RMI's Headquarters Building

Due to heavy construction in and around the building...
Tours of RMI's Headquarter building are limited.  
Please call (970) 927-3851 and confirm that a tour is available before visiting.

For more information on RMI’s Headquarters, see the HQ Photo Tour>>

The 4,000-square-foot building is passive solar, super-insulated, and semi-underground. It was built back into the hill near the north lot line, then bermed the north wall and earth-sheltered the roof for aesthetic and microclimatic reasons. (You wouldn't normally do that to save energy, as soil is a poor insulator and holding up its weight is very expensive.)

Because the building is super-insulated, it has no heating system in the usual sense, but is largely heated by passive solar gain through the windows and the central greenhouse. The greenhouse serves as the building's main "furnace": sunlight entering its vertical and overhead glazings transfers both radiant heat and warm air to the adjacent "wings" of the building and, when the heat is not needed, out the high vents in the back of the greenhouse arch. Extra heat is also stored in the arch, the greenhouse earth, the inner walls, the floor slab, and the soil beneath. Two wood stoves are used for backup heating in especially cold or cloudy weather.

Sunlight entering the greenhouse is blocked by the overhanging side arches from getting far into the wings at high summer sun angles — lest overheating result — but the low winter sun penetrates all the way back to the north wall through the arch's open back and sides. The curving walls also permit east, southeast, and southwest windows to inject heat and light all the way back to the north wall. Thus heat and light are automatically conveyed to the north zone, not concentrated only near the south facade. This "zone coupling" is the key to the building's brightness and (along with super-insulation) to its fairly uniform warmth.

The walls are sixteen inches (40 cm) thick, consisting of two six-inch (15-cm) courses of masonry sandwiching four inches (10 cm) of Freon-filled polyurethane foam (non-CFC foam was not available at the time of construction). Tempered by daytime heat stored in the outer masonry, the R-33 foam effectively insulates to about R-40. The walls curve in and out with a five-foot (1.5-m) radius; we could have used straight walls, but the curves are stronger and look nicer. The slab is four-inch (10-cm) concrete. The walls, slab, and a couple of meters of earth below it total about a million pounds of heat-storing "thermal mass" — so much that in a total solar eclipse in January, we would expect to lose less than 1 F° (0.5 C°) per day.

The ceiling insulation consists of a three-eighths-of-an-inch (1-cm) base layer of Freon-filled polyurethane foam; a polyethylene vapor barrier sealed at its edges to the wall insulation; and, depending on location, another four to eight inches (10–20 cm) of polyurethane. This yields an insulation value of R-60 to R-80.

Much of the building's thermal performance is due to its advanced windows, which were used here commercially for the first time. Virtually all are made of gas-filled (originally argon but most were replaced with krypton-filled windows in the 1990s) Heat Mirror™. They lose only 19 percent as much heat as a single pane of glass, but let in three-quarters of the visible light and half of the total solar energy. It is therefore advantageous to use a lot of glass: our building has 28 percent as much glass as floor area, or about twice the normal household ratio. Our windows' insulation levels (center of glass) range from R-5.5 to R-8 — efficient enough to capture more solar heat than they lose even if they face due north!

Heat Mirror™, a trademark of the Southwall Corporation, is an 0.002-inch-thick (25-micrometer) polyester film with special, almost atomically thin coatings which are transparent to visible light but reflect infrared (heat) rays. It comes in seven "flavors" for different climates; we use Heat Mirror™ 88, designed to maximize solar heating in cold climates. Suspended in a metal frame between two panes of glass, the invisibly transparent film traps heat inside the house. (By reducing the infrared which enters, it also helps keep the greenhouse from overheating in the summer.)

Total direct construction cost, excluding land and finance, was slightly over $500,000 (1983-84 US$) — just over $130 per square foot (about $1,425 per square meter), including extensive built-in furniture and counting all labor and donated or discounted equipment at market value. This cost may sound high, but building costs in the Aspen area are nearly twice the national average. The per-square-foot cost of this building is actually below the local median for custom buildings of comparable quality.

More importantly, the net additional cost of the energy-saving features (after subtracting the savings from not needing a furnace and ductwork ) was about $6,000, or $1.50 per square foot, or just over one percent extra. Compared with normal local building practice and with the cheapest conventional fuels (firewood and propane), the building produces an average of about $19 worth of saved energy per day — economically equivalent to producing a barrel of oil every day; but unlike oil, it doesn't pollute, can't be interrupted, and won't run out. Since achieving this savings raised construction costs by only about $6,000, but saves about $7,100 a year, it was paid back in 10 months. And that was 1983–84 technology. One could do better today.

The technologies and design principles responsible for this performance can be cost-effectively used in tract houses, custom homes, or larger buildings in almost any climate and architectural style.