ASHRAE Journal - February 2014 - 48

Column BUILDING SCIENCES

FIGURE 9 More Compartmentalization. You have to

FIGURE 10 Unit Ventilation. Do not run ducts and

think three dimensionally and treat your interior
walls like exterior walls. A minimum resistance
or air permeance of 2 L/(s·m2) at 75 Pa of unit
airtightness is necessary to control stack effect air
pressures and to limit airflow from adjacent units
and cross contamination.

shafts vertically. No central systems. You can't
make that work. You need to keep the ducts
within each compartment and vent directly to the
exterior. No complaints from you architects about
penetrations being ugly. Just deal with it.

of us guessed at what unit airtightness should be. I proposed a minimum resistance or air permeance
of 2 L/(s·m2) at 75 Pa.5 It seems to be
working. This level of unit airtightness is necessary to control stack
effect air pressures and to limit airflow from adjacent units and cross
contamination.
Let's say you achieve compartmentalization. You are not done.
Now, the mechanical engineer can
screw it all up by running ducts
and shafts vertically. No central
systems. You can't make that work.
You need to keep the ducts within
each compartment and vent
directly to the exterior (Figure 10).
No complaints from you architects
about penetrations being ugly. Just
deal with it.
The compartmentalization
principle can also be extended
to heating, cooling and domestic
hot water. Unit space heating and
cooling and hot water is provided
48

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by individual mechanical systems
located in each unit (Figure 11).
Rooftop penetrations are collected
and located in "doghouses," minimizing penetrations. All cable, duct
and pipes are run through walls
of "doghouses" (Photo 3). The "doghouse" lids are removable allowing
for access.
So, at the end of the day, how do
things stack up for us? In houses
we have learned to live with lower
neutral pressure planes by designing and constructing walls to be
more moisture tolerant, and we
have learned to compensate for
the lack of active chimney induced
air change by providing controlled
ventilation systems. In tall buildings we are learning to compartmentalize and to provide distributed ventilation, distributed space
conditioning and distributed hot
water. Carrying around the weight
of that ocean of air doesn't seem so
difficult anymore.

FEBRUARY 2014

FIGURE 11 Space Conditioning and Hot Water.

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.

PHOTO 3 Distributed Mechanical Systems. This

is why the Gods of Building Science invented
flat roofs: a place to stash mechanicals. Rooftop
penetrations are collected and located in "doghouses"-all cable, duct and pipes are run through
walls of "doghouses."

References
1. Emswiler, J.E. 1926. "The neutral zone in
ventilation." ASHVE Journal (32).
2. Handegord, G.O. 1998. "Building Science
and the Building Envelope." Handegord
and Company.
3. 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.
4. Lstiburek, J.W. 2005. "Multifamily buildings." ASHRAE Journal 47(12).
5. Lstiburek, J.W. 2005. "Understanding air
barriers." ASHRAE Journal 47(7).

ASHRAE Journal - February 2014

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