COLUMBIA — A recent amendment to the the city building code that requires extra insulation on homes built with slab foundations threatens to drive up construction costs and invite termite infestations, the Building Construction Code Commission has warned.

The Columbia City Council nevertheless approved the amendment at its June 6 meeting, setting aside the code commission's concerns and instead going with the recommendation of the Environment and Energy Commission, which believes the insulation requirement will make slab-foundation homes more energy efficient. The change came as part of an overall update intended to bring city building codes into compliance with the 2015 International Building Code.

Doug Muzzy, a member of the Building Construction Codes Commission and owner of Muzzy Builders, said it's important that homeowners get an adequate return on any investment they make in energy efficiencies. The codes commission didn't believe slab insulation would meet that goal, especially when the threat of termites is considered.

Installing insulation on slab foundations is unpopular among builders, Muzzy said, because it requires a change in construction method. Without insulation, builders use trench footings to support slab floors. If insulation is required, builders have to take the more expensive route of creating footings and walls for support.

Environment and Energy Commission member Dick Parker, however, argued the change in construction is unnecessary. "It's neater, and it's a better system, no doubt," he said. "But it's not needed to deal with the problem."

Termite concerns

The codes commission felt the change would make slab-foundation homes vulnerable to termites.

"Typically, the best way to be able to ensure you don't have termites is by seeing their trails go up into the wood of the house," Muzzy said. "There's been consistent interpretation that covering that visible area with insulation has risks associated with it."

The Environment and Energy Commission, though, said in its recommendation to the City Council that slab insulation increases a property's energy efficiency by 15 percent. The amount of savings that would produce depends on the size of the home.

The cost for treating termites also depends on the size of the property and the type of treatment, Larry Woods, vice president of pest control at Atkins, Inc., said. But it can range anywhere from $500 to $2,000.

Parker said he felt the code commission's warnings about termites were simply an excuse to avoid the insulation requirement. The Environment and Energy Commission also recommended the City Council change the code's probability of termite infestation from "very heavy" to "moderate to heavy." Failing to do so, it said in a memo to the council, "gives credibility to the idea that foundations should be uninsulated to allow for easy viewing by termite inspectors."

A termite infestation probability map included in the code places Missouri in the "moderate to heavy" area. The "very heavy" area includes states along the Gulf Coast and the coast of California.

Muzzy said a "heavy" rating "applies a conservative approach where termite damage is a real concern."

"Ultimately, the point was — whether it's a moderate termite risk or heavy — it was still considered to be too much risk to require foam insulation around the visible part of the concrete of the house," he said.

Preventing the pests

The new code also requires termite barriers that the Environment and Energy Commission believes would counter the threat that comes with slab insulation. Parker, in an email to the City Council, recommended it adopt a portion of the International Building Code that suggests builders place a metal plate between concrete foundations and the wooden bases of structures to keep termites from reaching the wood.

"This prevents termite damage since the termite tunnels are unable to make the turn over the thin edge of the tin which extends beyond the insulation," he wrote. "Termites can build tunnels between the foundation and insulation where they cannot be seen, but they are unable to reach the wooden portions of the house."

During a meeting between the two commissions, members of the building codes group argued that metal plates aren't a good idea. If they're poorly maintained, they can get bent and allow termites easy access to the wood.

Woods, who has specialized in termite treatment and prevention since 1973, said the same.

"In my career, I've treated at least 500 to 1,000 homes that had that metal sheet," he said. "I've never seen a metal sheet work on a slab house."

Woods said the main problem is that metal plates often are installed incorrectly on slab homes, allowing termites to get through. Even when they're installed correctly, they fail quickly, he said.

"You can come up with a lot of different ways to treat or protect a home from termites, but it all fails in time," Woods said, adding that when the shield fails, it's important to know before the termites do too much damage. That can be difficult when a metal shield obstructs one's view of the insulation.

"Termites are going to get into most every home in central Missouri," he said. "The main thing is detecting them before they get too far."

Given that the Building Construction Codes Commission lost the debate, Muzzy said there isn't much builders can do.

"We just have to meet what the code requires and what the City Council approved," he said. "I don't think there would be any additional steps taken, except to do the insulation as it's shown in the code."

Still, Muzzy worries the cost of the insulation might deter some potential homebuyers.

"We just hope the market can absorb it."

Supervising editor is Scott Swafford.

  • Reporter for Summer 2016. Undergraduate | Magazine Editing. Reach me at pashz7@mail.missouri.edu Twitter: @pstableford2150

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