On 1/13/2020 at 2:48 PM, scorecard said:

My investigation on this point is that some form of ventilation is needed to get the very hot air out of the roof cavity, otherwise the upstairs rooms will be quite hot from heat soaking down from the hot air in the ceiling plus the upper level room closest to the sun will be super hot. 

 

Further the professionals on this subject seem to suggest ventilation to get the hot air out and ventiliation to allow cooler air to get in.  

This is a no-brainer

1 hour ago, Kurtf said:

This is a no-brainer

I agree, but asking around earlier I noted that my Thai builder (professional well experienced company, built multiple houses in multiple villages) wasn't knowledgeable about this matter and when we asked him to show us some photos / adverts or whatever of suitable vents he had no suggestions at all.   

 

Quite some heated discussion. Nice!

 

Here some essential readings on natural ventilation that may be of interest to interlocutors.

 

 

Intro to Cooling Buildings by Nat. Vent.pdf Natural_Ventilation_Approach_in_Designing_Urban_Tropical_House.pdf

On 1/13/2020 at 7:40 PM, Mattd said:

The air inside the roof space is degrees warmer than the outside air, by some considerable margin, the heat is radiated in to the space from the roof, which is then exacerbated by the lack of movement, don't believe me, then try going in to the attic for a while!

At least if the space is ventilated it allows some of the hotter air to escape and creates movement.

 

Agree.  The guy who said vents are pointless was totally wrong.

 

Not only air in an un-vented a lot hotter, it will radiant down.   I keep reading some older TV posts with people saying that since the "ambiance" temperature outside was so hot, there was no way to cool the inside of the house with vents and windows.  Completely untrue. 

 

With heat convection effect, the air hot will rise and any air flow or breeze will provide cooling relief.   It is possible for the inside of the house to be cooler than outside with the right ventilation/insulation/shading even before using the air conditioners.

1 hour ago, Skylight said:

 

Agree.  The guy who said vents are pointless was totally wrong.

 

Not only air in an un-vented a lot hotter, it will radiant down.   I keep reading some older TV posts with people saying that since the "ambiance" temperature outside was so hot, there was no way to cool the inside of the house with vents and windows.  Completely untrue. 

 

With heat convection effect, the air hot will rise and any air flow or breeze will provide cooling relief.   It is possible for the inside of the house to be cooler than outside with the right ventilation/insulation/shading even before using the air conditioners.

While all of that is true the problem is that you will also have the same humility as outside. I manage to maintain the internal humidity at under 70% even when the outside is at over 95%., I’m usually at least 10~20% under ambient and a similar 10+15 degrees under the maximum daytime temperature, often without AC.

For me the lower humidity makes using just fans OK for most of the daytime 

47 minutes ago, sometimewoodworker said:

the problem is that you will also have the same humility as outside.

Just use AC.  Your humility will improve when you stop sweating.

3 minutes ago, bankruatsteve said:

52 minutes ago, sometimewoodworker said:

the problem is that you will also have the same humility as outside.

Just use AC.  Your humility will improve when you stop sweating

Didn’t you read the post?

my humidity and temperature is under ambient while not using AC most of the time.

1 minute ago, sometimewoodworker said:

Didn’t you read the post?

Did you?  Try again.  ????  (Clue:  spelling)

4 hours ago, bankruatsteve said:

Did you?  Try again.  ????  (Clue:  spelling)

Touché ???? that’s why you should never proof read your own writing and also never proof read important documents on a screen.

14 hours ago, sometimewoodworker said:

While all of that is true the problem is that you will also have the same humility as outside. I manage to maintain the internal humidity at under 70% even when the outside is at over 95%., I’m usually at least 10~20% under ambient and a similar 10+15 degrees under the maximum daytime temperature, often without AC.

For me the lower humidity makes using just fans OK for most of the daytime 

 

You are going to need either AC or dehumidifier if you need to reduce the humidity significantly.   A little breeze and air movement should still help though.