Installation Guide

Solution to improve floor warming response time
DITRA-HEAT-DUO
The challenge of concrete substrates
Concrete substrates can absorb enough heat energy to significantly increase the time it takes for floors to warm up, particularly when there
is no insulation layer below the concrete. In some cases, floors may never reach the desired temperature. There are solutions suggested
by other heating cable manufacturers to address this challenge, such as installing the heating cables at closer spacing for increased
energy output or installing a thermal break prior to heating cable installation to reduce heat loss into the substrate.
1
However, both of these
solutions increase material and labor costs.
A one-step solution
Schluter
®
-DITRA-HEAT-DUO offers the same functions as the Schluter
®
-DITRA-HEAT membrane, but also features an integrated thermal
break in the form of a thicker bonding fleece. The thermal break reduces the initial rates of heat loss to the substrate, and improves the
floor warming response time during temperature ramp-ups. Since an effective thermal break can be created with a relatively low R-value,
the DITRA-HEAT-DUO membrane is only 5/16" (8 mm)-thick, compared to DITRA-HEAT at 1/4" (5.5 mm)-thick.
Thermal resistance
The DITRA-HEAT-DUO thermal break was tested according to the ASTM C518 “Standard Test Method for Steady-State Thermal
Transmission Properties by Means of the Heat Flow Meter Apparatus” and determined to have an R-value of 0.35. This value may seem
low, but it is sufficient to improve the system warm up time. If improving overall energy efficiency is desired, and the floor warming system
is to be used for extended periods of time (i.e more than early morning and/or evenings) increased thermal resistance may be required.
Floor warming performance
In laboratory testing, when heating the floor from 68°F (20°C) to 78°F (25°C), DITRA-HEAT-DUO reduced floor warming response time by
approximately 80% (90 minutes) compared to DITRA-HEAT over a concrete substrate.
Wood substrates act as insulators and typically do not pose the same challenges as concrete substrates. In the same laboratory testing,
when heating the floor from 68°F (20°C) to 78°F (25°C), DITRA-HEAT-DUO only reduced floor warming response time by approximately
20% (5 minutes) compared to DITRA-HEAT over a plywood substrate.
Schluter
®
-DITRA-HEAT-E-HK heating cables were spaced at three studs in all of the above tests.
Results above are based upon laboratory testing. Actual results may vary depending on various factors, including concrete substrate
thickness, concrete substrate temperature, room temperature, heat losses, etc.
0 010 1020 2030 3040 4050 5060 60
67.0
68.0
73.0
78.0
83.0
88.0
93.0
69.0
71.0
73.0
73.0
77.0
79.0
81.0
83.0
85.0
70 7080 8090 90100 100120 120110 110
Time (minutes) Time (minutes)
Temperature (ºF) Temperature (ºF)
DITRA-HEAT
DITRA-HEAT-DUO
DITRA-HEAT
DITRA-HEAT-DUO
Figure 1 - DITRA-HEAT-DUO Performance over Concrete Figure 2 - DITRA-HEAT-DUO Performance over Wood
DITRA-HEAT-DUO 31