When you are cold you put a sweater on.
This keeps heat in.
If really cold out a jacket over the sweater. Thicker is better and increases the resistance or R factor making you more comfortable. Same principle as home insulation like the Pink Panther Insulation. Helps keep heat IN your house.
In cold climates putting insulation in our walls and in our attics helps resist heat loss.

But what does it do when you are trying to keep heat out?

Do you wear a sweater and jacket outside in August doing yard work? To keep cool? Shouldn't buildings in different climates be constructed to address the simple law of thermodynamics which is "heat always flows from a higher temperature to a lower temperature".

These are legitimate questions

The insulation in an attic of a home in a hot sunny climate is being bombarded by infrared heat traveling at 186,000 miles per second and heating up the insulation like a low level broiler.

Question: "If you went outside and held a R-30 batt of Pink Panther over your head to block out the sun (without the backing on it), do you think you can see light through it?
Of course you can. Glass is transparent to light and infrared heat. Standing behind a glass window with the sun shining through it proves this.
Are glass windows hot to the touch when sunshine is streaming through it? The same happens with glass fiber insulation.

We call it the "Sweater Effect". Visit our web site to learn how our patented products can mitigate this.
www.savenrg.com/sweatereffect.htm