PREFAB CONSTRUCTION: Green or Greenwashing?

by , 04/13/07

PREFAB CONSTRUCTION: Green or Greenwashing?, Prefab Construction, Prefab Houses, Sustainable Prefab Design, Bob Ellenberg, photos by Robert Ellenberg

A week ago, Inhabitat reader Bob Ellenberg contacted us, expressing frustration with all of the prefab housing companies jumping on the eco bandwagon and claiming their products are green simply because they are prefabricated. We thought he had a good point, so we are publishing his critique below. We’d love to hear your thoughts on the matter….

PREFAB CONSTRUCTION: Green or Greenwashing? By Bob Ellenberg
I don’t want to pick on prefab construction, as I do quite a bit of it myself as a design/builder and there are certainly many aspects of it that can be “green.” But some of the claims I see being made relative to overall sustainability of prefab houses are overstated and might even be considered “Green-Washing”. Let’s start with what is perhaps a debatable point–the fact that factories have a high overhead cost of operation compared to on-site building and in all probability a higher carbon footprint along with it compared to on site construction…

MATERIAL WASTE–This is one of claims I have the most problem with. One prominent prefab web site states, “Materials are ordered in such a way that there are only trace amounts of waste instead of the tons of debris produced building on-site.” and other websites make similar claims. Standardized materials are ordered by on-site builders and prefab factories alike. In fact, an on site builder will usually order the different lengths of lumber he needs for one particular job that produce the least amount of waste. A factory sometimes orders large quantities and pulls from their own inventory but they both buy the same size lumber that comes from the same mills.

“Extra materials in the factory can be stored and used on the next house as opposed to winding up in a landfill.” is another claim. If the above statement is true–what are factories storing their leftover materials? On some on-site jobs, the subcontractors don’t scrap out material as well as they should because they don’t get paid anymore for being frugal with the materials. By the same token, some factories have the same attitude because it cost them more in labor to have employees sort and use the scrap pieces than it cost them to cut up what is there at the work station and they save labor cost. On site can be as “green” in scrapping out material as a factory and a factory can be just as wasteful. The real question is how “green” the approach is of the people running the show.

PREFAB CONSTRUCTION: Green or Greenwashing?, Prefab Construction, Prefab Houses, Sustainable Prefab Design, Bob Ellenberg, photos by Robert Ellenberg

Factory produced modular homes often require more material than site-built homes, and this is definitely not green. When you build a house on site, you generally have a perimeter foundation and a slab on which you erect everything one piece at a time and the continuous foundation under those pieces hold them up. With a factory built house, you have to lift a large module, load it on a truck, haul it down the road and set it with a crane. Because all of these operations concentrate the load on specific points instead of it being spread as it is over a foundation or a slab, the support system must be considerably overbuilt. They typically use laminated veneer lumber (LVL) for perimeter floor bands that are doubled. In addition, some of the interior walls are usually doubled as the module must be closed in and give support for transport but then go back to back against another module when set in place. There will be variables but the factory built modular houses will always consume more materials than the same house built on site.

Shipping modular homes definitely adds to the carbon footprint as well. Truck loads of materials go to local suppliers, travel short distances to site built homes and stay there. Truck loads of materials go to factories, are built into houses and then travel hundreds of miles on oversized trucks with small trucks (called escort vehicles) running in front and behind while traveling through towns with police and local cars idling while traffic is stopped for them to go by. Then the crane which gets about 2-3 mpg travels to the job site to set the house and unless you are in a major city they could end up coming a long way.

Am I a foe of prefabricated houses? Absolutely not. I have designed them, erected and completed them and I live in one. In fact, I am designing some very green ones at the present time that I will be producing later this year. But I want to honestly question what is and what isn’t “green” about prefabrication and encourage others to do the same.

What do YOU think?

PREFAB CONSTRUCTION: Green or Greenwashing?, Prefab Construction, Prefab Houses, Sustainable Prefab Design, Bob Ellenberg, photos by Robert Ellenberg


Bob Ellenberg, Inhabitat Contributing Writer

Bob and Karen Ellenberg have been designing and building homes since the early 70’s. They have built on-site wood frame homes, masonry structure homes, prefabricated modular homes and prefabricated kit homes. They have built in warm humid Southern climates and in high altitude cold dry Southwestern climates. They have built entry level homes and they have built award winning custom luxury homes and are known for their attention to detail. In addition Bob has worked extensively in damage assessment in the aftermath of hurricanes, earthquakes, fires and tornados which has given him additional insight into what really works not only in terms of safety but in repair costs as well. Few designers or builders have such broad hands on experience and knowledge. Bob can be contacted at

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  1. lundy wilder September 12, 2008 at 8:29 am

    I just do not see any attention paid to dry stack concrete block houses. With the current chain of hurricanes entering the Gulf of Mexico, I am glad that I am building w/ a modular concrete system called Dac-Art. This is my second Dac-Art project, the first withstood a direct hit from Hurricane Ivan while our yard was filled with other\’s busted up stick built homes.

