Roofing Tile Ventilation

[scorpio1945]

When discussing the building plans for my upcoming house and the subject comes up about roof ventilation, I start talking about roof caps, eave screens/perforations and forced ventilation. Each time my engineer assures me that the tiles that they will used on my roof have adequate built in ventilation for heat to escape. Indeed when you look up on an existing roof there is a somewhat circular hole extending up along one side of each tile. In theory maybe this will be adequate with enough eave ventilation. I have googled and searched TV with no useful success. I can always go with forced ventilation, etc. at a later date if needed but I don't want to miss a bet with roof caps IF it would make a big difference and it would be more of a major retrofit.

Any opinion or experience?

I know I should probably put this in the housing forum but I am more comfortable here for now and the weather is a little different here..:jap:

[jubby]

I suspect the roof will be ventilated adequately, but also suspect improvements can be made. Are we talking about having a Cool house here ? . Its always worth looking at the traditional roof design's and why they were designed that way.

I do suspect insulation plays a major part in these things these days especially if your building on a relatively small plot on an Housing estate. More emphasis is probably put on keeping the rain out and the roof secure in storms. If on your own piece of Land then it becomes a very interesting subject with lots of possibilities and lots of things to take into consideration.

I have given this a lot of thought over the years and I'm not convinced the modern concrete roof tiles are the way to go.

I would browse through the Housing forum. there's lots of info on there already. Although as you rightly say, we have different weather up here.

[transam]

I have cement tiles. The roof overhangs the house walls by about 3 foot and has cement boards all round but at the rear of the house about 6 foot is replaced with a mesh, stops birds getting in and lets heat out.

[kandahar]

We have the concrete roof tiles. When I get in the attic, I can see out everywhere, under the tiles, when I look down the slope on the underside of the tiles. In theory, that is a lot of area for ventilation if you calculate it that way. However, all of the openings into the underside of the tiles are facing up the slope (so rainwater is held out, of course). If you know anything about convection, you know that the heat will just travel upwards long the roof slope until it reaches the peak, by-passing all of those openings. The heat will NOT decide to make a u-turn and go downwards along the tile and out into the open. The only way to make the tiles work as decent ventilation would be to install them backwards and then all the rain would run under the tiles into your house but the hot air would have a better chance of getting out as it travels up the slope of the underside of the roof. I am sure that someone has designed the tiles with the openings to give the house ventilation but it is a self defeating design. Our attic gets hot enough to kill a person in a short time and a LOT of that heat is radiated through the ceilings into the house.

Add proper ventilators and add enough opening for decent air intake to replace the air that is leaving. The roof tiles do add a lot of passive inlet capability but the air first goes through space between the two tiles (between the two layers) that the sun is shining on and is heated up as it passes through. You end up pulling hotter air into your house attic; you're bringing in hot air and venting hotter air. You will need to pull in fresh, cool air from somewhere other than over the roof tiles, ideally, from the shady side of the house or even from the crawl space (via a duct) under the house. Do it right the first time and the job will pay for itself in energy savings in the future.

If I am not making myself understood about the spaces between the tiles and how convection makes them useless, stop by. I can lay out two tiles on a slope and demonstrate with a cigarette lighter. It will be very obvious when the heat from the lighter flame travels up the first tile, passes by the opening between the first and second without turning and going downhill and burns your hand when it reaches the top of the second tile.

Now, if you're going to install a forced air system to ventilate the house attic, then the ceiling tile spaces will accommodate a lot of that hot air AND the tiles will be cooler because the air is being forced out that way, carrying away a good deal of the tile heat with it. But passive doesn't cost anything to operate and that is the way to go, especially with the cost of energy constantly rising.

Edited August 2, 2011 by kandahar

[jubby]

I'm sure they put insulation with a reflective surface under the Tiles these days. thats going to effectively seal the roof holes that KD mentioned , then your just left with the Louvre vent and the mesh that Transam mentioned.

