out the top, or a fan as you've got it.

Our place is big and the roof isn't a straight forward A frame type peak nor do I have any vertical face areas where I could put in a vertical attic vent then mount an exhaust fan on the inside. Former colleague had one in his attic in the US, on a thermometer, kicked on at a pre-set temp.

Looking at it today from a couple angles, I guessed I would need minimum of 4 vents at different peak/ridge areas to start making a dent in the heat accumulation issue. Photo shows 1/2 the roof area. The other side is less complicated but still has a couple peaks and ridges.

Visited the local hardware/construction shop today, quoted 200 baht for 3 sq mt of "stay cool" insulation, but could get it a bit lower in higher quantities, which is what we would need I suspect. I'm still leaning toward vents first as the least expensive option to try before it starts raining, see how they do, then move to insulation.

At any rate, in talking with the shop folks today, we have "chang tiles" so the CPAC prefab venting tiles I found one line would need an adapter, but it can be done I'm told. The prefab vents themselves weren't expensive at all, just need to get them installed correctly.

Thanks for your feedback, I'm still taking it all in, keeps pusing me toward vents and insulation, together, as the right way to do it.

J

[55Jay]

I'm still screwing around with this. Since learned our thin Chang tiles don't offer a pre-fab roof tile vent but the thicker concete tiles do - but one won't mate to the other. As you can see again, I don't have a A frame gabled roof where I can put in vents or an exhault fan - no vertical mounting area.

Do have rather large eave overhangs. What do you think about installing an exhaust fan on one of more of the overhangs?

Obviously fighting natural flow direction (up) and the fan would need to be very powerful. This is aggravating.

[isawasnake]

I had experience putting these in in the usa. they are amazing, but it was over a garage though. i thought the theory was once the hot air builds up, the spinners start, and that momentum of the turning pulls out more hot air than would just by a passive vent. like a vacuum effect. i dont know why people are saying they are a waste of money, it is literally hot hot air visibly being pulled right out for a VERY low price and easy install. visualize sitting in a car with cracked windows in the sun vs the same car but put a few big holes in the ceiling. i mean isn't it self explanatory? i think there are way underused here in thailand.

Edited February 14, 2013 by isawasnake

[watcharacters]

Put insulation on top of your ceiling is in my opinion a better solution.

b very careful

condensation

[Khun Jean]

A fan in the eaves can work, a little duct work will improve it. You need to extract the air from the top or close to it. Also have air inlets in the eaves otherwise you are trying to make a vacuum and then the fan needs to work much to hard and little air is moved.

[Naam]

I had experience putting these in in the usa. they are amazing, but it was over a garage though. i thought the theory was once the hot air builds up, the spinners start, and that momentum of the turning pulls out more hot air than would just by a passive vent. like a vacuum effect. i dont know why people are saying they are a waste of money, it is literally hot hot air visibly being pulled right out for a VERY low price and easy install. visualize sitting in a car with cracked windows in the sun vs the same car but put a few big holes in the ceiling. i mean isn't it self explanatory? i think there are way underused here in thailand.

if there is no breeze the hot air is not "pulled out" but the air flow is even hampered by the "whirly bird".

[55Jay]

A fan in the eaves can work, a little duct work will improve it. You need to extract the air from the top or close to it. Also have air inlets in the eaves otherwise you are trying to make a vacuum and then the fan needs to work much to hard and little air is moved.

Excellent, yes, thank you. I had the same thought yesterday when considering this work-around. I appreciate your feedback.

[55Jay]

I had experience putting these in in the usa. they are amazing, but it was over a garage though. i thought the theory was once the hot air builds up, the spinners start, and that momentum of the turning pulls out more hot air than would just by a passive vent. like a vacuum effect. i dont know why people are saying they are a waste of money, it is literally hot hot air visibly being pulled right out for a VERY low price and easy install. visualize sitting in a car with cracked windows in the sun vs the same car but put a few big holes in the ceiling. i mean isn't it self explanatory? i think there are way underused here in thailand.

if there is no breeze the hot air is not "pulled out" but the air flow is even hampered by the "whirly bird".

