04-12-2010, 06:32 PM
[quote]Originally posted by DanielP
Kathy,
If you have 10 ft. ceilings, then it is inside that needs ventilating. The hot air rises by convection to your ceiling, then heats downward radiantly. Install a couple of operable windows (awning style) at the ceiling level to allow that hot air to escape.
I'll make this as clear as I can: what hot air are we talking about that rises by convection? If the air inside is hotter than the ambient temperature (as it is in most homes), you must ask yourself why. People breathing and appliances generate some heat but very little. The air indoors is hot because the radiant heat of the sun comes through the roof, through fiberglass insulation and through anything that is not either sufficiently dense or reflective. That heat, when it hits objects that are dense, like the floor, the walls, the ceiling, the furniture, your head, heats up those objects. Those warm objects then transfer that heat to the air circulating around them. That is why you have hot air near the ceiling in a house.
(A side note: The reason the shade of a tree is cool is because the trees, being filled with water, are sufficiently dense to absorb the radiant heat of the sun and not allow it to pass through and heat up the ground below or you if you are lucky enough to be under one.)
The best solution is to keep out this radiant heat in the first place. Installing a radiant barrier is also the cheapest and easiest solution.
Kathy,
If you have 10 ft. ceilings, then it is inside that needs ventilating. The hot air rises by convection to your ceiling, then heats downward radiantly. Install a couple of operable windows (awning style) at the ceiling level to allow that hot air to escape.
I'll make this as clear as I can: what hot air are we talking about that rises by convection? If the air inside is hotter than the ambient temperature (as it is in most homes), you must ask yourself why. People breathing and appliances generate some heat but very little. The air indoors is hot because the radiant heat of the sun comes through the roof, through fiberglass insulation and through anything that is not either sufficiently dense or reflective. That heat, when it hits objects that are dense, like the floor, the walls, the ceiling, the furniture, your head, heats up those objects. Those warm objects then transfer that heat to the air circulating around them. That is why you have hot air near the ceiling in a house.
(A side note: The reason the shade of a tree is cool is because the trees, being filled with water, are sufficiently dense to absorb the radiant heat of the sun and not allow it to pass through and heat up the ground below or you if you are lucky enough to be under one.)
The best solution is to keep out this radiant heat in the first place. Installing a radiant barrier is also the cheapest and easiest solution.