New, Affordable, and Green in a Historic Neighborhood
General Specs and Team
Location: Blacksburg, VA
Cost (USD/sq. ft.): $98/sqf
7 duplexes (14 units):
- 2 to 3 bedrooms
- 1 1/2 to 2 1/2 bathrooms
- 1,038 to 1,360 sq. ft.
Builder: Community Housing Partners Corporation
Architect/designer: Community Design Studio, LLC
Engineer: Civil - Gay & Neel, Inc
Foundation: slab on grade; XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation. under slab and around perimeter (R-7.5)
Walls: 2x6, 24 in. o.c.; damp-sprayed cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection. (R-19)
Roof: 2x4 engineered wood trusses 24 in. o.c.; sprayed cellulose; vented (R-38)
Windows: double-pane, low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor., argonInert (chemically stable) gas, which, because of its low thermal conductivity, is often used as gas fill between the panes of energy-efficient windows. -filled; SHGCSolar heat gain coefficient. The fraction of solar gain admitted through a window, expressed as a number between 0 and 1.: 0.35; U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. : 0.33 (R-3)
Other details: insulated door and window headers (R-10)
Heating/cooling: 1.5-ton American Standard air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. with R-410A refrigerant, 18,000 Btuh, 15 SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive.
; Water heating: electric, 50-gal. tank-style heater (0.91 EFEnergy factor. Efficiency measure for rating the energy performance of dishwashers, clothes washers, water heaters, and certain other appliances. The higher the energy factor, the greater the efficiency. In some appliances EF reflects the percentage of energy going into the appliance that is turned into useful energy. )
HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. score: average of 75
Annual energy use: average 36.7 MMBtu per house
- Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. dishwasher, washer, refrigerator, and bath fans
- Energy Star and CFLCompact fluorescent lamp. Fluorescent lightbulb in which the tube is folded or twisted into a spiral to concentrate the light output. CFLs are typically three to four times as efficient as incandescent lightbulbs, and last eight to ten times as long. CFLs combine the efficiency of fluorescent light with the convenience of an Edison or screw-in base, and new types have been developed that better mimic the light quality of incandescents. Not all CFLs can be dimmed, and frequent on-off cycling can shorten their life. Concerns have been raised over the mercury content of CFLs, and though they have been deemed safe, proper recycling and disposal is encouraged. light fixtures
- Exterior lighting on photocell
- 0.91 efficiency rated water heater
- All ducts in conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. and mastic sealed
- Dual-flush toilet in ground-floor bath, low-flow toilets elsewhere
- Low-flow faucets and showerheads
- Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. washer
- 65-gal. barrels to collect rainwater for irrigation
Indoor Air Quality
- No-VOCVolatile organic compound. An organic compound that evaporates readily into the atmosphere; as defined by the U.S. Environmental Protection Agency, VOCs are organic compounds that volatize and then become involved in photochemical smog production. paint
- Ventilating range hood
- Ductwork protected during construction
- Underside of countertops sealed with low-VOC sealer
- No carpets
Green Materials and Resource Efficiency
- Advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope. techniques
- Engineered wood flooring
- Job-site recycling
- Fiber-cement board siding
- 50% of the project was designed on 2-ft. modules.
- Cellulose wall and attic insulation
- Open-cell porous pavingA paving material that allows rainfall to percolate through and infiltrate the ground, rather than contributing to stormwater runoff; can be asphalt, concrete, or porous grid paver.
- OSB wall and roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen.
- Concrete with 15% fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. Lumber, typically decking, made from plastic (often high-density polyethylene) and wood fiber or other agricultural by-products. Composite lumber often contains recycled content. Also called composite decking. for deck (Trex, reclaimed plastic and wood waste)
- Preserved mature trees and incorporated new trees for natural shading
Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. score: 73-77 (75 average score)
NAHBNational Association of Home Builders, which awards a Model Green Home Certification. Energy Value Housing Award: silver
A Local Organization Builds Practical Homes That Fit in with Others Nearby
Over the past two years, this group of affordable two-family homes in Blacksburg, Virginia, won numerous green building awards including 2007 Home Depot Foundation Award of Excellence for Affordable Housing Built Responsibly and Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. Award for Excellence in Energy-Efficient Affordable Housing. For Community Housing Partners (CHP), a community development corporation in Southwest Virginia, this is just one step in their mission of creating more sustainable opportunities for people in the region.
