Environmental Design + Construction - August 2008 - (Page 95)

SUSTAINABLE HOME Particle Diameter ( m) 0.01 2 3 4 5 0.1 9 8 7 6 2 3 4 5 1.0 9 8 7 6 2 3 4 5 10 9 8 7 6 PLANT SPORES MOLD CARBON BLACK Air Filter Efﬁciency Adapted from ASHRAE Standard 52.2 Composite Average Efﬁciency, E MERV Rating MERV 8 MERV 9 n/a n/a n/a n/a n/a E < 75% 75% 85% 95% E < 85% E < 95% E 0.3 - 1.0 Microns n/a 1.0 - 3.0 Microns 3.0 - 10.0 Microns 70% 85% 85% 85% 90% 90% 90% 90% 95% E E E E E E E E E ANIMAL MINERAL COMBUSTION BACTERIA VIRUSES ASBESTOS TOBACCO SMOKE FLY ASH E < 50% 50% 65% 80% 90% 90% 90% 95% E < 65% E < 80% E E E E E MERV 10 MERV 11 MERV 12 MERV 13 MERV 14 MERV 15 OTHER/MISC. AUTO EMISSIONS INSECTICIDE DUSTS MERV 16 Denotes particle size extends farther than what is shown. INDOOR AIR QUALITY Filters are tested in accordance with ASHRAE Standard 52.2 and assigned a MERV (Minimum Efficiency Reporting Value) number depending on their efficiency in the 0.3 to 10.0 micron size range (the average human hair is about 70 microns). LEED-H requires a MERV 8 filter at a minimum in a forcedair mechanical system under Indoor Environmental Quality Credit 7.1. One point is earned for a MERV 11 filter, and two points are awarded for a MERV 13 filter. At first glance, a higher-efficiency filter seemed like an easy way to earn this project a couple of points, but this wasn’t necessarily the case. Most modern residential furnaces use a blower motor with limitations on how much air it can push through the duct system. After factoring in the pressure drop across the cooling coil and the friction in the ductwork, there normally would not be enough static pressure left to overcome the pressure drop across a high-efficiency filter. Since there is no cooling at Cate School, we did not have to worry about the pressure drop across the cooling coil. The Carrier Infinity 96 furnace uses an electronically commutated motor (ECM), which is significantly more efficient than the standard AC motor and can provide a higher static pressure to the system. These factors allowed us to install a MERV 13 filter and earn the full two points. We also introduced a small amount of outside air into the mechanical system to further dilute indoor air contaminants. Proper ventilation can improve indoor air quality more than any other factor. ASHRAE Standard 62.2 dictates the proper quantity of outside air for residences based on the square footage, number of bedrooms, and fraction of time that the forced air unit is actually running. Too little outside air and the helpful dilution effect is lost; too much and energy is wasted tempering the outside air. THE LEARNING CURVE As a pilot project under LEED- H, there was definitely a learning curve to implementing the rating system requirements. There are more than 100 potential credits and many more nuances when implementing those credits into the design and construction processes. Project architect Larry Clark is no stranger to environmental design. He has been practicing architecture since the energy crisis of the 1970s when Title 24 was originated and embraces energy conservation principals as a part of every building he designs. Yet he warns, “With the new LEED for Homes system, a considerable amount of time and effort was spent just learning and documenting the process.” Fortunately, the project team’s strong team player approach made the LEED process go smoothly while meeting Cate School’s goals for energy efficiency, environmental construction and occupant comfort. Of course, the most significant impact that Cate School is making on the sustainability movement is the example set for the students. As LEED Consultant Michael Heacock points out, “These new LEED facilities will allow Cate School to teach the value of environmental stewardship while demonstrating a commitment to their students’ futures.” I’m excited that these young people are learning these lessons at a younger age Carrier’s Infinity 96 condensing furnace was chosen for its ultra-high efficiency and intelligent control system. Photo by Bill Regan. than I did. Who knows? Maybe they’ll do more than just recycle cans for some extra pocket change. Trevor Nelson, PE, LEED AP , is a mechanical engineer with Nibecker & Associates, a mechanical and plumbing consulting firm with offices in Camarillo and Irvine, Calif. (www.nibecker.com). Outside of work, you’ll probably find him kitesurfing or rock climbing around Southern California. Contact Trevor directly at tnelson@nibecker.com. 94 WWW.SUSTAINABLEHOMEMAG.COM http://www.shawhospitalitygroup.com http://www.bigelowcommercial.com http://www.maslandcontract.com http://www.invista.com http://www.aertinc.com http://www.bentleyprincestreet.com

Table of Contents Feed for the Digital Edition of Environmental Design + Construction - August 2008

Environmental Design & Construction- August 2008 Contents Editor's Note Web TOC Newsline New plus Notable Therapeutic Spaces On the Cover Surviving and Thriving A New Green Era of Luxury Special Section: Greenguard Indoor Air Quality Certification Getting it Right Extra Credit Product Focus 21st Century Schools Marketplace plus Classifieds Advertiser's Index Of the Earth

Environmental Design + Construction - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.