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Technical Advice: New Energy Code Requirements
By: Terry Kastner
In the latest edition of Higher Standard, the NWCB newsletter, there is an article on Washington State’s adoption/implementation of the 2009 Energy Code. The implementation of the Energy Code brings with it some of the most significant changes to the building envelope that have ever been mandated by code.
One of these directives is the requirement for a moisture barrier to also perform as an air/moisture barrier. In the United States, 48% of energy consumed is that used in buildings. Forty to 60% of the energy used in commercial and residential buildings is for conditioning the work space and over 30% of that is lost through air leakage. If, through the use of an air/moisture barrier, you could save 30% of your energy costs and subsequently, if your heating and cooling system had less of a demand and could be downsized, what could the additional cost savings be? The savings could be significant and the demand for more energy reduced. The goal of the Department of Energy is to one day have buildings be carbon neutral. In other words the energy costs for maintaining the building environment, through a variety of methods such as air barriers, thermal insulation, solar or wind generators, water collectors, and other technologies, would be zero. The buildings may actually get to a point where they generate energy income rather than consume it.
Unlike some code changes, the actual implementation or installation of an air barrier should not be that difficult for the wall and ceiling contractor to implement. We are all accustomed to installing water resistive barriers (WRBs) and converting the effective WRB to an air/moisture barrier will just up the installation a few notches. Most if not all manufacturers of WRBs have now added air/moisture barriers to their inventories. Along with the new products come manufacturer recommended details for accomplishing the air barrier. Sealing to fenestrations such as doors, windows, brick ties, and architectural features is fairly common and similar to what we have done for WRBs. The biggest challenges will be in when we interface with roof systems, foundations, and dissimilar materials such as brick or concrete structure. As with all aspects of construction, perfection is all in the details and the code requires that the drawings clearly indicate just how the air barrier is to be constructed and how interfacing with dissimilar materials is to be accomplished.
As I mentioned above, the manufacturers are on top of products that can be used to achieve the requirements of an air/moisture barrier. These products and methods will vary from the very low-tech method of using gypsum sheathing as an air barrier and sealing all joints and penetrations followed by installing a WRB, to the more common air/moisture barrier products such as polyethylene sheet products, self-adhering sheet products, and fluid/liquid-applied products. Each product will have its own short comings and strengths. For example the “sheetrock method” may be the least expensive but in reality it is probably not up to the task. For it to be even remotely effective a fluid-applied or self-adhering product will also be necessary to seal penetrations and interfaces with other building components. Sheet products may have an advantage over fluid-applied in that sheet products can be applied to a wet surface, but most sheet goods aren’t self- gasketing so a lot of attention has to be given to sealing fastener penetrations from the cladding installations and the sheet good itself. The exposure time for self-adhering sheet products, without suffering from wind damage, is better than typical sheet goods, but the self-adhering sheet products are more expensive and, in most cases, more difficult to install than standard sheet products. As with most elements it will generally come down to cost and performance and what the owner is willing to accept.
The most noteworthy change or code requirement of the air barrier is testing. The air barrier is required to undergo testing in accordance with ASTM E283 Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen. Wow... You know it’s going to get interesting when the title of the ASTM is as long as this one. Luckily, the wall and ceiling contractor does not typically perform the test. The testing will generally be performed by a building envelope consulting company. You just have to make sure that you install the air/moisture barrier in accordance with the manufacturer’s recommendations and the project documents. One side note on this: For the time third party has conducted routine inspections throughout the installation and can confirm the installation was in accordance with the project documents. This will most likely change in the future but for now we have been given some grace during the learning curve period.
Once construction has reached a point where the air barrier is complete and the building can be sealed, a series of fans are installed to either pressurize or depressurize the building. The test will then determine if air leakage is within the required tolerances. The tolerance or levels of air leakage have been established as .40 CFM. To give some perspective on how difficult it is to achieve a .40 CFM, the U.S. Army Corps of Engineers currently requires that air leakage be no more than .25 CFM. The Corps originally set the levels at .40 CFM but, once the bugs were ironed out, they started achieving such good results that they reduced the allowable leakage from .40 CFM to .25 CFM. (To see the results of the Corps testing go to http://www.stocorp.com/index.php/20110503613)
If you happen to fail the air barrier test, thermal imaging will most likely be the method used to determine where the leak is occurring. Thermal imaging is done with a specifically designed camera that shows areas of heat differential. If at all possible, the test should be performed while you still have access to the air/moisture barrier and before any cladding is installed. It pays to do it right the first time and it is also beneficial to have the third party inspections confirm that the installation was in accordance with the manufacturer’s recommendations and the project documents.
At one seminar I went to the presenter commented that, “if nothing else, because of the testing requirement, more attention will be paid to the installation and the end result will be a better air and moisture barrier.”
As with any new type of work performed by the wall and ceiling contractor, there is a learning curve that we have to go through. To make the learning curve more efficient and less costly, I strongly recommend that you deal with manufacturers that can provide seminars on the proper application procedures for their products and that have a track record of being there for you to answer any questions that may come up during the installations. If a manufacturer or an organization provides classes or certifications on how to become a certified installer, such as the Air Barrier Association of America (ABAA), take advantage and get your people trained before hitting the wall.
One other thing to keep in mind is that, in the past, the only time that the building envelope was really tested was when there were signs of moisture intrusion and these tests generally occurred well after the construction was complete. The cost to correct the condition could easily be greater than the original contract amount and determining actual responsibility for the failure was almost impossible. There are good things that may come out of the air barrier testing:
The testing will be performed before the building is turned over.
If the air leakage falls within the accepted range you are golden, not only as far as the air barrier is concerned, but also for water intrusion.
The project documents will clearly state that the structure was certified as being air/water tight, which may help to stave off future claims.
There is no doubt that the New Energy Code requirements will, initially, add to construction costs but hopefully, in the long run the investment will pay for itself by making our buildings more efficient and lowering energy costs