Those of you who were interested in the first article of this Philippine cool series will be happy to see I didn’t forget to keep going … the others, well maybe not so much. No problem, you’re welcome to sweat along with the rest of us while you surf around and find something you like better.
We closed the last article talking about the three ways heat energy transfers from a warm place to a cold place … radiation, conduction and convection. Remember it heat energy is similar in many ways to electrical energy, it only travels one way, from hot to cold. We mentioned that in the the US and other countries that get cold in the winter, the major mode of heat transfer we deal with is building paths against heat CONDUCTION. We work hard at keeping the expensive, relatively puny heat source inside from escaping into the infinite coldness of space. And basically, to be successful, we really only need to keep things sealed up as tight as possible and provide as many barriers to the conduction of heat from inside to outside in order to keep our utility bills and comfort level reasonable.
Thermodynamics in the Philippines operate exactly the same way as anywhere else on the globe, but the scale of heat energy here is way different than in the US. Our houses are virtually always warm enough, our problem is basically far different in scope. Instead of trying to keep the heat from a furnace capable of, at best, a few hundred thousand BTU’s of heat production per hour, (roughly 2900/3500 Watts per hour in a typical home)we instead have the sun … a thermonuclear furnace of vast proportions … estimated at 384.6 YW (yottaWatts, 10 to the 24th .. that’s 10 with 24 zeros after it). The differences is the scale of the problem are astounding. In more practical terms each square meter of you roof in the Philippines receives about10,000 Watts per hour when in full sun … a typical (small) roof would be perhaps 150 square meters, so at noon we are looking at something like 1,500,000 Watts of solar radiation hitting the roof. or, going back to US familiar terms 5,172,000 BTU per hour heat load … three hundred forty or more standard US furnaces on the roof, all trying hard to pup their thermal energy inside.
And remember our heat flow … warm to cold. If you have a room inside cooled to some comfortable level … say72/74 F or 21 or 22 degrees C, how hard do you really think it will be for our 344 roaring roof furnaces to start raising that temperature into the discomfort zone?
Actually, when you lay the figures out like this it seems impossible. Better stay home in the US of A. What the heck am I doing here? It’s 7:31 am and a cloudy day, yet I’m already starting to sweat in front of the computer room fan .. in a few minutes I’ll have to close the windows and start the air conditioner …because even if I can stand the heat, my computer can’t and it will go into a very slow, hesitating “max cooling” mode which drives me crazy (a short trip, by the way).
And yes I said cloudy. Just because the sun is behind the clouds doesn’t mean there isn’t tremendous solar radiation coming in from it .. may be slowed down measurably but a whole hell of a lot of heat is still a whole hell of a lot of heat, even if you cut it in half.
But it’s not hopeless, not hopeless at all. You just have to attack the problem in the way it needs to be attacked.
Packing the attic space full of insulating materials, as Fred described in the first article is not going to do much good. The sun’s energy comes to us directly as radiation .. radiant energy. When it strikes the roof, some significant portion of it is reflected or re-radiated. We’ll talk much more on those processes later. The remainder of the sun’s visible and infrared energy is conducted through the metal roof and heats the air in the attic (above the room ceiling) space via conduction and immediately circulates to warm the attic space by convection. In other words, in a very short time after sunrise, the attic spaces gets uncomfortably hot and it keeps on getting hot as the day goes on.
And what is that heat trying to do … always? Travel from hot to cold .. which in this case (relatively speaking) is the room you are trying to be comfortable in.
In the US and many other countries we are very familiar with the term “R” value. It is even a government-mandated term in the US and it stems from precise laboratory tests where insulating materials are placed between two calibrated and instrumented plates in a laboratory, one plate is heated and the flow of heat from the hot to the cold plate is measured. The higher the resistance to this conductive heat flow, the higher the “R” value of the material under test.
This is of primary concern where, as I illustrated earlier, we are trying to trap the relatively minuscule energy our home heating plant puts out and keep it from being conducted into the cold night sky.
But when we go into the reverse summertime situation, especially when we have summers like they have in Miami or the Philippines, the R value essentially becomes useless. It really doesn’t matter if you have a fiberglass bat umpteen inches thick, or some sort of polyurethane materials, or even cellulose (one of the most effective R value conduction insulators known) .. with those millions and millions of watts radiating the insulation itself going to eventually heat up and essentially not even be there. You can delay the flow from hot to cold but most of the heat is coming to you by radiant energy and conductive R value products don’t effectively stop radiation.
