Katherine Martinko is an expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto.

All the magazines and websites love prefab and manufactured housing. Even we here at Treehugger fill our pages with Dvele and Plant Prefab. But the number of these built is a rounding error compared to the manufactured housing industry, previously known as the mobile home industry, and even prior to that, the trailer industry.

According to the American Council for an Energy-Efficient Economy (ACEEE), 6.8 million manufactured homes are used as residences in the U.S., and 105,772 of them were shipped in 2021. Unlike conventional site-built housing or modular housing, these are built to the Manufactured Home Construction and Safety Standards (HUD Code), a national standard.

But when it comes to energy, it's not much of a standard at all and hasn't been updated since 1994. Now, after years of work and arguing, the U.S. Department of Energy announced new standards they say will save consumers "hundreds of dollars on their annual utility bills and slash carbon emissions by 80 million metric tons."

“DOE’s new energy efficiency rules will help save the 17 million Americans residing in mobile homes up to $475 per year on average on their utility bills,” said U.S. Secretary of Energy Jennifer M. Granholm in a statement. “The rules will hold manufacturers of these U.S. homes to cost-saving efficiency standards, giving residents more comfortable living environments and a much-needed break on their annual utility costs, while delivering cleaner air for their communities.”    

U.S. Department of Energy

However, it is not a very strong standard—the worst kind of compromise. It is still not as high a standard as site-built homes. And it has two tiers, with lower standards for "single-wides"—the least expensive kind of housing—that are little better than the 1994 rules. The DOE claims this was done "to balance the important objectives of energy efficiency, cost savings, upfront affordability, and housing supply challenges."

U.S. Department of Energy

But imagine you are in your tier 1 single-wide in North Dakota with the wind blowing under your home. R-22 insulation underfoot is ridiculously low for a floor and means you will be wearing boots inside. There are air barriers but no requirements for continuous insulation, and the words "thermal bridge" come up once in passing. Pack a family into this with cooking and showers and you are likely going to have condensation and mold in a brand new home.

The ACEEE doesn't get into issues of comfort and humidity, but doesn't think much of the standard either.

“Residents of poorly insulated manufactured homes have paid high energy bills for far too long. This rule gives manufacturers the green light to keep building models with the same problems,” said Steven Nadel, executive director of the ACEEE. “It’s going to leave many of the lowest-income households paying painfully high utility bills for even more years to come. Going forward the administration certainly shouldn’t make a habit of letting manufacturers make more-wasteful homes and products for lower-income people.”

It seems like half of the 362-page Energy Conservation Standards for Manufactured Housing is composed of cost-benefit analyses from the industry suggesting that the proposed changes will increase the cost of housing so much that people will be priced out of the market, and that the purchaser will never recapture the additional costs through the energy savings over the life of the unit.

“Manufactured housing is by far the most affordable home-ownership option in America—and the industry is currently building quality affordable homes that are already energy efficient and resilient,” said Lesli Gooch, CEO of the Manufactured Housing Institute, an Arlington, Va.-based trade association, to Bloomberg Law. “Instead, the significant cost increases to actual manufactured home-buyers far exceed the speculative energy savings the rule claims will take place.”

The industry also complains that increasing the insulation standards might mean changing construction processes and materials, such as switching to spray foam insulation. According to Bloomberg Law:

One of the problems mentioned in the DOE document is that adding more insulation means thicker walls and ceilings, in a building type where exterior dimensions are limited by road transport regulations, so any increased thickness comes out of interior space. Since Elmer Frey of Marshfield Homes invented the "mobile home" in the late '50s, it has always been a fight for inches, going from 10-wides to 12-wides. As Clayton Homes noted in its complaint about the new standards, adding a few inches of height can have big implications.

Switching to foam with its higher insulation value per inch could solve this, but raises all kinds of new hazards in the enclosed factories. When I was in the modular business and wanted to use foam—we thought it was green back then—I was told it would have to be done outside because of the fumes and the fire hazard.

U.S. Department of Energy

According to the standard, the increase for tier 1 is 1.2%, while the fancier multi-unit tier 2 is 3.9%.

U.S. Department of Energy

The DOE also estimated the cost savings and the payback period, but all of these calculations were done in 2021 and the heating and cooling costs might well be doubled under current prices. The ACEEE claims that "energy costs are about 70% more per square foot in these homes compared to site-built homes, and a quarter of their residents spend more than 10% of their income on energy costs." Imagine that doubling; we are looking at energy poverty in a brand-new single-wide.

U.S. Department of Energy

And don't let's forget that there is also a climate crisis happening. The proposed code changes make a big difference in the emissions of greenhouse gases and other pollutants, but they are mostly coming from the tier 2 multi-section units. They could be so much better.

U.S. Department of Energy

And it didn't have to be this way; it apparently wasn't even the original intent. ACEEE senior communications manager Ben Somberg tells Treehugger via e-mail:

Very different, indeed. Somberg notes this change might have had something to do with HUD, which apparently "expressed concerns about the adverse impacts on manufactured housing affordability" if they followed the original un-tiered approach.

In his 1997 book "Wheel Estate," Allan D. Wallis wrote:

This has not changed in 35 years. High-quality manufactured housing in well-managed developments could be a big part of the answer to the housing affordability crisis, but they can't be junk.

The U.S. government gives a $7,500 subsidy for each sale of an electric car. If people are so worried about the affordability of these tier 1 manufactured homes, why not give a $7,500 subsidy to the purchasers of a greener, well-insulated all-electric home by people who need it a lot more than someone buying a Tesla, instead of developing such a crappy standard?

"Biden Standard for Manufactured Homes Will Leave Low-Income Households with High Energy Bills." ACEEE. 18 May 2022.

"DOE Updates Mobile Home Efficiency Standards to Lower Household Energy Bills." Energy.gov. 18 May 2022.

Moore, Daniel. "Climate-Minded Housing Energy Efficiency Rule Finalized (1)." Bloomberg Law. 18 May 2022.

Clayton Homes. Comment Letter re DOE Rule. 23 Nov. 2021.

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