In a resting position the human body will produce about 400 Btu's/hour. This is about 300 Btu's more than we need to survive.
In order to "feel" comfortable, we need to shed these extra Btu's. A heating system is a mechanism is which we control the rate excess heat is lost.
The slower we lose heat, the warmer we feel.
In order to heat a space, something within that space has
to be warmer than the desired space temperature (hot to
cold).
In a forced air environment, the air coming from the duct
is between 120° and 140°, assuming a 72° desired room
temperature.
In a radiant floor system the floor temperature is between
72° and 85°, assuming a desired 68° room temperature.
Heat Transfer
All forms of heating work on three basic modes of heat
transfer: Convection, Conduction, Radiant.
Convection Heat Transfer is the most
familiar type of heat. All forced-air systems are
convective heat transfer systems. This includes hydronic
baseboards and fan coils.
Conductive Heat Transfer is energy moving
through an object. Place a metal pot on the stove and in a
few minutes the handle is hot.
Radiant Heat Transfer is the exchange of
energy from a hot source to a cold source. The sun is
typically used to illustrate this mode of transfer.
Regardless of the type of heating system used, all follow
one basic rule. Hot always moves to cold. Place your hand
under a lamp and your hand begins to get warm. This is
because the lamp is hotter than your hand and is trying to
lose energy to its cooler surroundings.