Precast Concrete Decks

Vermiculite Lightweight Concrete: Insulating Concrete over Precast Concrete Decks
Vermiculite concrete lends itself to providing both drainage slope and high insulating values to various types of precast concrete units such as core type structural slabs, channel slabs, and prestressed single and double tees. Vermiculite cast-in-place concrete provides smooth surface for applying the built up roofing membrane. Should additional venting be required the use of roof vents similar to McKinley Roof Vents should be installed -- one vent for each thousand square
"U" Factor Table (includes Built-up Roofing)
Thickness
of Structural
Concrete Deck
140 lb.
Density P.C.F.
Insulating Concrete -- Thickness and Weight
2" -- 4.16 Lbs./Sq. Ft. 3" -- 6.24 Lbs./Sq. Ft. 4" -- 8.32 Lbs./Sq. Ft.
No Ceiling
Heat Flow
Ceiling
Heat Flow
No Ceiling
Heat Flow
Ceiling
Heat Flow
No Ceiling
Heat Flow
Ceiling
Heat Flow
Up Down Up Down Up Down Up Down Up Down Up Down
2" .23 .21 .12 .11 .17 .16 .10 .10 .13 .13 .088 .085
4" .22 .20 .12 .11 .17 .16 .10 .096 .13 .13 .087 .084
6" .21 .20 .12 .11 .16 .15 .099 .095 .12 .12 .085 .083
Notes:
  • Add 6 lbs. per sq. ft. for built-up roofing.
  • Ceiling used in "U" value calculators is 3/4" Fiberglas lay-in panel.
  • Authority for "U" values based on ASHRAE Guide and test data by recognized independent laboratories.