Cooling Down Roof in summer Discussion Property News & Community Talk

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Cooling Down Roof in summer

Sunday, May 15, 2011 11:51 AM

In summers roof of my house always gets very hot and makes almost impossible to sit in the upper lounge without 1.5 ton unit running at 24°C or below. I wanted to find a solution to cool down the roof. Lately I saw an ad of ICI weather shield stating it can bring the temperature 5°C. So I thought to do an experiment on the roof. To my amazement the end result was amazing and actually today I am sitting comfortably in my upper storey lounge without AC while temperatures are :

inside : 33.7°C
Temperature outside: is 41.7°C (in shadow) & 43.5°C (in sunlight). (14th May 2011)
Difference: 7°C to 10°C

However, before the application, I did a recording of temperature, (probably 10 days)

Inside Lounge: 33°C
Outside: 38°C
Difference: 5°C

How I did this ?
The roof of my house is brick layered. I inspected and found it had lots of grime & dust. The only way I found was to remove it using metal wire brush. Here it is what the roof looked like:

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1943.jpg

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1944.jpg

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1945.jpg

So I had to hire laborers to get the roof cleaned with use of water & metal brushes. The result I wanted was red bricks should be visible. This is what it looked after the cleaning.

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1947.jpg

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1948.jpg

The next stages I did were 1 coat of ICI primer and 2 coats of ICI weather shield (5°C cooler - slightly expensive than normal ICI weather shield). The area I covered with this is approximate 750 sqft. In total 2 gallons of ICI primer & 2 gallons of ICI weather shield (5°C cooler) used. ICI primer 1 gallon mixed with 1.5 liter of kerosene oil. 1 gallon could only cover half of 350 sqft. Weather shield was mixed with water 1-1 ratio or may be a little less water. 1 gallon used for 1st coat to cover 750 sqft (approx) 2nd gallon used for second coat.

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1951.jpg

After the application, next day afternoon I checked the white surface with hand and a part of bare surface ( small area where I didn’t needed to apply the coat). The difference was huge to my amazement. I could keep my hand on the white surface as long as I can, but on the bare surface not more than 3-4 seconds.

I do not have a surface temperature meter, but used this digital thermometer. Remember it cannot go above 108°F and below 97.4°F. You can see at the bare surface thermometer rises to its limits and at the white surface it comes down to its lower limit. The difference is very easily noticeable with one hand at bare surface and one at the white surface.

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1956.jpg

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1957.jpg

http://i72.photobucket.com/albums/i182/vazim/home/IMG_1958.jpg

inside : 33.7°C
Temperature outside: is 41.7°C (in shadow) & 43.5°C (in sunlight). (14th May 2011)
Difference: 7°C to 10°C

Inside
http://i72.photobucket.com/albums/i182/vazim/home/IMG_1960.jpg

temperature in Shadow
http://i72.photobucket.com/albums/i182/vazim/home/IMG_1963.jpg

in Sunlight:
http://i72.photobucket.com/albums/i182/vazim/home/IMG_1965.jpg

The trick of weather shield could be white color and material itself as well. I chose white color to get the maximum result, as it reflects sunlight efficiently.

Benefits:
Inner surface (Ceiling) is now cool.
Inner walls are also cool.

Since the roof temperature is not climbing, it is not transferring heat to inner surface (ceiling) and ultimately to inner walls. Hence in the evening, it is now wonderful and I run ac at 28°C-30°C with no one complaining of being hot or whatever :). Before that heat used to transfer to walls, hence making the whole environment hot and impossible to sit without 1.5 ton AC running at 24°C and below even in the evening & night time.

Since Lahore has a very dusty environment, I might have to keep the roof clean every 2-3 weeks. Infact it drizzled yesterday (13th May) and dust stuck to surface, so I used water to get it cleaned. Also smoother the surface, better will be the result.

This could be solution to thermal insulation although not long term. I might have to re-coat the roof next summer, but i am sure next time a single coat will do as weather shield itself should be durable.

Hope it will be beneficial to some of visitors here.

[This forum doesn't show pictures(you might have to copy & paste links in your browser. I have posted it another forum, if anyone needs the link, drop your email and i will send link.]

Jameel replied on Sunday, May 15, 2011 12:52 PM

You are right all white surfaces reflect Light and hence are colder,
would you share what is cost of one gallon paint,
meanwhile can someone elase tell that what do you Mix in white cement to make white wash

Hussain Kaisrani replied on Sunday, May 15, 2011 05:21 PM

Thank you very much dear Muhammad Waseem. It is very much beneficial for me. Next summer I will also do the experiment.

dd replied on Monday, May 16, 2011 04:17 AM

Naveed Yaseen replied on Saturday, May 7, 2011 02:08 PM PST

I have conviction that most of our buildings would not need air conditioning or heating if we properly manage....
sunlight
earth's thermal mass
insulation
ventilation

This summer I have done following things....

