Dometic 10 - Manual (Page 8)

About Insulation
Before we go any further, let’s talk briefly about insulation. Most truck sleepers today are insulated with a
value of approximately R 1 to R 1.25. Compare this to the insulation of R 30 that is required in most new
housing construction. Even the “cold-weather packages” offered with some new trucks only have insulation
values of R 2. TMC recommended practices call for R 4.2 as a standard insulation package and greater
than R 4.6 in a premium package. This standard, once adopted by the industry, will go a long way toward
improving the performance of auxiliary air conditioning and heating systems.
If you are buying a new truck, you should order it with additional insulation. There are also a number of
measures you can take to reduce the heat load in your truck. If you have skylights, cover them. Insulate
the floors with foam under the carpet. Add insulation to the doors. Get heavy-duty curtains to separate the
sleeper from the cab. Cover the windshield and windows with reflective shades when parked. Park in the
shade whenever possible. Switch off heat-producing appliances in the sleeper.
Air Conditioning Units
Your first step will be determining the type of air conditioning units (split or self-contained) to meet your
requirements and space constraints, then sizing the units to meet the expected heat load.
Sizing the system can be a complicated affair, since it depends on a number of factors, such as the size and
shape of the sleeper, the amount of insulation (see above), the size and location of windows, the color of the
truck (darker colors absorb more heat) and the ambient temperature outside. The following guidelines are
based on TMC recommendations under “average” conditions. If you are operating in very hot regions, you
may need to consider extra capacity.
7,000 BTU/hr Day cab or smaller sleeper up to 48 with flat roof
10,000 BTU/hr Mid-size 60 sleeper with low or mid-height roof
14,000 BTU/hr Full-size 60-72 sleeper with high-rise roof
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