Section 7: THERMAL AND MOISTURE PROTECTION
Scope. This section covers various roofing systems and their
performance in a hot and humid tropical environment of frequent winds, driving
rain, and intense sun.
General Design Considerations
Roofing Systems. For the purpose of this handbook, roofing systems
include the roof deck, insulation if used, the roof membrane, vents and
drains, and any other element incorporated into the system. The following
roofing types throughout the tropical humid zones are predominant because they
have provided satisfactory service:
a) Built-up (Bituminous) Roofing (BUR)
(1) With Mineral-Surfaced Cap Sheet
(2) Smooth Surfaced with Reflective Coating
(3) With Gravel Surfacing
b) Elastomeric Roofing (Sheet-Applied)
Elastomeric Roofing (Fluid-Applied)
Corrugated Metal Roofing
Comparison of Roofing Systems.
For a comparison of roofing systems
and materials, see Table 2.
Built-up Roofing (BUR)
General. Built-up roofing systems in tropical-humid environments
have performed well, especially on roofs without insulation. Certain
installations however have not performed well -- gravel surfaced roofs, roofs
over insulation, and those installed on existing dead flat roofs. The gravel
surface, usually coral, blackens with algae and deteriorates, becoming a
growth medium for sprouting seeds.
Insulation. Insulating a BUR roofing system adds to the layers of
an already labor intensive installation with a greater chance of moisture
becoming entrapped in the system. The insulation provides a path for water
infiltration from minor leaks which would have been only a local problem if
the insulation were not under the roofing membrane. Where insulation is
mandated, such as for air-conditioned buildings, carefully and properly
install the roofing system to minimize these problems.