Opaque Envelope Residential General Audiences

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Opaque Envelope| Residential | General Audiences Summary The opaque envelope includes all the elements of a building that separate heated or cooled space from exterior space. The energy code includes requirements for walls, floors, and ceilings, as well as for slab foundation edges. These requirements promote thermal efficiency in constructing the building envelope. A poorly insulated building envelope wastes significant amounts of energy and prevents the building components from working together as an integrated system. Without a tight, well insulated building envelope, many other energy efficient measures will not function effectively.

Current Code The 2009 IECC covers the opaque envelope in Section 402.1402.2.2.1.

Previous Code Each subsequent version of the IECC has slight improvements in the stringency of insulation requirements.

Exemptions Requirements covered in the 2009 IECC Section 402.1-402.2.2.1 are mandatory, but not universal, for all climate zones. However, builders are not required to insulate the basement walls if they choose to insulate the floor over the basement. Conversely, builders can choose to insulate the basement walls and not the floor above. These exceptions apply to crawlspaces, as well.

QUICK FACTS Opaque Envelope - Section 402.1-402.2.2.1 2009 IECC R-Values need to be in accordance with code Conform to thermal barrier checklist Mandatory for all climate zones, but not universal Detailed information can be found at: PNNL “What is the Building Envelope?” DOE EERE Commercial building envelope Building envelope design guide from the National Institution of Building Sciences The Building Envelope: A little-known key to energy efficiency

Requirements All parties must be aware of the requirements covered in the 2009 IECC and need to ensure that: R-values used are in accordance with the code and visibly inspected to guarantee conformity The detailed table of thermal air barriers for Section 402.4.2 is followed The thermal barrier checklist is reviewed and field inspected Figure 1: Building Wrap

Typical Problems Standard issues/concerns that arise include: Hidden or unknown R-values in thermal barrier Breaches in the thermal barrier or insulation continuity

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