BE R1: Envelope Design

(Requirement)

PURPOSE

Reduce heat loss or gain through building thermal envelope components. Minimize energy loss and increase durability by providing better moisture control with a closed crawlspace. Avoid using an energy source for attic ventilation to prevent creation of an undesirable pressure profile.

CRITERIA

Fulfill the following criteria (as applicable): 

• Fulfill minimum envelope requirements in BE R1.1 Minimum Prescriptive R-Values for Building Envelope through prescriptive or trade off method via COMcheck 
• No vented crawlspace and no power attic ventilation

The project must meet or exceed portions of ASHRAE Standard 90.1-2013 Section 5 Building Envelope. Compliance with insulation and fenestration requirements may be verified using either the “Prescriptive Building Envelope Option” or the “Building Envelope Trade-Off Option”. All mandatory provisions apply. Architectural Drawings must indicate insulation and fenestration values for each building envelope component. In addition, COMcheck shall be completed (refer to Appendix A: COMcheck Overview and Appendix B: COMcheck Envelope).

Vestibules or revolving doors are required in climate zone 3 if the building is ≥ 10,000 square feet and 4 stories or more above grade; they are required in climate zone 4 if the building is > 1,000 square feet. Vestibules or revolving doors are not required in climate zones 1 and 2. Refer to ASHRAE Standard 90.1-2013, Section 5.4.3.4.

Demonstrate compliance with COMcheck through one of the following options:

A. Prescriptive Option:

Insulation and fenestration properties shall meet requirements in ASHRAE Standard 90.1-2013 Tables 5.5-1 through 5.5-8, and summarized in Table 1. A project may select the prescriptive option if the design meets the following conditions: 

• Vertical glazing does not exceed 40% of the gross wall area 
• Skylight glazing does not exceed 3% of the gross roof area

To demonstrate compliance through COMcheck, meet or exceed R-Value, U-Factor and Solar Heat Gain Coefficient (SHGC) requirements for each applicable thermal envelope component.

B. COMcheck Trade-Off Option (Refer to ASHRAE Standard 90.1-2013, Section 5.6)

For projects that do not qualify for the Prescriptive path, or prefer to redistribute insulation values for various envelope components to better serve the building design, the Trade-Off option may be used. An energy simulation per Chapter 11 of ASHRAE Standard 90.1-2013 may be used as an alternative to the prescribed criteria for meeting this requirement if approved by the ECLC Technical Advisor.

MAJOR RENOVATIONS: Alterations to the building envelope should follow ASHRAE 90.1-2013, Section 5.1.3.

Closed Crawlspace- If a crawlspace foundation is constructed, provide a closed crawlspace for the project. Carefully consider moisture management, combustion safety and termite control issues in the design of the crawlspace. A closed crawlspace located within the 100-year flood plain must have smart vents that are normally closed.

Include the following details in the design and construction of the closed crawlspace: 

• No venting allowed - all penetrations in crawlspace walls and floor to conditioned space above must be sealed 
• Wall connections are sealed with caulk, foam sealant and/or gasket: 
  • Foundation stem wall and the sill plate 
  • Sill plate and band joist
  • Band joist and subfloor 
• Termite shield or sill seal between foundation stem wall and the bottom plate (i.e. sill plate) 
• A minimum Class I, 6-mil (0.15 mm) polyethylene vapor retarder must be installed and secured to cover all exposed earth and extended at least six inches up foundation wall or above exterior ground grade level - overlap joints at least six inches and apply sealant 
• Non-residential buildings with crawlspace walls must be continuously insulated to the following minimum levels (insulation may be located on the interior or exterior surface of the crawlspace walls): 
  • Climate Zone 2: R-5.7 
  • Climate Zone 3: R-7.6 
  • Climate Zone 4: R-9.5 
• A 3 inch inspection gap must be included immediately below wood floor joists/sill plate to allow inspection for termites. A removable insulation piece shall plug this opening during normal operation. 
• Insulated and air sealed band joists - minimum R-13 
• Access doors completely weather stripped and insulated to the same level as the crawlspace walls - ensure access doors have adequate protection from bulk water intrusion 
• Install a dehumidification system to maintain relative humidity at levels of < 60%
• Install humidity sensor with alarm capability.

No Power Attic Ventilation- Vented attics should be passively ventilated.

Note: EarthCraft Light Commercial encourages unvented attic assemblies.

VERIFICATION

• Construction documents clearly identify types and properties of insulation and fenestration materials
• COMcheck file and COMcheck Envelope Compliance Certificate must be submitted before construction for Option A or Option B 
• Leave NFRC label on glazing for Site inspection OR provide photographs before removing 
• For Site-fabricated glazing, provide Certificate of Compliance
• Construction Documents clearly indicate closed crawlspace details 
• ECLC Technical Advisor will perform Site inspection

RESOURCES

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) www.ashrae.org

COMcheck Software www.energycodes.gov

ASHRAE Standard 90.1-2013, Section 5.4.3 Air Leakage www.ashrae.org