The case for the commissioning of air barriers in buildings becomes more compelling every day. The building energy consumers: heating and cooling equipment, lighting and appliances have benefitted from huge technological improvements that squeeze mor... [Read More]
The case for the commissioning of air barriers in buildings becomes more compelling every day. The building energy consumers: heating and cooling equipment, lighting and appliances have benefitted from huge technological improvements that squeeze more energy saving dollars out of the amenities these systems provide. The controls industry (using what has been described as variable speed everything) is increasingly able to almost instantaneously match delivery with demand so that less energy is wasted. Efficiencies unheard of just a few years ago are a reality today. For example: LEDs lighting is arguably the most efficient lighting source available; these coupled with smart controls can save from 40-80% of lighting’s current 19% share of electricity consumption. These industries are competing to be the most efficient part of our buildings. Wow!
It all reminds me of the ‘56 Chevy I worked on many years ago: a rebuilt engine, new clutch, remanufactured brakes, sweet radio, roomy back seat, cool wheel covers. Wow! But bad tires. Who cares; who looks at the tread? Listen to the radio, listen to the engine, it stops on a dime – but I couldn’t drive the Chevy very far for fear of a blowout, and had to slow way down to go around curves, and at the end of the day – nobody wanted to ride. For my car it was time to address some fundamentals - the tires. For most buildings it is time to address some fundamentals - the enclosure. Whereas, I wanted to keep the air in my tires, We all need to keep unwanted air out of our buildings.
I get bored with analogies so let’s look at some facts as seen on two of my favorite graphs:
The first graph from the Pacific Northwest National Lab shows how the increasing “stringency” of the commercial energy code since the mid-1970s has promoted an almost 60% “theoretical” improvement in the way the commercial buildings perform. How did this happen? Through increased efficiency for heating and cooling, for lighting, for appliances for motors, better windows, increased insulation and smart, integrated control strategies. Why it this “theoretical” savings? I’ll get to that in a minute.
The second graph is from Steven J. Emmerichand Andrew K. Persily of the National Institute of Standards and Technologyshows the best “apples to apples” comparison of air leakage data over the last 50 years. The amazing thing is that even while all the other building energy technologies have seen significant improvement, until recently there has been little to no improvement in commercial building air leakage.
A few things to point out: The average from this data set is about 2 CFM leakage / envelope area when the building is pressurized to 75 Pascals. The US Army Corps of Engineers standard requires a blower door demonstrated leakage of less than 0.25. How hard is that to do in a new building? Step 1) Read and follow directions, Step 2) Meet the other contractors and agree how to handle air barrier transitions. Air barriers in existing buildings can also be repaired resulting in significant improvement.
Air barriers actually do double duty. Think about how difficult it is for the energy efficient HVAC system to manage comfort if uncontrolled air leaks into the building? What about control sensors that are looking for accurate temperature and pressure sensors in a leaky ceiling plenum? And how well does all that insulation work if outside air is able to pass right on through? The Energy Code Stringency chart represents theoretical savings because – in part – those saving won’t be achieved unless a good air barrier is present.
As the other building systems have reduced their energy consumption, air leakage has become a much bigger piece of the energy pie. Reducing air leakage in commercial buildings is the, as yet, barely tapped opportunity for saving energy and making buildings perform.