MIL-HDBK-1011/1
Figure 3
Moisture Migration and Vapor Barrier
7.9.3
Sprayed in Place Polyurethane Foam (PUF). Polyurethane foam has
been used as roof insulation. However, the difficulty of obtaining skilled
applicators and the impracticability of applying it in windy conditions limit
its use in the tropics.
7.9.4
Polyurethane Board. Rigid polyurethane board insulation is
manufactured faced and unfaced. Facings include foil and perlitic fiberboard.
The boards are secured to the deck with mechanical fasteners or with hot
asphalt. In the latter case, the urethane is faced on one or both sides with
perlitic fiberboard. Rigid polyurethane insulation board is recommended for
use under EPDM single-ply roofing. In this case, use board that is faced on
the bottom side with fiberboard and top side with foil. When used with a BUR
system, add a second layer of fiberboard with joints staggered over those of
the urethane board below.
7.9.5
Fiberboard.
Fiberboard is not recommended as a roof insulation in
the tropics. It will absorb, conduct, and hold water. It swells when wet and
deteriorates. As a result the roofing system may blow off when subjected to
high winds.
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