    We have so little waste in this type of construction that we didnt have to use any waste removal method other than our curbside rolling municipal garbage pick-up container.

    What concrete scrap we have generated, we have found others who want it for bulkheads or fill in their own projects and have been willing to come pick it up themselves.
    This method of construction is not cheap, but then, neither are most of the wood based modular homes I see in Dwell Magazine or similar. Plus our house will be basically maintenance free from here on out. So many people are interested in what we are doign that I photo journal the construction on

  2. Nichoel Farris, Owner &... January 26, 2008 at 12:02 am

    As a designer and builder of Green Prefab , Modular, and Manufactured Homes, I would like to point out that I supply sustainable housing to families at $50 sqft who had never had the option to Build Green as it is so unafffordable to build at site for the average-income family, Further more, I have the EPA lable said my house is green. So what can be bad about providing affordable, healthy green homes to families, while reducing their utility bills, providing a healthier living environment, and keeping 4,500 lbs of greenhouse gases from the air! ( Source: I am very proud of what I do and belive in my product! And so do the rural, humble clients I build them for!

    Nichoel Farris
    American Home Sales
    Auburn CA 95603

  3. Gene Hymel November 14, 2007 at 2:06 am

    Looking for information re: retrofitting manufacturing facility for panelized homes, townhomes, etc.; any suggestions re: engineering companies, equipment companies and educational facilities?
    thank you!

  4. olaniyan oluwatoyin September 23, 2007 at 2:04 pm

    i like what i’m seeing, it gives a sense of power in construction. i’d like to know more about your techniques and methods. thanks

  5. David Taylor August 31, 2007 at 2:41 pm

    I don’t think broad generalizations about prefab being more or less green can be made. Prefab houses use about 20% more wood than a site built house, in addition to the extra foundation stem walls to support the narrow modules. Site building can waste a lot of wood, but I think 10-15% is more normal.

    Now, if you measure the energy used to build a house vs. that used to run the house, the energy to build is about equal to the energy consumed by the house in 5 years. So over the life of the structure, perhaps 100 years, a structure with lower operational energy use will probably be the most green, if one took the time to do the analysis.

    If I were to draw a consclusion from my research, which has covered many areas and conflicting sources, the greenest thing you can practically do today on a production – affordable – basis is to build a wood frame, blown insulation structure with a low framing factor, the Energy Star checklist for thermal bypasses and sealing; with a high efficiency properly sized cooling and heating plant, that is built on a slab with south facing windows to capture some passive solar radiation for heating. All the other components in the house that use energy have a short life and can be replaced when better items arrive. The shell is hard to change later, so put the money in the shell, and reduce operational energy use for the life of the structure. Be sure to include connections on the roof structure and the plumbing system for solar hot water heating, and electrical connections and structural mounts for solar electric panels.

    Interestingly, about 40% of the energy an average household uses is on transport. So moving the house where common services can be acquired on foot, and where there is a public transit option, can save a huge amount.

    Build green: reduce space conditioning energy demands, reduce transport, prepare for solar water and electric; everything else is lost in the weeds or will be improved over time as technology improves.

  6. John Wimmer August 24, 2007 at 4:42 pm


    Clearly, methods of prefabrication, whether modular, ICF, panelized or other kit-built cannot be easily rationalized in any market if the manufacturer is boutique in nature or building one-offs. The only instance where modular building, for instance, even approaches a sensible choice for one-off projects is the selection of a mosly unmodified catalog design. Prospective homebuyers in more rural areas often choose modular (as opposed to ‘manufactured’ homes, which of course are of the mobile home variety mounted on a chassis and built to HUD code rather than national standard codes) because rural mortgage products are more conducive to this industry. Rural areas are very often without the bureaucratic entaglements of municipal jurisdiction, and coupled with the reality that most manufacturing facilities are in outlying or otherwise rural areas the transport is usually shorter. Without an economy of scale, any means of prefabrication will struggle to convince owners or builders of its value when compared to conventional site building. ‘Sustainability’ must begin with patterns of development that beget more responsible behavior by its physical nature, and in truth no bamboo flooring, PV collectors, rainwater harvesting roofs, solar water heaters, xeriscapes or geothermal exchange systems will ever make a ‘sustainable’ difference if patters of behavior are not ‘sustained’.

