Energy Codes and the Building Envelope

Goal of Energy Efficient Design

A Few Acronyms

ASHREA = American Society of Heating, Refrigerating, and Air-Conditioning Engineers

ICC = International Code Council

IECC = International Energy Conservation Code

Codes, Standards, and Model Codes

Commercial Energy Usage

• Office, retail, and service buildings are the largest consumers of energy in the United States

• About half of this energy is consumed by lighting

• Energy Codes and Standards set a minimum level of energy performance with which the building must comply

Commercial Energy Codes

Commercial energy codes apply to all buildings EXCEPT:

• One- and two-family residential buildings

• Multi-unit residential buildings three stories or less in height

Energy Codes

• Codes and standards may be enforced at the state, local, or jurisdictional level

• Voluntary Energy-Efficiency Programs– Home Energy Rating System (HERS) – ENERGY STAR– Good Cents– LEED

Commercial Energy Codes• A few states have adopted the

most recent versions (dark green)

• Some states have no statewide energy code (white)

• Most have adopted an older version of ASHRAE/IECC but will typically update as code requirements periodically change

Most recent standard/model code is ASHRAE 90.1-2007/2009 IECC

Courtesy US DOE

We’ll Look at

• ASHRAE/IESNA Standard 90.1-2007• Chapter 5 of the IECC General

Prescriptive Approach• Use for ≤ 40% of gross wall area in vertical

fenestration• Use for ≤ 3% of gross roof area in skylights

2009 IECC Climate Zones

Code requirements are based on climate zones

Keystone Library

Commercial Energy Codes

What is a Building Envelope?

• Roof/ceiling

• Exterior walls

• Vertical fenestration (glazing) and skylights

• Lowest floor

• Slab edge

• Below grade walls

Building Envelope

Sealing Requirements

• All fenestration, openings, joints, and seams in the building envelope must be sealed with one of the following– Caulk– Gasket– Tape– Moisture vapor-permeable wrapping material

Insulation RequirementsBuilding Envelope Requirements for Climate Zone 5

Roof Insulation RequirementKeystone Library

Insulation entirely above deck: R-20 c.i.

SURFACING

INSULATION

METAL DECK

STEEL OPEN WEB JOIST

Where c.i. = continuous insulation

Wall Insulation RequirementKeystone Library

Mass wall above grade: R-11.4 c.i.

BRICK

AIR GAP

R-11.4 INSULATION

8” CMU

What types and thicknesses of insulation would meet the code in this application?

Floor Insulation RequirementsKeystone Library

Mass floor (slab-on-grade) unheated: no requirement

Note: When required, this perimeter insulation must be placed around the exterior edge of the slab.

Accepted perimeter insulation configurations

Opaque Door RequirementsKeystone Library

• Opaque doors have < 50% glass area

• Door type

– Swinging door: U-0.700 (or less)

– Overhead door: U-0.500 (or less)

Reminder: U-Factor

Fenestration

• All areas (including the frames) in the building envelope that let in light– Examples include windows, plastic panels,

clerestories, skylights, glass doors that are more than one-half glass, and glass block walls

• A skylight is a fenestration surface having a slope of less than 60 degrees from the horizontal plane

Fenestration Requirements

• Fenestration selection is often strongly influenced by energy codes

• U-Factor and Solar Heat Gain Coefficient may be specified in codes

Wonder Window, Co.

Fenestration RequirementsKeystone Library

Fenestration area must be less than 40% maximum of above grade wall area

Building Envelope Requirements for Climate Zone 5

Fenestration RequirementsDefinitions

Curtain Wall – Fenestration products used to create an external non-load bearing wall that is designed to separate the exterior and interior environments

Storefront – A nonresidential system of doors and windows mulled as a composite fenestration structure that has been designed to withstand heavy use

Entrance Door – Fenestration products used for ingress, egress, and access in nonresidential buildings, including but not limited to, exterior entrances that utilize latching hardware and automatic closers that contain over 50% glass specifically designed to withstand heavy use and possible abuse

Solar Heat Gain Coefficient (SHGC)

Overhangs and Fenestration Requirements

• Overhangs can decrease requirement for SHGC (in some climates)

• Calculate the Projection Factor, PF

B

APF

• Southern climates with high cooling loads– SHGC is more important than the U-factor in

promoting energy efficiency– Choose lowest SHGC possible

• Northern climates with insignificant cooling loads– Choose highest SHGC to promote solar heat

gain during cold weather

Solar Heat Gain Coefficient (SHGC)

SHGC RequirementsKeystone Project

• If : U-0.40 or less

• Otherwise: no requirement

25.0PF

Vestibule RequirementsA small entrance area between the outer door and the interior door

ConditionedSpace 3000 FT2

Vestibule

Self Closing Doors

Exterior Doors

ConditionedSpace 3000 FT2

Vestibule

Self Closing Doors

Exterior Doors

DOE

• Required at entrance leading to spaces ≥ 3000 ft2

• Doors must have self-closing devices

• Exceptions:−Buildings in climate zone 1−Doors from guest room or

dwelling−Doors for vehicles, material

handling, and adjacent personnel doors

Resources

Barlett, R., Halverson, M.A., & Shankle, D. L. (year). Understanding building energy codes and standards. Publication no. PNNL-14235: U. S.

Efficient Windows Collaborative. (n.d.). Retrieved December 15, 2009, from http://www.efficientwindows.org/

Department of Energy. (n.d). Building energy codes program. Retrieved December 15, 2009, from http://www.energycodes.gov/implement/

International Code Council (2009). International energy conservation code and ANSI/ASHRAE/IESNA standard 90.1 2007 energy standard for buildings except low rise residential buildings. Country Club Hills, IL: Author.