In article , "Edwin Pawlowski" wrote:

"Eric in North TX" wrote in message
roups.com...

Been there done that, pointless waste of time and materials. The floors
were nearly, if not, as cold after the install. We did a good job &
hung R-19 between the joists with chicken wire to hold it in place.
Warm air rises, cold air sinks you aren't really changing anything.


You certainly are changing things. Heat moves three ways, conduction,
convection, radiation. You are addressing only convection. While hot air
is rising, heat can also be conducted to the ground that is a lower
temperature. Heat always moves to where there is less of it. Laws of
physics, not opinion.

Were the floors as cold after you insulated? Any flat smooth surface is
going to feel cool at room temperature. It has to do with skin contact to
the smooth surface. Your body is about 97 degrees. The floor is about 70
degrees. Following the laws of physics, the heat from your body is drawn to
the cooker surface. A flat wood, tile, or concrete floor is going to feel
cooler than a carpeted one because of the greater surface contact as
compared to a bumpy one with air pockets.

Bingo! Air pockets.

Still air is an excellent insulator. Most insulation materials
are largely comprised of ummmm, air.

Putting insulation under the floor reduces the amount of heat that can pass
as it is drawn to the cooler area.

The OP already has some of that under the floor. His crawl space
is sealed (not vented) and shallow. Additional insulation will
help in theory but the effect will be insignificant in practice,
in my view.

If his crawl space was 3 foot deep and ventilated, that would
be a very different situation.

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