We live in Tagaytay and our bedroom is on the second floor, I use my AC every night except for the months of Jan, Feb, and March (started using in March), others may be able to do without but it does get warm, especially on the second floor.
When we finally do move, I will be certain the master bedroom is on the first floor.
jjcabgou has a great idea: put the master bedroom on the ground floor! I would put the guest bedroom(s), storage and a gym or rec room, if I had one, on the second floor. In addition to being cooler on the ground floor, mobility may become an issue as the years pass, so having the master bedroom and bath on the ground floor with the living room, dining room and kitchen makes perfect sense.
It does depend very much on location, but air does move faster above the ground away from the friction. If I were to build another house, which I won't, the main living area could be up on pylons with the master bedroom above that. I would use the ground floor space for a dirty kitchen, maids quarters and car parking.
Also, take a look at some of the very old traditional Philippine bungalows that have a single open bedroom above them, or sometimes a single row of bedrooms with an outside balcony.
My thinking has changed over the years and parhaps an alterative would be a compact bungalow, Australian outback ranch style, with very high insulation and double glazed windows.
Ever thought of feeding the hot air from the house through pipes buries well under the house to cool it. You could use computer fans powered by a solar panel to move the air.
Lots of ideas
