January 7, 2013
Future-Proofing Your Home Designs
Before you figure out where you might be going with the homes you build and sell in the future, you need to assess where you are right now relative to either current code requirements or some other level of performance (such as a green building standard). Many builders looking to revamp or refine their design offerings hire consulting companies like Home Innovation Research Labs as a one-stop resource to conduct these types of assessments. If you’re interested in gauging your own level of preparedness for the future, the information below should get you started.
Start with a Full Design Assessment and Simulations
The most logical first step in this kind of assessment is to catalog all of the energy features of the home for use in an energy simulation software program. The design assessment not only provides a comprehensive level of detail in understanding all of the house features together, but it also provides the necessary information to simulate the whole-house energy performance and how this performance fares relative to current code requirements. This will provide you with a base of the efficiency of your current designs; help you determine what might be feasible in terms of the new performance level you want to achieve; and guide you through the process of making various trade-offs with different features of your homes.
The biggest benefit of running a whole-house simulation program is the ability to adjust variables like product R-values (or system-values), installation quality, equipment efficiencies, and design placement of details such as windows or ducts, to achieve the maximum level of synergy amongst all of the home’s products and systems to provide the most value to your business and your customers. For instance, without the benefit of a simulation, you may estimate that upgrading your HVAC system will garner the most savings. However, evaluating an increase in insulation levels and improved windows might achieve similar energy savings and also result in a less costly HVAC system. And, this evaluation might benefit your preparedness for future energy code changes as well.
The simulations can also provide a way to understand how different energy features work together, such as higher insulation levels and lower infiltration, to decide where to make initial and ongoing investments in your house design improvements. The simulation results can help show you which upgrades, alone or in combination with other changes, might provide the most savings for your investment in terms of hard costs, labor, and what you believe you can market to homebuyers.
REMRate and EnergyGauge are two of the most commonly used programs used for whole-house energy simulations, but there are certainly other appropriate options available. If you are unfamiliar with energy simulation programs and would like to know a little more about each to help guide your decision, the Department of Energy (DOE) has a comprehensive Building Energy Software Tools Directory that includes Energy Simulation, among many other topics, on its website. This directory provides information on hundreds of tools for both commercial and residential applications, so it’s not necessarily where you want to start your selection process, as it can be a little overwhelming, but it might help you draw comparisons between a few options once you narrow the field. A short description is provided for each tool along with other information, including expertise required, users, audience, input, output, computer platforms, programming language, strengths, weaknesses, technical contact, and availability.
Proper Installation is Key
While simulations are very helpful, they are also somewhat idealized, not taking into account all the things that can (and do) happen on a construction site. Specifically, simulations assume the perfect installation of products and systems to achieve performance minimums. If you’re going to invest time and effort into developing a more advanced and/or more efficient version of your current or new home plans, don’t neglect details of the installation.
More than with typical home construction, high-performance homes have very little tolerance for deviation from the construction plans, and any significant deviation can have a negative “domino effect” on the efficiency of the rest of the structure. Make sure your crews understand all the nuances of proper installation, particularly when it comes to the building envelope and air sealing and/or any new framing details that you chose to implement. If you don’t already have detailed scopes of work for each of your trade crews, this would be the perfect time to develop and implement them. Working under DOE’s Building America initiative, Home Innovation Research Labs is continuing to develop and add to a growing online information resource on building high quality, high performance homes that can help guide you in developing scopes of work and other related tools to help prepare you for future changes at www.toolbase.org.
Verifying Performance
Conducting various types of performance testing/verification gives you the next piece of the puzzle in determining your efficiency starting point and goals. Performance testing on your current models can provide your own baseline of how well the building envelope and duct system limits air leakage. These test results can be used in the simulation software to provide a more accurate assessment of your current home design and construction. Once you’ve determined with your simulations what level of efficiency you’re trying to attain, but prior to construction of any new models, these tests are a barometer of how close (or how far away) you are to achieving your goal and where you most need to focus your attention. After you start building your new, more efficient designs, it’s a good idea to repeat the same tests to validate the details entered into the simulation program and the decisions you made as a result of that analysis.
Blower door and duct tightness tests are the most common performance verification tests because they are able to show measurable results of the cumulative effect of your efforts toward making a home more efficient. See the April article on performance testing requirement changes in the 2009 IECC for more information on these types of tests, or consult some of the following sites:
Duct Tightness Resources:
Building Tightness Resources:
Cost-Benefit Analysis
When all is said and done, product choices, simulations, and other planning tools can only be guideposts for the decisions you make with your home designs. Ultimately, you need to evaluate what enhancements you are willing and able to make, and at what cost, so that you achieve the right balance of market appeal and profitability for your business. However, the process can be repeated regularly to keep abreast of (or even ahead of) changing code and market demands. Investment in new products, establishing new trade contractor scopes of work, and even investing in new house layouts to both increase efficiency and limit cost increases need to be ongoing and dynamic processes to stay a couple steps ahead of changes in the building industry and the market.
The tools and techniques described here can help you take a more analytical view of your company’s construction plans and operations. They provide you the baseline information so you can determine the most efficient, cost-effective, and marketable trade-offs you can make without sacrificing the level of quality and performance you want to maintain in your homes. For more in-depth assistance, contact Home Innovation Labs at 800.638.8556.
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