The Environmental Consequences of Excavation

Pete and I visited some job sites in Southern California last week. One site, a rather large home buing built to be a net energy producer, was an excellent example of how important integrated design is. Here, Peter talks with the builder and the structural engineer, Bruce King about how the team re-thought the foundation system.



One of the challenges in this part of the country is earthquakes, so most foundations need to be somewhat over-engineered. The original design was for a pier and grade beam system which required a huge amount of excavation. Bruce wondered if switching to a mat slab would be a better use of materials and on paper it seemed like it was. Once the team started moving dirt around, though, the builder asked some questions. Bruce sat back down at his desk with a fresh pencil and discovered the hidden environmental cost of trucking out dirt and trucking in gravel.

Editor's note: please excuse my cruddy video editing skills. I just wanted to slap this together for a free-lance writer to watch as background info for an article. The picture and sound quality are not what we will get once Rob gets back from Virginia and edits this thing for real.

--Dan Morrison is managing editor of GreenBuildingAdvisor.com

Energy Value Housing Award -- Chino Valley, Arizona

An academic pursuit providing real world results

This luxury house won an NAHB Energy Value Housing Award (Gold) while also complying with several sets of standards including LEED, Environments for Living and ALA HealthHouse. It was designed to be healthy, durable and affordable - as should be the goal of any sustainable building. Every detail was carefully considered, making the home efficient to build as well as live in. Pre-manufactured components sped construction; thoughtful planning minimized site disturbance and preserved existing vegetation; meticulously installed insulation, a tight building envelope and a rainwater collection system minimize energy and resource demands. Methodical preparation and execution are likely responsible for this project’s high marks, but something else also makes it unique - it was built by university students.

At Yavapai College, in Prescott, Arizona, the Residential Building Technology Program immerses students in both the theoretical and practical sides of high performance homebuilding. Director Tony Grahame leads each class through every stage of design and construction to the completion of a marketable home. The students learn not only about the necessary integration of a building’s parts, but also about the cooperation that is necessary to make that building happen.
Although its source of labor may be atypical, this project is a great example of how smart design can facilitate increased sustainability within a typical budget. Some of the methods and materials used might have been new to the RBT students, but the guidance they received gave them an edge over experienced contractors without green building training. This point was clearly made by an NAHB Energy Value House judge’s comment - “if only every house built in the U.S. could have the oversight of this project - all of our houses would be energy efficient and durable.”


Team:
Builder: Yavapai College Residential Building Technology Program, Tony Grahhame Director
Architect/Designer: Yapavi College Architectural Design Students and Staff

Specs:
Location: Chino Valley, Arizona
Completed: 2005
Cost ($/sf): $90/sq.ft (not including cost of student labor)
Size: 3202 sq.ft.

Construction:
Foundation type and R-value: Combination - slab on grade xps foam at edge (R-5), crawlspace ICF (R-16), basement integral XPS and blown in cellulose ((R-26.5)
Wall construction and R-value: 2x6 @ 24” o.c., 2” XPS and 5 1/2” unfaced fiberglass batt (R-29)
Windows: Double pane, low-e, argon filled. SHGC = .30 - .59; U- factor = 0.30 -0.35
Roof construction and R-value: Engineered trusses, blown-in cellulose (R-38)
Garage: Thermally and pressure isolated from living space

Energy specs:
Conditioning equipment : 14 SEER AC system, 56,672/80,960 BTU dual stage direct venting gas furnace
Water heating equipment: Solar domestic hot water
HERS Rating: 90.5 (5 star +)

Water efficiency measures used in this project
· Low flow toilets, faucets and shower heads
· Water conserving dishwasher
· 1250 gallon rainwater collection system
· Gray water distribution system
· All hot water taps within 30ft. of hot water storage tank

Energy efficiency measures used in this project
· Whole-house Energy Star interior and exterior lighting package with CFL bulbs.
· Extremely tight building envelope (blower door test 0.96 @50 Pascals)
· Roof overhangs optimized for summer window shading and winter solar gain.
· Energy Star appliances including dishwasher, ceiling fans and ventilation fans
· Sealed ductwork, leakage measured at 0cfm @ 25 Pascals
· All ductwork is located within the conditioned space

Green materials and/or resource efficiency used in this project
· Decking, ICFs, wall and ceiling insulation all include recycled content
· Recycled cardboard and metal construction materials

Indoor air quality measures used in this project
· Balanced whole house air exchange system with MERV-10 and HEPA filtration
· All construction materials contain low or no VOC
· Low formaldehyde content in particleboard cabinets

Alternate Energy Utilization
Photovoltaic power: 2 KW
Solar water heating: 40.9 sq.ft. panel, 80gallon storage tank

--Rob Wotzak is Assistant editor at GreenBuildingAdvisor.com. Photos by Tony Grahame