A group of national and Colorado organizations is suing to overturn Denver building codes intended to address the effects of climate change by limiting the use of natural gas in buildings. The lawsuit filed Wednesday in U.S. District Court in Denver takes aim at a city ordinance that prohibits natural gas furnaces and water heaters in new commercial and multifamily buildings. Also targeted is an ordinance that takes effect in 2025 and requires installation of electric systems when gas furnaces and water heaters are replaced in existing buildings and when if it is cost-effective. Other communities in Colorado and in other states have enacted similar bans as they push to electrify buildings to reduce the effects of climate change and improve air quality.