Install Instructions

101
IM-PR 566442 1114 (Design Manual)
Back and Edge Heat Loss
Back and edge heat loss is the percentage of heat lost through the back and edge of the snow melt area.
Back and edge heat losses may add up to 50% to the snow melting load, depending on:
• Construction
• Insulation
• Exposure
• Operating temperature
• Ground temperature
A minimum of R-5 insulation below the tubing and on the sides of the snow melt area is recommended to
reduce back and edge heat losses and reduce response time. Outside of the slab, insulate all supply and
return lines with pipe insulation.
Figure 5-1 Minimum recommended insulation for snow melt systems. A polyethylene film is not
recommended when pavers or other porous surfaces are installed.
Next, use the multipliers found in Table 5-3 to
account for back and edge heat loss.
Procedure:
1. Use back and edge heat loss table to find the
multiplier (based on the application).
2. Multiply the snow melting load (from
Table 5-1) by the back and edge heat loss
multiplier to calculate the design snow
melting load.
Example:
Application: Full below but no edge insulation
% Increase multiplier: 10% (1.10)
Design snow melting load: 202 Btu/hr/ft² x 1.10 =
~222 Btu/hr/ft²
Back and Edge Heat Loss
Application % Increase Multiplier
Full Below and Edge 5% (1.05)
Below and No Edge 10% (1.10)
Edge and None Below 15% (1.15)
No Insulation on Slab 30% (1.30)
Exposed Bridge 50% (1.50)
Table 5-3 Back and edge losses will increase with increasing
tubing depth, soil conductivity, area-free ratio and decreasing
insulation. Back and edge heat loss multipliers assume R-5
insulation where specified. Always ensure that the insulation’s
compressive strength is rated for the application.
Concrete Slab
Foam Board Insulation:
24" min. height, 3" min.
thickness R-15
Compact Subgrade
Gravel
ViegaPEX Tubing:
Minimum ¾" height of thin-slab
over PEX tubing
Foundation Wall
Polyethylene Film:
6 mil (min.)
R-5 Insulation:
Refer to local code for insulation requirements.
(Ensure compression rating is suitable for
application.)
4"
45°