I even recently heard a fellow here in the Philippines tell me he was going to dump a lot of some sort of high R value insulation in his attic and to keep the heat from flowing in through his walls, he was going to cover the outside of his house with Styrofoam insulation board and then stucco over that.
While researching that idea if found a pretty interesting report of a US government test that mimicked quite a bit of what he was planning to do:
The Test: Researchers at Oak Ridge National Laboratory in Tennessee which is the technology laboratory managed for the U.S. Department of Energy, took homes in Miami FL, Phoenix AZ and Atlanta GA which were single-story, single-family detached houses with exterior walls constructed of concrete block, and interior walls of wood-framed drywall. (author’s note … this pretty much describes the typical Philippine single-story hollow-block home)They insulated the walls and applied stucco as follows,
"We attached two layers of inch-thick polystyrene foam insulation boards to the exterior walls, next a wire lath, and finally, stucco. After the stucco had dried, it was painted a light color. Total retrofit costs ranged from $3,610 to $4,550 per house, averaging $3.34 per square foot of exterior wall area to be covered with insulation."
The Results? "In all cases, insulating the walls resulted in a much lower rate of heat transfer through the walls when the outdoor temperature
exceeded the indoor temperature, but the added insulation also increased the retention of heat generated within the house when the outdoor temperature fell below the indoor temperature.
In some locations–particularly in Miami–the addition of wall insulation actually increased the cooling load during the spring and fall."
Note: "A lower RATE of transfer", not a reduction in the total amount.
It’s probably worth reading and thinking about those last two sentences again. The ones I highlighted in red. “R” value-rated insulation can slow the transfer of heat by conduction, but it can not block it. And the heat that we get in our attic spaces and thence into our room here in the Philippines is only 3 to 5% from thermal Conduction the remaining 90 plus percent of the heat flow is by Radiation, and typical R value insulation not only doesn’t stop this radiant energy, it may even INCREASE the overall cooling load on your Philippine house because it holds the heat in longer during the night.
Pretty depressing overall, eh? For years we have been following that cute Pink Panther down to the Home Depot store and buying all that itchy fiberglass insulation be cause even our own government told us it was good for us and good for the environment.
Well the US government wasn’t wrong at all, they were just advising us on how to solve a totally different problem than what we have here, living in the Philippines.
Nest installment? Some solutions .. some conventional and some, positively space age. Stay tuned.
Dave
My thinking is along the lines that the more mass you have via insulation foam stucco etc that the materials will heat up and store the heat then continue to release the heat into the house even as the outside temperature cools off at night.
Im thinking either some type of double roof construction with airspace between that lets the hot air flow from low vents(cooler) to high (hotter) via ridge vent type of vents.
Perhaps some type of space shuttle high heat resistant coating on the roofing panels that would prevent heat being conducted thru the roof to the house living area.
I am looking at from a uneducated engineering point of view.
But I am a knowledge junkie and just interested in this type of stuff.
Yep, you are in my head there, Neal. As I just commented to Fred, things may be delayed a few days, I am having a “bed net day” … but space age insulation techniques definitely figure into my plans, likewise roof ridge venting … I’m amazed that this idea seems totally unknown here, and a whole house fan. That’s not so amazing as the whole house fan I had in Colorado was the only one of two or three blocks. It worked great and it will work great here, even in our little tin roof bungalow without any other changes. One of the cheapest, most effective things you can do.
Dave,
You hit the nail on the head on the futility of stuffing the attic with bulky insulation. However, i have to quibble with you about the about of solar energy hitting the average roof in the Philippines. It can’t possibly be even close to 10,000 Watts per square meter since the average amount of solar energy reaching the top of the Earth’s atmosphere (the solar constant) is only 1,366 Watts per square meter.
http://en.wikipedia.org/wiki/Sunlight
At the Earth’s surface the insolation peaks around 1,000 Watts per square meter (to use a nice round figure). Even that is enough to easily turn your roof into a broiler if you don’t do something about it. Last year i installed a home-made whole house fan in our house on the California coast. It blows air from the house into the attic, which then pushes the hot attic air out through the attic vents. We only use it on the rare hot days. It makes the second floor habitable. I’m thinking of doing the same thing in my wife’s house in Manila.
