McClellan Architects, original photo on Houzz
Want to erase the boundary to the outdoors? Here’s what to know about materials, cost, energy efficiency, and more.
Architect Philip Johnson famously remarked, “I have very expensive wallpaper,” referring to the four see-through walls of his Glass House, completed in 1949. Even today transparency defines modern architecture. And our desire to connect our interior living spaces with the outdoors has only increased in recent years.
Establishing these connections, though, without completely sacrificing a building’s thermal performance has been very difficult. But the demand for spaces that open completely to the outdoors has spurred the development of larger and larger thermally efficient doors.
If you’re contemplating your own colossal openings to the outdoors, here’s what you’ll need to consider.
Material options for these doors essentially fall into one of three categories: metal, wood, and metal-clad wood.
Metal (Aluminum, Steel, Bronze, Cor-Ten, Stainless Steel)
Metal frames can withstand higher loads per given cross-section than their wooden counterparts. This makes metal an appealing choice if your preference is to reduce the amount of visible frame and obstructions between interior and exterior. Stronger materials yield narrower sight lines; that’s one of the big selling points of all-metal frames.
Watch for: With metal, it’s especially important to select a thermally broken frame. These are frames constructed to isolate the exterior metal from the interior metal to prevent heat transfer and condensation.
Metal finishes: Selecting the finish is an important decision not only for aesthetics but also for durability. Finishes vary based on the metal chosen.
The most common treatment of metal door components is a painted finish. Various methods are used depending on the manufacturer, substrate, and final finish desired, but the basic idea is to cover the bare metal with a durable, UV-resistant, weathering surface. You want a finish that will endure many years of exposure without fading or chalking (or maintenance). Painted finishes are available in almost any color and come with the longest warranties.
The beauty and warmth of wood, especially for interiors, is hard to match. Used on the exterior, it can be equally beautiful if maintained properly. Therein lies the conundrum: We love the look of natural wood but don’t love the maintenance. Over time, the elements can be particularly brutal on exposed-wood doors with even the best marine finishes.
Watch for: Wood can be sourced from sustainable forests, and the embodied energy is much lower than metal, which makes it an environmentally friendly option. Wood is a naturally poor conductor, so there’s less to worry about when it comes to thermal performance as compared with metal frames.
The trade-off comes with reduced structural efficiency. This means the frame profiles, or sight lines, are heavier, permitting less overall glass area. But as the image above clearly shows, you can compensate for this by stacking multiple panels end to end.
Wood finishes: All manner of finishes are available for wood: paints, stains, penetrating oils, and clear coats. Paint conceals the wood and provides color. Stains allow the grain of the wood to show through by varying degrees. Clear coats and oils preserve the natural new-wood look.
Describing each of these is beyond the scope of this idea book; suffice it to say that wooden doors are a long-term investment from a maintenance standpoint no matter which finish you select. Sanding and refinishing should occur at regular intervals: every two to three years on south- and west-facing doors and every three to four years on north- and east-facing ones. Over the lifetime of the door, this will substantially preserve your investment.
There is a way to have both the look of natural wood and the durability and low maintenance of metal. Enter the clad door.
The exterior cladding on these doors is typically fabricated from painted aluminum, which is available in hundreds of color choices; the interior is constructed from the wood of your choice and can be painted, stained, oiled, or given a clear coat to coordinate with your interior palette.
Watch for: Because the structure of the door is wood, you’re limited to beefier sight lines (see above), but you may find the lower maintenance more than compensates.
2. Opening Size
With some manufacturers offering lift-and-slide configurations exceeding 50 feet in width and 12 feet in height, the opportunities for connecting a living room to the great outdoors are virtually limitless. There are some physical limitations, however, as a door’s opening size is governed by structural constraints.
Another constraint is the size of the door panel, which is limited by the weight of the glass and the ability of the door hardware to perform under load. Large openings like the one above can be achieved by using a “biparting” configuration, which effectively doubles the opening width of a single panel.
