INSULATING FLOOR OF HOUSE ON STILTS 

QUESTION FROM ELENA FROM WYALUSING, PA:

I have a house on stilts and enclosed with plywood and ceiling is insulated but floors are cold.  I would like to insulate dirt floor and walls to  make my house warmer and save energy.

ANSWER FROM THE INSULATION DOCTOR:

In regard to insulating your house on stilts, I am assuming (and please correct me if I am wrong) your house built on stilts is due to the fact you have a high water table.  If this is the case, there is not an insulating product made that would withstand a high moisture content in a sealed area.  We would normally refer to your walls that are plywood enclosures as "curtain walls".  If you were to install blanket or roll-type insulation on these walls they would act as a wick and absorb any moisture from the ground where the insulation touches the ground.  
 
The only thing we can recommend would be to drape the insulation from the underside of the floor to approximately one foot above the ground level.  This would not be 100% efficient but would cut into your heat loss.  You could also install a foam board type insulation on the outside of the plywood from one foot above ground level into the ground another foot.  The downside of this would be it could cause the plywood to rot due to the fact you are trapping moisture.
 
Insulating the dirt floor is not recommended because doing so will trap the moisture between the underside of the insulation and the top of the dirt floor.  Thus creating an ideal incubator for mildew and mold.
 
Bruce Jones
The Insulation Doctor