Literature Review on Building Envelope, Heating and ... - Beeshive.org

lowest life cycle cost. The building envelope incorporated a continuous vapour barrier,
and the construction was designed to be airtight. A pile foundation elevated the building
600 mm (24 in.) above the ground to keep the underlying permafrost from thawing.
Heating system: The residential units are heated by a hydronic baseboard fin-tube
system that uses a central fuel oil boiler.
Ventilation: Heat recovery was incorporated into the design, because of the large
temperature differential between indoors and outdoors. An individual HRV was provided
for each residential unit. The HRV supplied air, as per ASHRAE Standard 62-1989 v
(ASHRAE, 1989), to centralized occupied areas within each residential unit. The return
air grilles were located in the kitchen and bathroom(s). It was an air-to-air plate type heat
exchanger with counter-flow airstreams.
HRV defrost: The potential for defrost is present eight months of the year, where the
mean monthly temperatures are below -1ºC (30ºF) except for June to September. Defrost
was provided by recirculation of the exhaust air stream back through the supply to the
heat exchanger. Defrosting by preheating supply air significantly reduces recovered heat
benefits. The defrost cycle was designed to be initiated when the outdoor temperature
was less than -2ºC (29ºF) and continue until the temperature of the air stream entering the
HRV heat exchanger is 1ºC (33ºF). The defrost time was limited to no more than 20% of
the operation time at design conditions.
Supply air diffusers: Location and selection of the supply air diffuser were important to
avoid dumping cold air into the room. As recommended by the ASHRAE (1992), ceiling
diffusers were used for the supply air whenever was practical. Sidewall diffusers were
used when it was necessary to accommodate architectural restraints.
Indoor humidity: Outside air at winter design temperature of -39ºC (-38ºF) passes
through the HRV and enters the occupied area at a temperature of about 4ºC (40ºF) and a
relative humidity of essentially zero. Thus, an excess ventilation rate is not desirable,
because it could result in reduced indoor air comfort. Ninomura and Bhargava (1995)
commented that, 20% relative humidity is considered optimum during winter for arctic
residences. At a relative humidity of less than 20%, occupant’s discomfort and
complaints might increase. Experience in the arctic showed that a relative humidity above
20% could result in condensation and mould growth.
Energy savings: The fuel costs in Kotzebue, Alaska, in 1993, were $1.6/gal for # 1 fuel
oil and $0.1844/kWh for electricity. The net savings were calculated to be $464 per year
with a pay-back time of seven years. (The HRV installation cost was $1,500.) Ninomura
and Bhargava (1995) concluded that HRVs were an economical way to provide
ventilation that complies with ASHRAE Standard 62-1989 and saves on operational
costs. The extreme low temperatures of the arctic presented challenges in the
incorporation of HRVs in the ventilation design.
PERD-079: Task 2 - <strong>Literature</strong> <strong>Review</strong> 82