This course is part of the Custom Home Academy

Glazing was central to the project. Naturally, new windows would be installed in the sunroom addition and bedroom, but the old double-hung windows throughout the main house would also need to be replaced. And while it was highly important to the owners that their new windows provide security and energy efficiency, they still wanted to maintain the home’s original colonial revival style. With this idea in mind, the architects laid out a plan for windows that would blend seamlessly into the architecture, as if they had always been there.

The owners chose a high-performance double-hung window with a contemporary classic look–one that maximizes views but doesn’t clash with the colonial revival style. The windows offered energy efficiency, an auto-lock feature for security, and durable hardware. In the end, they were able to choose from a multitude of traditional sticking options and profiles to meet their design goals and performance expectations.

The renovation was not without a few surprises. When the old windows were removed, they discovered that the home had been built with interlocking, structural clay tile that was covered in stucco. Before being replaced by concrete masonry units, structural clay tile was commonly used throughout North America in the late 19th and early 20th centuries, although it’s uncommon to find Seattle-area homes built in this way.

The unique building material did, however, provide an unexpected benefit; the extra thickness of the masonry wall allowed for greater setback with the new windows, which provided more coverage and protection from Seattle’s challenging temperate marine climate. Because the windows are not flush with the exterior wall, the masonry acts as an umbrella, shielding the windows from precipitation. To account for the recess, the project’s architect worked with finishing carpenters to trim out the windows, giving them a seamless appearance with the exterior wall.

And then there was the sunroom. To optimize views and comfort, the designers chose a mix of large direct glaze and operable casement windows for cross ventilation. Despite their lack of traditional embellishments, the windows in the sunroom work beautifully within the context of the rest of the home, while at the same time giving the space its own unique identity within it.

For this project energy efficiency was not just a personal choice for the owners. Washington state energy code requires meeting .30 U Value, which is higher than some other states. The array of big glass design options—and flexible customization—supported the project goals well, and helped introduce more light, air, and views, while keeping the historic aesthetic intact.

THE SCENIC EVOLUTION: BIG-GLASS TECHNOLOGIES AND TRENDS

Window and door designs have evolved significantly over the years, with manufacturers introducing a range of new materials, technologies, and styles in order to enhance their functionality, security, and aesthetics. Each type of door and window has its own origin story, but one of the best examples of how big-glass products have evolved is in the case of patio doors.

Patio doors were traditionally made of wood or aluminum, and they were designed for the simple purpose of providing quick and easy access to outdoor spaces. In the 1950s and 1960s, sliding patio doors became more widely available and affordable, and they quickly became a popular feature in modernist architecture and suburban homes. By the 1970s, sliding patio doors were incorporated into residential construction across North America.

These early sliding patio doors had large glass panels that allowed natural light into the home, as well as easy access to air and views. But these earlier doors were not very energy-efficient and could be prone to leaks and drafts, which made them less popular in colder climates. The door operation was not always reliable in terms of durability and function. They were limited to a basic look that could only go so far in contributing to aesthetic design. Security was also a concern, and patio doors in this era had basic locking mechanisms that were relatively easy to bypass.

Technology and design innovations have significantly changed the status of patio doors—and all windows and doors—opening the proverbial door to big-glass possibilities. New materials such as vinyl, fiberglass, and composites have helped make doors and windows more durable, energy efficient, and lower maintenance. They incorporate energy-efficient features such as low-e glass, argon gas fills, and insulated frames to improve insulation and reduce energy costs. These modern doors and windows are designed with robust locking mechanisms, tempered glass, and impact-resistant materials to improve security and protect against break-ins. They are available in a variety of styles, finishes, and sizes to suit different architectural designs and preferences.

New technology has also advanced windows and doors with automated opening and closing systems, smart locks, and built-in blinds–all of which provide more convenience and advance their functionality. All these technologies have advanced occupant health, safety, and well-being, by making possible products that enhance views, natural light, and natural ventilation, as well as support thermal comfort and emotional security.

Architects looking to incorporate big-glass designs into a project can consider several window and door products and design configurations. Sliding doors, including patio doors, lift and slide doors, multi-slide doors, and bifold doors, are common for exterior glass design and can be utilized for big-glass looks that offer more opportunities for natural light, natural air, and views. Swinging doors, including pivot doors, are also options for big-glass looks since they can be specified with large glass panels in heights and lengths that exceed standard door sizes.

Double-hung windows, casement windows, awning windows, and sliding windows are popular choices for architects who are considering big-glass designs that enhance natural light, natural ventilation, and views.

When deciding on the specific configuration for a door or window system, designers should take into consideration size and weight, available space for the system, and the specific design goals of the project. They also need to consider several performance attributes, including energy efficiency, acoustic performance, security, durability, aesthetics, and sustainability.