I’m pretty sure that wind-driven roof turbines (ventilators) are available in the Philippines. I think those or maybe a line of passive ridge vents combined with a lot of eave vents would go a long way towards lowering attic temperature with no electricity required.
Installing a radiant barrier sounds like an excellent idea. I Googled around and it looks like you can get reflective insulation in one square meter boards at Wilcon. http://www.wilcon.com.ph
The U.S. DOE has an informative web page on radiant barriers.
http://www.ornl.gov/sci/roofs+walls/radiant/rb_01.html
In “vernacular architecture”, indigenous people living in hot and humid climates build houses elevated off the ground to maximize cooling breezes and with low thermal mass materials to minimize heat absorption. They also have steep roofs to shed rain, high ceilings to direct hot air away from occupants, and shaded windows and porches. I’m planning to keep these ideas in mind when i get around to designing my retirement home in the Philippines.
I didn’t mean to turn this comment into a blog entry in itself, but here is one last thing: Australia has a tropical zone. The government publishes lots of info about building green in hot and humid areas. See this link for ideas on passive cooling. http://www.yourhome.gov.au/technical/fs46.html
oops: make that “about the AMOUNT of solar energy” and not “about the about of solar energy”.
Huh? You mean that decimal point means something when it’s in different places? Geez, who would have think it.
Sorry for the order of magnitude error … and thanks for reading and keeping me honest, I appreciate it. The premise remains the same, but making gross erros like that is not a good way to make one’s point. Mea culpa.
Yes reflective insulation materials are readily available here in the Philippines, although woefully under utilized. And yes, based on my previous experience with whole house fans they would be of great advantage here in the Philippines. It’s been said, with some degree of accuracy, at least in urban areas that “night is the Filipino winter”. The difference between peak day temperatures and night minimums is often around 6 to 8 degrees C, which in my area is about the same as peak daytime temps in, say, June and December. But if it takes most of the night to allow the oven over your head to dissipate, it’s a huge waste of time.
Powered and non-power commercial ventilators are available, again I have seldom, if ever, observed them used on residential buildings.
Australia, IIRC correctly, once had a research program on double corrugated steel roofed building … trying to prove that a second layer of “GI sheet” placed atop the main roof, leaving an inch or so airspace, open at the peak, would be economical in terms of heat rejection. I’d love to find out more details about that. Rural (Outback) homes in Australia often have many similarities to rural Philippines homes.
Anyone who has been to Hong Kong should have observed that a large percentage of taxis (often Toyota Crowns) have, what Toyota used to sell in Japan a “Tropical Roof” option, which is a second roof “skin” spaced just a half-inch or so above the “real” roof and open on all sides to keep the car’s actual roof in constant shade.
I don’t know much about the engineering data, but I know a few things about cab drivers, and I suspect this is a proven technique, or why would so many opt for it? Crosses my mind as a useful retrofit business here in the Philippines where labor to make such roof panels would be cheap.
One thing for sure, there is plenty room for innovation and relatively low cost experimentation here but the number one problem is not the technology, it’s the attitude of not allowing anything “different”, even for those willing to pay for it. Makes for interesting days at times.
I would love to have a house engineered to be built there in RP taking all of this into account. Maybe designed with low intake vents around the perimeter walls and high roof/ridge vents of even a roof mounted power exhaust fan that would suck in the cooler air and force it out thru the upper vents to assist the natural way that heat rises.
I have NO aircon here at all all I have is a 36 in whole house fan that does just that. Yes my house gets warm but as soon as the sun goes down and the outside air cools I open all the windows I flip on the fan and the cool air comes in and the HOT attic air is forced out all the roof vents and the house cools off sweet.
Combine that with a deep drilled heat pump/exchanger and it may be able to cool a house there in RP pretty economically. Not to mention solar power/hot water.
Im getting carried away here ooops
We’re schedules to do some work on the home owner association well here in my subdivision soon. Thanks for the heat pump idea, I’m going to get the engineer to get my some water temp readings from our medium depth well … about 260 feet IIRC. It seems to me a guy could “hybridize” an expensive heat pump set up by having a simple circulator pump … tiny flow … bring up deep water and just cool the outdoor condenser on an energy efficient split unit DC inverter aircon. Doesn’t sound practical at the costs of well drilling back in the US but some things can be done really cheap here. Time will tell.
