By Marty Biskup, AGC Glass – Guest Contributor
The topic of Energy Codes has a far-reaching impact on individuals, businesses, and governments. Beyond the obvious of saving money, reduced spending on energy allows capital to be used for purchasing goods and services which ultimately better the economy. Most importantly, the reduction of America’s dependency on foreign nation’s energy resources minimizes the need to negotiate political positioning with unfriendly foreign countries, in order for us to meet our energy consumption needs. Reducing our nation’s energy consumption protects our natural resources and reduces greenhouse emissions which result in costly health-related issues.
The International Energy Conservation Code (IECC) is the nationally recognized energy code that governs the requirements of each state for commercial and residential building types. The IECC provides 2 compliance paths, Prescriptive and Energy Cost Budget.
The American Society of Heating Refrigeration and Air-conditioning Engineers ( ) Standard 90.1, provides the minimum requirements for the energy-efficient design of most commercial buildings. Standard 90.1 has 3 compliance paths, Prescriptive, Prescriptive with Trade-offs, and Energy Cost Budget. However, this particular standard is considered a “codified” standard since it is not an official code. The IECC permits the use of the ASHRAE 90.1 Standard as an alternative compliance path by reference in the energy code. The IECC is currently the only compliance path for residential buildings.
The IECC is reviewed every 3 years and updates are made for energy efficient improvement by amendment to the code. The amended code is submitted to the Secretary of Energy which has a period of 12 months to review and determine if the modifications provide a cost benefit to the US. Once a determination has been made, the DOE authorizes its implementation and individual states are given a 24 month review period to assess the appropriateness for adoption. At the end of the period, the state must submit in writing to the Secretary of Energy, their intent to adopt or to provide valid reasons to delay or forgo adoption. Extensions are granted to states that appear to be acting in good faith and need additional time to review or implement the code. States are allowed to operate under their own energy code providing it is deemed to meet or exceed the national code.
Prescriptive methodology is used in 80% of today’s building designs, particularly those with limited glazing. This methodology uses a component value for each element of the building façade including wall, floors, roofing, vertical fenestration, and skylights. Meeting the specific requirement for each component ensures compliance with the energy code. This “easy button” approach provides a simplified method to building façade design, but can greatly limit the design options, particularly the glazing in southern climates.
- Approximately 75-80% of all buildings are designed using this methodology
- Uses set component values for each element of building facade
- Addresses building envelope: walls, floors, roofing, vertical fenestration, skylights
- Vertical fenestration is limited to 30-40% depending on code adoption
- Skylights limited to 3-5% of roof area depending on code adoption
- Reality: Prescriptive Methodology generally over- prescribes performance needed to meet energy codes
Prescriptive with Trade-offs:
Prescriptive with Trade-offs only applies to the ASHRAE 90.1 standard. This methodology allows greater design flexibility by permitting the increase or decrease of performance values of individual components in the building envelope. Energy code compliance is achieved by providing an overall building envelope performance that meets the requirements of a defined budget building. This methodology can be used where on all fenestration percentages and is particularly useful when exceeding the limits of the Prescriptive methodology. ComCheck can be used to validate acceptability of compliance.
- Pertains to ASHRAE 90.1 only
- Can be used beyond 40% fenestration area
- Trade-off performance of individual building envelope components by Increasing or Decreasing values of each component to meet or exceed the overall envelope performance factor of the budget building.
- Example: Increase roof deck insulation for lower glass performance
- Use ComCheck Software to validate
Prescriptive with Trade-offs is a win for the design architect and building owner. Broader selection of glazing options and the opportunity to reduce the cost of the glazing.
- Greater flexibility for design architect
- Wider range of glazing configurations
- Greater range of aesthetic options
- Diverse performance options
- Can reduce cost of materials
Energy Cost Budget (ECB)
Energy Cost Budget is a more complex approach that takes into consideration a greater range of building systems. Unlike the Prescriptive with Trade-offs methodology that only looks at the building envelope. ECB takes into account the building envelope, lighting, and mechanical systems for total building performance. Simulations of building performance are provided using complex DOE approved simulation programs. These types of evaluations are most frequently used on large project
- It can be used for all proposed design as long as it has a mechanical system
- Energy usage simulation
- Trade-offs can be made between all building systems that affect total energy usage (not just the building envelope)
- Must meet or exceed performance of standard reference building when modeled in computer simulation
- Approved Software Programs
Energy Code Compliance and Glass Selection:
Understanding the design goals of the building are key to selecting the right type of glass. There are many factors that ultimately send the selection process in one direction or another. This list only considers some factor relative to energy code compliance and does not consider product application, processing, life safety, building code, etc. There are many things to consider when evaluating a project for the correct glass types.
- Which Energy Code and version:
- Goal: Meet, Exceed, or Green Building Program
- Building classification and usage
- Building orientation
- Is there more than 40% fenestration
- Desired aesthetic of glazing
- Are there shading devices
- How will light be managed
- Will ComCheck be utilized in design phase
- Plus many more considerations/requirements – life safety, etc.
** Please note that Adler Windows accepts no responsibility for the content within this article. The source of any/all information is Marty Biskup of AGC Glass North America, he can be contacted via 646.937.1614 for further clarification and information.