Energy Efficient Residential Roofs and Ceilings

Authored by: Kevin Hyland, Principal Engineer- Fire Resistance and Containment, UL and Elliot Seibert, EPA ENERGY STAR Certified Homes

There are many performance expectations for a modern residential building, including being safe, functional, durable, energy efficient and healthy. Model building codes tend to focus on these expectations individually, which sometimes puts them in conflict with each other. Tested and certified fire-rated roof-ceiling assemblies achieve a fire rating in a practical way, but they may not always include best practices to also achieve a desired level of energy efficiency. For example, fire-rated roof-ceiling assemblies are very specific as to where attic insulation can be placed due to its effect on the fire rating. This creates a challenge for designers and builders who seek to create high-efficiency buildings, such as ENERGY STAR certified homes and apartments. Fortunately, there is no need to choose between fire performance and energy efficiency because assemblies are available that meet the code requirements and high standards for both.

Passive Fire Protection

Model building codes combine two approaches to fire protection in the built environment: active and passive. Active fire protection is generally a system or combination of systems that actively controls or extinguishes a fire, such as fire sprinkler systems, or notifies occupants and emergency responders, such as fire alarm systems. Passive fire protection is construction that restricts the spread and passage of fire and smoke through the selection of proper materials and use of products and assemblies to contain a fire. Fire-rated roof-ceiling assemblies are an example of the fire containment approach that are intended to restrict the vertical passage of flames and heat from the top story of a building to the attic space above.

The building codes direct when a fire resistance-rated roof-ceiling assembly is required. This fire resistance rating is determined by demonstrating compliance with the fire test UL 263 (ASTM E119), the Standard for Fire Tests of Building Construction and Materials. This large-scale fire test evaluates an assembly’s resistance to heat (temperature rise) and flame passage while maintaining the applied structural design load. The ratings are expressed in hours. When a test assembly complies with the acceptance criteria, the assembly details are published as assemblies (designs) in UL Product iQ®.

ENERGY STAR Residential New Construction Program 

While fire performance has been a long-standing building code concern, energy efficiency concerns are more recent and advancing quickly. Current model building codes require newly built homes to use only half as much energy as one built in 1975 and many homes are built with even better performance than required by code. In fact, today, over 2 million homes and apartments have earned ENERGY STAR recognition by meeting strict program requirements for energy efficiency developed by the U.S. Environmental Protection Agency. ENERGY STAR certified homes and apartments are at least 10% more efficient than homes built to comply with the adopted residential building codes and achieve a 20% improvement on average. Homes and apartments achieve this level of performance through a complete package of building science measures. Throughout the construction process, an energy rating company works closely with a builder or developer to help utilize energy-saving construction techniques and conduct required on-site diagnostic testing and inspections to document eligibility to earn the ENERGY STAR label.

Quality Installation of Attic/Ceiling Insulation

An energy-efficient shell keeps a building warm during cold weather and cool during warm weather. To that end, ENERGY STAR requires quality installed insulation and a continuous air-barrier. These two elements work together like a wool sweater and a windbreaker on a blustery day. When it comes to an attic or exterior ceiling, insulation should be in continuous, direct contact with a horizontal air-barrier. An air barrier is a durable solid material like gypsum board or sheathing that blocks airflow and is sealed at its edges and seams. ENERGY STAR further requires that insulation achieves Grade I installation per the ANSI/RESNET/ICC 301-2019 standard by neatly filling in around framing, wiring, and pipes without gaps or voids.

When a fire-rated attic assembly is not required, as in many low-rise residential buildings, ENERGY STAR requirements are typically achieved using either batt or loose-fill insulation installed directly above and continuous with the ceiling gypsum board that acts as the air barrier.

However, when a fire-rated attic assembly is required, installers need to contend with the resilient channel that is part of most fire-rated assemblies. This metal channel holds gypsum board ½-1 ½” off the ceiling framing. If batt insulation is installed at the framing plane, an air gap will be left between the air barrier (ceiling gypsum board) and insulation, degrading the insulation’s performance. If there is an accessible attic space, a common solution is to install loose-fill insulation after drywall is hung. Loose-fill insulation, by its nature, packs in tightly around the resilient channel.

However, builders have struggled to identify appropriate assemblies that achieve both a fire rating and Grade I installation quality when there will be no accessible attic space such as in flat-roof townhouse and multifamily buildings. The solution lies in a group of UL roof-ceiling assemblies that include an optional layer of wire mesh or netting to temporarily support loose-fill insulation prior to the gypsum board installation. These previously obscure assemblies provide a good option that is fire-resistant without sacrificing energy efficiency.

Insulation in Fire Resistance Rated Roof-Ceiling Assemblies

Insulation needed for energy conservation and energy efficiency rating is known to affect the fire resistance-rating of the complete assembly. In some cases, the addition of insulation in the concealed space between the gypsum board ceiling membrane and the roof structure may reduce the hourly rating of an assembly. Consequently, when insulation is allowed in the individual UL roof-ceiling design, that insulation must be of the type and thickness specified and the method of installation must match the design construction details to ensure the required fire rating is achieved. The design specifications also dictate resilient channel spacing and gypsum board fastener spacing.

The balance of both fire performance and energy efficient construction in buildings can be a challenge, but it is achievable. Insulation is crucial to providing energy efficiency to a building, and its installation details are critical to maintain both Grade I installation quality and the fire rating of the roof-ceiling assembly. Selecting the right assembly is the first step to creating safe, efficient, high-performance buildings.

Discover the benefits of ENERGY STAR new homes and apartments at EPA’s consumer webpage and for more information on the program requirements and helpful guidance for professionals visit the Partner Resources page.

ENERGY STAR New Homes Consumer Page: www.energystar.gov/newhomes

ENERGY STAR New Homes Partner Resources: www.energystar.gov/home