Hello,

how much wood ( in inch thickness) would be needed to do the same thermal mass properties as 4" concrete? I am thinking of hard wood beam floor instead of a suspended slab for passive solar heating...

thanks

Alexis

Concrete has a specific heat of .156 Btu/lb/°F and a density of 144 lb/cu ft. Pine is .45 & 34. That means it would take roughly 3 times the pounds of wood to store a thousand Btus as concrete, and since it weighs only about 1/4 as much the volume would be about 4 times as much per pound. It would take roughly 50" of pine thickness to store the same amount of heat as 4" of concrete. Oak is .57 & 50 so it would take only about 30" of oak! Not practical!

I concur.