Understanding Heat Dynamics: Conduction and Radiant Heat

First off, basically there are 2 different factors to consider when we are looking at heat transfer/travel in these various materials: Wood, Polyvinyl Chloride(PVC–plastic) and Alluminum. They are Thermal Conductivity and Radiant Heat transfer.

I will not go into a deep scientific discussion on these but will attempt to shed a little light on the way heat (mainly sunlight) impacts these materials.

Conductive heat is measured by the rate at which heat travels through a material by “conduction”. The value for conductive heat rates are K and R. We should all be familiar with “R”. R is used to rate the performance of the material as it concerns insulation applications. K is the reciprocal (opposite) value of R. K lets us know how quickly our material might heat up or cool off when heat is introduced into the equation. Both R and K are good indicators as to how various materials respond to to the introduction of radiant heat to their surfaces.

SO… WHAT TO MAKE OF ALL THIS.. Lower K values for materials indicate slower conductive heating throughout the given thickness of material. Meaning they are not as resilient at absorbing heat. This would then go on to say that lower K materials respond less quickly to heat and will subsequently take longer to heat up.

Higher R valued materials as most of us know, insulate and retain heat better.

HERE ARE RESEARCH NUMBERS;

Aluminum “K” Value (btu/in/hr/sq. ft./ degree F = 1,643 Wood ” ” = .333 PVC ” ” = 2.4

Thus PVC is less likely to heat up as quickly by conductive heat than the other two materials. NOTE!!! Aluminum has a K value that is 1,493 times higher than PVC. IT IS EXCELLENT AT HEATING UP VERY QUICKLY.

On the other hand, materials with high R values loose heat at lower rates.

Aluminum R Value = .00086 Wood = 3.03 PVC = 2.4

Wood retains heat the best, followed closely by PVC.

Color has much to do with the way radiant heat travels through materials. WHITE OR OPAQUE COLORS ARE BEST AT REFLECTING RADIANT HEAT. Painting houses white or having silver roofs would neglect some radiant heat waves minimalizing the amount of heat absorbtion.

With this info, you can see that aluminum houses HEAT UP more quickly than PVC (plastic) or wood houses. On the other hand, they cool down more slowly. This is not all bad and I feel there is a place for all three materials. Some are better than others and I have my opinion. ANY HOUSE MUST HAVE COMPONENTS DESIGNED TO ADDRESS HOW THE MATERIAL WILL BEHAVE WITH THE ADDITION OF HEAT. No ventilation is NOT a good thing. All houses must address ventilation, that is if you are considering efficiency.

Although the material has major influence on heat up, VENILATION and INSULATION also play KEY roles in remaining comfortable in our Homes.

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