The 2012 International Residential Code (N1102.2.4) requires insulation at all hatches and doors that separate conditioned and non-conditioned spaces. These locations are typically found at openings to the crawl space and attic. The insulation R-value must be equivalent to the insulation used in the surrounding area. The openings must also be weatherstripped.
The Washington State energy code has similar language in section R402.2.4.
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