Don't know if you can make use of one of those chimney stack type ventilators I've seen on factory roofs to get rid of some of the rising heat. can't recall seeing it on houses here.

You going to have a Nice Wood Fire with a Chimney for the Winter Scorpio1945 ?

A sprinkler system would be a cheap and relatively easy fix for a hot roof on the hottest days. but not if you don't have your own free water supply

Edited August 2, 2011 by jubby

[kandahar]

I'm sure they put insulation with a reflective surface under the Tiles these days. thats going to effectively seal the roof holes that KD mentioned , then your just left with the Louvre vent and the mesh that Transam mentioned.

Don't know if you can make use of one of those chimney stack type ventilators I've seen on factory roofs to get rid of some of the rising heat. can't recall seeing it on houses here.

You going to have a Nice Wood Fire with a Chimney for the Winter Scorpio1945 ?

A sprinkler system would be a cheap and relatively easy fix for a hot roof on the hottest days. but not if you don't have your own free water supply

Actually, the roof that uncle has just put on his new house next door is a new style roof tile. It does not have anything underneath to act as insulation or as a reflector. However, they are the new flat style, which means they also have no opening between tile layers. That is good because in a driving rain with high winds, the rain water doesn't get pushed uphill under the tiles and into the attic, as happens with the older styles.

[extexthai]

I just went through that last year. Come to Phayao and see what I did. I had a real Thai carpenter (with a tablesaw, even) make me some gable louver vents, that actually pass air, not those tiny little cute things they sell at the home stores. I went so far as to make a mock up so he fully understood and he made them accordingly. However, you have to be careful when those are made and make sure that the angle of the slat is adequate to insure no wind blown rain coming in...we presently have that problem upon the rare occasion. I will be having to go up inside the attic and make adjustments to keep the wind blown water out. I had him use wood about 15cm wide for the slats so the opening would be large. I now have a perfect design for those by the way, since I have had time to rethink them. I also used that vented soffitt around the entire perimeter of the overhang. My roof design is such that with 4 gables, the attic space interconnects, I have the east and west gable louver vents almost 2 m wide at the bottom and it goes all the way up the rake of the roof for optimal heat dumping as Kandahar pointed out, heat does indeed rise...straight up usually. I probably get too much ventilation in my attic area, but that is okay with me until we get one of those blows and we have already had that twice this year. Thank goodness for concrete rendered walls and tiled floors....mop and go. I will enclose some pics so you can get the general idea of what I did. Feel free to ask about anything regarding passive, self-cooling house construction. Good luck....ett

[kandahar]

I just went through that last year. Come to Phayao and see what I did. I had a real Thai carpenter (with a tablesaw, even) make me some gable louver vents, that actually pass air, not those tiny little cute things they sell at the home stores. I went so far as to make a mock up so he fully understood and he made them accordingly. However, you have to be careful when those are made and make sure that the angle of the slat is adequate to insure no wind blown rain coming in...we presently have that problem upon the rare occasion. I will be having to go up inside the attic and make adjustments to keep the wind blown water out. I had him use wood about 15cm wide for the slats so the opening would be large. I now have a perfect design for those by the way, since I have had time to rethink them. I also used that vented soffitt around the entire perimeter of the overhang. My roof design is such that with 4 gables, the attic space interconnects, I have the east and west gable louver vents almost 2 m wide at the bottom and it goes all the way up the rake of the roof for optimal heat dumping as Kandahar pointed out, heat does indeed rise...straight up usually. I probably get too much ventilation in my attic area, but that is okay with me until we get one of those blows and we have already had that twice this year. Thank goodness for concrete rendered walls and tiled floors....mop and go. I will enclose some pics so you can get the general idea of what I did. Feel free to ask about anything regarding passive, self-cooling house construction. Good luck....ett

Nice job! Lovely and well thought through. Now, if a guy could just fix an external vane to them so that when the wind came up from that direction, the vane would press a leveraged arm that closes them, overcoming a weak spring that holds them open.

