ASHRAE Journal - July 2019 - 55

COLUMN BUILDING SCIENCES

PHOTO 7 Penetrations in Exterior Walls. Yes, there
need to be more of them.

ventilation in many units resulting
in contaminant build-up and other
complaints.
And then the big, big, big 800 lb.
gorilla in the room-exhaust-only
ventilation. Exhaust-only ventilation
leads to excessive negative
pressures. We have been here
before ("Unintended Consequences
Suck," ASHRAE Journal, June 2013).
In multifamily buildings this leads
to drawing contaminants from
neighboring units. Are you kidding
me? You think this is acceptable?
Can you make the compartments
tight enough so air is not drawn
from neighboring units? No, not
using less than extraordinary
methods. The 0.3 cfm/ft2 at 50 Pa
level of "tightness" is not sufﬁcient to
deal with exhaust only ventilation.
Balanced ventilation, yes. Exhaust
only, no. How tight do you need to
go for exhaust only? My guess is
probably less than 0.2 cfm/ft2 at 50
Pa and good luck with getting there
on a regular basis.
How about tight compartments
with a hole in the exterior wall? No.
How about tight compartments and
leaky windows? Don't laugh, but
we have been there, but we have

FIGURE 6 Space Conditioning and Hot Water.
The compartmentalization principle can also be
extended to heating, cooling and domestic hot
water. Unit space heating and cooling and hot
water is provided by individual mechanical systems
located in each unit.

PHOTO 8 Elevator Lobby. Enclosed in a vestibule, or
"air lock" that isolates the vertical communication
from the horizontal communication.

used tight windows that we then
put a hole in. Balanced ventilation
is the only way to go. Let me repeat,
balanced ventilation is the only way
to go.II
We are not done yet. You
need to deal with the vertical
communication that elevators cause.
The elevators now have to go into
vestibules (Photo 8).
The compartmentalization
principle also can be extended
to heating, cooling and domestic
hot water. Unit space heating and
cooling and hot water is provided
by individual mechanical systems
located in each unit (Figure 6).
Distributed systems are the future-
remember computing.
The principles behind all of
this are pretty straightforward.
The approaches are pretty
straightforward. The need to do this
is pretty straightforward. Execution
is anything but. Execution
involves architectural rethinking,

II This is also the case with single-family detached: negative pressures in newly constructed code-compliant, single-family detached houses due to exhaust-only ventilation systems
lead to the ingress of soil gas such as radon and contaminants from garages.

engineering rethinking, contractor
and trade rethinking and owner
rethinking. The good news is that
we did it almost a century ago when
we ﬁrst started to go big and tall. I
think it is time again. Think of the
possibilities that new materials and
new systems can bring to the table.
Compartmentalization,
distributed ventilation systems
coupled with balanced ventilation
is the solution to indoor pollution
in multistory residential buildings.
We need to seal the right walls in
multistory residential buildings and
ventilate according to need.

Bibliography

Emswiler, J.E. 1926. "The neutral zone in
ventilation." ASHVE Journal, 32.
Handegord, G.O. 2001. "A new approach
to ventilation of high rise apartments."
Proceedings of the Eighth Conference on Building
Science and Technology, Ontario Building
Envelope Council, Toronto, Ontario.
Lstiburek, J.W. 1998. "The pressure
response of buildings." Thermal VII,
ASHRAE/DOE/BTECC, December.
Lstiburek, J.W. 2005. "Understanding air
barriers" ASHRAE Journal, (7).

J U LY 2 0 19

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ASHRAE Journal - July 2019

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