Respect the built and the natural environment
CHP's design team, Community Design Studio,LLC used vernacular architectural details to blend the homes seamlessly into their historic neighborhood. The urban infill lots were picked because the convenience of nearby public transportation and other amenities made them as practical as they were affordable.
Because CHP feels that community and sustainability go hand in hand, it set aside 10 percent of the land to build a new town park, installed welcoming front porches on the houses, and connected everything with new sidewalks and footpaths. It curbed some negative impacts of development by preserving mature trees and using permeable paving and rain gardens to absorb storm water runoff. Rain barrels at each house also reduce runoff by collecting water for gardening, and even served as a temporary water source for construction staff.
Affordable to build and to live in
In designing this group of homes, Community Design Studio, LLC referenced Enterprise's Green Communities criteria, a comprehensive set of strategies to build more durable, healthy, energy efficient and affordable housing with the primary goal of improving peoples' well-being. The houses were built with methods that conserved resources during construction and that will conserve energy for years to come. Nearly 1000 pounds of packing materials and pallets were recycled, and half of useable wood scraps were given to people in the community.
Advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope. techniques used less lumber and left more room for insulation. Floor plans based on 2-foot modules led to even more efficient use of building materials. CHP chose cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection. for its low environmental and economic costs and good R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. . Compact fluorescent lights, Energy Star-rated appliances and high SEER(SEER) The efficiency of central air conditioners is rated by the Seasonal Energy Efficiency Ratio. The higher the SEER rating of a unit, the more energy efficient it is. The SEER rating is Btu of cooling output during a typical hot season divided by the total electric energy in watt-hours to run the unit. For residential air conditioners, the federal minimum is 13 SEER. For an Energy Star unit, 14 SEER. Manufacturers sell 18-20 SEER units, but they are expensive. electric heat pumps with variable speed indoor air handlers help keep electric bills below average.
Meeting people's needs
Even though sustainable construction techniques play a big part in its work, Community Housing Partners' main focus is always serving local residents. Downtown Blacksburg and the adjacent campus of Virginia Tech offer a wide range of jobs, but thriving college towns often drive up real estate prices.
The term "affordable housing" was actually a bit of a stumbling block when this project was proposed, but Community Design Studio, LLC successfully broke the stereotype with these attractive and practical homes. Many of the new residents are able to walk to work and all of them are thrilled that they're able to finally own a home in a community they've enjoyed for years.
Because Community Housing Partners strives for sustainability on a large scale, this project involved people from the local level on up through the regional, state and even national level. The process caused local residents and officials to gain awareness of and embrace many of the driving principles behind the Roanoke-Lee project. They saw how integrated designBuilding design in which different components of design, such as the building envelope, window placement and glazings, and mechanical systems are considered together. High-performance buildings and renovations can be created cost-effectively using integrated design, since higher costs one place can often be paid for through savings elsewhere, for example by improving the performance of the building envelope, the heating and cooling systems can be downsized, or even eliminated. can foster cooperation and efficiency and they became more aware of needs of their own community.
They also realized how strategically planned developments can preserve open space while giving people better access to resources and to each other. They now also look at buildings from the perspective of performance. The success of this neighborhood has allowed CHP to take on more ambitious projects. A larger scale development went into the planning phase shortly after these houses were built. In this new project CHP would retain 30 percent of the site as open space and adhere to the standards of Earthcraft, a well-respected regional green building program.
Rob Wotzak is assistant editor at GreenBuildingAdvisor.com
- Colin Arnold
- Toshi Woudenberg