Author Topic: Passive Cooling  (Read 10911 times)

Offline Palawan Aussie

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Passive Cooling
« on: May 14, 2013, 10:09:41 PM »
Frosty writes,

Quote
It sounds like insulation is an after thought when building a house. What has everybodying been using to insulate the outside walls?



There's good information regarding passive-cooling here .. in fact, the whole website is excellent ..

http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm


For example, here's a simple research initiative that people might like ..  (I wouldn't use lime on an aluminium or tin roof though)

http://www.builditsolar.com/Projects/Cooling/WhiteRoofExperiment/WhiteRoof.htm (snipped)

From David: My roof needs replacing anyway, so I thought I would do an experiment to see the effects of painting it WHITE. I have already placed digital thermometers in the attic for previous experiments so I could easily monitor progress.

I started off with a product made for the purpose... a highly reflective "elastomeric" roof coating. However, a 5 gallon bucket of this product costs $60.00. I figured I needed TEN of those 5 gallon buckets to cover my 1300 square foot roof. That put the cost up around $600 dollars. TOO MUCH MONEY for a little experiment.

So I opted for the EL-CHEAPO method of using HYDRATED LIME mixed with 50% water to do the job. Two bags of Hydrated Lime cost $14.00 total!!  It is available in the concrete department of any hardware store for $7.00 per 50 pound bag. This stuff goes on kinda GRAY looking when it is wet. But when it dries it is BRILLIANT WHITE.
 
Lime kind of burns your skin, so don't get it on your skin or eyes. I did all the mixing right on the roof so I wouldn't have to lug all that water up the ladder. Just kept the water hose running while  worked. Painting was easier by just dumping a gallon or so at a time right on the roof and just rolling it evenly. It took about 6 hours of work to accomplish the task.

Here are the results of this experiment: Attic temperatures were reduced by about 30 to 40 degrees.... and house temperatures were reduced about 8 or 10 degrees. Some folks might think 8 or 10 degrees isn't much... but, it is right on the edge where we don't even need to run the air conditioner! I personally would not use AC at all.... but the wife still likes it ON occasionally.

If a simple home-owner like me can accomplish reducing my attic temperature by 40 degrees by using fourteen dollars worth of paint... why cant these roofing companies come up with something that can reflect the heat without breaking my bank account?

It has rained a couple times since painting... and the lime seems to be holding on OK and not rinsing off. Don't paint if its going to rain in the next 24 hours though. ONE neighbor asked what i was doing. I explained I was "coating my roof with special reflective coating" to reduce air conditioning costs. If he had objected, I would have mentioned that president Obama recommended doing this in one of his speeches!  Right now, this looks "unusual"... but in a few years i believe white roofs will be very common to reduce greenhouse gases and electric bills. One village in Greece has ALL their roofs white.




« Last Edit: May 14, 2013, 10:58:46 PM by PalawanAussie »

Offline Art, just a re(tired) Fil-Am

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Re: Passive Cooling
« Reply #1 on: May 14, 2013, 10:47:58 PM »
It all sounds and looks practical, but who would want an all white roof that doesn't fit the scheme/theme of one's subdivision, unless one lives in Greece or on the Greek Isle of famous Santorini where everything is all white washed, except for a few blue dome roofs!
We're in the Philippines and anything is possible, if one wants it to be and where there are no restrictions!   

https://www.google.com.ph/search?q=pictures+of+santorini+greece&rlz=1C1FDUM_enPH474PH476&tbm=isch&tbo=u&source=univ&sa=X&ei=W06SUbLkD8iZiAeU0YDYBA&ved=0CCkQsAQ&biw=1120&bih=635
« Last Edit: May 15, 2013, 12:09:58 AM by Art, re(tired) Fil/Am »
"Life is what we all make it to be"!
"It's always a matter of money"!
"Do on to others as they would do on to You, but do it first"!
"Different strokes for different folks"!
"Que Sera Sera"!

Offline paulgee

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Re: Passive Cooling
« Reply #2 on: May 17, 2013, 03:00:25 AM »
Our sub division has red, blue, orange and brown roofs on the houses. We went for the whitest roof they did, which is a creamish colour.
Not sure what difference it makes, but one can only try.

Paul

Based in the UK, and part time in our San Fernando, Pampanga house

Offline Frosty

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Re: Passive Cooling
« Reply #3 on: May 17, 2013, 12:46:38 PM »
I think the lighter colour roof is a great idea, maybe not white but a light gray or tan maybe even a light blue.

Did you notice the roof vents thats another good idea, you don't want to trap all that hot air in the attic space it needs away out.
My brother put in a solar attic fan he told me it works great in the summer to help cool the house.

Offline wildbill

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Re: Passive Cooling
« Reply #4 on: May 17, 2013, 07:18:11 PM »
no need to insulate the outer walls of most houses in the philippines because they are made of cement hollow blocks etc...:)

Offline paulgee

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Re: Passive Cooling
« Reply #5 on: May 17, 2013, 07:53:16 PM »
Our house was built in our absence, with only family there to check things out. So we had no chance to do anything more about insulation etc. When we are there full time I hope that we can do something retrospectively to vent the roof space, or cover the ceiling there with insulation.

