Healthy Envelope Design
FRESH AIR SUPPLIED DIRECTLY TO EACH SUITE
TRADITIONAL DESIGN
In most apartment buildings, fresh air is supplied to each suite through the common
halls. The air is delivered through a common system directly into the hallway at a
constant volume and at a rate that is designed to change all the air in the building every
three hours (1/3 air change per hour). The air enters the suite either under the door
or through a duct from the hall into the suite. While this means of supplying air can work
well under ideal conditions, the hallways need to maintain a constant positive pressure in
order to prevent air from backdrafting from the suite into the hall. The required positive
pressure can be negated simply by having open windows in a suite when a wind is blowing,
resulting in contaminated air entering the hall and thus other suites. Furthermore, the
air, which is heated and usually cooled, is supplied on a continuous basis no matter how
few people are in the building resulting in a constant operating cost for gas and power.
FRESH AIR from a central system is delivered directly into common hall at a constant rate and enters suite under the door, also escaping through the elevator shaft. EXHAUST AIR leaves suite mechanically and through leakage. Suite air can flow back into hallway if suite is more positively pressurized causing wind in summer and stack effect in winter.
GRANDIN GREEN SEALED SUITE DESIGN
In Grandin Green each suite is completely sealed off from the halls and fresh air is
supplied directly into each suite through a heat recovery ventilator. Designed to provide
optimum air changes while recovering heat from the exhaust air to pre-heat the fresh air,
the system will be designed to provide the occupant with complete control over fresh air
supply. If an owner wishes it can even be turned off when the suite is unoccupied. The
benefits of this type of system are that it eliminates air contamination from other suites
thus ensuring the quality of fresh air supplied into each suite, the user can control the
costs of supplying the fresh air by turning the unit off when no one is home and the warm
stale exhaust air is used to pre-heat the fresh air. The end result is guaranteed
uncontaminated fresh air and substantial cost savings. An additional benefit to this
approach is the virtual elimination of the stack effect, a process by which air escapes
out of a building through the elevator during the winter months resulting in heating
losses.
FRESH AIR is supplied directly to each suite at a variable rate from zero
to a maximum one third air exchange per hour. A small amount of fresh air is
supplied directly to the common areas by a central system. Suite doors are sealed on all
four sides to prevent air exchange with common hallways.
EXHAUST AIR leaves suite mechanically via bath and kitchen fans. The elevator shafts and equipment rooms are sealed to prevent energy loss from air leakage.