New rules imposed by Denver and Colorado that require large buildings to reduce pollution will be too expensive and are at odds with federal regulations, groups representing owners and developers of office towers, hotels and apartment complexes allege in a lawsuit filed this week. The Colorado Apartment Association, the Apartment Association of Metro Denver, the Colorado Hotel and Lodging Association and NAIOP — an association representing commercial real estate developers — said the green-energy rules preempt a federal regulation that governs the quality and performance of new heating and cooling systems and other appliances in large apartment complexes, hotels and commercial office and retail buildings. The groups, in their lawsuit filed Monday in U.S.