keeping house cool

I believe one of the most significant problems here in Thailand when trying to cool a space is the high humidity which makes nearly any temperature uncomfortable. Double wall construction and insulation are all good at controlling heat gain but unless you stop the moisture from entering your house you will continue to feel uncomfortable. The best way to stop moisture from entering the house is to use a vapor barrier in the walls and ceiling. This is typically a plastic sheet or styrofoam sheet or plastic membrane installed in the wall between the insulation and the interior wall and/or ceiling. All homes constructed in high humidity Florida for example use vapor barriers of some sort. Additiuonally, installing foam weatherstripping on all windows and doors will help control the amount of moisture entering the house. It also goes without saying that you will also need to seal all the cracks and crevices with caulking as well.

Finally, is the way most people here in Thailand use air con units (let's assume they close the windows and doors before turning on the a/c unit) . Homes located in the southern US (especially Florida) exist in a climate similar to what we have here in Thailand. Air conditioned homes constructed in the southern United States all pretty much operate 24/7 during the hot part of the year. This is done in part because its much easier and efficient and less costly to maintain a set temperature & humidity in the house than to contantly try to cool & dry it from scratch. Additionally, its easier to maintain an interior temperature of between 78-80F (25-27 C)deg if you run the a/c 24/7 assuming you have a vapor barrier installed in your home. Remember when you cool your home you also cool the contents, floors (especially tiled/concrete floors), walls, ceilings etc. These cooled surfaces all act to help maintain the cool temperature therby taking some of the load off your air con unit.

Installing a vapor barrier is not particularly difficult in both new and existing construction. The use of "super block" (lightweight aerated concrete block) in new construction will provide both insulation and a vapor barrier. They are the white colored block available all over Udon now. They are easy to work with and the end cost will be similar to brick.

Existing homes can be painted with an exterior paint which provides a moisture barrier.

I don't claim to be an expert in this field but after living in Florida for nearly 30 years you tend to acquire this kind of information along the way.

I hope this helps.

Sorry your right. My mistake. If you are going to use a paint as your vapor barrier it should be applied on the inside wall of the house and not on the outside.