Introduction

In a sustainable building, the architecture itself is intended to provide comfort for its occupants.

A passive solar building is designed to maximize the use of natural systems to maintain thermal comfort for the occupants.  The overall goal of passive solar strategies is to successfully integrate the site, the local climate, the sun, and local materials in order to minimize dependence on external energy sources. Here at the Solar Concept House compound, although both residences feature high capacity forced air furnaces which cycle on as needed in winter, mostly at night, passive systems were incorporated into the design of both solar residences that not only save resources, but celebrate the process as well.

In passive solar design -- part of the modern "green building" movement -- windows, walls, and floors are made to collect, store and distribute solar energy in the form of heat in winter (passive solar heating), and reject solar heat in summer (passive solar cooling).  

This is called "passive" solar design (or "climatic" design) because, unlike "active" solar design (e.g., photovoltaic (PV) solar roof panels, mechanical systems, water tanks, wind turbines, etc.), passive solar systems do not require the use of mechanical or electrical devices, fans, pulleys, pumps, etc.  

The term "passive" implies a conceptually simple approach that uses few, if any, moving parts or input energy.  Among many other benefits, the house is far quieter and more restful as a result, compared with conventional houses.

There is nothing to maintain, nothing to wear out or break, and harmful pollution or waste byproducts are drastically reduced.  By way of illustration, in passive solar design, thermally insulated windows serve as the solar collector.   In active solar design, solar panels collect the sun's energy, converting photons to electrons, i.e., converting sunlight to direct current (DC) electricity.  Most active systems also include alternating current (AC) inverters, and some include batteries for storage.  Active solar houses that are "off the grid" also typically depend on gas-powered backup generators for times when sun isn't plentiful.

The central philosophy behind passive solar design is to design a "planet-friendly" building in harmony with nature, and with all the natural resources of the site.  As with all green building design and construction, passive solar design is intended to create environmentally friendly and resource-efficient buildings.   Compared to conventional construction, passive solar buildings are far more environmentally responsible, and offer far greater sustainability.

Passive solar design involves a holistic approach to architecture, integrating systems based on reliable scientific principles such as thermodynamics.  Careful arrangement of rooms completes the picture in designing the ideal passive solar home.  At the Main House, additional options for configuring and reconfiguring the floorplan were added by designing a "flexible floorplan of movable walls," discussed in more detail on the Main House page.

Among the goals in designing an effective passive solar building -- commercial or residential -- is to best take advantage of the local climate, and the sun path, i.e., various aspects of the sun at different times of day, and in different seasons, as relates to the buildings.   Some of these design elements include window placement, orientation, size, and "glazing" or glass type, thermal insulation, thermal mass, and shading for warm days.

The U.S. Dept. of Energy (DOE) endorses vertical glazing as "the overall best option" for solar buildings.  Over the years, "roof-angled" glass (as in a greenhouse) proved to be undesirable for passive solar houses, while vertical solar collector windows, such as the Window Walls at both luxury residences on the compound, proved to be ideal for passive solar design.   Vertical glazing also proved to be much easier to maintain, and to shade.  

In the northern hemisphere, the most efficient solar collectors are south-facing windows, which face the equator.  That being said, thoughtful design for solar buildings balances energy performance issues with other important factors such as views, "daylighting" of the interiors, the slope of the site, interior design goals, the direction of prevailing breezes for summer cooling, etc.

Generally speaking, the solar glazing on a passive solar house (the solar collector windows) should be exposed to sunlight with no obstructions within an arc of 30 to 45 degrees on either side of true south.  Accordingly, the Main House at the compound faces south, and features solar collector windows facing south, southeast, and southwest -- the top three sides of the diamond-shaped Main House.  

The Guest House similarly features solar collector windows facing both southeast and southwest, and the glass-walled sleeping loft above enjoys a southern exposure, tempered in summer by the shade of the aspen forest.  In winter, when the aspens shed their leaves, the cozy sleeping loft is warmed by the sun to the south, and as sunset approaches, from the southwest as well through the walls of glass in the loft.

Here at this private compound, high thermal mass was also a key design component, achieved most artfully by the architects, discussed in more detail below.   Other ways in which passive solar design was implemented in both the Main House and the Guest House are discussed on the individual pages here on this website for the Main House, and the Guest House.

Choosing the Site

Careful site selection and building placement are essential for optimal daylight and solar utilization.

