Back a few years ago to my bike riding days, after a long ride, I'd have soup at a variety of outdoor places.  The coolest by far were the places with grass roofs.  The next coolest were the ones with steel roofing that had thin sheets of aluminum-covered insulation glued underneath.  Steel roof without the insulation were next, but noticably hotter.  Roofs made of fiber board were a bit hotter than the steel without insulation.   

We replaced our original fiber board roof with the steel panels that had the thin foil insulation.  Then we added 4" batts to our ceiling.  Had the foam-backed insulation panels been available then, I would have opted for that.  

In the end, you want to do everything possible to limit the heat bearing down on the roof and coming through the ceiling.  

A few years ago, we replaced our older air conditioners with Daikin inverters......smaller size than what we had, but with the new roof and ceiling insulation, the house stays cool even in the hottest of days.

If the sun hits the sides of your house, I'd suggest planting rows of palms.......if you babysit them for the first year with plenty of water and mulch/fertilizer, they'll grow quickly.  

In Thailand, the sun is your enemy if you're trying to keep your house cool.

 

12 hours ago, SomchaiCNX said:

Correct, but my house is just the last one in the row and there is a gap of about 10 m with the next one. Depending on the season I get a lot of airflow through that gap. 

That will help for sure. Also if the air is cool that will cool the space as well. 

11 hours ago, sometimewoodworker said:

Humm.

 

First the foil installed just under or touching the underside of the roof doesn’t act as a reflector, it acts as an extremely poor radiator, about 5% to 7%.

 

In the floating roof design the main heat transfer method between the 2 roofs is radiant and since you have cut that down by 93%~95% that is better than most other methods.

 

The foil gives the most cost effective reduction in radiant heat transfer at a vastly lower cost than fibreglass.

 

The foil on the top surface of the fibre glass will quickly loose its effectiveness as dust builds up so reducing it’s reflective properties.

 

The foil is able to reduce the effective heat from  my steel roof from 63^oC to 37^oC so as to laughing yes I am, all the way to the bank.

 

You do have to install the foil shiny side down for it to be effective.

 

Of course the film is only one part of the insulation but it’s so cheap to install when building you would be a fool not to include it at about 14~28 Baht per square metre

Sorry that’s total BS. DC is not, can never be 3 phase. The phases are related to the sign wave of AC current.

True, though with good design we never hear the outside units, the inverter cassette in the living room, when on doesn’t vary its fan speed and our bedroom AC has a silent mode so can’t be heard.

 

even better are the MrKen fans that on low speed move plenty of air and are virtually silent.

 

so with double AAC walls & high quality laminated IGUs we drop about 25db and between 20%~30% humidity. We also don’t have a storage heater for our roof material.

I won't argue with you about the foil. My roof already had it as I mentioned and the insulation made a vast difference. Do you seriously believe anybody would invest in insulation if a few baht of foil would do as well? 

 

Also I won't argue with you about 3 phase inverters but am providing links so you can educate yourself. I spent several years as an electronic design engineer designing these and now alas, I find out I wasted all my time as did the companies that paid me and sold my controllers and  their customers who bought them ? Not. 

 

Sorry, but you are wrong. Now I'm curious what you think the inverter thing is all about with aircons, refrigerators, generators, etc. Follow the links and learn something new.

 

Don't worry about apologizing, fortunately there is a cure for ignorance. 

 

https://en.m.wikipedia.org/wiki/Brushless_DC_electric_motor

 

https://www.homemade-circuits.com/50v-3-phase-bldc-motor-driver-circuit/

 

https://www.elmos.com/english/produkte/motor-control-ics/brushless-dc-motor-controller-ic/bldc-motor-controller/e52342.html

 

 

Finally, thanks for the loads of info about fan noise levels at your house but it's irrelevant to the topic. 

3 hours ago, RocketDog said:

I won't argue with you about the foil. My roof already had it as I mentioned and the insulation made a vast difference. Do you seriously believe anybody would invest in insulation if a few baht of foil would do as well? 

If you read my post you would notice that I don’t say that foil does the same job as fibreglass. Using the correct type of heat reduction strategies for the location is important and there is nothing as cheap and effective in reducing radiation as foil. Using the correct terms is also important as using the wrong ones leads to complete confusion.

 

with heat radiation there are two different preventative strategies 

1) reflecting heat  <reflective barriers>

2) not radiating heat. < radiant barriers>
 

that the same film can do both does not mean that it is, or is in the correct location for the barrier you want.