indoor-outdoor air leakage of apartments and commercial buildings

from outside California. As a result, we can draw no definitive conclusions about the situation
in California. However, the data suggest the following with regard to commercial buildings
overall:
1. Within a given building activity (education, retail, etc.) there appears to be little
systematic variation in leakiness as a function of construction type.
2. Within a given construction type (metal-frame, masonry, etc.) there is some evidence
that schools and public assembly buildings tend to be somewhat tighter than average
and that warehouses tend to be leakier than average.
3; BUildings with small "footprints" (i.e. small roof area), under 1000 m 2 , tend to be 25% to
50% leakier, per unit envelope area, than buildings with large footprints.
4. Taller buildings appear to be slightly tighter than shorter buildings (with single'-story
buildings being perhaps 10% to 25% leakier than taller buildings, per unit envelope
area), but (a) the scarcity of tall buildings in the database gives us little statistical power
to address this issue, and (b) almost all of the tall buildings are office buildings, so we
cannot distinguish a height effect from an effect of building type (item 2).
5. For buildings of a given construction type and activity, footprint size, and height,
leakiness per unit envelope area is approximately lognormally distributed, with a
geometric standard deviation between about 1.7 and 2.2.
6. On average, commercial buildings may be about twice as leaky as single-family houses,
per unit of building envelope area.
The deficiencies in the available commercial building data could be addressed through
an experimental program to measure air exchange rates or leakage parameters in a
representative sample of bUildings. If such a program is to be undertaken, it should not rely on
the usual past practice of using a "convenience sample" of buildings that happen to be available
to the researchers or in which the building owner or operator is especially motivated to
participate in an experimental program. The use of convenience samples has been very
important in the past - indeed, if not for this practice we would have no commercial building
measurements at all! However, any future research program needs to be large enough to make
measurements in at least 10 buildings in each category on which it focuses, and those buildings
should be selected to be statistically representative of their categories. Ideally, a stratified
random sample of the buildings in California would be conducted, with stratification used to
ensure that some buildings are sampled even for unusual building categories. Such a program
could provide useful, accurate, quantitative data concerning building leakiness. A much less
ambitious program would focus only on specific issues. Rather than simply sampling fewer
buildings of each type than would be sampled in an ideal program, a less ambitious program
could reduce the scope (in terms of the types of buildings sampled) but still sample at least ten
of each type. For instance, an obvious question of practical interest is whether buildings are
getting tighter (and thus, generally, more energy efficient) with age; this could be addressed by
sampling, say, 15 new medium-sized office buildings and 15 old medium-sized office buildings,
41