Air Leakage Testing and Air Sealing of a House in Takoma Park (part 2)

September 2008

We start at the top of the house to find the air leaks. The picture below shows the "thermal envelope" of the house underneath the attic and roof structures. The red area is the junction between the attic and the ceiling of the top floor.

House for Air Sealing Case Study

Attic to house plane is the most important for Air Sealing Case Study

When a blower door test is running, air leaks can be felt with the hand. In this house it turns out that two of the rooms on the top floor were built not with a drywall board ceiling but using ceiling tiles. Air can be felt blowing out of each of the cracks between the tiles!

To seal up these leaks, a new drywall ceiling is being installed over the tiles in these rooms.

Air Leakage through Tile Ceiling in Takoma Park

NEXT: Kneewalls (to be continued) ... This is an ongoing project which I work on as I have time, so updates may not happen every week.

 

 

Air Leakage from top floor to attic

In the winter, a leaky house acts like a chimney. Warm air expands and rises upward and leaves the house through cracks and holes between the ceiling of the top floor and the attic. Air Leakage to the attic is an the most important leakage path in most homes.

These cracks and holes are found at the tops of walls, light fixtures, recessed lights, exhaust fans, duct registers and can add up to a large area of holes. Air leaving the house is made up by pulling cold air in at the bottom of the house through wall penetrations or the joint between the foundation and walls.

Air Sealing an attic

  • Air sealing a house is done from top to bottom, because first sealing the leaks from the top floor ceiling to the attic can stop the chimney effect in the house.
  • Up in the attic, insulation is pushed aside to expose the tops of all the walls and other openings in the attic.
  • a high expansion foam that hardens in less than a minute is used to cover cracks and holes in the ceiling below the attic.
  • For large openings, foam board, plywood, or sheet metal sealed with expanding foam can be used to bridge openings.
  • Once air sealing is complete in the attic, the insulation can be restored and additional insulation can be added.
  • Insulation should NOT be added to an attic if air sealing is not done the extra insulation will NOT stop the air leaks and moisture transfer.