Thermal Performance

Posted on January 09, 2014
Posted By: Rick Barnett
 

Thermal standards for homes were established to improve thermal performance by strengthening the barrier between outside and the conditioned interior.  A checklist of thermal standards is included in every jurisdiction's energy code.  For example, wall insulation in Oregon has to be rated at least R-21.  A building inspector verifies compliance for each component of the thermal shell:  foundation, underfloor, walls, roof, skylights, doors and windows.

Residential code is changed through a rigorous process involving national and regional agencies and committees.  Standards are raised only after a rated building product is broadly reviewed and commercially available.

Recognized policy proposals for efficiency include elevated code standards as a tool for reducing energy consumption.  For example, in 2012, the American Council for an Energy Efficient Economy ( www.aceee.org) and MIT (www.mit.edu/energy-efficiency ) released "The Role of Local Governments and Community Organizations" about efficiency trends.  The report includes a section about the "New York City Green Codes Task Force" (2008), which involved over 200 people and generated 111 code change recommendations.  The report states that "each of the 111 proposals includes sample statutory language, an explanation of the background issues and rationale, analysis of costs and savings, precedents from other jurisdictions, comparison to LEED credits, and implementation information."    After a year, while several recommendations were still in the approval process, only 4 had been enacted by a New York City agency.  This example of using the code as a driver for more efficiency points to the bulkiness of the code development process.

Other reports about "driving more efficiency" look at financing and/or marketing, without mentioning the building inspector. As an example, "Unlocking the Value of an Energy Efficient Home" was released in August, 2013 by "The National Home Performance Council" ( www.nhpci.org ) and CNT Energy ( www.cntenergy.org ).  While providing analysis about elevating the role of the real estate industry in promoting more efficient homes, the report does not mention the added dimension and expense of meeting code standards.

While many would agree that the slowly evolving energy code is addressing its original purpose of improving residential energy performance, this goal is rarely verified with post-construction measurement. At the same time, several scoring systems to measure performance have been developed. Performance scoring generally functions as a pre-construction marketing tool for efficiency upgrades.

Thermal shell improvement is the only type of efficiency upgrade that lends itself to post-construction measurement.  This is particularly important because thermal retrofits reduce energy for conditioning interior space, the largest use of household energy.  Savings to a consumer from upgrades to lighting, HVAC, thermostats, appliances, sensors and other equipment are difficult to measure.

Nothing in the code prevents using a performance score to determine compliance with thermal shell requirements. Rather than a checklist of separately inspected features, a performance score would indicate compliance with a single number.  This would allow flexibility in the choice of shell components. Using the 2008 version of Energy Trust of Oregon's "Energy Performance Score" (EPS, www.energytrust.org), a code home would have an "energy score" of 85, and an Energy Star home would score 75.  With EPS, a lower number indicates better thermal performance, and the best score, 0, is for a "net zero" house.

EPS also produces a "carbon score", which quantifies eliminated carbon emissions from improved performance.  Again using the 2008 version of EPS, a code home would have a carbon score of 175 (17,500 pounds of carbon emissions) and the Energy Star home would score 150.  Again, lower is better.

The carbon score creates a connection to carbon emissions and utilities. When aggregated, the results from scored retrofits could benefit utilities because they eliminate emissions rather than functioning as a more speculative offset.

In a previous post (http://www.energycentral.com/enduse/energyefficiency/articles/2734/Thermal-Optimization) I described "Thermal Optimization" as an efficiency option that employs performance scoring.  .  While measured performance improvement offers emission-related value to utilities, their broader use of performance scoring could separately foster simplification of the energy code.  Thermal Optimization programs by utilities would provide the code development process with a commercial scale demonstration of performance testing.   This could be all that's needed for the adoption of scoring, and less code.

 
 
Authored By:
Rick Barnett has a B.A. in psychology (UCSB) and an Interdisciplinary Master’s in Environmental Management (Oregon State University, 1981).  Before becoming a builder, Rick introduced the Oregon waste management industry to recycling in 1976, and over the next few years convinced many to offer recycling as a service.  Oregon has been a national leader in recycling ever since.Rick started Green Builder in 1996, and was recognized in 1998 by Sustainable
 

Other Posts by: Rick Barnett

Efficiency Gap - March 07, 2016
Energy Asset - January 21, 2016
After Weatherization - September 25, 2015
Energy Customers - April 08, 2015
 
 

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