Roof Insulation for Tropical Climate

Thanks for your comment Fredski, my project is in west Africa with limited access to reflective coatings thus the option for using insulating material which is cheaper and more accessible than the coatings. However, if there are cheap sources of durable reflective coatings it could also be considered.

What - like silver-coloured paint, for instance?

Google 'cool roof' and 'flat roof construction'. You will see that there are several options, I can't make a recommendation. It may depend on the construction method (wood frame?), building plan, and final roof selection. I agree with Fredski, a reflective roof is important - I'd recommend a single-ply of some kind. Also, if possible, shade is your friend.

thanks Bigg. The project is in west Africa where construction is typically from cement blocks with wooden roof trusses and corrugated metal sheet cover to comply with building standard. Like I pointed out to Fredski, the availability and pricing of reflective coating may make this an unattractive option thus the choice of insulation.

You may fond this off the wall but creating a fully watertight roof and then planting vegetation is a very effective coolant- we used it for an underground house and it worked wonders both for heat and cold- also can be attractive- just have enough slope so you can have run off and no pooling

Any kind of white reflective coating will help a lot. If you can't get a permanent white surface, even white paint or whitewash that has to be re-applied every few years, would be worth using for the cooling it provides.

My thinking would be: White surface/roofing material/insulation/vented air gap/second layer of insulation. On the side(s) of the building that get the most sun I'd use long overhangs to extend the roofing material to help shade the side(s) of the building too. If you can't do that, then plant trees or shrubs to provide natural shading.

I'd research what insulating materials are available at your installation, site first. Bringing in an esoteric but phenomenal material will only make all aspects of logistics much more difficult.

If only the insulating quality were important, I'd consider utilizing a silica based Aerogel. I suspect that this material will be outside of your time and money budget windows but if you only want the best then you must be willing to pay the most.

aero gel for a small project in Africa? maybe NASA or the military! its true the aero gels are amazing insulators, recently a carbon based aerogel knocked off silica as the king of the insulators, but not for this project or any like it

I did hear that a carbon aero gel recently surpassed silica for thermal insulation. With the temperatures and moisture content of a rain forest, I just thought the natural anti-fungal properties of an inorganic material would be wise.

I did start my hyperbolic reply by advising the OP to investigate what insulators were available locally. Buying local will most likely be the most cost effective approach. The locals should know what materials they have will withstand their climate best.

Forum protocol also does say not to post any e-mail adresses.

Just saying!

You need a radiant barrier installed under the roof, possibly as a ceiling in the dwelling..possibly fiberglass in the attic space, minimal as it might be...or you could build a sundeck on the roof that would provide shade and minimize sun exposure directly to roof....

http://www.aerogel.com/products/pdf/Pyrogel_XT_DS.pdf

http://www.coolflatroof.com/flat-roofing-materials.php

My concern would be for the pitch of the roof over other issues, you must have your reasons for needing a flat roof which must outweigh the advantages of a pitched roof.

Consideration shuld also be iven for effective air circulation through the roof space to prevent moisture retention and associated mould growth.

This will also remove a lage amount of heat from the ceiling which would otherwise be conducted through your ceiling into the rooms below.

Yes--Why flat roof? Look at the construction of houses in the equatorial areas of the Pacific, and you will see a pitched conical type roof, with two separated layers, an vent at the top, protected from rain, an airspace in-between, and constant air circulation from shade through the roof vent. Make it a 3 layer roof, with more air between the spaces, and it is even better. Look at a basic Indian TeePee (sp), and see where the smoke goes. Also, look at what the Bedouins and other tribes wear in the Saudi deserts, =---many light layers, all moving air between them.. Plus--more headroom!

Think about wall materials roof,lot of heat gets in via walls. Orient the building in such a direction to get minimum solar heat & apply reflective paint on walls & select recommended material.

2" of Styrofoam with a white vinyl liner cover, over a 3/4 inch OSB deck, use this combo for flat roofs a lot in Arizona and Oklahoma ... easy to install and very low maintenance.

I am not a civil engineer- so this is pure suggestion.

Can't you use fiberglass sheets? Are tiles not available?

Long ago I had come across a cloth which can be worn by fire brigade personnel to walk though fire. It could withstand over 600 deg C. it was made by a French company and demonstrated on HORIZON programme in BBC decades ago. This black cloth can be a layer above some other rigid surface.

Speaking from 14 degrees N, what I do to relieve the effects of direct sun on the roof is to use super-cheap (free) and readily available materials: leaves laid on the top. Try banana leaves or the big grasses - a couple of layers do as well as an inch or so of foil-covered foam insulation under the roof. They are not permanent, of course, but so effective and cheap. In the rainy season they are not needed. You might consider a roof with soil and growing grass if the structure is up to it.

Bear in mind that if you put insulation under a concrete or metal roof, the roof gets super-hot and continues radiating its heat long after sunset. Good luck!

Use plastic bottles-covering the whole roof,filled partially with water (10% approx) !!

- It is lowering the temperature drastically !!

This is experience gained by myself. the bottles last at least several years...

If you are going to try it-please refer the results acchieved

Best Regards Jacob

Please check this. http://in.answers.yahoo.com/question/index?qid=20070723084816AANubOa Regards

Personally, I would never ever build a flat roof in almost any part of the world....pitched roof are easier to build strongly with less material and not prone to leaks when done correctly, just in case it ever rains where you are.