Finally, the project’s engineer must perform a careful analysis on the wind loading that’s present. The factors listed here are things a homeowner should be aware of, but know that reputable manufacturers of lift-and-slide doors have an in-house engineering team experienced in the design and detailing of these types of openings in harsh conditions.
3. Panel Configuration
There are three general categories of panels: sliding, fixed, and pocket. In general terms, the operable panels must have somewhere to slide and stack when open. Above, the panels can be seen stacking over a fixed panel to the left. Obviously, the more panels that slide, the deeper the track must be to accommodate them.
Because the doors don’t slide into a pocket in an exterior wall, this configuration usually means that the door remains a physical obstruction in the space.
If free and clear is what you’re after, the pocket lift-and-slide door may be a good solution. With only the tracks at the head and sill reminding you that this is actually an exterior wall, the pocket system is as invisible as it comes. Depending on the width of the opening and the number of door panels, these pockets can be quite thick (one foot wide and larger).
Manufacturers with experience in pocketed lift-and-slide doors are critical partners in the design process. They can provide advice on best practices, especially with regard to the joints surrounding exterior pocketed doors.
4. Thresholds and Sills
Keeping the weather outside is one of the basic functions of any door. When those doors double as the exterior walls of a living space, it’s of paramount importance. Work with your architect or designer to determine the best fit for your space.
Above, the threshold is fully protected by a deep overhang. This track is continuous at the floor. Note that in higher-traffic areas, this type of sill, even one with a very low profile, can be a tripping hazard. Continuous tracks offer better weather resistance than a recessed, flush, or staggered threshold.
5. Insulating Qualities of Glass
Because these openings are by nature mostly glass, it’s important to pay attention to the insulating qualities of the glass. Double- and triple-pane glass is available for many of these units, but you should always consult the manufacturer about availability. The increased efficiency of triple-pane glass comes with a 50 percent increase in weight over a double-pane unit. As you can imagine, this has a real impact when it comes to large sliding door panels.
As much as we’re enamored with the outdoors, we’d prefer that winged, biting, and blood-sucking creatures stay out. Fortunately, screens are available for most colossal doors. Remember that the track depth will increase with every screen panel you add. The drawback, of course, is that screening, no matter how invisible the manufacturer claims it to be, is an obstruction. But for ventilation and converting your room into a vast screened porch, it’s perfect.
The old adage, “If you have to ask, you probably can’t afford it,” may apply here. There are myriad factors affecting price, and the more specialized you get in terms of opening size (width or height), material, finish, or operation, the less useful my estimates will be. But as a general starting point, I tell my local clients they can expect to pay $1,000 per linear foot of opening. This means that if you have a pocketed opening, you must count the full width of the pocket too. So for three eight-foot-wide panels stacking into a pocket, I would generically estimate $24,000. Using the same overall opening but stacking the panels would be roughly $16,000. Unfortunately, Johnson was right: We’re talking about very expensive wallpaper.
We have practical reasons for walling off our living quarters from the outside, but we choose places to live based on the surrounding environment, and doors like these allow us to be immersed in that environment. They open our interiors to the exterior and all that comes with it: the changing seasons, the weather, the sounds and smells, the breezes. These are things that a more typical modern home would seek to insulate us from. Using these monumental doors to slide away that barrier refocuses us on what’s right outside and brings that experience inside.
As a humbler alternative to the colossal openings we’ve been fawning over, I offer the ingenuity of this architect’s solution, shown above. Aptly named Sixteen Doors, this home features more common, off-the-shelf sliding French doors that achieve, albeit on a smaller scale, much of what we’ve been discussing. And, I would expect, at a fraction of the price. For rough budgeting, assume that a good-quality, eight-foot-wide, clad, sliding French door costs around $4,000, or about $500 per linear foot.
I hope this inspires you to think about using colossal doors to connect with the outdoors on your next project.
Eric Reinholdt is a residential architect practicing on Mount Desert Island. Learn more about his approach, and view his projects, at: thirtybyforty.com.