Neal;
My roof is a flat slab of concrete with 3 rubber barriers between each pour/and re-bar. It serves as a waterproofing, system (11 years without a leak) and further as a limited insulator. The reasons I went with the slab roof are simple, they don’t blow away during typhoons, I’m not residing under 300 degree medal roof, and it’s a nice patio in the evening. Between the roof and my ceiling is insulation, and I have many large, sliding glass, tinted windows, for cross ventilation, each with an awning to prevent direct sunlight. So the only room I air/can is my bedroom, as the rest is comfortable during the day. But the smartest thing I did was build the house on a mountain, where it’s always ten degrees cooler than them flatlanders.
Paul
Im interested in your roof, so there are 3 layers of rubber roofing sandwiched between concrete slabs. This cannot be the normal construction there as If I recall almost all are tin roofs. You must have some serious concrete colums holding up that roof as well as concrete interior load bearing walls. I definately will check out your construction when I go there and visit. If all goes well I will be making my amphibious landing there this Jan/Feb.
Neal;
Not columns that are visible, but massive hidden beams to support the roof, similar to building a two story house. My house in Florida and Puerto Rico had slab roofs also.
We certainly have to talk, and soon, Paul. Right now I am weighing the idea of a new steel truss/quality metal sheeting roof or a slab for a renovation project. Much to my surprise the engineer I have been working with suggested the slab himself … he said the cost difference on our project would not be much different between the trusses and attic space versus the flat slab (and I feel we really need the outdoor living space, as the lot is really small and with some shaded areas on the roof there would be some nice outdoor living areas). I was really thinking a bit against the slab becuase I was worried about all that mass over our heads soaking up the sun for all those hours …but clearly, it hasn’t been a problem for you?
The most important reason I went with the slab is typhoons, the only houses on my street in Puerto Rico that had a roof after hurricane Hugo, were the 4 (mine included) with a slab roof. I weathered 3 typhoons here with minimal damage, small things like a broken windows and an awning ripping off. My back yard had pieces of 3 of my neighbors tin roofs piled there. I gave it back and they used it again. The downside to a slab is you must install large drains and keep them clean. Or the roof can become a nice swimming pool. So far in 11 years I’ve not had any trouble with that.
I am sitting here watching, next door. At what I guess is a typical Filipino construction job for a house. All the while giggling to myself, dig a hole put some tiny re-bar in hole prop it up right (for columns), pour a little bit of concrete to hold it up right. Then dig trenches to put in hand-made cement block, with re-bar an concrete. That was 10 days ago, we have had some really good rains lately lots of mud in holes for columns.
It will be interesting to see how it progresses!!
It does no good to laugh to your self if you have not found at better solution.
How to insulate your self cool.
http://www.sibonga.com/philippines_insulating_concrete_forms_icf.htm
Fred;
There is a better solution; do not build a house during the rainy season. One would think that solution would have been figured out a century or two ago.
Paul, I see you are making a common mistake I thought an old hand like you wouldn’t make … applying logic to an illogical situation
It’s not only here in the Philippines that people don’t think about the rainy season either. When I worked as a project planner/manager in Japan I was presented a proposal by a well-respected engineering company (US-based) with a _LOT_ of experience working in Japan. Going over the figures I saw no allowance for lost days in the rainy season. I scaled back what I told my boss we could accomplish in the time and money budget we had, and told the contractor to go ahead … guess what? That particular year the rainy season was exceptionally dry … and “Mr. Planner”, me, got all kinds of kudos for having money and time left over at the end of the project. Hey, I don’t mind taking credit for the weather … I’ve been blamed for it too LoL.
Thanks Fred. The ‘Net is really bad for me today, the next article may be a little slow. I have used the sibonga.com site many times in the past, they have some good info … thanks for reminding me.
wall insulation is really needed if you want to save on energy bills, wall insulations help save in heating cost’,,
Madelyn, thanks for commenting, but did you even read anyhting here? This is the Philippines, why would we care about saving money on heating costs? Most of the time we are trying to stay cool.
Or are you using one of those abysmal comment spamming tools that just searches the net for keywords and drops off comments no matter how inane they are? A sad waste of time, IMO, from someone who actually does make money online, rather than spam folks to try to grab a penny or two. By the way, that site you left in your URL field, (which I deleted), isn’t even working … if you want to use my blog to build links, wouldn’t it make sense to have the target site up and running first?
