Washington State (where I live) has defined any house built after July 1986 as being "unusually tight construction." Washington has adopted the International Mechanical and the International Fuel Gas Codes from the International Code Council so all construction is required to be in compliance with those codes.

These two codes combine information from the Southern Building Code Council (SBCC), the Building and Code Administrators (BOCA), and the International Council of Building Officials (ICBO). The SBCC, BOCA, and ICBO merged several years ago to form the International Code Council (ICC), which is working for nationwide acceptance of the International Mechanical Code, among others.

Basically, "unusually tight construction" meets the following requirements:

Walls exposed to the outdoor atmosphere have a continuous water vapor retarder with a rating of one perm or less with openings gasketed or sealed; and
Openable windows and doors which meet the air leakage requirements of the International Energy Conservation Code, Section 502.1.4; and
Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and at other openings.

Homes built in Washington before 1986 are normally considered "ordinary construction" unless the house was upgraded to meet the requirements described above.

Because not every state and/or community has adopted the International Mechanical Code, you will need to meet with your own building officials to ensure that your building or remodeling project is in compliance with local and state codes. It's about safety, it's about saving energy, and it's about saving you money, so be sure to get those permits and inspections.

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C.R.S., Inc. · Spokane, Washington · USA