Insulating Floor Joists – The Original Foil Insulation

Take a look at this short post showing Infra insulation, the original reflective foil insulation used to insulate wood floor joists.  The three examples are:

  • In Floor Joist
  • In Floor Joist – Radiant heat in floor joist
  • In Floor Joist – Radiant heat imbedded in concrete

The italics text below is an excerpt from the Simplified Physics of Vapor and Thermal Insulation, by Alexander Schwartz.

The applications are the same today, see how to insulate floor joists with modern materials.

Radiant Heat and Wood Floor Techniques

Heat flow in Conduction and Radiation is from warm to cold in any direction.  The ground or the cellar area below a floor is usually colder than the inhabited rooms above, so there is considerable wasteful heat flow downward; first by direct conduction through the floor, then by radiation from the under-surface of the floor to the cold ground or cellar floor. 

Multiple accordion aluminum has negligible conduction through its air spaces.  (In any air space, heat flow by conduction is only 5% to 7% at most.) There is no convection downward.  The preponderant heat flow downward is by radiation.  This will be reflected back 97% to augment the heat which the floor emits upward at a 90% rate.  Multiple accordion aluminum can reduce original and upkeep heating cost.

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