    Is prefabrication inherently more sustainable than conventional building? Probably not- in fact there’s likely much more chance that it will be wasteful and unsustainable than not but that’s why responsibility relies on stewardship. Expecting a prefabricated product to be sustainable by default is tantamount to handing an algebra book to an unsupervised 12 year old student and expecting the mastery of subject to simply transfer from the pages to the child’s brain. Stewardship requires effort, and I’m sure we can all agree that systems, products or methods can only be as sustainable as we allow them to be. Think of the type of compact development that architects such as Ross Chapin and John M. Campbell are building, and you can then see the viability of prefabrication as a cost effective design because of its scalability. Regarding preference of style, traditional vernacular will appeal to most and therefore endure, but crisp modernism has a growing base of appreciative consumers beyond the readers of Dwell magazine. Michelle Kauffman has been commissioned to design some affordable housing units for a developer in Denver, and the client is ecclesiastical in nature.

    I remain optimistic about the prospects of prefabrication, but not because it is inherently sustainable (as some suggest) but because it allows rapid development of similar components in a controlled environment. Building more thorough, compact style multi-unit developments may offer the best chance to influence human behavior in a positive way, and without that, arguing the sustainability of one method over another just seems to miss the point.

  7. Isaac Lassiter August 4, 2007 at 9:29 pm

    Most of the homes built that would fall under the term “prefab” are wood framed panelized homes, followed by SIPS homes and then production wood-framed modular homes.

    A discussion of the term “prefab” is for the most part a discussion of the most minute percentage of the smallest portion of the building industry, the modular or panelized homes that are considered “modernist” and are built by boutique production facilities that ship very few homes per year. Our company is a distributor of more traditional, custom and production modular homes, and we work with many contractors that primarily site-build their homes and are being turned on to modular construction. I can assure you that the materials used in the “prefab” homes are more sustainable, and anecdotally I understand that the processes used in these factories delivers less waste to the landfill.

    However, it is hard to believe that, as Bob quoted from one web-site, that in prefab factories “Materials are ordered in such a way that there are only trace amounts of waste instead of the tons of debris produced building on-site.” We are based in California and I find that i disagree with many marketing claims in the factory built housing industry about the way that on-site general contractors here build their houses and operate their businesses. Out of economic necessity and sometimes for more noble green purposes, the contractors build quality homes that are exhaustively plan-checked and inspected locally. Because of cost, waste is kept to a minimum by any contractor that wants to stay in business, especially those that are building more than a few homes where the waste cost line-item becomes substantial. Because of the strict contractors license laws, most homes are completed and livable except for very few flaws that the contractors come out to fix in the first year when they come up. We all know that on a case-by-case basis bad things can happen, but having seen numerous poorly built and managed modular homes, i think that it does come down to the mindset, both economic and of sustainable practices, of the on-site construction manager and developer.

    The larger production modular home factories deliver less waste to the landfill for less noble reasons than the “prefab” companies. These larger companies, owned by conglomerates with tens of billions of dollars in market cap are driven to reduce waste by the market factors: Cost of disposal, cost of storage, and efficient use of materials paid for. These companies do not allow processes that let 2X4s go out the door, only to later used other 2X4s for blocking. If there are remainder cut materials they are saved for the next house, rather than needing to use uncut material on a smaller cut for the next home on the line. My understanding is that a factory or onsite builder that builds less homes has less of a need to re-use materials and to set up processes to recycle more than the bottles and cans that workers drink soda out of on the job site. This applies to low volume scattered lot site-builders and to low-volume “prefab” and modular factories. Anyone can put on their webiste that they are green. I believe that fewer pay for the labor and logistical costs of disposing of many of the materials that they could recycle.

    This is a primary reason that custom building one-off homes on greenfield land starts off not being green, and has to come a long way, in my opinion by using strict sustainable materials and going completely off-grid for energy, to be a sustainable home. Greenfield development is going to happen. Arguing against it is unhelpful, and trying to sue or regulate it away (which is common in California) is a short-term solution. Eventually the population will need more housing in that area and the political forces will come into line to break the building permit or parcel splitting logjam. A better way, and i believe a realistic way to deal with this issue in the short-term here in California, is to require strict adherence with a LEEDS or comparable program which will either create the incentive to build in less strict areas or force sustainable development on the greenfield lot.

