In many older homes, there is a porch over the foundation wall and basement or crawlspace that is protected by an overhanging roof. This is essentially a ceiling that must be made airtight. If major exterior work is planned, the porch should be made airtight and insulted from the exterior if space permits. Where the existing exterior finishes and membranes are to be left in place, the enclosure assemblies around the porch must be made airtight and insulated from the interior.

This air sealing and insulating procedure is meant for exposed protected porches over living space at the house perimeter that cannot be readily vented. It should not be used f or conventional flat roofs or vaulted ceilings. For guidance on air sealing and insulating a ceiling from the interior, see the Guide entitled BC Housing - Best Practices - Interior Retrofit.