OTHER CONSIDERATIONS FOR BIG-GLASS DESIGN

Sills are a key performance consideration for water management. Swinging doors require different types of sills than sliding doors but the details and configuration of each need to work with the door panel to achieve the needed level of protection. In cases where lower levels of water and weather protection are needed, then a flush sill is possible. In cases where higher levels of protection are needed (i.e., the door is fully exposed on the exterior) then the manufacturer's choices should be reviewed for both leakage resistance and proper drainage. It is worth noting that in some cases, the sills for sliding doors actually have greater performance results than sills or thresholds for swinging doors.

For operable windows, a sill should be designed to manage water that may collect on the surface of the sill or flow into the window opening. The sill should be sloped away from the window to allow water to drain properly and prevent water from infiltrating the homes. Other considerations include condensation management, material selection based on the climate, aesthetics, and accessibility. The sill height should comply with accessibility guidelines to ensure the window is usable by all occupants.

Home Automation

Home automation is becoming increasingly popular and combines well with big-glass design.

The ability for homeowners to control aspects of their home such as lighting, temperature, and security systems, all from a single device, such as a smartphone or tablet, is appealing to busy people as well as those who require assistance. Home automation helps save energy costs because the systems can be automated or controlled from afar, tailored only to when occupants need to use the energy. It also adds a level of security that gives homeowners peace of mind–emotional comfort–by making it easier to lock window and door systems.

There are always new innovations for home automation, but here are a few that architects can consider when designing big-glass projects.

Lock Status Sensor and Remote Operation
Some operable windows and doors can be upgraded with sensors that are installed in the factory and fully concealed in the product. They can be wired or wirelessly connected, sending a signal to the homeowner’s integrated smart home security system to indicate if windows and doors are closed and locked or unlocked. These types of lock status sensors are an open system, so they are compatible with other smart home systems, which also allows for flexibility if a homeowner needs to change their security system in the future. Operable windows and doors can sometimes be specified with remote control devices. These devices can be a good choice for large doors and when occupants require assistance.

Photo courtesy of Marvin

A wall can serve as a canvas for architects to create their vision for more natural light, natural ventilation, and breathtaking views, but this type of design can be a complex process that presents both engineering and design challenges.

Big-Glass Window Design

Window technology has increased durability and energy efficiency and given architects more design freedom. The expansion of window options also allows architects the opportunity to directly combine these high-performance windows into aesthetically striking window assemblies that–in some cases–nearly open entire walls to glass. With window mulling, a wall can serve as a canvas on which architects feature a variety of conjoined window shapes and sizes to support their vision for more natural light, natural ventilation, and breathtaking views. Mulled window assemblies are two or more separate windows that have been joined together to fit into a single opening in a wall. When specified and installed correctly, mulled windows improve the potential and practicality for achieving a higher glass-to-wall ratio, compared to installing a series of individually framed windows or a single, large window.

owever, as building professionals know, the process is not as simple as joining several high-performance windowpanes together. Despite the technological advances in windows, window mulling can be a complex process that presents both an engineering and design challenge. The more glazing a design combines, the more the assembly must be interrogated to uphold its durability and energy efficiency qualities. Window mulling requires careful consideration of multiple factors, and architects need to have a thorough understanding of the options available and the impact of each option on the performance and aesthetics of the building.

There are different types of window-mulling configurations, including horizontal, vertical, and unitized, and each configuration has its own set of advantages and disadvantages. The choice of configuration will depend on factors such as the building's design, the location of the windows, and the desired aesthetic.

Window mulling can impact the performance of the windows in terms of energy efficiency, sound transmission, and water penetration resistance. Architects need to consider factors such as the size and spacing of the windows, the type of glazing, and the quality of the sealant to ensure that the mullions do not compromise the performance of the windows.

Window mulling also requires coordination between multiple trades, including the window manufacturer, the installer, and the general contractor. Architects need to ensure that all parties involved in the window installation process understand the specifications for the mulling configuration to ensure a successful installation.

“There have been situations where our products have been put in applications without an understanding of the product limitations and environmental stresses,” says Jeff Siverhus, a senior product manager with Marvin. “The contractor could be installing a PG 40-rated window assembly when a PG rating of 50 or 60 is required.” Inadequate reinforcement could lead to leaking or even catastrophic window wall failure.

Many of the challenges surrounding mulled windows are addressed in the factory. There, the individual units are fastened together securely into finished assemblies for more modest big windows, or into two or more subassemblies that are designed to be joined together in the field for larger installations. The maximum size of a subassembly is determined in part by shipping restrictions that make it difficult to transport a unit larger than 8-feet-by-8-feet.

Building codes also are critical in the big window wall world, as the beefy headers needed to distribute the load over an enhanced window opening places hard limits on how big your window wall can be. In recent years the challenge of mulling windows, even in residences, has become even more complicated by the fact that window assemblies are growing larger and larger. This makes it more difficult to address key engineering questions about assembly and performance.