After perhaps keeping the rain out, airtightness is the most important thing we can do to make our buildings energy efficient and comfortable. That’s a building science fact. A fully functional air barrier is fundamentally important to the proper functioning of the building. Consequently we should take necessary steps to ensure that the airbarrier works, not just on the last day of construction but until the last day of occupancy: 50 years, even 100 years in the future. And we should help optimize its ability to succeed through the materials and means and methods we use to construct the air barrier.
In our quest for greater airtightness, the Airtight Drywall Approach (ADA), which was developed in the 1980s, does not sufficiently optimize chances for success, nor does it last. Consequently ADA has lost its usefulness.
Let’s look at the reasons why:
1. ADA connections are often inflexible. Air barrier connections should be flexible. Buildings move. Components expand and contract. Taped gypsum board joints are not flexible. Often, after the first winter, there are cracks in taped joints (see above photo). Often, the spray foam and caulking used to connect gypsum board to wood framing elements harden, embrittle, shrink, crack and fail after just a few years. Even if hiding behind base and crown moldings, the holes are lurking.
2. ADA is not continuous. Continuity is an essential characteristic of an air barrier. Gypsum drywall, the primary air sealing material, is not continuous. It stops and starts at floor and ceiling construction and often at perpendicular interior walls.
3. ADA is a sacrificial layer. Air barriers should not be sacrificial layers, they should be protected from damage. Occupants cut, hit, bang and otherwise assault the drywall – don’t leave your air barrier’s fate in the hands of unruly occupants.
4. ADA doesn’t minimize the number of penetrations. Every penetration is a potential failure point. We should minimize the quantity of penetrations and ADA does the opposite – every electrical outlet box and every wire going into the box multiplies the chances for failure. The best practice instead, is a service cavity.
5. ADA is not vapor intelligent. Gypsum wall board is vapor open and vapor retarding paints are not intelligent. With an inboard air barrier, in a cold climate, there is a unique opportunity to combine air control and vapor control in a robust system by utilizing vapor intelligent membranes like Pro Clima INTELLO and DB+, thereby minimizing wetting potential, maximizing drying potential and increasing the drying reserves and the safety of the assembly.
For these five reasons ADA doesn’t ensure success; it ensures failure. So like single pane windows, exhaust only ventilation, and code minimum insulation levels before – as we push for higher performance – it’s time to remove ADA from your tool box.
Instead, for a complete approach to robust, resilient and long lasting airtightness see: