Part A: Understanding Balcony Thermal Bridging
A.2 Balcony Design Considerations The basic function of a balcony is to provide
exposure to rainwater, seawater, or other
private or semi-private outdoor space,
incompatible materials. Thermal bridging can
expanding the physical living space and
also lead to condensation buildup within the
range of activities possible in a dwelling unit.
connection posing a threat to the durability of
It is also a key part of the architect’s toolkit
the structural material.
when developing the overall aesthetic and composition of the building.
In addition to the balcony structure itself, it is important to understand the support
Although the primary focus of this report
requirements for balcony doors and glazing
is the thermal performance of the balcony
systems, and to ensure required support is
connection detail, thermal performance is
provided; for example, in high performance
just one of several considerations of balcony
building envelopes doors and glazing systems
design. There are other attributes in balcony
should be located in plane with the insulation
design, both in the construction of the balcony
in the opaque assembly, while other door and
itself and its impact on the overall building that
glazing systems may require continuous sill
need to be considered.
support. In balcony connection details where
Structure
structural material is not provided directly below the wall, door and glazing system,
The structural integrity of the balcony and
additional structure may be required to support
safety of its occupants is fundamental to
the sill of the door and glazing system (Figure 1).
the balcony design. The balcony generally
Thermal Performance, Occupant Comfort and Resilience
cantilevers or is connected laterally back to the building and must resist dead, live, and lateral loading as well as meeting local seismic
Most of the focus in discussions around thermal
requirements.
bridging mitigation is to quantify and reduce
The size of a balcony’s structural connection back to the building’s primary structure is directly related to its weight and loading requirements. By reducing the weight of a balcony, through its size, construction or materiality, the size of the structural connection back to the building can also be reduced.
the associated heat loss. While this is important in tackling the carbon footprint associated with buildings’ operation, of no less concern is the impact on both the building itself and its inhabitants due to the thermally compromised detail(s). These include: nj Thermal resilience—the ability to
This in turn decreases the amount of thermal
provide shelter despite power outages
bridging through the building envelope. When
or extreme weather events;
optimizing the balcony structural connection,
nj Occupant comfort—eliminating
the stability or perceived “bounce” of
discomfort due to radiant heat loss,
cantilevered balconies must also be taken into
removing the risk of mould growth and
consideration to ensure user comfort levels.
associated indoor air quality issues;
The durability of the connection materials
nj Building resilience—providing protection
must be considered when specifying a balcony
against rising energy and carbon
connection detail. Concrete or steel balconies
costs, and increasing overall durability
can be at risk of deterioration either through
by reducing condensation risk. 6