1) Spread on roof a quarter inch of pure white marble chips (smaller 'number 9' usually used for walls). It costed like Rs 4 to 5 per square foot of roof.

This works due to chips' white color and loose thermal connection with roof. I had also experimented with some cheaper yellowish and greyish shades of chips, but found pure white grades are feasible even when expensive. Yellowish shades were a bit worse and greyish shades were quite worse (but still better than nothing).

Although it didn't flow a grain in recent medium rains, but to be careful I arranged steel strainer at drains. And made a wide backup hole a bit high in case when strainer clogs.

I plan to collect these chips into side-heaps during winter and monsoon and then re-spread next summer.

2) Painted all sun facing walls with white cement slurry. Cost was negligible, perhaps only a few paisa per square foot of wall.

3) Placed light colored sun-shade in yard. Cost was like Rs 8 per square foot of air-breathing plastic sheet, bought new from Landa Bazar Lahore. I plan to have this shade only during summer months.

4) Removed carpets to improve thermal connection with earth. Cost is wasted carpets.

The results are good. The house is not 'cool' yet, but considerably less hot than it used to be.

The next step I am considering is to utilize groundwater's coldness (and warmth in winter) to improve it further.

If the groundwater alone doesn't bring temperature down enough then I would thermally connect air-conditioner's condenser with groundwater to improve efficiency (and perhaps cost by using smaller tube as condenser).

To save on groundwater pumping energy costs I would probably be using an inverted U topology of pipes with both open ends inside groundwater, which would allow smaller pump due to siphon principle.

ali11 replied on Monday, May 16, 2011 05:05 AM

@ Kaisrani,

welcome.

@Jameel,

Total cost was Rs. 7000/- for 750 sqft approx.

ICI primer is for Rs. 1020 and weather shield is for Rs. 1355
2 gallons of each used.
others = 650
cleaning by labor = Rs. 1500/-
paint by myself

Muhammed Waseem

Naveed Yaseen replied on Monday, May 16, 2011 07:24 AM

I think ICI's '5 degree cooler' claim for white, although true, is a marketing gimmick. Most white surfaces would do almost equally good.

However in colors other than white there does exist a genuine technology called 'Cool Colors', where some pigments have better infrared reflectivity while maintaining similar shade to eyes. Such 'cool colors' are now required by law in California and some other US states.

Some inexpensive iron-oxide pigments used by our traditional painters, like 'Sienna' and 'Phal' pigments, have been categorized as 'cool colors' by California because they have good infrared reflectivity. But do know that white is almost always cooler than shade colors, no matter how 'cool' the colors are.

Following up on white marble chips performance on roof, it is still going satisfactory. In fact, after initial abrupt change in temperature, now day by day we are feeling house even further comfortable, in contrast to summer which is heading towards peak. That is probably because earth's coldness is now slowly taking over sun's heat on building structure.

But experienced a couple of problems which were not anticipated before.

1) A cat has chosen a hidden corner for excretions. Trying to get some cat repellent for that corner. Or otherwise I would put a night light on the roof.

2) We cannot broom the roof anymore. However I think we should be ok because as of now macro-dirt (like leaves, paper, polythene bags etc) are manageable by hand with a 5 minutes pass once a couple of weeks. And the dust is getting cleaned by rains. In recent rains it 'auto-cleaned' itself pretty well.

Also felt an unexpected benefit which was not anticipated before. That is better security in night. Any activity in white background is now very visible to neighborhood, even when power is out.

Naveed Yaseen replied on Monday, May 16, 2011 07:51 AM

Referring brother Jameel's question...

> meanwhile can someone else tell that what do you Mix in white cement to make white wash

Many sources recommend 50-70% cement and rest hydrated lime mixed in 4 times water (by volume). However I was not too sure about it's durability. I had plain grey cement plastered walls and wanted to avoid vicious cycle of painting them again and again. So I just got it painted with plain white cement (Maple Leaf) mixed in around 2 times water. Watered the walls very well before painting, and did it in evening.

Faced a couple of unexpected issues. In initial days, it was leaving white powder on things rubbed against it. But after the rains it is not doing that anymore. However that came at a cost, with rains the opaqueness has decreased a bit. When it is wet, it is not opaque at all. But when it is dry it is reasonably opaque, though not up to my liking. I guess a second coat may improve it.

