A Steel Prefab Treads Lightly on a Desert Floor
Steel is just about the most recyclable building material on earth. You could be well reading this in an office building built with steel originally smelted from iron in Julius Caesars day.
So it makes good green sense to build eco prefab houses with steel…
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Steel does not spread fire. Building with steel allows for a lighter load, so it does not require a huge concrete foundation. Making concrete is one of the most carbon intensive building industries there are, producing the heaviest carbon footprint.
And steel framing makes for construction simplicity: these homes are able to be erected by hand and do not require welding, special torque tools or specialized inspections. This allows an entire house to be framed and enclosed in less than five days.
The sustainable elements are built in onsite, such as what appears to be an industrial-strength radiant flooring system, (maybe someone can correct me in the comments if I’m wrong in assuming that’s what this is)
Again, it looks like these workers are blowing on a thermal mass to create a warm radiant heated floor for cold desert nights, and this could be powered by a solar thermal system on the roof to heat the water. However no mention of radiant flooring or solar is made on the prefab site at Blue Sky Homes so I could be wrong. But if not, why not? The site looks decidedly off grid.
To grade a traditional home pad would have irreparably damaged this beautiful site, instead the house stands above the terrain on legs, which is becoming an increasingly common new eco building vernacular: because this allows local wildlife to continue to move freely underneath the house without disturbing the human interlopers in their land. And vice versa.
This part prefab system offers 500 square foot modules that can be combined in any combination to create houses of any horizontal configuration and up to three stories tall. At the center is a factory built “core,” where the bathroom, hot water tank, air handler, washer/dryer and electrical subpanel are all located:
This core unit is constructed in a factory, shipped to the job site as a pre-assembled element and lifted into place with a small crane. The only on-site work required is hooking up rough plumbing and electrical to the “core,” which takes a few hours as opposed to the weeks it traditionally takes to install these elements on-site.
Designed with assistance from a team of engineers and the LA Architectural firm 02Arch this sustainable desert prefab home by is framed with cold-formed, light-gauge galvanized steel to create a bi-directional, moment-resisting frame.
This Blue Sky Home is sited 4,000 feet above sea level amid massive weathered boulders and ancient piñon and juniper trees.
Images: Blue Sky Homes
Lucas - I think it is a lightweight thermal mass being blown in there….not concrete. It looks fluffier than concrete.
Steel versus wood - just that you can reuse the same steel over and over century after century…not that we have many centuries of building ahead of us likely now with climate catastrophe looming…but maybe. Gotta try.
Hey guys,
sorry, didn’t check in for a while.
First, radiant vs. thermal mass floor: Just for the sake of non-techies, those names are thrown out a bit, especially in the context of hydronic tubing in concrete slabs, and they are not the same thing. In a hydronic concrete floor, the hydronic=radiant, the concrete=high thermal mass. In those kinds of floors, one can use the floor itself as storage cuz it’s got all that concrete. But in environments with high diurnal swings in temperature, it’s not neccesarily desirable– it’s all a matter of scale– you want a well-tuned design for the integrated thermal mass system.
Hence my comment about separate thermal storage– I’m thinking about ganging up a bunch of old water heater tanks, or maybe something bigger if you’ve got the space. One set of tanks would hold solar-heated water to use during the night, the other set would use night-sky cooled water to use during the day. For that kind of system, you’d probably want a bit of a ‘lighter’ thermal mass/hydronic floor so that there’s a good turnaround in temperature.
article on night-sky radiant cooling:
http://www.buildings.com/ArticleDetails/tabid/3321/ArticleID/6089/Default.aspx
Concrete vs. Steel:
I tend to agree with Susan– high embodied energy is actually the least of my worries in terms of Life Cycle Indicators, and steel is technically very reusable and eminently recyclable.
Concrete is more impactful in terms of CO2 emissions, but I say that as long as the concrete is being used as a part of a good thermal mass system, then that’s ok. How much is actually used in such systems intentionally? Too small to count– and that’s the problem statement in my opinion.
need more detai /environmental burden i.e. recycled content. Wall assembly with R values. Detail of connection maximum size etc.
what is the roof assembly dtl and R value??
Tom T.
A well built concrete home is good for a very long time whereas wood has a much shorter life. The initial carbon footprint is larger but long term is small.
A concrete house can more easily be made air tight.
The wires in the floor appear to be electrical radiant heating although poorly installed. Either radiant heating or ‘temp wire’ for spreading/equalizing the heat during cooling in the concrete should be spaced up off the steel concrete deck. Not to be confused with rebar - it is not for strength but only for equalizing the temperatures. Definitely not tubing for a hydronic heat system as they would be at least 12mm diameter.
The concrete (actually probably a sand/cement mixture) layer will not be much of a mass when they are pumping it over the lightweight flooring/decking. It is definitely a pumped sand/cement mix. You can see in the photos it is a thin layer.
The steel they are using is thing cold formed shapes - this structure will be somewhat flexible in nature. It has nothing to do with what you see in a traditional commercial steel building.
The steel, being light gauge, is easily cut with a steel cutting blade in a circular saw.
The floor will need serious insulation under it - steel makes a rather good thermal bridge.
The framing being made from 70% recycled material is a good laugh. Virtually all construction grade steel is made by melting scrap. I have seen this claim to green other places as well but it is a fact of the steel industry. In melting scrap many pollutants are released - zinc, cadmium etc - anything attached to the old steel.
They say nothing about insulation - how much. R or U values, types which would be most applicable.
Construction time is the one advantage this type of unit has over a concrete home - this is a fast relatively simple building.
No mention of the ceiling, roof support. type of roof, many details on their site.
The 250 USD per square foot cost (1000 ft2 = 250,000 USD) is a bit fantastic - maybe they plan on building a couple then retiring? When companies come in with a realistic cost then it will be more interesting.
Metal can be recycled but I would guess that it takes more energy to recycle it that it takes to use lumber which is naturally recycled. (not to mention pollution) Metal is a very poor insulator. I doubt impact on the desert for this footprint would be a major problem for wildlife.
I would have to see studies of fire performance before I made a determination on that subject.
Adobe works great. You think native Americans might have known a thing or two about sustainable living?
Great article on Steel Framing.
I have learned a lot about them from this and other articles like the ones i found at Industrial Machinery News (http://www.industrial-machinery-news.com) It’s cool to watch how they form them using roll formers.
Thanks,