With a goal of reducing energy use while increasing efficiency and cutting carbon emissions, the U.S. Department of Energy (DOE) in June proposed the first new energy efficiency standards update for manufactured homes in more than 20 years. The changes would cumulatively cut energy use by an estimated 30 percent over a 30 year period compared to the current standard and include a focus on the thermal envelope/insulation as the foundation of energy efficiency.
Getting Energy Smart
DOE’s proposed standards are based on the recommendations of its Manufactured Housing Working Group, which began its work by examining the 2015 International Energy Conservation Code (IECC), the current code for site-built homes. The group recommended modifications to make the proposed standards suitable for manufactured housing, among them, a consolidation of climate zones from eight to four.
In an acknowledgement of the importance of the thermal envelope in reducing energy usage, the proposals also include two approaches to address this key element:
- The prescriptive approach would require meeting criteria, including a specific R-value for wall, floor and ceiling insulation as well as a specific solar heat gain coefficient for windows
- The performance approach would set a maximum building shell heat transfer requirement or U-factor
The prescriptive model is easy to understand and implement, while the performance-based requirement allows manufacturers more flexibility. The working group did not include provisions to allow manufacturers to use the Energy Rating Index, specified in the 2015 IECC as this approach won’t be used for manufactured homes.
Updated insulation requirements will be based on the 2015 IECC, but adjusted to reflect the design and transportation needs of manufactured housing. The proposed standard would also replace the requirement for the maximum building thermal envelope air leakage (which is difficult to test in homes that are shipped in parts), with sealing requirements that can be visually inspected. Further, it includes many of the 2015 IECC sections without revision, such as requirements for programmable thermostats, certain hot water systems, and heating and cooling equipment standards.
Looking Beyond the Purchase Price
Manufactured housing accounts for just 6 percent of all homes in the United States. The average purchase price of manufactured single-family home is $68,000 compared with the average cost of a site built home of $276,284 (both figures are for the structure alone and don’t include land costs). Sales of these homes increased nearly 10 percent from 2014 to 2015, from 64,344 in 2014 to 70,519 in 2015.
These homes serve as affordable housing options, particularly for low-income families. However, the operational costs to the homeowner isn’t reflected in the purchase price, thus cost of ownership is a consideration. Typically, manufactured housing owners have higher utility bills than comparably sized site-built homes in part due to different criteria for energy conservation and variability among building codes and industry practices. DOE’s proposed news standards are aimed at addressing energy efficiency, which of course, impacts home energy use and the cost of ownership to buyers.
The share of household income spent for energy falls disproportionately on lower- and middle-income families earning less than $50,000 per year before taxes. The 59 million U.S. households earning less than $50,000 before taxes spend an estimated 17 percent of their after-tax income on energy, compared to just 7 percent for those households earning higher than $50,000 annually. The average homeowner spends approximately $2,200 annually on home energy bills (for a traditional home). DOE estimates the move will save manufactured home owners $345 annually in 2015 dollars.
Energy efficiency should include homes at lower price points. Further, understanding the burden of energy costs on the homeowners can help builders sell the value of energy efficient homes. Reduced energy bills from homes built to 2012 or 2015 IECC add tens of thousands of dollars to homeowners’ wallets after recouping the added cost of energy efficiency improvements in one to two years.
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