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2012 IRC & Multi-Family: Don’t Forget the Blower Door Testing

posted Mar 30, 2015, 2:19 PM by Stephen Mogowski   [ updated Mar 30, 2015, 2:19 PM ]

The 2012 IRC was a quantum leap with respect to energy efficiency.  For the first time in residential construction, all homes built under the 2012 IECC have to be tested by a 3rd party for whole house air leakage (blower door testing) as well as duct tightness if any portion of the duct system (unit included) is outside the building thermal envelope.

The multi-family arena qualifies under the IRC in almost all circumstances and is subject to these changes.  Most multifamily units will incorporate closet air handlers or pancake units and ducts within the floor system or drop soffits allowing for the exemption of duct leakage testing.  However, there is no exception for the envelope leakage testing.

Most municipalities will allow you to “sample” in order to keep the scope of work and costs reasonable.  There is little to be gained by testing each individual unit if the construction practices are uniform throughout construction.  The only way to know your municipality’s requirements is to ask—and even then you may get conflicting responses.  A good “default” is RESNET Chapter 6 Sampling Protocol.  If your city or town doesn't have a method in place, go ahead and suggest they follow that standard.

A major problem with testing small homes in general is that they have a disproportionate ratio of common leakage areas.  For example, a 2700sf 4BR 3BA home is likely to have a range vent, dryer exhaust, 5 or so exhaust ducts and a fresh air ventilation system.  A 1350sf 3BR 2BA apartment may have the exact same amount of exhausting appliances sans a few exhaust fans.  The result is that as the square footage (or more accurately, volume) increases, it does so in a way that favors larger homes.

Multi-family homes face another dilemma.  They are designed with adiabatic (shared) walls that are typically not air sealed due to the fact that the adjacent units will be conditioned as well.  Energy raters should take note that the sealing of receptacle boxes in the same stud bay for different units must be sealed per the 2012 IFC (fire code).  Proper execution of the fire code will help reduce infiltration between units.  Regardless, special consideration should be taken to these walls as well as exterior wall systems since the leakage at final will not be isolated to the exterior wall systems.

Lastly, even with ICAT rated can lighting and other quality building practices, there will be some amount of connection between the ceiling/floor system and the livable space.  Common areas of connection include failure to seal supply and return cans/boxes to drywall, gasket failure on ICAT lighting, duct leakage, top plate to drywall intersection and other ceiling penetrations.  If the systems are connected, you can pull air from adjacent units to either side if the units are not properly compartmentalized.  Again, a continuous firewall should help this area but in real world scenarios—we do see unsealed pipes and wires go unnoticed.

In summary, there are a lot of ways that multi-family units can fail the blower door test at final.  Proper planning should be taken to ensure there isn’t a major problem at final that will delay the project being turned over and incur unexpected repair costs.

In the conceptual phase, ensure the building thermal envelope is defined and there are no major points of breakdown.  Ensure your mechanical designer or contractor use install dampers where needed.  Go ahead and put it in someone’s scope of work to seal the exhaust fans, supply boots and return can(s) to the ceiling drywall with generic acrylic-latex caulk.  This is a small detail that is a good building practice that can reduce headaches later on.

While framing, have your energy rater perform a site walk to ensure there are no major problem areas.  Look at a few different unit types in a few different layouts (i.e. Unit A –Ground, End, Unit A- Top Mid, Unit B, Mid Mid, etc).

If you’ve done everything thus far, you shouldn’t have to hold your breath while the blower door fan kicks on at final.  The biggest obstacle we see in the multi-family arena is that our builders are unfamiliar with the process.  Hopefully this article sheds some light on the situation.

And, as always, the biggest piece of the puzzle?  Communication!

Thanks for reading,
Stephen Mogowski