This energy-efficient grain bin house uses foam and fiberglass insulation, plus computer-assisted passive solar heating.
On thousands of farms across the continent, round metal grain bins (called “grain silos” in some regions) are standing empty or being torn down and sold for scrap because they’re no longer in use. Architects and builders have started to use these durable, inexpensive structures to construct grain bin homes, storage buildings, offices and barns. After the bin is in place, it requires virtually no maintenance.
There are all sorts of interesting ways to use individual bins or group them together to make an attractive, comfortable home. We encourage readers to explore unique uses for metal grain bins — especially used bins — and we talked with several people who live in these structures to learn what there is to like about a grain bin house.
Earl Stein, of Summit County, Utah, says, “My grain bin home, ‘Montesilo’ (inspired by Monticello), is designed to be energy efficient. After ‘talling’ (raising) the silos, we cut our way in and framed the interior with 2-by-6s on 1-foot centers. To insulate, we sprayed 2 inches of low-VOC foam against the metal and followed that with blown-in fiberglass insulation. Montesilo is easily one of the strongest and tightest buildings in the county.”
Stein’s structure utilizes passive solar heat that’s assisted with computer technology. The windows allow winter sun to warm the rubber-covered concrete floor. A computer controls draperies to retain the heat at night. For added comfort, Stein installed electric radiant heat in the floors. “Even when indulging myself with warm morning floors, my heating bills have been a fraction of what it would cost to heat an 1,800-squarefoot house in this harsh Utah environment at 7,100 feet,” he says. “Experimentally, when no extra heat is applied, the lowest recorded interior temperature was 62 degrees Fahrenheit in midwinter.”
Stein chose steel because it’s unique, eco-friendly and low maintenance. “My main motivation in building a house from a galvanized steel bin was that I never wanted to pick up a paintbrush again,” he says. “In 50 years, my shiny steel home will only mellow to a gray patina, but I won’t have to paint it.” After moving in, he realized there were also advantages to living in a round structure. “There’s a certain non-empirical value,” he says. “It does something to your head — it’s soothing and inspirational. We’ve had incredible brainstorming and musical jam sessions in the house.”
And building the house, even using new steel bins, turned out to be a good financial decision. “Even with all the custom work, Montesilo came in below $200 per square foot — well below average building costs for the area,” Stein says.
Brian Liloia lived in a straw-bale-insulated grain bin at Dancing Rabbit Ecovillage in Rutledge, Mo. “Living in a grain bin was a pretty novel experience,” Liloia says. “For the most part, it worked pretty well, but careful consideration is needed around designing windows and doors. Overall, it was great living in a round structure, and telling people you live in a grain bin makes for some great reactions.”
Louise and Vance Ehmke turned a steel grain bin into a structure where they can live and work. It serves as a scale house (where grain trucks are weighed) on their farm near Healy, Kan. “Our grain bin office/scale house/residence is just cool,” Louise says. “It turned out far better than our expectations. Everybody who comes here — including the Governor of Kansas — says it is one of the neatest things they have ever seen. The structure itself, a real grain bin, is clearly unique, but the rustic and high-tech interior takes it off the charts!”
A Bin Within a Bin
Mark Clipsham, an architect from Ames, Iowa, is working on a new technique for using steel grain bins to produce strong, energy-efficient homes. His main concept is to put one round steel bin inside another and fill the space between them with foam insulation, which creates a single, monolithic structural insulated panel. Following is an interview with Clipsham in which he describes the idea, where to find bins, insulation and more.
Why would anyone use a grain bin as a house?
Metal grain bins are strong, inexpensive — especially if you buy used bins — and can be recycled when you’re done using them. Plus, they’re round and have conical or domed roofs. Ironically, these attractive curved forms are used in either the most expensive and prestigious buildings or the most utilitarian and primitive ones. These forms have evolved out of use because of changes in available materials, labor costs, and prevailing building methods. But why not use something utilitarian and affordable — a grain bin — to build what is otherwise in the realm of the expensive and exclusive?