Passive solar design begins with selecting the best kind of lot for the purpose.   The Southern Rockies offer some of the most temperate climates in the U.S. -- relatively cool in summer, and relatively warm in winter, with plenty of sun year-round.  Here in Telluride, our unusually temperate mountain climate and strong, high-altitude sunshine is ideal for passive solar design applications, and Lot 47 in the Telluride Ski Ranches was a particularly sunny south-facing lot, up on Telluride's ski mountain, nearly 1000 feet above the historic Town of Telluride in the box canyon below.  It was a special blessing that this very special south-facing lot stared out unobstructably at Telluride's "fourteener," 14,017 ft. Wilson Peak, and thus no accident that the architect chose this particular lot to build an upscale passive solar house for Telluride's resort market.

Not only do you need a building lot where homes can be properly oriented towards the sun, but deciduous trees (leaf-shedding trees), like the thousands of aspens surrounding all the Ski Ranches homes, play an important role as well, in shading the house in summer, and then exposing the house to more sun in winter, after the trees have dropped their leaves in late Fall.  

And in the Telluride area, a heavily forested lot up on the ski mountain was always going to be cooler in summer than anything in town, so the sun could be invited in to warm the home with less risk of overheating.

The path of the summer sun is high in the sky, with less direct sunlight to pour through the Window Walls.  Winter days are shorter.  And the winter sun's path is considerably lower, and reflects off the snow covering the grounds, allowing more sun to reach the interiors when you need it, to warm the house.

Thirty years ago, when the first lifts went in and Telluride became a ski resort, local builders had their choice of building sites.   Lot 47, one of the first lots built on in the Ski Ranches, was carefully chosen for the construction of a passive solar model home for its ideal south facing slope, the breathtaking views of mighty Wilson Peak, the privacy, quiet, close-in proximity to the new ski resort, and the trees.

Frank Lloyd Wright wrote about houses that were "of the hill, not on the hill," in his discussions of organic architecture.  Lot 47 in the Ski Ranches provided an unparalleled place to illustrate his point.

"It is in the nature of any organic building to grow from its site, come out of the ground into the light -- the ground itself held always as a component basic part of the building itself.  And then we have the new ideal of building as organic.  A building dignified as a tree in the midst of nature."   Frank Lloyd Wright, "The Natural House," Times Mirror/New American Library, 1954.

First the main house, and later, the guest house, were both built into the south-facing slope, deflecting cold north winds and stabilizing exterior wall temperatures facing the slope at +/- 45 degrees year-round.   The unusual site allowed this textbook passive solar design element to be implemented, and yet, the occupants would always be looking directly out at Telluride's "fourteener," Wilson Peak, at 14,017 ft. above sea level, from anywhere in the house.  This iconic mountain, the Wilson Massif, is the most photographed in Colorado, and serves as the mountain on the Coors® can.

When the Main House was first built, a clearing was cut through the forest to the south, opening the Solar Concept House to the sun.  In the same clearing today, there are lawns in summer, tall grass blinds for deer to sleep in at night, and a path down to a custom-made 10 ft. log bench of Englemann Spruce carved by "the Norwoodsman," Kevin Hauze, looking out over the West Meadows.  Looking out from there to the west, you can see the runway at Telluride's airport near Aldasoro Ranch, and the homes in the distance in Aldasoro, across the valley.  

From this unique view corridor down by the southern corner of the compound, looking out across the San Juan Scenic Highway to the southwest, not a single home is visible, per local covenants, across the West Meadows -- and beyond, looking out over the vast expanse of foothills below Mt. Wilson.  The multi-million dollar building sites in the West Meadows are all downhill, below the highway -- looking up at Wilson Peak from the foothills. Only Roudy's historic tack shack, from days gone by, is still visible from the road, and stands as a reminder of when "Ride with Roudy" was just across the street.   When the West Meadows lots were developed several years ago, Roudy moved his trail horses to Aldasoro, and winters them in Norwood.

Interestingly, the Telluride airport just received, for the first time, approvals for night flights beginning with the 2011-12 ski season, and so lights from these aircraft will soon be visible at night from the view bench near the south corner of the lot, as flights take off and land in the alpine meadows across the valley near Aldasoro Ranch.

Finally, surrounding the lot is the Zoline Remainder, named for the family that developed both the Telluride Ski Ranches and the West Meadows.  This large parcel of open space begins with the Fox Farm Meadows, and then wraps around Lots 47 and 48, heading south along the San Juan Scenic Hwy all the way to the Vance Creek entrance of the Ski Ranches.  The Remainder is a refuge for wildlife and birds, and there are plans for walking and bike trails connecting the Fox Farm Road entrance to the north, with the Vance Creek entrance to the south.   More details about this remarkable site can be found on the View Lot page.

