TM 5-852-9/AFR 88-19, Vol. IX
should be considered in the design process. Prefabricated concrete buildings have been successfully utilized
for major construction projects in arctic and subarctic regions. Where repetitive patterns can be used, precast
concrete panels should be considered for walls and roofs because they have proven more economical than
cast-in-place concrete, even at remote sites. Use of a prefabricated system generally reduces construction
time. Particular attention should be given to caulking the joints and connections of prefabricated items.
Caulking is discussed more fully under TM 5-805-6, and in paragraph 2-6 in this chapter.
(2) Concrete masonry units. Characteristics of concrete masonry units (CMU) with added
reinforcement are similar to those of concrete construction. Disadvantages of concrete block construction
are the relatively high costs of shipping, breakage, labor, and longer construction time. Therefore, these units
are not generally used in remote areas. The inherent multiple horizontal joints tend to collect and hold
moisture, especially at extremely wet sites. Most types of concrete blocks have to be sealed and painted or
covered with another material for weatherproofing. The covering must breathe sufficiently to allow internal
moisture to escape. Trapped moisture causes increased deterioration. Over the life of a building, maintenance
can become costly. Concrete block construction is more practical when the source of supply is near the
building site. Thermal breaks are also required in concrete masonry unit construction [see paragraph 2-
2c,(4)], but concrete masonry units are inherently thermal bridging. The concrete web between the indoor
and outdoor surfaces conducts heat past the holes which may contain either air or insulation. Even special
blocks designed to incorporate maximum insulation and minimize the cross section of concrete between the
inside and outside are usually not suitable for arctic or subarctic construction. Metal masonry ties between
blocks and another masonry layer represent another type of thermal bridge, even when insulation is present.
An exterior insulation layer can avoid problems with breaking thermal bridges across walls with masonry.
Differential settlement which often occurs with foundations on permafrost can cause problems with CMU
walls and this factor should be considered in the design process.
b. Metal. Metal buildings constructed of rigid steel frames or columns and beams with metal siding and
roofing may be composed of standard steel products or components prefabricated at the factory and
assembled at the construction site. The basic advantages of prefabricated metal buildings include lower cost
of manufacturer's stock items (constructed with revisions to meet the arctic wind and snow loads), and
erection speed. Stock sizes can be factory-modified to space members or fasteners closer to meet greater
wind and snow loading design criteria. If only air transportation is available to remote sites, consideration
must be given to the size and weight of members. Many prefabricated buildings require only standard
equipment for erection. A positive thermal break (such as cellular plastic or wood isolators installed in
compliance with local fire codes, as illustrated in figures 2-1 and 2-2) is required in heated buildings to
prevent cold conduction through the structural members. If conduction is present, frost, and ultimately,
dripping water, can form on the interior walls. A continuous, sealed vapor retarder is necessary on the warm
side of exterior walls in all heated buildings to minimize condensation within the wall insulation.
(1) Metal frame, siding, and roofing. Metal frames may be erected rapidly at the site; however, to
obtain a given fire rating additional fire-resistant treatment may be required. Covering the surfaces with
noncombustible, heat-resistant materials may be necessary. Fastening the siding and roofing to the framing,
whether by screws, bolts, or welding, will cause through-metal-conduction problems. Through-metal
conduction, and resulting condensation and ultimate frost buildup inside of buildings where such
accumulation would create problems, must be prevented or minimized. Minor frost buildup caused by
through-metal conduction may be tolerated in subarctic areas, however, for such structures as automotive
maintenance shops, heated auto storage buildings, etc. Thermal-break insulation for components is available
from most manufacturers but careful selection must be made to assure suitability for arctic construction.
Figures 2-1 and 2-2, following page, show how wood or cellular plastic, when installed in compliance with
local fire codes, can be used to prevent through-metal conduction. Voids in thermal walls and roofs should
either be filled with insulation to curtail the chimney effect, or adequate draft stops should be provided. Metal
roofing fastened directly to the steel frame is apt to leak in time as thermal movements stress the fasteners.
The newer standing seam metal systems, which are supported on clips with a sliding feature, have improved
long-term performance.
(2) Insulated arctic metal panels. The advantage of using these panels is rapid field installation.
Panels may be used in lieu of separately installed metal sheets, insulation, a vapor retarder, and the interior
finish. There are also disadvantages, however: the possibility of damage during transportation and installation;
2-2
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