[kandahar]

A rope and pulley would work for operating them from ground level but it wouldn't work when you aren't home.

[meatboy]

I'm sure they put insulation with a reflective surface under the Tiles these days. thats going to effectively seal the roof holes that KD mentioned , then your just left with the Louvre vent and the mesh that Transam mentioned.

Don't know if you can make use of one of those chimney stack type ventilators I've seen on factory roofs to get rid of some of the rising heat. can't recall seeing it on houses here.

You going to have a Nice Wood Fire with a Chimney for the Winter Scorpio1945 ?

A sprinkler system would be a cheap and relatively easy fix for a hot roof on the hottest days. but not if you don't have your own free water supply

Actually, the roof that uncle has just put on his new house next door is a new style roof tile. It does not have anything underneath to act as insulation or as a reflector. However, they are the new flat style, which means they also have no opening between tile layers. That is good because in a driving rain with high winds, the rain water doesn't get pushed uphill under the tiles and into the attic, as happens with the older styles.

see my reply to you topic leaking roof,real est.housing,land forum.

[Thighlander]

I have a 1946 cottage in Phoenix. It is way hotter here than Chiang Rai. I have a gable vent on each end of the house, and there is a master flow fan attached to one of them that has a built in thermostat--that I set on 90F. It slows the heat down during the day, and makes the house cool off quicker in the evening, and keeps it cooler during the day. I just replaced the gable vent a few weeks ago, as a part of a paint job. My vent is 18"w x 24"l. The new vent is sheet metal, about 2 inches thick and cost me 17 us.

http://www.homedepot.com/Master-Flow/h_d1/N-5yc1vZyt/R-100014195/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

[rmacdon61]

With the standard Thai tile roof system, which I really like for looks, venting is quite simple with a ridge cap system at the top and soffits along the underside (to keep birds out). You can get wind powered venting caps installed as well that suck out hot air to increase ventilation. Best place 2 as near the top as possible and on the non viewed side of the house for appearance. Caps are steel.

[Thighlander]

I had two of those turbines installed for about 5500 including the adapters for the higher pitch. They work great, but will let in more noise--especially if you don't have ceiling insulation.

[rmacdon61]

I had two of those turbines installed for about 5500 including the adapters for the higher pitch. They work great, but will let in more noise--especially if you don't have ceiling insulation.

Agreed, noise is one reason for non-use and the issue of wind, the vent works most when not needed (windy) and least when needed (no wind). Being thailand (sun) solar power is obvious, so maybe solar powered fan vent. I know of 2 types, 20 watt and 30, 12inch and 14 inch. I have never heard one run but would imagine fairly quiet at those low output. They install same as turbines but carry a cost with them above mechanical.

[maidu]

lot of good responses on this thread. I built louvered screened windows under the upper eaves of my roof. One on each side, so air flows through the attic, in one side, out the other. I agree that terra cotta tiles, if they have small openings, will not be effective. As mentioned eloquently earlier, heated tiles will not enable air to exit from inside, and when there's a driving rain (sometimes horizontal, particularly in May and June) - water will find its way up those openings. Good luck.

[Thighlander]

I had two of those turbines installed for about 5500 including the adapters for the higher pitch. They work great, but will let in more noise--especially if you don't have ceiling insulation.

Agreed, noise is one reason for non-use and the issue of wind, the vent works most when not needed (windy) and least when needed (no wind). Being thailand (sun) solar power is obvious, so maybe solar powered fan vent. I know of 2 types, 20 watt and 30, 12inch and 14 inch. I have never heard one run but would imagine fairly quiet at those low output. They install same as turbines but carry a cost with them above mechanical.

http://www.homedepot.com/h_d1/N-5yc1v/R-202321544/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

about 7500 thb in the States--a good choice, but it doesn't seem to take much wind to get the turbines going. The wind turbines are most popular here, but I was trying to reduce roof objects and I like the active fan. We had 48c in June and I do not have a/c.