Burlington set out in 2021 to help tenants and fight global warming by requiring landlords to seal leaky windows and insulate drafty attics — a practice known as weatherization. But more than three years later, only a handful of rental properties have been updated. Officials are blaming the statewide shortage of qualified workers for the delays. Both the city and state plan to offer training programs that would bolster the "green" workforce, but in the meantime, the city won't meet its self-imposed timeline to weatherize hundreds of homes. Enforcement of one of Burlington's marquee policies is effectively on hold until councilors figure out new deadlines. "If [landlords] made best efforts and they couldn't get the work done, it wouldn't be right of us to fine them for that," Councilor Mark Barlow (I-North District) said. Councilors passed the ordinance following a 2019 housing summit that aimed to make the city's rentals more affordable for tenants. The rules apply to buildings that use 50,000 or more British thermal units, or BTUs, per square foot to heat the space each year. An insulated 2,000-square-foot home in northwestern Vermont heated with natural gas, for instance, typically uses 40,000 BTUs each year, assuming an indoor temperature around 70 degrees in winter, according to Tim Perrin, director of energy management at VGS. The city works with utilities such as VGS, which provides natural gas used to heat the majority of Burlington rentals, to determine a building's usage. If a property is out of compliance, landlords could take steps such as insulating crawl spaces or installing new windows to make the building more efficient. The ordinance says landlords only need to pay as much as $2,500 toward these projects, though they would have to spend more if their first effort doesn't bring the property into compliance. At a council meeting in 2021, then-mayor Miro Weinberger said the ordinance would lower fossil fuel use, edging the city closer to its goal of achieving net-zero carbon emissions by 2030. Calling the rules enforceable, Weinberger said the effort would "support job creation and retention for weatherization contractors and help the broader Vermont clean energy economy." That vision hasn't come to pass. The city estimates that about 730 of the city's 3,070 rental properties need to be weatherized. More than half that number should have been weatherized by now but are instead on a waiting list, either for an…