Comparative Insulation Efficiency

Page 45

K-Factor

“K” is the thermal conductivity of a material as

defined by ASIM (American Society of Testing

Materials) as follows:

The amount of heat (BTUs) transmitted through

(1) square foot of material (1) inch thick, in (1)

hour with a temperature differential of 1°F

between the two surfaces of insulation, @ the

average or mean temperature of the material.

BTU One (1) BTU is approximately the amount of

heat required to raise the temperature of one (1)

pound of water.

Mean Temperature:

The artthemtical average between hot and cold

faces of insulation.

Example: Pipe temp 200°F, outside temp of

insulation 80°F: 200+80 ÷2=140°F (Mean Temp.)

Comparative Insulation

Efficiency

The lower the “K” value the better the insulation.

R value = Thickness of Insulation ÷ “K” Factor

Material K Factor @ 75°F

Foam glass 0.37

Rock Wool (Batts) 0.32

Asbestos Fibre 0.30

Styro Span 0.26

Fibreglass AF 320 3/4 LB 0.26

Fiberglass AF 327 1 LB 0.24

Rigid coated duct 0.24

Fiberglass AF 545 0.23

Fiberglass pipe insulation 0.22

Urethane Foam 0.12 –0.16