ASHRAE Journal - June 2013 - 53

Photo 1 (left): Compartmentalization Air Sealing. Gypsum board is run up to the underside of the floor sheathing above and
sealed with joint compound. Photo 2 (center): More Compartmentalization Air Sealing. Bottom of walls are sealed fabulously
well when gypsum concrete floors are used. Photo 3 (right): Airtight Electrical Box. Putty pads are used to seal electrical boxes
airtight. Joint compound is used to complete the seal between the electrical box lip and the cut opening in the gypsum board.
Photo 4 (left): WeatherStripped Door. A beautiful
thing if you are worried about
fires; an ugly thing if you need
makeup air. Photo 5 (right):
High Tech Big Hole. Good for
about 25 cfm (12 L/s), so you
need three or four per apartment. They diffuse the incoming
air to avoid cold spots and
drafts.

of the compartmentalization. It has to come from the outside.
Duh. But to keep the pressures reasonable you need a really big
hole.‡ No one is ever going to do this. The big hole will lead to
comfort problems (Photo 5).
The Standard 62.1 and Standard 62.2 folks say that you are
not required to use exhaust-only ventilation. You can use supply ventilation or balanced ventilation. That is true. But what
is also true is that both Standard 62s effectively eliminate the
use of exhaust-only ventilation because it no longer can be
made to work in apartments and condominiums constructed
to the required tightness standards. The only remaining good
news is that exhaust ventilation can still be made to work in
single-family detached houses without atmospherically coupled
combustion appliances—although as an approach exhaust-only
ventilation is a pretty poor excuse for ventilation.
So how do you actually do this? How do you meet the ventilation rate requirements and the tightness requirements and
get something that works? One way is to install a rooftop unit

that preconditions the air and then duct it down to each corridor
and then into each individual apartment unit. You couple this
with bathroom exhaust and kitchen exhaust. As an engineer,
I do not have a problem with this. This is actually pretty darn
good. It is just that I don’t think folks understand that there
is a new sheriff in town and that this is now the deal.§ What
else can you do? You can do a balanced system such as heat
recovery ventilation (HRV) or energy recovery ventilation
(ERV) (Figure 2). As an engineer, I would love to do this in
units. I like Porsches too.
We are not done yet. At the flow rates we are now talking
about, we have a part-load humidity problem in many parts
of the Republic. Note that we are actually building energyefficient houses, apartments and condominiums. We have
great windows with low SHGCs (solar heat gain coefficients),
compact fluorescent lighting and enclosures that are actually
insulated well. Ah, here is the rub. No load, no cooling, no
dehumidification from cooling. Oops. Now we need dehu-

†It

is 20 cfm per 100 ft2 (9 L/s per 9 m2) of compartment surface area at a pressure difference of 0.2 in. w.c. (50 Pa) for Standard 62.2. Does anyone who
voted for this even know what this means? This is ultra-tight and not achievable without extraordinary effort. The number comes from one building done in an
extraordinary manner in NYC. It is way tighter than the LEED multifamily compartmentalization number, which in itself is not easy to do—but can be done with
effort. I did not ever think I would say this, but the LEED number is a pretty good number. Please don’t tell anyone at LEED that I said something nice about them.
‡How about a bunch of small holes? How about trickle vents? Sure. Each trickle vent gives you about 7.5 cfm (3.5 L/s), so you only need 10 of them per apartment. OK this is meant as a joke. It would be dumb to put 10 holes in the wall per apartment.
§Actually, what this will mean is that Standard 62.1 or Standard 62.2 will not be adopted by most jurisdictions for multifamily construction, and they will sit on
the shelf like most standards that make themselves irrelevant because they overreach. Standard 62.2 is currently being ignored by the International Residential
Code committee for this reason.

June 2013

ASHRAE Journal

ASHRAE Journal - June 2013

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