ASHRAE Journal - July 2019 - 50

COLUMN BUILDING SCIENCES
Joseph W. Lstiburek

Sealing the Right Walls in Buildings and Ventilating According to Need

Compartmentalization,
Distribution and Balance
BY JOSEPH W. LSTIBUREK, PH.D., P.ENG., FELLOW ASHRAE

The focus seems to be "air barrier" this and "air barrier" that. And then we get the
chant "Build tight and ventilate right." Tight buildings are the way to go. I don't have
an argument there. But everyone is running around sealing the outside of buildings
and I think we are getting it wrong with multistory residential buildings. We should be
air sealing the interior of these buildings. We should be sealing the interior demising
walls and isolating ﬂoors from one another if we really want to improve the building
performance of multistory residential buildings. We should be compartmentalizing.*
And to add more gas to the ﬁre, I think we are
ventilating them wrong-the residential multistory
ones. In multistory residential buildings central rooftop
exhaust ventilation systems lead to over-ventilation in
upper units, under-ventilation in lower units, excessive
pressures within units and contaminant movement
between units. Aside from that they work ﬁne. We
need individual unit ventilation so that we ventilate
according to need, not according to a generic guess. Not
all units are the same and not all units have the same
occupancy and not all units are occupied all of the time.
And the ventilation needs to be balanced supply and
exhaust so that interior pressures don't get out of hand
and interunit airﬂow is limited.
So I think we are building them tight wrong and we are

ventilating them wrong. Reminds me of the arguments
relating to central computing versus distributed
computing-central control versus individual control.
Guess who won when you look at your laptop?
Back to the focus on "air barriers." On the exterior
of the building the water control layer and air control
layer have pretty much merged into a single material
or product typically called the "air barrier." It is pretty
obvious that the water control function that "air
barriers" handle is signiﬁcantly more important than
their air control function. Owners rarely get a call at 2 in
the morning saying their building is leaking air, but the
calls regarding water leakage happen 24/7.
The good news for "air barriers" is that "air barriers"
have turned out to be magniﬁcent water control layers.

* The compartmentalization concept is based on G.O. Handgord's work that he didn't get around to publishing until 2001. Gus was onto
this very early, he just didn't always write things down and get them published and peer reviewed in a timely fashion. He ﬁnally wrote it
all down in 2001. I ﬁrst heard it from him when I took his class at the University of Toronto in 1982, and he was talking about it much earlier
than that. I was sold and began pushing compartmentalization when I ﬁrst started working in the United States in the mid-1980s. See Handegord, G.O. "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, February 2001.

ASHRAE JOURNAL

ashrae.org

J U LY 2 0 19

https://www.ashrae.org/

ASHRAE Journal - July 2019

Table of Contents for the Digital Edition of ASHRAE Journal - July 2019