Naam,

Current work-around idea of eave exhaust would be from the lowest point of the attic space, right on the same line as the 1st floor gypsum ceiling. Front 1st floor balcony you can see in the photo provides easy working access to the eave for this and future fan cleaning/maintenance/trouble shooting. All other eave areas are precarious to get at, so this front balcony is it.

Is there a foruma or some ROM guidance to get at what size fan I should try? I would rather err slightly bigger, not smaller and regret it.

I would flush mount fan on balcony eave and run X size ducting from fan intake side up and suspended at or near highest peak(s) in attic.

Have a 2'x2' attic tile in a 1st floor bathroom on the non-sun side of the house, providing (cooler) air replacement into the attic space

Appreciate your thoughts and input in general, and on the fan specifically.

J

[isawasnake]

I never looked up once in the daytime and saw ours not spinning, wind or no wind. Anyway.... i wish the op luck, i think the things take heat out, others think they keep more heat in? Ok

Edited February 16, 2013 by isawasnake

[Mike45]

How about adding a small ventilation dormer to your existing roof?

[55Jay]

Thanks for your input.

I started on the whirlybird idea but have gone away from it. I do not disagree entirely, I think whirlybirds provide a benefit on their own as a stationary vent, with some level of enhanced performance given the right external conditions (wind/breeze).

----

In the absence of mathematical feedback, playing around on this site now. http://www.engineeri...ors/airflow.htm

Found a company in BKK on-line with all sorts of air handling machines and fans, hoping to find one in Korat. BKK quoted me 10k for a cylindrical model and 15m of duct hose in varying inlet sizes 200 to 50mm. My/Khun Jean's idea is to turn that around though, and mount the fan in the accessible eave space where I can get at it/apply power, etc, and run the duct up into the higher attic peaks as the suction point.

[cooked]

I have seen these kind of discussions going round and round in circles for a year or two now. I still haven't got around to doing something about our ceiling yet, but I will have to do something, that's for sure. I have a sun oriented wall without insulation but this never gets as warm as the underside of the ceiling, which would provide a decent source of heating in northern climes.

My first step (not an option for everyone) will be to put in simple vents, mosquito proof, at both ends of the roof at the highest point. I won't install a fan because maintenance access will be difficult after I install insulation above the ceiling, with reflective foil on both sides. Condensation? If you have adequate venting this shouldn't be a problem but I will be taking care to close the gaps with tape.

Roof heat extractors (whirly gigs): I never understood how these would work better than adequate venting, even if the wind would be helping them along sometimes.

There are all sorts of things to consider and I have come to the conclusion (along with a heating/refrigeration engineer that I know) that it needs considerable experience to find the right solution for any individual house/roof type. I'll just be trying one thing at a time and leave installation of a fan that no one can fix if it goes wrong as my last alternative.

[55Jay]

How about adding a small ventilation dormer to your existing roof?

Yes, thank you, that is an option. Before I get into minor construction/alteration of the roof, think I'm going to give this eave fan idea a shot.

Had I been here during design and construction, and know what I've come to learn now, I would of have a dormer built in from the get go.

[wayned]

One thing that I have not seen in Thailand is a whole house exhaust fan. I had one when I lived outside of New Orleans, which has a very nasty summer climate, actually worse than Thailand due to the extreme humidity, and it worked well. It's a very large louvered fan mounted in the ceiling the draws the hot air out of the house and exhausts it into the attic. The pressure differential created then exhaust the air through the attic ventillation ducts. All of the ceilings were still insulated with R6 insulation and there was always the aircon, but not ususlly needed at night. I've never seen them used here.

[55Jay]

I have seen these kind of discussions going round and round in circles for a year or two now. I still haven't got around to doing something about our ceiling yet, but I will have to do something, that's for sure. I have a sun oriented wall without insulation but this never gets as warm as the underside of the ceiling, which would provide a decent source of heating in northern climes.