As I remember it the ceiling structure was composed of  thin metal struts, as picture below. I am not sure one could crawl round the loft space supported by them!

Paul

Based in the UK, and part time in our San Fernando, Pampanga house

Offline Tally J

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Re: Passive Cooling
« Reply #6 on: May 17, 2013, 09:20:04 PM »
The builder is currently installing the furring strips to hold the gypsum board for the ceiling in the house I am having constructed.  I am trying to get them to install insulation while this is being done as the ceiling supports are certainly not strong enough to support my "excess" weight.  I am still running into resistance "as this is not the way it is done here" not to mention having a hard time locating insulation that is at least 3 to 6 inches thick rather than the 3-4 mil they will install.  The insulation will make a significant difference in the inside temperature on the second floor of the house.

I have my brother-in-law trying to track some down for me though.

Offline wildbill

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Re: Passive Cooling
« Reply #7 on: May 17, 2013, 10:07:11 PM »
Tally Colin says they have the thick insulation in CITI hardware but im still looking around no citi here where I live I will posts it if I find any

Offline Tally J

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Re: Passive Cooling
« Reply #8 on: May 17, 2013, 10:54:48 PM »
Thanks Widlbill.

House in the Angeles city area. I Googled CITI but there does not appear to be a location in the Angeles area.  Cannot locate insulation on the Wilcon, Home Depot or Federal web sites so that is why I asked my brother-in-law to see if he could locate some.  Building is hard to do long distance.

I may just have to buy it here in US and then ship it along with my household goods.

Offline Gray Wolf

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Re: Passive Cooling
« Reply #9 on: May 18, 2013, 12:34:44 AM »
no need to insulate the outer walls of most houses in the philippines because they are made of cement hollow blocks etc... :)

Typical hollow blocks act as heat sinks and will retain heat built up during the day well into the evening hours.  I know of several people who have added sheets of foam insulation to the interior walls to reflect that heat away from the interior.  Some have even used foam insulation on the outside of the walls to prevent the heat from building up in the first place. 

Colin, and others, used thick foam panels in construction in lieu of concrete walls.  They were then skim coated with a thin layer of concrete to add solidity to the walls.

"It's not done here" is a typical response given by builders in the Philippines.  But keep in mind, these same people think that temperatures in the 70's (20'sC) are "nippy".  Go figure.   ;)

Insulation, both foam and fiberglass, is available in the Philippines.  You just have to do some work to find the proper supplier.
Louisville, KY USA

Offline Frosty

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Re: Passive Cooling
« Reply #10 on: May 18, 2013, 09:21:07 AM »
GW your right about block walls heating up during the day, without any insulation to prevent the walls from heating up the air con will need to work over time to keep up with the outside tempture.

Offline wildbill

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Re: Passive Cooling
« Reply #11 on: May 18, 2013, 09:24:19 PM »
Yes it does heat my outside walls as well some times I put the hose pipe to work in the afternoon just to try an cool the wall down.

Offline Frosty

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Re: Passive Cooling
« Reply #12 on: May 19, 2013, 10:24:29 PM »
My brothers and I built my parents house. 3 of my brothers are engineers and they all thought they were the boss,and they were all a pain in my a_ _, anyways back to my point. one of my brothers figured out where the sun was during the different seasons of the year. Winter time the sun is low in the sky the windows on the south side of the house were placed so they got the max amount of sun light. In the summer they figured out how to keep the wall on the south side of the house in the shade by the overhang of the eve, we ended up with a 2 foot overhang for our location, only the bottom of the wall gets any sun during the day this is not a big deal it helps with light in the basement and the basement is always cooler.
I was thinking that before anyone starts to build they should take a tape measure and walk around and check out the shadows on walls and where the sun is hitting the wall. In the long run it will save money on the power bill.

Wildbill
Have you thought about some kind of water mist, I've seen them down in Las Vegas outside where people are walking around it helps to cool them off
« Last Edit: May 20, 2013, 12:02:37 AM by Gray Wolf »

Offline wildbill

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Re: Passive Cooling
« Reply #13 on: May 20, 2013, 09:51:37 PM »
water mist no I havent but thanks it would really help I think

Offline BingColin

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Re: Passive Cooling
« Reply #14 on: May 23, 2013, 07:44:34 AM »
I have been away for a few days visiting El Nido so have not been able to respond until now.

I think it important to insulate walls even if you are not planning to use much aircon. Take a look at this section of my web site. http://thephilippinejournal.wetpaint.com/page/Design  We use very little aircon and the house is noticeably cooler most of the time even with the windows open. A hollow block wall has an R value of around 1.0 and my 3 inch polystyrene walls around 11.0. That is 11 times better; they are cold even if the sun is on them all day. If you want to use aircon then you will have a big reduction in electricity bills. We only have fans in the lounge and master bedroom, but I do use a small aircon more often in my study. There are other aspects of house design that you need to consider to make it comfortable, and I cover them on my web site.

Whatever you do with the walls, it is essential to insulate the attic space and give lots of ventilation. We used 6 inch foil bags filled with fibreglass from Citi Hardware, but they then stopped stocking it at our local store. You should be able to buy the rolls of fibreglass at building supply stores.

 


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