    Sustainable housing must be produced not just with green materials, but must be done efficiently in a way that makes it possible for the producer to follow sustainable principles and stay in business. Many of the companies that tout their “prefab” greenness have built no or few homes, and certainly haven’t built a house for a median income level family in California that shows a scalability of their product. In my opinion, this won’t happen in the future because the look of the product isn’t mass marketable. Even with our modular product, we have built a very few homes for median income level people, because most were on a one-off basis. The ones that were built are simple, ranch style homes. Half of our homes could have been sold to median income people if the product was scaled out in a neighborhood volume of homes. To cause a change to more sustainable building, if you accept that neighborhoods on greenfield land will be built, is to build the neighborhoods sustainably. Changing the market by creating the economic environment to support sustainably built housing requires that producers and developers come together to take the risk that the production process and the finished product will meet the standards of a group like this, arrive to market at a time when they will sell, and sell at a price that shows the next developers that it is a money making adventure worth the risk. None of the “prefab” companies, in my opinion, come close to offering a solution to this problem because the “prefab” product is built in low production factories and is rarely styled in a way that a neighborhood of people would want to buy. It is a niche product at a niche price with a niche architectural style. Outside of the Bay Area and southern Los Angeles county, we don’t have many people asking for modernist styled homes.

    Over-Engineering: it couldn’t be more true. If you have to be in a wood-framed building during and earthquake, i would pick a modular over on-site construction any day. I think that Lloyd’s point about the possibility and simplicity of moving a modular in the future is a valid point. Although we don’t like to have any implication that our homes are a mobile structure, it is much more easily relocated after all of the strapping and lag bolts are removed. One additional item from California is that every approved foundation plan that I have seen has a continuous stem wall at the marriage lines rather than a pony-wall. This uses much more concrete. It makes it easier to set the houses and probably makes the home stronger in an earthquake, but wastes concrete and would not be done in most site-built homes.

    Shipping: the shortest distance that our homes are shipped is 350 miles, with some homes coming to California from Idaho, Colorado, and Nebraska. The Nebraska plant (we have never ordered a home from them) is 1241 miles from Los Angeles, and the plant that we order a lot of homes from in Colorado is 1,058 miles. For economic reasons, this is bad math. The common invoice is $11,000 per load.It also burns up an unbelievable amount of carbon and creates pollution that anyone but the truckers would like to avoid. Logistically, it is very difficult and inefficient. Yet to develop a market for this product in California, we have been forced to have homes built in these far-flung places. Here is the good news; based on the proof that this market exists that has come from our company and many like us in California, other factories will open closer to the market. This will reduce fuel consumption, carbon emissions, and pollution, all things that this group can agree are good things. There remains the need to distance the factory from market enough to build in a place with lower labor costs and lesser regulation, but not so much that it is mitigated by the higher fuel costs. There are such places much closer to California than Colorado and the like.

    In closing, i hope that my post gets across that without a scalability of the solution with an architectural style that people want to buy, “prefab” visions of green greatness will never turn into a million Prefabhauses where there could have been a million KB Homes. I wholeheartedly support the time, thought, and efforts of the “prefab” set of companies that have developed this idea of sustainable and affordable housing. These ideas and some government regulation are affecting developers of housing in California. The next step, of which we will contribute as much as we can, is to put together the right groups of people so that successful and sustainable projects in higher volume can happen. Only then, through that success, will the copycat nature of developers come into play and change the market to more sustainable development.

  8. Steven B. April 24, 2007 at 4:45 pm

    This has been a most remarkable exchange of opinions & ideas. Good food for thought on a number of fronts. The issue,of course,being responsible consumption of resources.Land,water,timber,(also known as trees) other building materials etc.And what we leave in our wake, like pollution. Upfont and over the long haul. Ultimately Mother Earth will let us know whether we passed or failed in our attemps to get it right.(Watch “Children of Men” including bonus footage.) I’m afraid there may not be enough of you consciencious builders to make any real,lasting,difference. Until some of you guys build entire nieghborhoods with “little feet and frugal habits” that is. Also, the “Clean Slate” opportunity that exists in areas affected by Hurricanes,Sunami,etc. are being exploited by to few, including our government, whom should be leading the way as an expression of what the people want and need. A good, sustainable,quality of life. This, is, attainable.
    As I continue to rebuild,and harden, my home after a couple of the storms hit us here in Florida, I’m constantly reminded of my limited choices. I must use “approved” building practices with “familiar materials” to or above “code” using products with the appropiate “product approvals” These are the things I purchase for use @ the local home centers,and building supply houses. As far as over engineering goes. When you ride out the big ones; because evacuating’s not an option; you don’t call it that. You call it “insurance”, which in and of itself has become a dirty word here abouts.
    In closing I’d like to beg all you builders and architects to get involved in you local governments community development. Better yet run for office. It’s your knowledge and skills we need brought to the table of reason.
    We will follow.

    P.S.I would like to thank Inhabitat for providing a forum, such that attracts this passionate group of professionals to the same table.Except for Michael V’s use of a four letter word, this has probably been the best use I’ve yet seen of the potential this medium can serve us with.

