From Quonset huts to double-wides, prefabricated and modular buildings generally have not enjoyed a stellar reputation for quality, style, or eco-friendliness. However, this is starting to change. Advances in factory processes, building materials, design systems, delivery, and construction techniques are making prefab buildings better, sleeker, more versatile, and greener than ever - and pricier, too.
"Prefab" includes both modular buildings (sections built in a factory and assembled on-site) and manufactured buildings (the entire finished building is factory assembled). Most of the recent advances in green prefab are for the residential market, both single and multi-family dwellings. Commercial options are increasing - although many vendors of traditional bare steel buildings (for storage, workshops, etc.) are now marketing those products as "green," especially if they're built from recycled steel.
The most basic reason why prefab buildings might be considered "green" is the resource-efficiency provided by factory assembly of components- which tends to generate far less materials waste (wood, drywall, concrete, etc.) than traditional on-site construction. Consequently, the National Association of Home Builders' draft green building standard, released Aug. 13, 2007, focuses on the efficiencies provided by modular building techniques (release ). Comment period is currently open. NAHB: Calli Schmidt,  800-368-5242 x8132.
Also, prefab building companies often can bring down the cost of premium environmentally friendly materials, such as bamboo flooring or high-efficiency thermal barriers, through high-volume purchasing. This also translates into energy-efficiency, for the creation and processing of materials as well as assembly and transportation costs.
Although prefab buildings have always been popular with the lower end of the housing and commercial markets, today's prefab buildings are now selling to wealthier, more stylish customers in upscale settings.
VISUALS: Green prefab is an especially appealing story for TV, magazines, and online media. Prefab home companies typically offer ample photos, B-roll, digital video, interactive 3-D animations, and more multimedia materials.
STYLE: The inherently "boxy" look of many prefab buildings has come into vogue as "industrial chic." See Slate, Aug 8, 2007, overview of prefab housing.  One of the most popular resource and community sites for prefab homes, FabPreFab,  focuses on modernist designs.
You'll see many of these designs in the November 2006 issue  of the swank print magazine Dwell.
Even the humble trailer home is getting a modernist look. 
SIZE MATTERS: On the other end of the market, for many eco-minded homebuyers, small isn't just beautiful - it represents efficient use of land, resources, and energy. While "McMansions" are still popular in many markets, more and more homebuyers are looking to downsize - in footprint, if not in cost or quality.
The green housing blog Inhabitat recently covered the top five tiniest prefab homes.  You'll find generally diverse and thoughtful discussion in the comment thread - worth reading.
Tumbleweed Houses  markets, designs, and conducts workshops on some ultra-small homes that cater to a "simple, slower lifestyle" by architect Jay Shafer. Serves both the do-it-yourself and prefab markets: 707-736-6248, email. 
Perhaps the ultimate on the recycling side of prefab is building houses out of shipping containers. Canadian architect Keith Dewey,  250-360-1162, used shipping containers as the basis of his zigloo domestique home.
Of course, green prefab doesn't have to be small or modest. Right now, Wired magazine and the prefab manufacturer LivingHomes are building a luxurious, eco-friendly, energy-efficient, 4000-square-foot,
Of course, green prefab doesn't have to be small or modest. Right now, Wired magazine and the prefab manufacturer LivingHomes are building a luxurious, eco-friendly, energy-efficient, 4000-square-foot,$4 million prefab home:  "a showcase of the best in sustainability, technology and design ...in an exclusive enclave of Los Angeles."
- Release.  LivingHomes: Lisa Jackson,  323-966-4605; or Haily Zaki,  323-966-4606. Wired magazine: Alexandra Constantinople,  415-276-4962.
- More  at Sustainable Industries journal. Blogger J. Thornburg is aptly skeptical  of this project, asking: "How low impact is a $4 million house?"
WHAT WILL THE NEIGHBORS THINK? Some people have encountered community resistance to their prefab home plans, no matter how green or elegant. Some homeowners associations even have clauses prohibiting prefab construction. See the Marin Independent Journal, July 24, 2007. 
RESPONSE TO DISASTER: The old joke about trailer homes is "God hates those things." Hurricanes (especially Katrina) and earthquakes have spurred the demand for affordable disaster-proof housing. New prefab designs have recently debuted intended to keep the lower end of the housing market safer.
- The Perrinepod,  an Australian modular home, is built for durability, energy self-sufficiency, and eco-friendliness. It's also stackable (up to 30 units can be joined into a multifamily dwelling). More discussion at Inhabitat. 
The Federal Alliance for Safe Homes (FLASH) can offer expert insight into disaster-proof construction for all types of buildings, including prefab. Press: Sue Ellen Smith,  877-221-7233.
In January 2007 the Healthy Building Network's Unity Home program  unveiled the first model in its line of green modular homes in hurricane-ravaged North Gulfport, MS, as a way to speed the rebuilding process. While not specifically disaster-proof, the homes built by this program will offer improved safety and indoor air quality for low-income homebuyers and renters. Unity Homes: Lillie Bender, 228-365-0126. North Gulfport Community Land Trust: Jason Mackenzie, 337-321-2427. More on this program. 
Many architecture, design, and manufacturing companies are marketing prefab buildings as "green." One current leader in the field is Michelle Kaufmann Designs.  Press: Rebecca Woelke,  510-271-8015 x125. This company recently self-published a book explaining its designs, techniques, and philosophy: "Prefab Green."  Treehugger review.  Feb. 2007 audio interview  with Michelle Kaufmann.
Inhabitat presents weekly "Prefab Friday" features, such as this.  These posts tend to attract considerable discussion which sheds ample context on many aspects of green prefab.
- National Association of Home Builders, Building Systems Council: Serves the needs of a variety of prefab housing vendors. Find local members.