Best practices for specifying movable glass walls

Andersen Windows - Movable glass walls

When open, folding doors, such as this model from Andersen’s Architectural Collection, fold up to beautifully frame the view. When closed, they create a stately wall of light.

As options for large glass doors continue to evolve, AIA partner Andersen Windows offers recommendations to consider if you’re new to the space.

One of the most dominant trends in home design is the blurring of lines between indoors and out, with seamless connections that allow fresh air to flow and natural light to infiltrate. Advances in window and door technology have dramatically increased the methods designers can use to accommodate the growing demand by incorporating large walls of movable glass.

But while this blank canvas offers a range of options, it can also pose a challenge. Because of the almost unlimited options for large doors, it’s important that architects understand how to make the selection process, rather than which specific door to choose. The specification process should include client aesthetic expectations, environmental conditions, building performance, and durability concerns.

Weighing the options

Large doors are grouped into several types:

  • Gliding or sliding
  • Multi-glide or multi-slide
  • Lift-slide
  • Hinged or swinging
  • Folding or bi-fold
  • Pivot

While the inclination is to find a product first, successfully incorporating large doors initially requires an evaluation of the project’s space and needs.

Design considerations: Questions architects should first ask clients is how often they intend to use the door. Will they use it frequently but prefer it out of the way? Use it occasionally and prefer a service door?  Do they want the door to be a focal point in the design? How large of a clear opening will they need?  

These factors play a role when deciding on a door type. For example, folding doors have more stile width because they rest side by side when closed, while sliding doors overlap; however, if the layout does not have space for a pocket, folding doors will typically provide a larger clear opening.

Understanding sill requirements is also important. The flooring will often dictate what kind of sill, and ultimately what type and style of large door, is appropriate. Sills must work in unison with the space in terms of both function for the door and also to ease transition for occupants.

Function considerations: Understanding the space, flooring type and transition requirements are critical to specifying the most appropriate large door. The mounting and operational features of large glass doors will greatly impact the type and style of product specified. For example, bi-folding doors have a single track, so sill systems are narrow and discreet; multi-panel sliding doors, on the other hand, have several tracks based on the number of panels and stacking direction. This consideration is especially important in retrofit applications.

In addition, specific occupant needs must be considered, as some large doors may require more effort to operate.

Structural considerations: The size of the opening will often dictate which types and styles of large glass door are suitable. For top-hung doors or any large opening, the header and structural supports over the span of the opening must be appropriately engineered to accommodate the load. Wall thickness should also be evaluated.

In new projects, designing walls to incorporate multi-slide pockets for doors may be possible, while a folding door with a single track is a more obvious choice for retrofitting an existing space where walls are traditionally thinner. However, there are tradeoffs with each choice. Pocketed panels require more wall and may mean additional interior finish work. Also, live and dead loads must be calculated when altering existing spaces or designing new projects. 

Also consider whether overhangs are present. In areas of extreme precipitation and high wind, a lack of deep eaves could require a door system with more protection from the elements.

Performance: As with any window and door specification, local climate and a client’s efficiency goals will greatly impact the decision-making process. Daylighting, UV radiation, glare, solar gain, and U-factor all need to be understood and addressed as well. Commercial buildings may require additional safety considerations. Finally, projects in high-wind or hurricane-prone areas will require code-compliant doors and framing. Always consider local building codes before selecting a specific door type and style.

Putting it all together

Taking these decisions into account, consider the following scenario: The remodel of a retired couple’s Midwestern home will see an exterior wall transformed into a large opening leading to a patio and swimming pool. The potential space is 12 feet wide, and the client does not have the resources to rebuild existing walls or structure.

For this project, there are several key factors: the aging-in-place needs of the clients, their performance expectations, and how important it is to them that the doors maximize a clear and accessible opening.

In this case, the physical needs of the occupants take highest priority. Door types can be narrowed to those that will be easiest to operate and have a low threshold. Structurally, the home already has wide overhangs that provide ample protection from expected weather conditions, allowing for a more forgiving durability standard for the door. Finally, the clients plan to entertain friends and family often and require the maximum amount of available opening be accessible.

With these considerations, the architect’s best choice is a folding door. The smooth operation of an Andersen folding door requires little effort to open or close, and the existing overhang will help protect it. Also, folding doors offer a low-profile or flush sill. Because the project was a retrofit application, there were concerns about jamb depth, making a folding door a natural fit; however, it is important to make sure the header is sized appropriately for the weight of the door.

For more details on designing for movable glass walls and additional residential and commercial scenarios, contact Andersen for the CEU “Large Doors: How to Select the Right Door.”

AIA does not sponsor or endorse any enterprise, whether public or private, operated for profit. Further, no AIA officer, director, committee member, or employee, or any of its component organizations in his or her official capacity, is permitted to approve, sponsor, endorse, or do anything that may be deemed or construed to be an approval, sponsorship, or endorsement of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Image credits

Andersen Windows - Movable glass walls

Andersen Windows

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