Achieving High Thermal Mass

Doug Reinhardt, the local architect who designed and built the Main House, was determined to achieve high thermal mass in order to keep the building warm when the sun couldn't heat it, and to avoid overheating the house on warm summer days.   He was also determined to find the most artful ways to build high thermal mass into his design.  His thoughtful efforts and original design concepts were successfully realized in a strikingly beautiful, one-of-a-kind home that never overheats -- even on the warmest summer days.   Throughout the winter, the house is naturally warmed by the sun each day, while high thermal mass interior walls and floors absorb and store the sun's energy during the day, to give it back at night as heat.   

For people on a budget building passive solar homes, less effective (but still useful) techniques such as "sun tempering" may be used in lieu of building high thermal mass into the walls and floors, which is admittedly expensive.  Fortunately, there were no such budget constraints when Mr. Reinhardt built his Solar Concept House on Lot 47 in the Telluride Ski Ranches, and he had a free hand to design and build what he wanted.  

When the matching Guest House was later designed and built by local architect Vern Burke, who had worked closely with Doug Reinhardt on the Main House, high thermal mass was achieved with interior masonry walls which were then plastered or stuccoed, and finally painted a light color (throughout both residences, "Vanilla Tan" in an eggshell finish from Pittsburgh Paints) to achieve the desired reflectant values that are part of creating a sunny, light-filled home.

An excellent example of how Mr. Burke artfully achieved high thermal mass at the Guest House was a special  "Trombe" wall -- named for its inventor, French engineer Felix Trombe -- an interior masonry wall on the south side of a solar house positioned inside a window wall, painted dark colors on the sunny side for maximum absorption of solar energy, and then typically painted a light color interiorly.  In the Guest House, Mr. Burke designed a Trombe wall not only to further energy performance goals, but also to function as a privacy wall for the bedroom in the large, open master suite.

With a Trombe wall, sunlight enters and is then trapped by the glass, allowing it to be absorbed by the masonry wall throughout the day.  The heat then radiates into the interior of the home in the evening and nighttime hours.  More about this is discussed on the Guest House page on this website.

Years ago, when the Trombe wall was first installed, local artist Mary Duffy, inspired by the site, painted a wonderful mural of an aspen forest to complement the real one surrounding both residences in the private compound.  Working closely with the architect, Ms. Duffy painted her mural entirely from a palette of dark colors, for the solar collector side of the Trombe wall.

Finally, a series of large, operable sky windows by Velux was installed above the bed in the Guest House master suite, shaded in non-winter months by tall aspens, thoughtfully designed to connect the occupants with the stunning night skies at this high alpine elevation.  

Properly designed, high thermal mass in passive solar houses, among its other advantages, stabilizes interior temperatures day and night, throughout the seasons, thus avoiding or mitigating significant swings of temperature.  In summer months, for example, a high thermal mass masonry wall can absorb a great deal of heat, cooling the building naturally.  At night, with windows open, cool night air "flushes" the masonry walls, so they're ready to absorb heat all over again, the next day.  It's more expensive to build this way, but well worth it.

In the Main House, where Mr. Reinhardt's solar design called for expansive two-story Window Walls, the direct gain from the sun's energy was balanced by installing black quarried slate over a concrete slab foundation (known as "slate over slab") throughout the large Great Room.  In warmer summer months, the concrete slab foundation serves as a "heat sink" to absorb the sun's powerful energy at this high altitude (nearly 10,000 feet above sea level), captured on the surface of the floor by the black quarried slate, preventing the house from overheating.  

In winter, warm air rises from the Great Room -- created by direct gain from the sun, and/or from the fireplace in the living room, and/or from the woodstove in the dining room -- to the bedrooms on the upper floors, through natural convection.  On cold winter nights, the setback thermostat may also trigger the backup furnace, and warm air from the furnace also rises usefully to the bedrooms on the mezzanine and upper floors in the loft-style Main House.  In a well designed solar home, no heat is ever wasted.

Natural quarried slate was and still is one of the best (and most expensive) flooring materials available, and virtually indestructible in use, as evidenced by how well it's held up after over thirty years in the Main House.  As with other natural rock products, it can always be cleaned and resealed to look new.  Spares are stored in the garage, but so far, they haven't been needed.

Also central to the design of the Main House, Mr. Reinhardt understood and fully implemented an important earlier discovery of the Swiss architect known as "Le Corbusier," who created the concept of "brise-soleils" or interior "sun breaks" in passive solar design.  This involved strategic placement of masonry walls within the dwelling, preventing the sun from overheating the interiors.  

In the Main House, these "brise-soleils" can be seen dividing the main seating area in the Great Room from the library, and the main entry area from the kitchen.   As a result, in the late afternoon sun during the summer, it's considerably cooler in the library than by the fireplace in the living room, and considerably cooler in the kitchen than in the main entry of the Great Room.  So in the late afternoon before the sun sets in the summer, you can stay cool while preparing supper in the kitchen, or reading, or watching TV, in the library.