Habib replied on Monday, May 16, 2011 08:24 AM

Naveed I would Like to ask you how these Chips behave in heavy rain Like was there any problem of being stuck to drains.

Anyone aware of Aluminum Foil a bit thicker than usually used on paper wrapping , Has anyone trid it on the top of shades ? How does it react

KAR replied on Monday, May 16, 2011 08:47 AM

@ Naveed Yassin,

What is the underground water temperature in Lahore during summers? I guess your idea about the chilled water should work provided you have a good chiller mechanism to convert the water temperature into air.Try that and share your results..

Naveed Yaseen replied on Monday, May 16, 2011 08:58 AM

Brother Habib, we have not had the heaviest rains yet, but it did not move at all in recent medium rains in Lahore. If and when the heaviest rains move it, as noted in earlier post...

> to be careful I arranged steel strainer at drains. And made a wide backup hole a bit high
> in case when strainer clogs

On Aluminum foil, I don't think it would work as good as white surface, because it's reflectivity is about as much as white but it's infrared emissivity is very poor compared to white surfaces.

KAR, I haven't measured the groundwater temperature yet. Looking at US groundwater temperature maps of different latitudes (reference), I guess that at Lahore's latitude it would probably be not more than 26 degree centigrade, thus useful. However I would measure it soon and share the results.

ali11 replied on Monday, May 16, 2011 09:12 AM

@Naveed Yaseen,

Have these stones caused any dampness ? I have a pretty bad experience in my old house. There was a pile of stone although at the corner, but in rainy season it never went dry underneath and cause pretty good damage to roof in respect to dampness.

Also can you check if the ceiling remain cool during day ? Since last 5 days, after application, the ceiling of my house is cool, even yesterday & today when termperature is around 43-44C.

Offcourse white surface perform better than any other color. However,
yellow color is also good reflector, grey & other darker colors absorb sunlight.

For cheap solution, any white material can be used. The main question is durability. IMO whitewash & paint are not weather worthy.

I think ICI weather shield (5 C cooler) is available in various colors and not just white. This one is more expensive than normal weather shield so ICI may have used some pigments etc. Why i am saying this is that exterior walls of my house are graphic layered in light brown color. I used some leftover weather shield to paint a small part of the wall in terrace to see the effect. The result is amazing, even in sunlight one can feel the warmth difference by hand and painted surface also cool down quickly than non-painted. My next plan is to use paint on the exterior wall with another lighter color.

ali11 replied on Monday, May 16, 2011 09:43 AM

Found this useful link:

http://karachi.metblogs.com/2009/06/07/beating-the-heat/

Naveed Yaseen replied on Monday, May 16, 2011 09:51 AM

Ali, the dampness issue hasn't showed up yet in couple of spells of rains in last 3 weeks. Perhaps because the quarter inch layer is not that thick.

They do absorb some water. I remember like 6-8 hours after rain the chips were somewhat dry, and in like 24-48 hours they were dry like normal. However it is dry and hot season, we would know better in monsoon.

The roof is certainly lot cooler (a better word is 'less hot'). I remember by the touches before and after.

An interesting incident, a couple of days ago I was in a small store room with direct roof on it, I didn't have the whitened roof in my mind and I was expecting the usual scorching heat in it, but it was not hot at all. So I instinctively thought "Nice! it is cloudy out today". But then when I came outside expecting cloudy, only to find out scorching full noon without any trace of cloud, then I realized it was due to the roof work :)

ali11 replied on Monday, May 16, 2011 10:24 AM

@Naveed Yasin,

That's good. Can you please take a picture and post the link in this thread. It will be beneficial to many i guess.

Also please add this to hot topics.

Iqbal replied on Monday, May 16, 2011 12:34 PM

How about insatlling the Jumbo Dimond Foam on roof. Is it work good for minimizing the temprature. Has any one insatlled and what is the result?

LRE Hot Topics replied on Monday, May 16, 2011 12:55 PM

Post added to useful posts list. View MORE Useful Posts Click on >>> LRE Hot Topics

Patriot Systems replied on Sunday, December 25, 2011 01:20 PM

There are various industrial strength solutions available which are far better then weather shield.

Additionally a major portion of the heat entering a building or home is through its windows.

The use of a Solar Control Window Film is the ideal and most cost effective solution. Newer ceramic films offer unto 99% IR Heat Reduction.

www.patriot.com.pk

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Cooling Down Roof in summer,