  9. Chris April 23, 2007 at 1:51 pm

    The article refers to all these pre-fab companies on the green bandwagon . . . I am struggling to find a pre-fab company in the NY metro who is willing to integrate sustainable materials and systems. I know they are all over the west coast, but can anyone stear me to a company that is local to me? Mid-Atalantic? New England even? I am all ready with projectS in hand, just need the right company to work with . . . Please e-mail me at

  10. andrew k from az April 17, 2007 at 4:11 pm

    Hailing from a city that is completely focused on production housing (Phoenix) I can say that prefab must be very,very bad before it can compare with the sprawl of today’s suburbia.
    Most of the skilled labor in the Phoenix area drive substantial distances to the jobsites, and while there, create substantial dust problems. Even in a subdivision where there are two homes in similar stages of construction directly next to each other, material waste is fairly staggering, it’s common to see each structure with its own dumpster. Combine material theft into the mix, and the whole process is very, very unsustainable. The exceptions to this are expensive custom homes that are built by builders dedicated to the environment. There aren’t really that many of these, certainly not in Arizona.
    In addition, it seems as though a relatively well-informed homebuyer who is concerned about the environment can fairly easily find a truly green prefab home.
    Whether this hypothetical person can find a lot in a subdivision where such a structure is legal is another issue for another time.

  11. keith Dewey April 16, 2007 at 4:04 pm

    I too felt that the “green” label was being thrown around quite liberally when I considered what prefab dwellings might look like. I took the unconventional approach of using ISO containers … EOL (end of life) ISO containers that were about to be shipped overseas and recycled. This reduced the energy consumption necessary to both ship and break down the material. I also saved enough in the construction by using containers, that I could spend more money on highly energy efficient appliances and mechanical systems. I hope to retrofit wind and solar energy collectors when our building code allows it.
    The construction phase is very well documented on my website:

    -Keith Dewey

  12. Michael V. April 16, 2007 at 3:01 pm

    All of the “Greenwashing” has gotten me RED!

    As consumers we are being sold a crock of shit about our “carbon footprint”, “LEED”, “ECO friendly”,
    “EnergyStar”, “Prefab”, etc… All this is an elaborate marketing scheme to scam good hearted and forward thinking people into buying what’s “NEXT”!

    If as a species we really want to preserve our planet, the eco system, wild life and maybe a better place for our future generations we need to “STOP CONSUMING” energy, materials, fossil fuel.

    America “STOP CONSUMING” all that: McDonald’s food, Walmart junk galore, Exxon gasoline and oil, IKEA forests, Toys’ R Us plastic toys, Budweiser aluminum cans, Dell landfill laptops, GAP dog fur coats, etc…

    Great article BTW Bob:)

  13. whit April 16, 2007 at 2:02 pm

    I’m trying to get some traction for a new project idea at GreenBlue where we create an “honors” program for green building certification. The honors program would recognize an adherense to most all of the issues raised here. Once a building received its LEED, EarthCraft or GreenBGlobes certification it would then be able to apply for honors. So even a prefab couldn’t get honors without fully incorperating the full range of requirements like everyone else, some material related, some practice related.

    Honors would consist of 100% mandatory measures, like no vinyl for instance, or solvent based adhesives, or fiberglass insulation (that ought to get the debate going. I know its cheap (thanks to immigrant installers typically) and can be encapsulated. But it ain’t that much cheaper, it is a known carcinogen, I repeat, a known carcinogen, the “encapsulated” batts have wide open ends, workers practically never use proper protections, it’s a hazard when remodelling or disposing, and we have so many better materials that perform better). I digress..

    There are too many other components to spell out here but the basic jist is to differetiate the sales talk from the builders who are walking the walk. So what if you sourced a percentage of your materials from within 500 miles if you used 25 different subs from over 100 miles away and the project took a year of them driving hither and yond? Honors would require that all sub-contractors participate in offsetting programs as a possible tenant.

    For that matter ,the term green building is an oxymoron without specific guarantees that certain things took place. In fact I would argue that to really get the highest honors for green building the project would have to demonstrate a regard for land-use such that a greenfield development simply could not be considered at the highest level of environmentally conscious without some serious prerequisites, if at all. As I said it’s a new idea that is forming and needs some debate. This seems to be a particularly well informed bunch and I welcome your opinions. Greenwash can’t be stopped, but defining and constantly pushing the re-defining of the state of the art sets the bar at the top. Maybe an honors program could achieve this.

