Boulder County has adopted revisions to BuildSmart, its residential energy efficiency and green building code. The revisions will go into effect on April 1, 2010. Boulder County retained Populus Sustainable Design Consulting as its consultant to perform energy analysis in furtherance of the BuildSmart revisions.
Most notably, the revisions to BuildSmart now provide a prescriptive pathway alternative to the HERS rating performance pathway for homes up to 6,000 square feet. For any addition or new construction projects where the total conditioned floor area is 6,000 square feet or greater, the performance pathway (HERS rating) must be used. The prescriptive pathway applies to additions, remodels and new construction. While the prescriptive pathway is intended to provide an alternative to a HERS rating, the energy performance requirements are designed to be as stringent as the HERS pathway. The prescriptive pathway still requires that a HERS rater perform an insulation inspection and air infiltration / duct leakage testing as applicable. In order to proceed under the Prescriptive Path Option (Chapter 11 Energy Efficiency, Section N1105.2.5.4), your project must meet the following requirements:
- Maximum Glazing to Floor Area Ratio = 18%
- Maximum Air Leakage = 5 ACH at 50 Pascals for New Construction and 7 ACH at 50 Pascals for additions and remodels
- For Any New or Replaced Appliances = ENERGY STAR Labeled
- Lighting Fixtures = 80% CFL or equivalent
- Insulation Installation Standards = RESNET Grade I Standards
- Furnaces and Boilers (additions/remodels only need to meet if replaced) = 92% AFUE with ECM Blower Motors
- Water Heaters (additions/remodels only need to meet if replaced) = 82 EF
If your project does not meet these requirements, you must proceed under the Performance Path Option by having a HERS rating performed. Projects designed and constructed to comply with the Prescriptive Option must also meet the requirements of Tables N1102.1 and N1102.1.2 (below). For new construction/additions with conditioned floor area between 3,000 to 6,000 square feet, there are mandatory requirements for photovoltaics (see Tables 3 and 4 of the Chapter 11 Energy Efficiency code) and a requirement that the gross wall to floor area ratio not exceed 1.0. For any projects where the gross wall to floor area ratio is greater than 1.0, the Performance Path Option must be used.
| Table N1102.1 |
| Fenestration U-Factor |
Skylight U-Factor |
Ceiling R-Value |
Wood Frame Wall R-Value |
Mass Wall R-Value |
Floor f. R-Value |
Basement Wall R-Value |
Slab Edge R-Value and Depth |
Crawl Space Wall R-Value |
Underslab R-Value |
| 0.35 |
0.45 |
54 |
19 +10 (R-19 cavity + R-10 insulated sheathing) |
18/24 |
42 |
15/20 |
15, 3ft. |
15/20 |
10 |
Table Notes:
Mass Wall R-Value – the second number applies when more than half the insulation is on the interior
Basement Wall R-Value – the first R-value applies to continuous insulation, the second to framing cavity insulation; either insulation meets the requirement
Slab Edge R-Value and Depth – R-5 shall be added to the required slab edge R-values for heated slabs
Crawl Space Wall R-Value – the first R-value applies to continuous insulation, the second to framing cavity insulation; either insulation meets the requirement
| Table N1102.1.2 |
| Ceiling U-Factor |
Wood Frame Wall U-Factor |
Mass Wall U-Factor |
Floor U-Factor |
Basement Wall U-Factor |
Slab U-Factor and Depth |
|
|
|
|
| 0.35 |
0.45 |
54 |
19 +10 (R-19 cavity + R-10 insulated sheathing) |
18/24 |
42 |
15/20 |
15, 3ft. |
15/20 |
10 |
Table Notes:
Mass Wall U-Factor – When more than half the insulation is on the interior, the mass wall U-factor shall be the same as the frame wall U-Factor.
To see all of the Chapter 11 Energy Efficiency revised code requirements, download it here.
In addition to HERS rating and consulting services, Populus Sustainable Design Consulting offers consulting, insulation inspections and field testing for compliance with Boulder County’s prescriptive pathway. For a proposal, contact Laura at 303-325-7650 or learn more on the Populus website.
Populus is a full service sustainable design consulting firm that focuses on high performance, net-zero and near-net-zero custom residential and multi-family projects. Populus guides architects and builders through the requirements of mandatory green building codes and optional green home certification programs, providing HERS rating, LEED for Homes Green Rater services and municipal energy code consulting. In addition, Populus offers an Energy Code Workshop for architects and municipalities, as well as LEED for Homes training. Visit Populus at www.popboulder.com.