How much do new bins cost?
Prices vary depending on the cost of steel, your location and the season. Bins cost as little as $30 per square foot — sometimes even less. Because there are so many variables, get estimates from several companies before making a decision. Buying a used bin is the most cost-effective option.
How do you find used bins?
In Iowa, and I’m sure many other places, we have what are referred to as “government bins.” They are invariably 18 feet in diameter and about 18 feet tall at the eaves. These bins are no longer deemed commercially viable and are routinely scrapped. To find used bins, put an ad in farm magazines, check Craigslist, or talk to a local bin dealer or bin erector.
How do you move an old bin?
Companies that sell and install bins can usually move them also. Bins up to 36 feet in diameter can be moved “whole.” The bin is first separated into two sections, then the top is collapsed onto the bottom. Cradles are used for moving 18-foot-diameter bins tipped on their sides.
You can also disassemble a bin to move it, but use new bolts when you reassemble the bin. The gauge (thickness) of metal is usually mixed in the same bin — thicker toward the bottom. Be sure to label the sheets as you take them apart so that you put them together correctly.
If the two bins are the same size, how do you reduce the size of one grain bin so it fits inside the other?
Undo enough bolts on one unit to allow you to use a cable and squeeze it down to a smaller diameter, and then install new bolts and holes as necessary.
How do you get one bin inside of another one?
Use a crane to set the larger unit around the smaller one. To allow the crane to lift the outer bin, fasten cables through bolt holes at the ridges of the roof sheets near the fill hole and around steel bars that fit into the roof sheet ridges in at least six evenly spaced locations. (The fill hole is the opening at the top of the bin where grain is dumped in.)
On the outside of the inner bin, use tapered shims, preferably made of rigid insulation, at least 2 feet long and thick enough to resist being crushed by the outer bin as it’s lowered. The bottom of the shims should guide the bottom of the outer bin into the desired position (wall thickness). Use a minimum of six shims.
What kind of foundation do you recommend?
Footings can be concrete, a bearing plate of galvanized steel, or treated wood on compacted, crushed stone.
Which type of insulation system do you recommend?
My preferred insulation for this building system is closed-cell foam at least 3 inches thick on the inside surface of the exterior bin. Ideally, fill the entire cavity between the inner and outer bins with slow-cure, pourable (or fast-cure, injected) foam through small openings cut into the inner bin. A continuous 3 inches of 2-pound foam gives an R-value of about 15 and also acts as a vapor barrier. (The International Energy Conservation Code recommends R-13 to R-21 for walls.)
If you use only one bin, you could spray on insulation or line the interior of the space with straw bales and finish the bales with natural plaster. If you use straw bales for insulation, you should still use at least 1 inch of rigid insulation (fastened in place with adhesive) on the inside of the bin to prevent condensation on the inside of the bin wall. Otherwise, the warm, moist air from the conditioned interior will migrate through the straw, hit the cold steel and turn from water vapor to water, and the straw won’t dry out.
Is it possible to install a second floor in a grain bin, or can these only be built with one level on a concrete floor?
You can easily install a second floor. You can use standard joist hangers for floor framing as long as you drill holes for the supports on the peaks of the corrugations. This may mean using hangers that are for larger joists to ensure getting enough fasteners in each hanger. The metal must be thick enough to hold the fasteners, too.
For vertical point loads (such as where your main floor frame meets the walls), you can use support columns down to a traditional footing. Fasten the columns to the wall for added stiffness.
Can you install windows or additional doors?
Yes, but be sure to reinforce the edges of the breaks in the bin structure. Doors and windows can be installed using a modified bin “human door frame” designed for grain bins. The frame has a built-in drip cap, but you need to extend the vertical frame to use it as a door.
Before You Start Building
While not absolutely necessary, professional services and support are recommended for implementing these concepts if the bins are to be modified in a substantial manner. All applicable building codes should be followed for safety and compliance reasons.