Crafting the Intersection Between Indoors and Outdoors

An in-depth look at multi-panel door systems
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Sponsored by LaCantina Doors
Amanda Voss, MPP
This test is no longer available for credit

Bringing More Green To Your Buildings: Sustainability and Environmental Benefits

Multi-panel door systems not only open up design opportunities by erasing the border between inside and out, they also enhance the sustainability of a structure. The benefits of a multi-panel system are not confined just to their operation–a thoughtfully selected product has environmental advantages inherent in the very materials it uses.

Natural Daylighting: Allowing for more glass and light, multi-panel door systems can be a good passive heat source and minimize use of electricity for daytime lighting.

Energy Efficient: Most multi-panel door systems offer dual-paned tempered glass, creating an insulating barrier between the inside and out. Manufacturers may offer advanced low-e glass options to help reduce cooling costs in the summer and heating costs in the winter. Overall U-factors (insulating factors) in the door panels can be achieved at or near the common fenestration target of 0.30 or better depending on specific glazing selections made for low-e or other coatings. While no piece of fenestration can match the insulating performance of a wall, having the highest-performing glass and door systems installed in designated openings supports the overall performance goals of the project.

Fresh-Air Ventilation: A critical aspect of green design evaluates the indoor air quality for healthy living environments. Indoor air quality (IAQ) refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Common pollutants can occur and build up indoors, creating the risk of indoor health concerns. Using multi-panel systems opens up areas typically blocked by walls and aids in whole house air circulation, bringing clean and fresh air into any structure and replacing existing, stale air.

Local Manufacturing: Finding a domestic or local manufacturer contributes to green design by minimizing fuel and transportation costs normally associated by importing products from areas outside of the United States.

Recycled Packaging and Materials: Certain manufacturers pack and ship systems using recycled materials, providing safe transport and smart use of renewable resources.

LEED Projects: Multi-panel door systems can help to earn a LEED designation for projects. Architects and project owners can submit many of these characteristics for point consideration within their project. Please note that as LEED v4 becomes fully enforced, points may be categorized differently.

Possible LEED v3 points opportunities: • Energy & Atmosphere Prerequisite 2
• Energy & Atmosphere Credit 1
• Materials & Resources credit 2
• Indoor Environment Quality Credit 4.4
• Indoor Environment Quality 6.2
• Indoor Environment Quality 8.1
• Indoor Environment Quality 8.2

Responsible Materials: If wood or clad multi-panel door systems are under consideration, certain manufacturers offer FSC-certified wood. The Forest Stewardship Council (FSC) sets forth principles, criteria, and standards to guide forest management and practices toward sustainable forestry worldwide. FSC certifiers verify that companies claiming to sell FSC-certified products have tracked their supply back to FSC-certified sources. This chain of custody certification assures that consumers can trust the FSC label.

NFRC, the Meanting of Green, and Mutli-Panel Door Systems

Classifying and labeling the real thermal performance of door and window systems is the focus of The National Fenestration Rating Council (NFRC), a not-for-profit trade association. In 1993, NFRC developed the first consensus method for evaluating the thermal transmission of windows. Today, NFRC 100: Procedures for Determining Fenestration Product U-factors is the accepted standard for rating windows, doors, and skylights for U-factor. A U-factor is typically rated between 0.20 and 1.20. This standard establishes standardized environmental conditions, product sizes, and testing requirements, so that architects and others can make informed choices fairly and accurately by comparing the performance of different products.

One of the most important improvements that NFRC 100 offered the industry was a determination of heat loss from the entire window unit, rather than heat loss solely from the glass. Under this all-encompassing evaluation, a multi-panel door system earns credit for all of its energy-efficient features, including energy-efficient glass, thermally improved frames, and even down to such minutiae as the spacers used between layers of insulated glass.

NFRC testing also looks at other overall performance characteristics, including the solar heat gain coefficient (SHGC), which measures how much solar energy passes through a particular glazing, creating heat gains inside a building. A SHGC is expressed as a number between 0 and 1. In areas where heat gains are a concern, coatings are applied to the glass to allow less transference.

NFRC testing also responds to green building standards by assigning a value to the visible light transmittance (VT). Values are between 0 and 1. VT determines the effective light available for daylighting, helping gauge potential offset of electricity costs for lighting a building’s interiors.

In addition to thermal performance, codes, and standards, including those of the NFRC, have increasingly recognized air leakage (AL) as a very significant factor in fenestration performance. Today’s window and door products must meet minimum standards for air infiltration and be tested, certified, and labeled for this performance. The total system must be able to withstand wind pressures associated with its geographic location, and air leakage must be controlled not only for energy performance but also for occupant comfort and long-term durability of the fenestration system. NFRC expresses AL as a number ranging between 0.1 and 0.3.

U-factor, SHGC, VT, and AL are all disclosed on an NFRC label for an individual product. The lower the U-factor, the better the insulation level of the unit, meaning less heat loss to the outside or, in cooling dominated climates, less heat gain from the outside. A low SHGC means more solar energy will be blocked, eliminating passive heat gain from outside into the building. The higher the VT, the more natural light is transmitted through a product. A higher AL means greater air infiltration over the life of the product.

Typical high-performance multi-panel doors have U-factors of 0.32 or less and SHGC of 0.30 or less, depending on climate zone. The most suitable AL rating for an energy efficient building will be at or near 0.1; VT is dependent upon climate zone and client preference.

Multi-panel door systems capture energy efficiency, natural daylighting, and boost indoor air quality. The multi-slide doors open this home dramatically to its environment.

Photo courtesy of LaCantina Doors

Multi-panel door systems capture energy efficiency, natural daylighting, and boost indoor air quality. The multi-slide doors open this home dramatically to its environment.


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Originally published in Architectural Record
Originally published in December 2015