  14. David Eubank April 15, 2007 at 11:51 am

    Systems and how they all fit together are important. What if Home Depot or Loews could be motivated to begin stocking retrofit, green sustainable building components? What if they sold green systems, solar wind and such that could be introduced into the urban markets? What if they with the buying power they have began changing the systems? What if we all asked them to do it and showed them how, as collective individuals.

  15. Gerald April 15, 2007 at 2:30 am

    Richie: try the soon to be released LOGICAL HOMES. How about this approach, “…No wood… no wasted wood!”

  16. Richie April 14, 2007 at 3:51 pm

    Great Stuff folks ! I’ve enjoyed reading all the posts. Here’s a thought… what about focusing on a new ‘kit of parts’ that could enable cost effective, green designs which could be site built, prefabbed, or built by local builders/craftsman/ or owners ? Why not take the whole mystique out of the process and create a ‘by the numbers’ set of protocols that could enable various building methodologies to be combinjed within a single structure. For example, what about combining ‘Earth Bag’ ( )constructed walls for part of a dwelling, along with steel moment frames, SIP’s, Bamboo I-Beams… all within a single dwelling ? Lets get creative… get outside of the box. Gabion walls anyone ?

  17. ben G April 14, 2007 at 2:20 pm

    this discussion is very interesting and its critical aim carries much hope, i think overall ‘prefab’ is another buzzword to make small packaged suburban units more acceptable in our environment, to drive profit [which by the way equates to collective losses over time] the heart of all of our problems is the way inwhich zoned parcels and variously programmed constructs fit together. prefab, as has been widely expressed so far on the construction scene, does not really chanllenge this as i am not sure what can besides local and ultimately federal government. in any case PREFABRICATION IS AS IMPORTANT AS “PRE_DESIGN” nothing can replace good quality design, the way inwhich all of our constructed environments fit together and operate within our remaining natural resources AS ONE EFFICIENT ENTITY…the PREFAB issue is almost as insignificant as the issue of changing lightbulbs…issues and responses are much more profound than trying to enable our current political, economic, social and spiritual conditions to continue the way they do,,, i applaud and admire all those who continue to address real problems, and attempt to make real changes happen instead of resting once their lightbulbs have been changed to fluorescents….thank you Bob for your comments in challenging our understanding of the green movement to inevitably make it more relevant and truthful…we shall overcome.

  18. David Eubank April 14, 2007 at 12:59 pm

    I think until prefabs move away from traditional materials and methods they only contribute tot he problem and do not really offer any green alternative to site built homes, which if build in a traditional method offer no real solutions. Out first step should be to stop new development of undeveloped land. In fill in developed areas, urban renewal and of course remodeling older structures with sustainable methods. I like the container houses. What kind of materials are laying around wasting away can be redesigned and used. Having more than 40 years experience in building and historic preservation I do not advocate the use of OSB or MDF materials in building. The hazardous material cost out way the benefits. Not only are millions of tons of carbon spent to produce these products but millions of tons of chemicals like formaldehyde are released into the atmosphere and ground water as well. The permeation of mold throughout entire building are locked into theses materials. Bamboo has the same problem in its production. We need to scale back un-necessary construction and development. We need to build sustainable living systems with long life spans that can accommodate new technology. Our focus should be on retrofitting existing structures if we really want to be green in the future if we want a future, prefabs may or may not be part of tha answer.

  19. adam April 14, 2007 at 11:42 am

    I agree with Jorge, in fact he pointed out everything I wanted to….quicker and better.

    An additional point I wanted to make from Bob’s initial analysis, that is about lumber. I worked for a truss and panelized wall manufacture, our lumber did not come from the same places a on site builder would get their lumber to build a house. That is because we would actually get longer members that are also spliced to ensure of straighter and “cleaner” lumber. This was done by and supplied directly from the saw mills. Where as an on site builder has to go through a lumber yard. Another middle man, in nominal sizes, that are cut to length and the remaining tossed aside. If Bob manages and optimizes lumber use for his hired framers, good on him. Oh yeah, he still needs to collect the waste, store, and send to the next job site. That is why you can not brush off the optimization that happens in a manufacturing atmosphere. That is all manufactures do, optimize processes.

    Just as important, as optimized processes performed in manufacturing, is time. Time spent on site. One third the time using modular and panelized construction. Both of which would take only one-two weeks. Where as an on site framer could take 4, 8, and even 12 weeks to frame a house (all based on size and how busy your framer is). Of course delivering modular sections, wall panels, or roof trusses all require additional lifts and even cranes. But the impact is still less because, as Jorge pointed out, time and travel to and from the site. A crane may be bigger than a framers truck, but it is there for one to two weeks. The crane also minimizes the amount of additional labors and framing apprentices to fetch and clean up lumber. A typical on site framing crew could be as small as four guys, four trucks, four weeks. Cutting down the time on site reduces the impact.