Another opportunity to create high thermal mass was designing a large, beautiful rock hearth surrounding the fireplace in the Great Room's main seating area, overlooking the lush grounds and looking out directly at our 'fourteener," Wilson Peak.   It's very pleasant to read the paper or a book on the couch in the main seating area, looking out at what locals call "the Wilsons," with a fire in the fireplace over your shoulder.  A little music from the adjacent media room/library, and there you go.

Frank Lloyd Wright believed, for many reasons, in building both exterior and interior walls of concrete masonry wherever he could.  This is still one of the strongest building materials known, and pestproof, and fireproof as well.  Following Wright's lead, the Main House architect chose architecturally exposed concrete, poured on site, and infused with indigenous river rock for beauty and strength, to create the multi-level main interior walls throughout the home.

With these thick masonry walls, the architect achieved several goals, including creating walls with the highest possible thermal mass, which could absorb the sun's energy during the day, and give it back as heat at night. As a summer cooling strategy, the mass is cooled with night air so that it's ready to absorb heat the next day.

To avoid overwhelming the occupants, the architect designed most of the walls to be triangular, rather than square or rectangular, and this scheme worked remarkably well.   As noted elsewhere on this website, the highly original design for the interior walls included another Wrightian element:  see-throughs, pass-throughs, and walk-throughs that allow the occupants to easily see or pass through the concrete walls, thus avoiding even a hint of a "bunker-like" effect, which had burdened less successful solar designs elsewhere throughout the West.

Instead, a remarkable, highly tactile, and aesthetically pleasing effect was achieved, while providing great strength, as in a fortress, along with accomplishing the most important thing from an engineering standpoint in a passive solar house: high thermal mass.

Over the years since then, the somewhat "industrial" effect of using architecturally exposed concrete walls as an alternative to plaster or drywall has become very popular in mountain architecture; e.g., as designed and built by top architects in Aspen, Vail, Jackson Hole, etc.  

If you look closely at architectural magazines focused on U.S. mountain homes today, you'll often see these architecturally exposed concrete walls, as tactile alternatives to plaster or drywall.   In addition, you'll also see the sliding screen walls deployed by Doug Reinhardt, the Main House architect.   The popularity today of these unconventional design elements in many upscale or "high end" mountain homes throughout the Rockies stands as a testament to Mr. Reinhardt's forward thinking design, anticipating these trends, when he boldly created the Main House years ago as a model home, a "concept house" he designed and built to demonstrate to prospective clients just what he could do.   His unique accomplishment is even more impressive today than it was when it was first built.

Passive Solar Design Implementation

"Perhaps most important of all, it is by way of glass that the sunlit space as a reality becomes the most useful servant of a higher order of the human spirit."  Frank Lloyd Wright, "The Natural House," Times Mirror/New American Library, 1954.

The three top sides of the diamond-shaped Main House are all glass, a two-story Window Wall of vertical, "double-glazed," high efficiency insulating glass which serve as natural or passive solar collectors, as opposed to active solar design elements such as photovoltaic "solar panels."   These solar collector windows that comprise the Window Wall face south, southeast, and southwest.   In this way, not only do these Window Walls connect the occupants with the extraordinary views, and the beautiful grounds surrounding both residences on the compound, but throughout the day, the expansive Window Walls benefit from facing towards the equator, in a "glass house" ideally built into the south-facing slope, in classic "textbook" passive solar design.

State-of-the-art "low-E" (low emission) insulating glass was chosen for the windows on the first level, largely to protect furniture from fading.  These windows have special coatings, not visible to the eye, that achieve their "low-E" goals, and allow the house to be warmer in winter, and cooler in summer.

For summer cooling, a series of copper-clad awning windows in the Great Room take full advantage of natural convective air currents, allowing warm air to rise and escape through the oversized wing windows and the clerestory windows on the third floor, in the master suite.

Throughout the day during Telluride's long winters -- from early November through the end of April -- the forced-air backup furnace is rarely needed at all.  At night, a digital "setback" thermostat lets the furnace know if and when it's needed, to raise interior temperatures a few degrees.  During summer months, even with Telluride's cool nights, the furnace is rarely triggered, with interior temperatures stabilized by the building's unusually high thermal mass, as detailed above.

For more on all the ways passive solar design elements have been incorporated into the designs of both the Main House and the Guest House, check out the individual pages for each of these private residences here on this website.

On the Main House page, for instance, see the section entitled:  "A 'Solar System' Home."  Main House page.

On the Guest House page, see the section entitled: "Solar Design Implementation."   Guest House page.

Call or email us anytime for more information, from the Contact Us page.

We hope you enjoy exploring this website.  

Passive Solar Design