PRINCIPLES/DESIGN AND CONSTRUCTlON
When the commitment to thermal envelope integrity is lacking, problems arise in many areas. For
instance, the efforts of the various design disciplines (architectural, structural, mechanical,
electrical) will not be coordinated with the continuity and integrity of the air barrier and insulation
systems in mind. Problems in these as well as other aspects of envelope performance will arise
when the activities of these separate disciplines are not considered in relation to one another. Poor
communication, a segregated approach to developing design details and a lack of commitment to
thermal envelope integrity in the development of these details can result in envelope system that
can not be effectively insulated or air sealed (Kudder). Kudder presents an example of such a
problem that concerns the edge of a floor slab, as shown in Figure 2.4.1. The structural drawing
showed only the spandrel beam supporting the floor slab, but did not show the wall. The
architectural drawing included the wall, but did not show the beam located just inside the wall. The
structural drawing implied that there was free access for the installation of fireproofing on both sides
of the beam, and the architectural drawing implied that there was free access to the wall for the
installation and finishing of the drywall all the way up to the floor slab. In fact, due to the location of
the beam, the drywall screws could not be installed and the drywall joints could not be taped,
leading to the leakage of interior air into the wall cavity. This problem occurred because their was
no commitment to an air barrier system and because of poor coordination among the design
disciplines.
ARCHITECTURAL DETAIL
COMBINED DETAIL
STRUCTURAL DETAIL
Figure 2.4.1 Example of Poorly Coordinated Detailing (Kudder)
It is important for the various participants in the design and construction process to understand
each others roles, motivations, limitations and abilities. While this is more easily said than done, it
is absolutely essential. Designers need to develop details with consideration of the fact that the
construction workers have no design background and should not be forced to guess the designers
intention or play the role of designer. The role of construction worker should be to build as carefully
as the details were developed. Therefore, construction details need to be precise, easy to
understand and buildable, with no guesswork left to the workers (Perreault 1980). Too often, the
design process involves copying design details from previous jobs or published details that contain
no air barrier system and include significant thermal bridges, as opposed to designing the envelope
as a system and considering each detail in relation to this system.
PAGE 2.4-2
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