Aspen’s 2021 Energy Code Adoption

Aspen’s adoption of the 2021 I-codes is heavily modified. This article looks only at the energy conservation parts of the adoption. And this is just a summary of the most perennate changes that may influence design.

Link here to the actual adoption documents… 

Four compliance paths:

  1. Prescriptive/Building UA/R-value alternative +23% including all additional mandatory requirements
  2. Performance +5%
  3. ERI +5% (2021 ERI 50.35)
  4. Existing building, Chapter 5

Notable modifications to mandatory residential energy requirements:

  • Prescriptive envelope requirements: R60 roof, R40 walls, R20 basement walls, windows max U-factor of .26 (inert gas with uncapped breather tube units don’t count)
  • Max 30% glazing to wall area (garage and sunroom glazing counts)
  • 1.5 ACH50 air leakage
  • ERV/HRV and flow testing required
  • Duct leakage testing was stricken for the Prescriptive path
  • Special provisions to avoid Thermal bridging
  • Commissioning
  • Sign Up for Building IQ benchmarking program (data gathering)
  • Sensible electric ready provisions
  • New triggers for energy efficiency requirements for alterations

Commercial Energy Changes:

  • Prescriptive, 2019 ASHRAE 90.1 or Performance
  • Envelope infiltration testing; Dwelling and sleeping units .30 CFM50 per square foot of envelope, everything else .40 CFM75 per square foot of envelope.
  • ventilation flow testing
  • Enhanced envelope, especially walls
  • EV requirements
  • Electric ready provisions
  • New triggers for energy efficiency requirements for alterations

Expanded REMP:

  • Heat tape, gas fireplaces, outdoor heaters will now need to be offset
  • Gas fireplaces will be required to be sealed combustion
  • 200,000,000 BTU/year cap for all exterior energy
    • Snowmelt 2414 ft2 OR,
    • Pool 603 ft2 OR,
    • Spa 466 ft2 OR,
    • Heat tape 3125 linear feet of typical heat tape

Incentivize All-Electric New Construction:

  • Expedited Permit Review
  • AC units must be heat pumps

A practical example:

What if a project needs to break with the Prescriptive path? For instance, how can a house go about complying with more than 30% glazing? The project would be forced to try and comply by using either the Performance Path or the ERI (Energy Rating Index) Path.

Minimum Performance goal would be…   2021 Building UA +23% & 72% of Energy costs

Minimum ERI goal would be…                   2021 Building UA +15 % & ERI 50.35 – PV

Both of these goals would have to be achieved without help from PV solar.


We do that…

Please give us a call and we can help navigate the process in the most cost-effective way. And optimize your construction for performance.

Jump to Energy Conservation Code Hub for; the western slope of Colorado; Aspen, Telluride, Mountain Village, Town of Snowmass Village, Basalt, Carbondale, Glenwood Springs, Pitkin and Eagle County…