I have NEVER EVER seen a flat roof that did not need regular maintenance.....and leak repairs.

In tropical areas it can be an "almost flat" roof if snow/hail are never a problem.

Flat roofs are possibly OK in desert regions where the yearly rainfall is "0", but there are generally ugly anyway....

Light colours generally reflect more heat, as do some light coloured roofing metals, aluminium for example. Even corrugated steel panels, when carefully used are OK if not pretty, but a good quality paint of the correct sort, with maybe a motif/advert can look quite good.

Having an air gap under the roof to cool the reverse side, to keep the heat out of the working/living areas, is usually a good idea and where a pitched roof can be easily organised so that air is drawn in under the eaves, picks up the heat and is expelled via suitable vents at the apex, simply using convection, where a flat roof will need a fan or similar....noise, electricity Bills and maintenance.

Think about using the roof to supply hot water heated by the sun for washing bathing....

Cover the actual roof that is under the "outside" roof with aluminium foil or boards so made, to reflect heat back out.

You should get lots of help here on CR4 with regard to the main materials to use, but locally made/sourced will be cheaper, even if you need to use more of the insulation to get the full effective insulation values needed. Plan ahead carefully....

In Africa you need to think about possible insect damage to the structure as well before starting to build....

Best of luck.

Many good thoughts from Andy Germany. The air space, hot water heater as "insulation", the pitched roof which can make space for insulated hot water storage tank using convection without a circulating pump, etc. Planning before building is so much less expensive, and getting more from less makes acquiring the stuff you do not have to get much much easier. Right on! or is it just right, now?

In India in small towns people cover their flat roofs with old jute bags and sprinkle the water during summer. It lowers room temp. to very low level and it is like sitting in AC room. This is because evaporation of water cools the room. Very low cost method you can try it out.

Yes, evaporative cooling can be great in low humidity. Not so effective in tropical Africa or here in S.E. Asia where the R.H. rarely falls below 70%.

In an area such as yours with a very high water content to the air I would try to get Dow Chemical Blue Board in the 3" size. It will hold up to the heat and as it will not absorb water keeps the r value constant. I used it here in Florida where the summer conditions are tropical to say the least. The 3" has a R rating of 15 and comes in 4' x 8' sheets. While other product may have a higher R rating to begin with this material maintains the rating the life of the product.

You can also get many types of foam sheets with both sides foil backed for reflectivity. I use them when we are doing open beam ceilings, with furring strips, and 5/8ths drywall.--I can get R-30, out of 4 inches and foil laminated..

In Arizona we use clay shingles. The last 50+ years very good in high temps. From what I under stand they allow air flow to help remove heat from Attic space.

What are day shingles?

I did a Google search and the first find was a disease......UGH!!!

Clay not day LOL

AH!!!! thanks.

We call them tiles - roof tiles!!

I thought Shingles were always made of wood......

They call them shingles here no biggy.

4 degrees

Coolaroo takes care of that.

If some more long term solution is required, build a tropical roof. I.e. a roof on a roof.

The tropical helmet and the tropical roof of cars and jeeps (land rover) are examples.

I hope you have no hurricanes because a flat roof has the highest lift coeff.

I'm glad someone said it, GA. The principle was rediscovered recently in the US when it was noticed that buildings' aircon loads were reduced, the benefit resulted from fitting solar panels on the roof. Land Rover called it the Safari Roof.

I think (but not 100% sure)- that round roofs have the highest lift coeff.

Do you have the formula to prove it? (only to remind myself....)

Shape, but mainly position of wings by airplanes? Look around.

Hi Vokolo, I have lived in the tropics most of my life - & quite a bit of experience with insulation.

Last house I lived in got so hot by 10 - 11 am that it was much nicer to go and sit under the mango tree with the ants. After insulating, sitting under the mango tree was so hot, it was much nicer to go back indoors!

In the tropics it is only necessary to insulate against radiant heat. The little insulation against cold you might ever need can be had by just throwing on a shirt or a jumper!

By far the best tropical insulation is reflective - called 'Sisalation' in Australia. It can reflect up to 97% of the solar energy. It is also the most cost effective, in most places - check the local price. Bulk insulation is not necessary & often does not last as long as reflective. Bulk is less good for the environment, (esp foams) much more shipping cost.

To install reflective, best performance can be achieved by putting one loose layer on top of roof battens, then one tight layer above. This creates an air space which can stop dust build up which can reduce its reflectance. If the edges can be taped together, that will increase the performance by preventing the hot air leaking from above the barrier to below.

One single layer will also be very effective, but perf. may drop over time for dusty environments.

It is best to run the foil from one eave to the other - cover the complete roof, not only above the ceiling - as a fair amount of heat can come through the eaves, then radiate onto the walls.

If you want to test the effect first, get a square metre or so, & place on top of the roof around sunrise with some bricks on, to make sure it doesn't blow away. Then around midday check the ceiling temp of the bit under the insulation, vs the temp not insulated. I think then you will be convinced of its value.

You ask for 4° below ambient - reflective should give you much less temp rise during the day from minimum. You will lose the 'living in an oven' feeling.

Open up at night to let cool in, close up during the day if possible.

Good luck, Stuart in Thailand.