With zero energy buildings emerging as the new norm, there’s no doubt that the state of California is leading the way in building energy efficiency. That being said, local ordinances and jurisdictions across the country are choosing to adopt and enforce energy standards for new construction, additions, and alterations that exceed their statewide standards. With mounting concerns over energy consumption, it’s becoming clear that energy efficient homes and buildings are a top priority for more and more regions nationwide.
One Step Ahead
San Francisco, Palo Alto and San Mateo all have approved local energy standards that exceed the 2016 Building Energy Code, and excel in energy efficiency and renewable energy. The city of San Francisco, for example, established its own city building code requiring all residential buildings to be 10% more efficient than the state mandated Title 24 Energy Efficiency Standards. And the first of its kind globally, the city of Santa Monica approved an ordinance requiring all new residential construction to be net zero energy buildings.
Beyond California, the International Energy Conservation Code (IECC), the International Residential Code (IRC), and the International Building Code (IBC) are most commonly adopted by states and local jurisdictions to establish minimum energy efficiency requirements.
But this is where compliance and enforcement gets complicated across a region! Let’s take the state of Colorado for example.
Per the American Council for an Energy-Efficient Economy, “Colorado is a home rule state with a voluntary building code for residential and commercial construction.”
Still to this day, there are jurisdictions in Colorado who choose not to adopt and enforce building codes, and many who do, enforce a dated edition of the International Code. Furthermore, some enforce multiple editions of the International Code, while others create their own version by adopting local amendments on top of adopting the International Code.
Although local jurisdictions are left without state guidance, leading-edge cities like Aspen, Colorado, continue to aim for energy efficiency. With focus on efficient building performance, the city has amended a prescriptive residential fenestration U-factor value of 0.28. That’s considerably lower than the 2015 IECC prescriptive residential fenestration U-factor value of 0.32 commonly adopted across the nation for colder mountainous climate zones.
Working nationwide with the varying, and rapidly increasing, energy efficiency standards is something that requires an additional level of management and expertise for today’s engineer, architect, builder and manufacturer. With tougher energy targets put in place, will the building industry be ready to play its part in an energy efficient future?
A thought-provoking discussion for any building professional is to evaluate where the energy standards are today and to prepare for the energy standards of tomorrow.
Title 24 Update
As of January 1st, 2017, the new Title 24 energy standards, known as the 2016 Standards, are in effect. The goals set by this multifaceted program are aggressive, thorough, and impactful. Residentially, these standards are cumulatively more stringent, and target several building components.
A thorough look at the 2016 Energy Code Requirements are discussed in 2016 Building Energy Updates: What You Need to Know for 2017 and Beyond.
Not familiar with California’s Title 24 Energy Standards? Scroll down the page to Title 24 Compliance Options and NFRC Thermal Certification for a quick review.
2013 Energy Standards for Windows and Doors
With ambitions to generate net zero energy buildings that make as much energy as they consume, the Title 24 codes target several building elements. A key target in the 2013 version, are standards affecting residential fenestration, and with good reason. Effective July 1st, 2014, the energy code standards impacting fenestration products were updated in order to reduce energy loss, and further enhance building performance.
“Fenestration accounts for a large impact on heating and cooling loads of residential and high-rise residential space conditioning loads, the size, orientation, and types of fenestration products can dramatically affect the overall energy performance of a house.” - 2013 Residential Compliance Manual
Although energy standards are on track for the future net zero energy goals, awareness, compliance, and enforcement take time to reach full integration in some areas. Continuing education is key for improving consistency across the industry; let’s take a step back and review the impactful residential fenestration changes that took place between the 2008 Standards and the 2013 Standards.
Newly Impemented Mandatory Measure
Previously added to the 2013 Standards, the building envelope requirements added a maximum fenestration U-factor, which is a new fenestration specific mandatory measure that must be met regardless of the compliance approach used. The new requirement states that all fenestration must meet a maximum U-factor of 0.58 or a maximum weighted average U-factor of 0.58 that separates conditioned space from unconditioned space. This means that all windows, doors and skylight products require a U-factor of 0.58 or lower, or weighted-average (which is the average of all fenestration products across the home or building) U-factor of 0.58 or lower that separates the space we live in from the space outside.