    Good talk.

  20. Chuck April 14, 2007 at 9:33 am

    1) Building costs of several of the prefabs featured on this website show some costs in the $100 to $250 per square foot range. This does not appear to be affordable housing.
    2) Architecturally, the boxes are aestheticaly very unappealing, even when architects are creative in how they stack them, and design them to try to make them look ultra-modern.
    3) Having acted as my own contractor to have a timber frame, enclosed with structural insulated panels, house built, it occurs to me that the factory could be brought to the jobsite with a modification of this method of construction. Perhaps we need to borrow the best method form factory and on-the-job techniques, instead of thinking either-or. For example, why not bring a semii truck that opens out into an on-the-job manufacturing construction unit. It could have state of the art manufactoruing technology that could deploy at the site, with on-site assembling of components, minimizing the transportation issues of structures built in a traditional factory.. If you have a frame erected, and then use structural insulated panels, like those that have interlocking parts and electricity chases built in, you pay more in materials, but, you save a lot on fabrication expense-even with a crane-and you shorten assembly time a worthwhile amount.
    4) Here is the other advantage of a framework and SIP construction. It is strong, and the SIP walls evelope the house in insulation like a thermos, so it performs very efficiently on heating and cooling costs.
    5) Aesthetically, you get a very different kind of structure.
    6) Now perhaps you are going to raise the issue of where do you get the large timbers, and the crafstmen to do the frame? This can be done in glue-lamianted beams. SIPS are being used more often these days in “conventional” construction. Yes, CAD-CAM technology, and design of an on-site manufacturing unit, are major captial expenses at the outset, but I beleive the cost-effecdtiveness could be demonstrated. This method could also be deployed when faced with the aftermath of disasters like Katrina.

  21. Bob Ellenberg April 14, 2007 at 12:34 am

    I don’t say prefab isn’t green–I just have a problem with exagerated claims. There are absolutely some prefab companies that are very conscious of their methods. Lloyd points out a company burning their sawdust for fuel as an example. As I eluded to in my article, the attitude and steps taken by the builder, whether site-built or factory, is the primary factor. I do believe there are advantages and disadvantages of buiding in a factory but few of them affect how “green” it is as most of those measures can be carried out in either location. WIth your own research you can determine the factors that matter to you and seek a builder that has similar concerns.


    I would agree that site-built and prefab can be blended such as what the LVL house does in a kit. However, the definition of “the best of both worlds” vaires from person to person. When we are discussing a custom house with a client our main focus is in helping that client determine what they really want, what motivates them and can they afford what they want. We don’t focus on the sale because we only want to make a sale if we think what we offer is what they really want. You asked, “any advice?” and my advice on this subject is too lengthy to post here (it will be on our web site later this year) but relates more to the bulding process. The most important is this–Many people jump into the process without enough information. We believe people should thoroughly examine what all the process entails and decide IF they want to build before considering WHAT they want to build. Above all else, if you choose to build, relax and make it an enjoyable process. Life is too short to get stressed out over material goods!


    I know that you have more knowledge than many people on this subject and perhaps some partiality–but that’s OK as I would hope you are passionate about what you do.

    I won’t dispute the studies you refer to in Canada though I would be interested to know who did them and who paid for them and what all did they entail. What does “as much as 30%” mean–that in some cases waste was that much? What were the circumstances? Was it commercial and residential? Your statement, “In a prefab factory, nothing is stolen, nothing is thrown out, even the sawdust is used for heating”, is a blanket statement as if that is the norm in a prefab factory. If that is true in Canada, we need to figure out how we an institute such compliance in the US. I suspect the best example meets that standard but I’d be very surprised if that is the norm. As to your statement, “An onsite builder orders materials with a little bit of surplus to cover waste and may not have another job to take it to; in a factory it goes back onto the rack.”, you simple can’t make such statements as you can’t know that is what most on site builders do. I was very careful in my article to state that it depends on the builder and you are making some domatic statements that can’t be substantiated. If I understand your statement in OVERENGINEERING, you are saying it takes 10% more but I think you are implying that with savings in waste you are still 20% more efficient. That would mean excluding the overengineering, you are saying a prefab can save 30% on the basic building. I invite you to respond and give even a few examples of how this can be true.

    CARBON FOOTPRINT I would think this would have an incredible amount of variables but if the workers at your factory live within 20 minutes that is less than 2/3 of the average commute in Canada and is great.

    Some of your last points don’t seem to take issue with the points I was making which is simply for all of us to be as honest as possbile about the advantages and disadvantages and not exagerate.

