3. Super-Seal the Building Envelope
- Set an airtightness standard of 0.6 to 1.5 ACH at 50Pascals and create an airtight barrier around all six sides of the home. Depending on climate, a 2.0 ACH may be sufficient.
- Use a Thermal By-Pass Checklist short form to identify areas that need sealing. The Green Building Advisor has excellent air sealing diagrams, available for free if you sign up for their 10-day free trial.
- Ensure that exterior sheathing materials should does not have any gaps, and joints are mechanically tightened.
- Seal the outer sheathing and the drywall ceiling before the inside drywall is installed. To learn more about exterior air sealing, see Airtight Wall and Roof Sheathing: Arguments in Favor of Exterior Air Sealing, and view the Exterior Air-Sealing video.
- Use glue, caulking, spray foam, and/or products, such as Ecoseal or Siga Airsealing Tapes, depending on the size and location of the leaks. For more on sealing air leaks see Tape It? Seal It? Glue It? Sealing Weather Barrier Seams.
- During the sealing process, check for air leaks with your hands and/or with a smoke stick while the blower door is running. Then seal the leaks and recheck. This is called Blower-Door-Directed Air Sealing. View the Blower Door Directed Air Sealing video.
- Complete the air sealing along with the subcontractor and crew – be fanatical, systematic and persistent in finding and sealing every leak, checking your success with the blower door as you go.
- After the sheet rock has been installed on the walls, seal the inner envelope while again checking with the blower door in order to identify and seal all remaining leaks while the blower door is running. View the Sealing the Interior Walls video.
- Seal electrical boxes and plumbing penetrations after all electrical and plumbing work is complete. Consider using airtight electrical boxes on all exterior walls.
- Minimize penetrations of the airtight envelop by:
>>> Having all Ducts Inside and using track lighting, pendants, or recessed cans in soffits to keep the air barrier intact instead of using typical recessed can lighting. View the Ducts and Cans Inside video.
>>> Using the Energy Efficient Whole House Ventilation System, either an ERV or HRV, instead of standard bathroom or kitchen vent fans, provided the ERV or HRV vents are sized properly for venting the bathrooms and/or kitchen, and that this is allowed by local code, which it often is.
Twelve Steps to Affordable Zero Energy Home Construction