The exception for this measure allows for the greater of 10 square feet or 0.05 percent of the conditioned floor area to exceed the maximum 0.58 U-factor requirement. An example of this exception is if a project wanted to use a single pane or stained glass specialty window in one area of a home or building.
New Methods and Procedures for Obtaining Compliance
Prescriptively, the updated 2013 Standards eliminated the 2008 prescriptive component package options (C, D, and E) with pre-defined performance levels for various building components, and established a simplified single component package, Table 150-1-A Component Package A, for all prescriptive requirements. The table lists fenestration energy performance identifiers including U-factor, Solar Heat Gain Coefficient (SHGC), Fenestration Area, and West-facing fenestration values.
The 2013 prescriptive U-factor for all climate zones was noticeably reduced to 0.32. This is a significant energy reduction when compared to the varying 2008 U-factors of 0.32 for Package C, 0.40 for Package D, and up to 0.57 for Package E.
Similarly, the 2013 maximum Solar Heat Gain Coefficient (SHGC) was reduced to 0.25 for all extreme climate zones 2, 4, and 6-16 while the milder coastal climate zones 1, 3, and 5 are exempt from the standard. This is another significant reduction from the 2008 maximum SHGC of 0.40 for all climate zones except 1, 3, and 16.
To further improve clarity and consistency in compliance, the 2013 performance component modeling software has been revised to use a single modeling engine, California Simulation Engine (CSE). Also, more accurate mass simulations (going from one simulation per hour to thirty simulations per hour) are being implemented, and the same Compliance Manager plug-in will be used to produce a single interpretation of the performance compliance results.
A New Energy Performance Identifier
Visual Transmittance (VT) is listed as a new 2013 fenestration energy performance identifier and calculates the amount of light transmitted through the glass of a window or door product. Residentially, this identifier value is for information purposes only, but must be tested and labeled per NFRC procedures.
The Big Picture
The increase in the 2013 fenestration energy efficiency requirements reduced the opportunity for performance method tradeoffs; for example, it’s harder to offset window and door performance values and makeup for it elsewhere in the building envelope. For projects desiring large glass openings, this is a critical part of the planning process. Early identification of the desired fenestration products can become the primary driver for the energy package.
For a more comprehensive list of fenestration requirements see the 2013 Residential Compliance Standards Table.
2016 Energy Standards for Windows and Doors
Known as the 2016 standards, most 2016 U-factor and Solar Heat Gain Coefficient (SHGC) performance targets are the same, but the building envelope requirements are about 28% tougher overall. Compared to the 2013 Standards, this means even fewer opportunities for tradeoffs between building systems when using the performance approach for compliance.
What's New With Fenestration in the 2016 Standards?
As defined in the 2016 Residential Compliance Manual, the mandatory measure for air leakage requires all fenestration products to leak no more than 0.3 cubic feet per minute per ft² of the window area. This mandatory measure now requires pet doors to meet the same minimum.
In addition, the fenestration maximum or weighted average U-factor of 0.58 is the same as 2013, but the exception now allows for 30sqft dual glazed greenhouse windows to exceed this mandatory measure.
As large areas of glass continue to be in high demand in today’s architecture, the need for high-quality fenestration products will only increase as we move closer to 2020. The skilled design team recognizes that choosing the fenestration manufacture early and working closely with the design team will yield the best results for design demands, functionalities and energy efficiency targets.
For a more comprehensive list of fenestration requirements see the 2016 Residential Compliance Standards Table.
Window and Door Technologies
In the fenestration industry, the trend towards large spans of glass is a common design challenge frequently encountered by industry professionals. The desired function to artfully blend indoor and outdoor spaces, frame expansive views, or capture energy saving natural light and ventilation requires a balanced approach. In the past, designing homes with expansive glass openings meant that energy performance was sacrificed and homes were susceptible to unfavorable conditions like heating and cooling loss, thermal discomfort, and condensation.