My first step (not an option for everyone) will be to put in simple vents, mosquito proof, at both ends of the roof at the highest point. I won't install a fan because maintenance access will be difficult after I install insulation above the ceiling, with reflective foil on both sides. Condensation? If you have adequate venting this shouldn't be a problem but I will be taking care to close the gaps with tape.

Roof heat extractors (whirly gigs): I never understood how these would work better than adequate venting, even if the wind would be helping them along sometimes.

There are all sorts of things to consider and I have come to the conclusion (along with a heating/refrigeration engineer that I know) that it needs considerable experience to find the right solution for any individual house/roof type. I'll just be trying one thing at a time and leave installation of a fan that no one can fix if it goes wrong as my last alternative.

Agreed. Ran across 2010 TV posts (through a Google Search) which served to reinforce what I've come to consider logical priorities.

#1, most important, have natural or forced attic venting to prevent or significantly reduce heat build up and migration down into living areas, including heat transfer of wall and ceiling materials.

#2, insulation, whether than be under roof tile or ceiling laid, or both.

Doing second without addressing the first is, in my opinion now and in my situation, cutting off the head to solve the headache.

Given my situation, this eave fan with ducting is a relatively inexpensive work around, and is least invasive to the integrity of my existing roof.

I don't have any leaks now, and don't want any.

Cheers,

J

[55Jay]

One thing that I have not seen in Thailand is a whole house exhaust fan. I had one when I lived outside of New Orleans, which has a very nasty summer climate, actually worse than Thailand due to the extreme humidity, and it worked well. It's a very large louvered fan mounted in the ceiling the draws the hot air out of the house and exhausts it into the attic. The pressure differential created then exhaust the air through the attic ventillation ducts. All of the ceilings were still insulated with R6 insulation and there was always the aircon, but not ususlly needed at night. I've never seen them used here.

Naam has one in his place. That is the concept I'm after now, modified as our current house is 2 stories with a large attic space whereas believe he's got a ranch style. At any rate, the concept and end state is basically the same, I'm just not looking to suck the entire house, just the massive attic cum oven I've got sitting on top.

[Mike45]

I thought Naam had a naturally ventilated attic space and only used the powered fan for a short period of time to draw cool air into the house and exhaust air into his attic space.

Perhaps I don't understand how you plan to use your powered ventilator. Will you use it during the day or night or both?

Perhaps your right about not causing roof leaks. I just don't understand these tiled roofs.

Back in the states I've never had a Wooden roof with asphalt singles leak.

With that type of roof I also wouldn't hesitate to cut onto it and add a dormer because I know it would be easy to seal. But I wouldn't have to. I would simply cut along the ridge and install a ridge vent. It's so easy to ventilate a roof at home and here it seems to be rocket science. These tile roofs don't seem to be reliably sealed.

[55Jay]

I thought Naam had a naturally ventilated attic space and only used the powered fan for a short period of time to draw cool air into the house and exhaust air into his attic space.

Perhaps I don't understand how you plan to use your powered ventilator. Will you use it during the day or night or both?

Perhaps your right about not causing roof leaks. I just don't understand these tiled roofs.

Back in the states I've never had a Wooden roof with asphalt singles leak.

With that type of roof I also wouldn't hesitate to cut onto it and add a dormer because I know it would be easy to seal. But I wouldn't have to. I would simply cut along the ridge and install a ridge vent. It's so easy to ventilate a roof at home and here it seems to be rocket science. These tile roofs don't seem to be reliably sealed.

You are probably right on his attic, don't know, but he's go a whole house fan.

Yes, would much rather have simple ridge vents if there was a pre-fab solution for what I've got. Putting in a dormer is more than I had in mind right now but it was good, added it to my list. I would envision running this proposed eave fan for a couple hours around sunset. If I can find a variable speed, might even leave it on low from mid morning until after sunset.

I post here because this sort of thing is not my realm. Maybe not rocket science but invariably somebody says something I hadn't thought of, or I had and feedback serves as validation / reinforcement.

[Khun Jean]

You could run the fan on a temperature sensor.

Don't know a specific type but they are available.

Might be more effective then using a timer.