Table 1: U Values for various Construction Materials


U Values,BTU/hrF ft2


Roof and wall coverings


Glass,single layer
Glass,double layer,1/4" space
Glass,triple layer,1/4" space
Polyethylene film,single layer
Polyethylene film,double layer
(separated)
Fiberglass reinforced panel

Wall Materials

Concrete block,8"
Cement asbestos board,1/4"
Concrete ,poured ,6"
Soft wood,1" nominal

Greenhouses with thin thermal
blankets


Perimeter

Uninsulated
Insulated


1.1
0.7
0.5
1.1
0.1

1.0


0.5
1.1
0.8
0.6


0.4_ 0.5

BTU/hr F ft


0.8
0.4


Notice: The roof and wall materials that are most used
 (in Florida) are Polyethylene (double layer) and
 Fiberglass.


Material