Luckily, expert window and door manufactures are well equipped to design products with energy conservation in mind. Incorporating sophisticated technology, advanced fabrication techniques, and keeping informed with current energy standards ensure a high-quality fenestration product capable of supporting the vision of the designer, and in preparation for the future of zero energy buildings.
With the unveiling of several advanced window technologies, manufactures can now utilize stronger frame materials, thermally broken profiles, dual and triple pane glass, low-emissivity coatings, and special gas fills to improve product performance.
For a well-designed energy efficient home or building that maximizes large glass spans, it’s important to choose a window and door frame material that is inherently strong, durable and long-lasting.
Wood as a frame material is traditional, timeless and energy efficient, but lacks permanency and is susceptible to warping, decay and pests.
Vinyl and fiberglass frame materials are commonly seen in today’s fenestration market as they offer good insulating performance at a good value. But take into consideration that for extra-large openings that require heavy glass, the vinyl frame lacks stiffness and rigidity, and is susceptible to breaking at the fused joints. Fiberglass is better structurally as it is mechanically joined at the joints, but consequently not as watertight. Both materials often lack architectural sophistication and elegance.
Today, thermally broken metal frame materials are a highly feasible material option when compared to wood, vinyl, or fiberglass. Large glass openings require a material with superior structural integrity, and steel stands out as the frame material of choice because of its unique technical and physical features that other frame materials simply can’t measure up to. The shear strength and durability of steel, combined with current fenestration technologies creates a vastly innovative and energy efficient product that will prevail in architecture for many years to come.
The development of thermal barriers, or thermal breaks, in fenestration has taken thermal performance and condensation resistance to the next level. This is especially true for metal frame materials that readily transfer hot and cold energy. The modern solution to limiting energy loss is the insertion of a thermal break between the interior and exterior framing components. When hot or cold energy come in contact with the frame, it dissipates at the thermal barrier.
It’s important to note that not all thermally broken window and door frame profiles are designed and manufactured the same. Select cutting-edge thermally broken profiles are designed for maximum shear, torsional and flexural strength. A high quality thermal break uses a tough fiberglass reinforced polyamide extruded strut. The polyamide extruded strut is then pressure injected with high-density polyurethane resin creating a monolithic bond between the two components. This unique fabrication technique adds strength, and an impenetrable insulation seal to the joining of the two roll formed halves.
Other common fabrication practices mechanically glue or crimp the thermal break, making the profile less structural as well as less water, air, and sound resistant.
For oversized fenestration products, it’s equally important to consider the structural integrity of the thermal break, and how it connects with the two roll formed halves. While some thermally broken profiles use two thin strips, choosing a thermal break engineered with a thick central section will provide superior strength and a significant increase in the structural performance of the fenestration product.
Dual & Triple Pane Glass
Long gone are the days of single pane egress windows and doors in a high performing building envelope. Insulated glass units (IGU), made up of multiple panes of glass, increases thermal performance of windows and doors by utilizing the air space between the glass panes to resist thermal energy transfer. Installing dual pane glass into a window or door product reduces the U-factor, or energy loss, of a fenestration product by half. Triple pane glass units add an additional layer of glass and gas to further reduce energy flow and increase insulating value. To meet desired U-factor values for energy efficiency, triple pane glazing is now commonly implemented into fenestration products by the manufacturer. The limitations of adding additional panes of glass into a unit is the reduction of natural light and desired heat gain from the sun.
Low-Emissivity Coatings (LOW-E)
The goal of limiting energy flow through the glass of a fenestration product is greatly reduced when coating the surface of the glass with a low-emittance material, and orienting the coated pane between the gap of the dual or triple glazed units. This valuable insulating technique, in return, blocks a good amount of radiant heat from the sun and provides the same beneficial energy values to the fenestration product as adding an additional pane of glass. What’s so state-of-the-art about low-emissivity coatings is its ability to be optimized for desired solar heating, cooling and daylighting by altering the reflection spectrum of visible and infrared light.
Specialized Gas Fills
Thermal performance can be taken one step further when the gap between insulated glass is filled with specialized inert gases like argon and krypton. The specialized gas fills slow down the rate of temperature induced circulating air, and thus, limit total energy transfer between the glass panes of the fenestration product. The use of specialized gases is best optimized when the gap between the glass panes is spaced at ½ inch for argon-filled units, and ¼ inch for krypton-filled units. This is a useful technique for improving thermal performance without affecting natural light and solar heat gain coefficient.