    Green Modern Kit–
    I wasn’t going to address Lloyds comment about vinyl but since you also brought it up, I will. I assume the references are to vinyl windows in the pictured house since that is the only PVC. I recently read his post on Tree Hugger where he has decided to agree that in the areas of long live materials such as windows and piping that PVC is very acceptable. So much so that LEED has decided NOT to give credit for not using it.

    Jorge–Thank you, you got it. I wasn’t saying prefab wasn’t green or in any way picking on it. I simply don’t want to see people who can have positive influences on others making exagerated claims and hurting the credibility of all who want to honestly do all they can for the environment.

  22. Jorge April 13, 2007 at 10:30 pm

    I think that it is a fair analysis. He obviously has first hand experience in the field and raises some good points. One thing that I’d be mindful of, is that not all prefab houses are built equally. So some of the points that he makes while important, are areas that a properly green designed prefab house should avoid.

    Some prefab houses that claim to be environmentally friendly, claim to be so because they are prefab houses. Others, such as some that you have featured on the site, bring something extra and that’s what is worthy of highlighting.

    I can pick any building material that you can name, say, for instance, that of a sandwich panel (an EPS layer sandwiched between concrete) and name how those panels shouldn’t be considered green because the EPS panel has ozone depleting chemicals on it. Unless, such sandwich panel was created using a process that avoids such chemicals, or significantly dimishes them as to make the impact relatively negligible, in which case you’d mention that such EPS panel is green but not all of them are.

    So, to summarize, I think that his analysis is correct, all prefab houses are not green, and people should be made aware of why. And if a prefab house is being featured as environmentally friendly, then they should also be made aware as to why that is, not just so because they are prefab houses (though the fact that they are properly manufactured would be reason enough)

  23. Green Modern Kits April 13, 2007 at 9:03 pm

    I totally agree with you, *and* with the immediately above post.

    Regarding vinyl: Our architect often says in a funny voice, “No vinyl, THAT’S FINAL!” (Ok it sounds better when he says it)

    One thing we’re doing is to try to have our designs partnered with the closest manufacturer to the client. And the contracting/foundation/finishing is done locally. By employing local labor and educating them, they then realize they have one more skillset and can market their green building skills in the area profitably… for all of our benefit.

  24. Lloyd Alter April 13, 2007 at 6:47 pm

    I work with a prefab manufacturer as my day job and would like to respond to the points raised here.

    Studies in the Canadian construction industry have shown that as much as 30% of materials are wasted through theft, water damage, or offcuts being tossed in the dumpster. In a prefab factory, nothing is stolen, nothing is thrown out, even the sawdust is used for heating. An onsite builder orders materials with a little bit of surplus to cover waste and may not have another job to take it to; in a factory it goes back onto the rack.

    absolutely true, probably 10% more material than in conventional houses. However we are still 20% ahead of the game and it is actually going into the house and making it stronger. I know of cases where a lot is getting redeveloped and the house is taken apart and sold to someone else and is still strong enough to be picked up and recycled on another lot. That is worth something.

    Again, true, we have big honking trucks and escorts and cranes travelling hundreds of miles. For one day, after building the house in the plant in ten days. Most of the workers in the plant live within 20 minutes of the factory. On a conventional jobsite you have workers driving long distances (for country properties I have known carpenters to drive an hour and a half each way) for ten times as long, usually in big honking Ford F150’s. Then they run out of nails and have to run an hour into town. We did a study for a grant application and compared the carbon footprint of a conventional house to a prefab and came up that prefab used one quarter the fuel, primarily because of speed in the plant, reduced man-hours and employees who drove regular cars a short distance to a full day’s work rather than living out of pickups for months.

    I agree that there is an element of greenwashing going on, for like the picture shown, most prefabs are still built of vinyl and formaldehyde and sitting in unsustainable locations dependent on car transport. They are also mostly still trying to mimic the ugliest of conventional construction. However however you look at it, building a house while you are standing in the rain or snow using handheld equipment is going to be slower and less efficient than building in a factory with sophisticated tools.

  25. Mark April 13, 2007 at 5:20 pm

    I’m assuming there must be a blend of site-built and prefab that can be prescribed to sensibly gain the best of both worlds? I’m specifically thinking of Rocio Romero’s LVL Home, shipping wall kits to be assembled, but leaving the foundation, windows, and other elements to site-built construction. Any advice?

  26. Preston April 13, 2007 at 5:08 pm

    Bob, this is an excellent article and you’ve made some great points. After reading your article, I’m tempted to walk away thinking prefab can’t be green, but you point out that you’re designing some green prefabs right now. I think you’ve articulated where some of the greenwashing comes from, but as a person with real expertise in the production side of prefabs, can you articulate some of the possible green benefits of prefab as well?

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