CONDENSATION RESEARCH
4)	 Where concrete balconies/projections 
bedrooms, some had above-slab insulation 
and others did not (Figure 4).
3	 MECHANISM  
OF CONDENSATION
Think of condensation as occurring  
when warm, humid air meets a cold,  
condensing surface.
Examples include breathing onto a 
window to play tic-tac-toe, the bathroom 
mirror after a hot shower or grabbing a 
cold drink from a summer BBQ’s cooler.
3.1	 COLD,  
CONDENSING SURFACE
Per Figure 4, the bedrooms’ stained 
baseboards and wet flooring overlap 
with uninsulated concrete balconies/
projections, which are heat loss pathways 
that respond to outdoor temperatures.
If the outdoors is sufficiently cold, it can 
reduce the wall corner’s temperature to 
dew point, creating condensation. This is 
supported by comparing the bedroom’s 
coldest surface temperatures (14-15°C) 
against the indoor dew point (23°C /  
56 per cent RH  13.7°C) – measured at 
a location with observable moisture  
(Figure 1, Figure 3).
Note that these surface temperatures were 
measured on a 10°C morning. Overnight 
lows and colder winter months would 
worsen this cold, condensing surface.
3.2	 WARM, HUMID AIR
For Vancouver’s climate, BC Housing 
suggests maintaining 18-24°C and 35-60 
per cent RH to mitigate wintertime 
condensation (www.bchousing.org/publi-
cations/Maintenance-Matters-3-Avoiding-
Condensation-Problems.pdf).
The unit’s indoor conditions were 23°C 
and 56 per cent RH, which lands in 
BC Housing’s higher range. The facility 
manager recently replaced the unit’s 
Energy Recovery Ventilator filter. Also, its 
supply/return air grilles had consistent, 
measurable airflow. The tenant is a family 
of four occupying a three-bedroom unit, 
which should be accounted for by modern 
HVAC design. There was little evidence to 
suggest that the HVAC system  
was malfunctioning.
Anecdotally, my own 2000s apartment 
(with fewer people than this tenant’s) 
hovers around 21°C and > 50 per cent 
RH during winter – probably not 
much ventilation happening through its 
undercut suite door.
Does the tenant’s lifestyle create high levels 
of warm, humid air? Or does the crux lie 
with concrete thermal bridging creating 
cold, condensing surfaces?
4	 CHALLENGING ADAGES
Despite higher heating bills, uninsulated 
concrete balconies remain a common 
feature in BC’s construction market. 
Perhaps the industry’s notion is that in 
Vancouver’s mild winters, heat loss  
through concrete balconies is safe from 
significant condensation. 
In contrast, this case study’s condensation 
was so severe that flooring near balconies 
FIGURE 5: NE BEDROOM, NORTH ELEVATION VIEW IN THE FEA MODEL.
FIGURE 4: LAYOUT OF INVESTIGATED UNIT.
FIGURE 6: NE BEDROOM'S INTERIOR VIEW IN THE FEA MODEL.
14  BCBEC ELEMENTS  A BCBEC PUBLICATION

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