When building a new residential home, there are two compliance methods that can be used to gain permit compliance. The two paths for obtaining compliance are called prescriptive and performance methods. In addition to these methods, mandatory measures must be installed.
Energy values that MUST be met for energy code compliance are referred to as mandatory measures. These measures are required to be implemented into the building’s energy budget no matter what compliance method is used.
The prescriptive method is the most time efficient and straightforward approach at meeting minimum energy requirements for a home or building. This approach is the simplest way to rate performance, but requires each envelope component (fenestration, lighting, electrical) to meet established minimum efficiency values per climate zone.
The performance method allows for the best flexibility and accuracy in the development of a good home or building energy plan. Certified component modeling software provides an averaging of the building’s systems to come up with an overall energy budget for the building envelope. An example would be that window and door performance values can be offset with wall insulation and electrical performance values. Another possible tradeoff is when less efficient windows are combined with more efficient windows for a product average.
NFRC Thermal Certification
In California, the NFRC (National Fenestration Rating Council) has taken on the responsibility of regulating the testing and certification methods for windows and doors. To achieve certification, each fenestration product is modeled using special component software, and then physically tested to verify the model. The result is a certified core product rating that can be altered depending on the glass type that is used. Complying with most energy codes used today require participation in the NFRC certification programs.
Unique fenestration products that have not been NFRC certified use the applicable default U-factor and default SHGC numbers set forth in Table 110.6-A & Table 110.6-B. It’s important to note, default rated products can be combined with certified products for an overall average rating to meet the required local ratings.
Energy flow in fenestration is measured by the following NFRC energy performance identifiers:
Air Leakage (AL)
Affecting interior thermal comfort, air can infiltrate through small spaces in a fenestration assembly and can be altered by wind and temperature pressure changes within local climate conditions. Quality constructed fenestration products can more easily control air leakage with tighter sealing sash, frames, and weatherstripping.
A measured rate of heat loss or gain through a fenestration product. The direction of temperature driven heat flow is always from hot to cold by the combined effects of conduction, convection and radiation. In fenestration, this process occurs between the inside and outside of a home or building. The lower the U-factor number the better insulating performance of the product.
Solar Heat Gain Coefficient (SHGC)
Solar radiation, or heat from the sun, passes and absorbs through the glass of a fenestration product and creates interior heat gain regardless of the outside temperature. In California’s warmer climates, choosing a window or door product with a lower SHGC value contributes to lower air conditioning costs.
Other significant NFRC energy performance identifiers for fenestration include visual transmittance, and condensation resistance.
Visual Transmittance (VT)
The amount of light transmitted through the glass of a window or door product is measured as visual transmittance. Although VT does not contribute to heating and cooling performance, there are several beneficial features (natural light, views, privacy, controlled glare and interior fading from the sun) that make VT a meaningful factor in choosing energy efficient fenestration products.
Condensation Resistance (CR)
When humid indoor air comes in contact with a cold window or door surface then condensation in the form of water vapor occurs. This is a common problem with poorly insulated metal window and doors products. Today, the use of high quality thermal breaks limit hot and cold transmission through the product frame, and creates a high level of insulation and condensation resistance. Other factors in condensation resistance include a well-designed frame with good U-factor values, and the use of highly insulating glazing such as multiple panes of glass, low-emissivity coatings and specialized gas fills. Condensation resistance in fenestration products is the measured value of interior resistance to condensation.
Looking to the Future
Reaching towards the 2020 net zero energy building for residential new construction is an ongoing process. Although some industry professionals are resistant to the changes, many architects, engineers, builders and manufacturers are prepared; many times, working together at the onset of a project in order to approach the building design as a whole. This comprehensive effort is a great approach to creating energy conservation solutions without limiting the look, feel and functionality of the home or building.
More Resource for the 2013 & 2016 CA Building Code Updated
Want to know more about what’s new and what’s changed for the building energy code standards? You can learn more by visiting the following websites and resources: