Yes, vinyl windows are considered highly energy efficient under the new Colorado building codes, provided they meet specific performance criteria.

According to the provided information, the energy efficiency of these windows depends on the following factors:

• Regulatory Standards: Denver has adopted the 2021 International Energy Conservation Code (IECC). This code sets strict thermal performance standards for all replacement windows to ensure they provide year-round efficiency in Colorado’s variable climate.
• Performance Ratings: To be compliant and efficient, new vinyl windows must meet specific maximum U-factor and Solar Heat Gain Coefficient (SHGC) ratings.
• Energy Star Certification: In most cases, Energy Star certified vinyl windows already satisfy Denver’s energy code provisions, making them a reliable choice for meeting state standards.
• Local Variations: Different municipalities have specific requirements. For example, Lakewood follows an updated 2025 energy code, and Aurora requires a permit that specifically includes energy compliance verification.

Using high-performance vinyl windows is described as a smart investment for Denver homeowners to reduce drafts and lower energy bills while staying compliant with evolving local codes.