Energy efficiency is a by-product of deliberately building quality homes – homes that are safe, healthy, durable, comfortable, and efficient. Building homes to reach high levels of energy efficiency, Energy Star® or above, involves changes in a builder’s practices. But the benefits to making these changes can dramatically increase the quality and performance of the homes, which in turn, will reduce callbacks, customer complaints, and liability. No matter the quality and performance of a builder’s current product, some changes in material, installation, and quality assurance will be necessary to achieve new levels of performance. This doesn’t mean that increasing energy efficiency needs to lead to headaches or increased cost. It does mean that the builder has to embark on a deliberate process of planning, design, and testing to understand the necessary changes, communicate these changes to the trades, and ensure that the changes are being appropriately implemented.
First, it must be noted that achieving Energy Star® performance levels isn’t rocket science. It can be as simple as increasing insulation and/or sealing ductwork, and selecting higher performance windows and mechanical equipment (see Energy Star’s website for builder option packages). But it’s widely accepted in the industry that by taking the simple route, a builder bypasses many of the benefits that can be gained by taking a more holistic approach to increasing energy performance and quality. For little extra effort and a basic understanding of building science, builders interested in increasing the energy performance of their home can also increase building durability and quality, and decrease risks to occupant health and safety.
This article will explore the changes necessary to achieve higher levels of energy performance and quality by highlighting key issues and focus areas, and will illustrate the process of changing a home from standard energy performance to energy performance levels that meet the Department of Energy’s Building America Program standards. These performance levels equate to 40% above Model Energy Code 1993, or a HERS (Home Energy Rating System) score of 88. The HERS score is a rating tool that quantifies the energy efficiency of homes.
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A jump duct allows for balanced pressure between rooms and improved comfort conditions.
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Things to Consider
So, what are some of the key areas of process and technology that must be addressed to increase the energy performance and quality of homes past Energy Star® requirements?
Appropriately Size the HVAC Equipment
Standard practice with HVAC contractors is often to size equipment based on “rule of thumb”, and many of these decisions are based upon antiquated home characteristics. Over the last 20 years, a variety of factors including increased airtightness, better windows, and more effective air distribution have dramatically changed (and improved) the performance of homes. Unfortunately many contractors are still following a 20-year-old rule instead of performing an engineered analysis according to ACCA Manual J and D. Additionally, even when providing an adequate analysis, contractors may make design assumptions that are overly conservative in terms of window performance because they are unsure of the true window characteristics. Bottom line, make sure the HVAC contractor is aware of the true characteristics of the home, and is appropriately sizing the system.
Insulate the Basement
Particularly in northern climates, it’s important to consider employing appropriate basement insulation strategies. In addition to increasing energy performance, properly applied basement insulation systems can reduce occurrences of mold, and create a more comfortable and habitable space. This provides more livable square footage and a great opportunity to increase sale price.
Unvent the Crawlspace
Vented crawlspaces can create a greater heating or cooling load in homes, thus creating inefficiencies. In addition, IBACOS’ research has shown that vented crawlspaces are susceptible to very high humidity levels that can lead to moisture problems and mold growth. So, in homes with crawlspaces, it’s a good idea to modify practices so that the crawlspace is unvented and conditioned. This creates a much more stable environment, similar to that of a basement.
Tighten the Envelope
Building envelope airtightness is important not only to reduce energy consumption, but also to alleviate customer comfort complaints due to drafts or uneven temperatures. Particularly, issues arise in overhang areas such as fireplaces, bay windows, and rooms beside unconditioned spaces (like attics and bonus rooms). Common practices to address these issues include draft stopping using sheathing materials, and utilizing caulk and foam sealants for smaller penetrations. Additionally, in homes with an attached garage, it’s extremely important to isolate the garage by using appropriate airtightness techniques. In this case, airtightness increases energy performance, but just as important, it also assists in keeping pollutants from the garage from infiltrating the house.
These topics represent a few of the key areas that must be addressed to achieve levels of energy performance above Energy Star®, but it’s certainly not an exhaustive list. Improving the airtightness of the building envelope by using low-emissivity windows and addressing water management (flashing, drainage plane, etc.) as well as mechanical ventilation and advanced framing strategies are also key to increasing the quality and performance of homes. For more information on these advanced techniques, visit www.housingzone.com.
Beyond Design/Specification: Teaching New Tricks
Because of increased performance expectations, new materials and strategies may be necessary. These new expectations sometimes require trades to learn new tricks, and you’ve got to account for this in planning. In the initial stages, notes Chris Payne, Purchasing Manager for Washington Homes, it‘s necessary to increase communication with trades, particularly the HVAC contractor because of changes to the duct design and equipment size. “The contractor had questions because of the redesign, but was very receptive,” says Payne. “It benefits him because we went from two HVAC units to one, so less material and time were involved.”
Even when the changes aren’t technically challenging for the trade, a certain amount of handholding is necessary to ease them into new practices. After all, most people are resistant to change even when it’s for the better. For example, many HVAC contractors are initially resistant to downsizing mechanical equipment, or to using zoned systems with fewer units as a replacement for no zoning and more units. Andrew Nevitt with Medallion Homes in San Antonio, Texas, experienced exactly this resistance when Medallion first began building their homes to reach Energy Star® levels of performance. “Because of the recommended changes in our practices to increase performance, we were able to downsize our equipment by a half ton. This worried our contractors, as they were concerned that they’d experience increased callbacks because of comfort issues.” This hasn’t been the case. Medallion Homes is currently building all of their homes to reach Energy Star® levels of performance, and is taking extra steps to learn practices that will push the performance of their homes even further.
This article, written by IBACOS' Stacy Hunt, originally appeared in Professional Builder Magazine and is reprinted with permission.
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