Standards, Measurements and Tools: An Energy Management Primer
Today, designing and building residences requires adherence to not only structural and mechanical principles. Development must also take into consideration energy code requirements, according to both local and federal mandate and customer preference. But meeting energy efficiency standards can be a complex process for many reasons. Compulsory codes vary between regions. Customers may desire a house that goes well above and beyond the minimum. The variety of components within the house envelope that affect energy usage creates complexity in the design and construction of the residence.
This post provides a high level introduction, to some of the standards, methods of measurement, and tools available for designing energy efficient housing. The information herein should by no means be used as a comprehensive guide to achieving energy compliance; rather, it is a starting point for more detailed research.
Mandatory – Suggested – Exemplar
One of the most commonly referenced set of guidelines is the International Energy Conservation Code (IECC)®. The majority of the United States and the U.S. territories use the IECC in some portion in state-specific energy codes. However, what is mandatory by state varies widely, and might include amendments by individual municipalities within a state.
The IECC addresses new construction and additions, as well as remodels and repairs, including window replacement. The code provides requirements for both building envelopes and water heating and electrical equipment, among others. Furthermore, the IECC requirements differ depending on where the residence is constructed - the regions associated with the eight climate zones defined by the code. Along with the IECC, architects and developers should know about: the Energy Star International Residential Code (IRC), Title 24 in California, the Massachusetts Stretch Energy Code, and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard. Although this post doesn’t detail the specifics of these codes, it is important to know of their existence and requirements, if relevant.
One of the most stringent energy efficiency building standards available is the Passive House (or Passiv Haus) standard. Passive houses are built toward the goal of net-zero or nearly net-zero energy consumption. This highly energy-efficient construction is attained via “a very well-insulated, virtually air-tight building that is primarily heated by passive solar gain and by internal gains from people, electrical equipment, etc.” (from http://www.passivehouse.us/passiveHouse/PassiveHouseInfo.html.)
Measuring up
If there’s a single measurement index that you need to know about when designing energy efficient homes, it’s the HERS index. Developed by the Residential Energy Services Network (RESNET), the HERS index provides an industry-wide standard method for determining a home energy rating. The index yields a rating relative to the HERS Reference Home, which has a score of 100. Houses that are less efficient will have a score higher than 100, while those that are more efficient will score lower than the HERS Reference Home. On this scale, net-zero houses will achieve a HERS index of zero.
Most likely, you have heard of LEED (Leadership in Energy and Environmental Design) as a system of measurement. LEED is a quantitative rating system where a project earns credits for being environmentally sound, based on a six-part checklist of standards. There are hard limits wherein a project can receive certification depending on how many credits it earned. LEED is different from HERS in that HERS focuses on the energy efficiency of the final house, while LEED tries to assess the overall environmental impact of the house. LEED ratings are often awarded based on both the energy consumption of the residence as well as its overall impact on the environment, such as whether the construction material was purchased from a local dealer instead of a remote vendor who had to consume more energy to transport the material to the building site. LEED Energy & Atmosphere (EA) credits comprise one part of the six-part LEED rating checklist. LEED EA credits represent the energy efficiency of the final house and are calculated directly from the HERS Index, and can be in turn used for incentives or to demonstrate compliance. Both HERS and LEED are well-known, valid methods to describe the energy efficiency of a building.
Tools
Knowing where to begin is useful for any project. But even with the knowledge of which codes, requirements and measurements you must apply to any given design, the complexity of computing energy ratings and comparing those against mandates can be an arduous process. Put all of that together with many clients’ primary concern – budget – and you might find yourself overwhelmed.Fortunately, there are tools in the market that do the work for you, but few that are certified by RESNET for HERS ratings. REM/Rate is one of those examples; it is one of the most commonly used tools by energy raters in the New England area. REScheck™, a software tool developed by the U.S. Department of Energy to compute code compliance by state, is also an option for architects and developers looking to calculate energy ratings of their projects. However, the limitation with existing tools like RESCheck and REM/Rate is that they give only the code-compliance of a house based on the description that the user provides to the utility. Additionally, tools like RESCheck do not incorporate the projected cost of the energy consumption for a building.
New tools, such as Ekotrope’s HomeSEED™, allow the user define a specific goal for energy consumption of the residence. Then, based on the value of that measureable goal, HomeSEED derives specifications for the house envelope and other energy-related components of the house. HomeSEED provides decision-making support for achieving the best energy- and financial-related decisions when designing a house. HomeSEED not only incorporates HERS and LEED into its proposed designs; it also reflects the most recent energy consumption laws at both the federal and state levels.
A New Perspective
Although designing with energy conservation in mind can be an involved process, knowing where to begin is half the battle. Always review the location-specific energy codes before you begin and ensure that you are knowledgeable about any federal laws concerning energy requirements for building, including new construction as well as redesign and updates.
If you would like more information on Ekotrope’s HomeSEED product, contact us for a free demo, or visit our website at https://ekotrope.com.