I am planning to renovate the house of my parents in Cavite area and I am thinking of using the attic to where there is a good space for 3 additional bedrooms. I am planning to replace the roof with light colored long span GI,then with insulation and to close it from the interior with gypsum board.drywall. However, i read about SIP roofing materials which can be used to be a good heat barrier compared to GI sheets. Can you advice me if this SIP can be used to be installed on the steel struss which is already in place? Is is advantageous for me to use SIP rather than the GI with drywall and foil insulator? Thank you.
Hello Raymond, thanks for writing in. I am unfamiliar with the SIP product but I went and looked at their site and I am now quite interested.
But I’m the wrong guy to ask about specifics, such as installing on existing trusses, etc. Why not go direct to the source. http://www.thermasip.com/ContactUs.html
I’m unfamiliar with anyone using Sheetrock ceilings here in my area. I wouldn’t touch it. myself, manly because of the extra labor costs and, in participial the mass (weight). Did you read the article you are commenting on here?
The main point is the more insulation and mass you put into the walls and roof in this climate the hotter it’s going to be, insulation/no insulation. Sheetrock is heavy, it’ll hold heat al night, radiating into the rooms below. Exactly7 what you do not want.
My thought would be to look into Hardiboard, also a concrete product as this SIP board seems to be and overall I think a lot less mass.
The idea of the SIP being finished both sides really appeals to me, I’m thinking of doing a roof renovation by rebuilding defective wood trusses with new, properly done trusses and leaving them exposed… the resultant cathedral style ceiling so make the room much cooler. Let me know what the company has to say. Godspeed.
im also interested with sip board,just dont know how long it would last
Thanks for all this information.
We are thinking of buying 500sqm land in mindanao & building a typical squater home to start then plan & build a concrete home.
2unit home 3bed down stairs 4 upstairs (ie down 2bed &sala up 2bed on left and top 2bed down 1bed & sala on right.) Each bedroom would hold a queen bed & cabinet and no kitchen inside.
bathrooms & kitchen shared outside sort of like a carport.
These are just thoughts currently Not planned out.
Would love to be able and keep it mid 70 to low 80′s.
Whole issue is keeping costs down & having a home that will last. mainly would love to hire locals to help them feed there families also.
I like the idea of The layered roof. Could also turn the roof into a partial garden & hangout spot at night. Garden especially for those on limited space.
Will try & read more of your site & familiarize myself with it. Good information Thank you for having this blog setup.
Just need to find a way to do everything less expensive but with lasting quality.
And learn more on getting the right visa to live & have the family start a business.
I was in Dobrovnik Croatia a few years back and there they had a pretty good amount of solar radiation as well what startled me was when i went to one of their towers and despite the heat and humidity outside the tower was very cool..it had a high ceiling and a vent somewhere hidden as you can feel the hot air being sucked out by physics as warm air rises..i agree with the ineffectivity of insulation and would rather have a ventilation duct aided by a fan to cool things down I think this would cool it more effectively than mounds and mounds of insulation.
Throughout the middle east you see a similar mode of construction. The towers there also create a steady breeze and i noted that most of these buildings felt comfortable in warm weather. In the US southern states many homes have high small windows placed on the southern (warm) side and lower large windows on the cooler and shaded northern side. I believe these are similar passive techniques which might be adapted to the philippines.
A method to transfer cool air into these flows might be from below ground; if you’ve been in a cave in PI you know the temps are very cool. In the states underground homes have been built and they capitilize on temps that average at or below 60F to reduce heating and cooling costs. Another way this has been used is to bassically dig a pit fill it with rock and draw air across them. I guess a large concrete slab could be buried and piping run through it to provide a sink for heat; it would just be very expensive. The point I try to make is that the earth provides a large mass that could pull a lot of heat away; maybe simply sinking 10-20 foot lengths of piping then drawing air across them. Anyhow, thanks forfor the excellent reminder and tutorial that frames the problem.
good day fellows.yuo have good observation re cooling houses in the philippines.ive done may shareand did it on my own house.using hot air rises principle and creating openings for cool and hot air,developing an alternative to louver for hot air vent that effectively moved hot air out and not allowing water to grt in in strong rain,my house always have cooler temp than outside.and there is always a presence of moving air.and also.i have skylight without thr suns heat and glare,in mot using electrical light from 630 am to 6pm.