[Strawbale] Perception of temperature: Radiant, conductive, convective, and forced air heating.

[Sherwood Botsford]

Let me throw a little calming gasoline on this discussion.

With a slab heater in a tight house, the slab is just barely warmer than 
the air.  While not forced air, it really isn't radiant heat either.  
I'll call it conductive heat.

With hydronic baseboard heaters, while the heaters are significantly 
warmer than the air, they are usually shielded from direct line of 
sight.  They mostly heat the air next to them and let if waft away.  I 
call it convective heat.

When you have a wood stove glowing bright infrared, or a natural gas 
radiant heater along the ceiling, now you have radiant heat.

The perception of heat/cold depends on many factors:
If you have windows, with serious cold outside, then there is a sheet of 
cold air running down the window.  This sheet has a ravenous appetite 
for bare ankles.  It also has a tendency to pool and form mounds behind 
chairs and ottomans, gathering strength for an attack at the kneecaps.


If you have a leaky old house then there are countless drafts -- moving 
air seems colder.  These are spritely spirits that seem to have a strong 
preference for necks.

If the air is very dry, then your body will work at keeping the layer of 
air next to the skin at 30% RH.  Evaporating water to fill this pulls 
therms from you.

In an old drafty house the air at the floor tends to stratify, and be 
10-20 degrees colder than the air at the ceiling.  Since your feet were 
cold all the time, you feel cold.  In a tight house, there is less 
stratification. Whatever the heat source, you will be happier at a lower 
temp. 

A leaky house with a hydronic slab feels warmer, I think, because the 
heat at the bottom destroys the stratification.

This is one reason that putting a ceiling fan in a room makes it more 
comfortable.  The air isn't pushed hard enough to be a draft, but the 
room air is mixed to a very even temperature.

One place I worked had a shop with a gas fired radiant ceiling heater.  
If you turned off the lights it would glow a just perceptable red.  You 
KNEW when it was on.  The shop was usable 10 minutes after turning on 
the heat.  When you went in, you arranged your work so that there was a 
clear line of site between your hands and the glow tube. If you sat at a 
table to work, your knees and feet were under the table -- and were 
cold.  I saw the kids working in T shirts, long pants, long johns, and 
snowmobile boots.  A shielded thermometer read -10 C.  One laid on a 
work table near the heater would read 20-30C depending on the color of 
the table.