Air Sealing

Everyone who has lived in New England knows that cold drafts can make a home uncomfortable in winter. When heated or cooled air leaks out of a building, heating and cooling equipment must work even harder, increasing energy consumption.  Air leakage can cause about 40% of the heat loss in a building!!!

Air leaking into or out of a building or between different spaces in a building can also carry odors, humidity (water vapor), and other airborne contaminants.  Pests also travel through some of the same holes.

Buildings are full of air leaks. Some air leaks are due to material selection and how elements are installed, such as windows, plumbing, or fire walls. Some leaks are because different parts of wall assemblies are not fully connected. Other leaks may have developed over time because of pests. The goal at Castle Square has been to track down these leaks and then seal them.

At Castle Square Apartments, air sealing is being added at two locations –

1) Air sealing is integrated as part of the super insulated shell.   A liquid-applied air and water control membrane is actually painted onto the exterior of the building’s original brick walls and mineral wool is also applied to reduce air leakage behind the super insulated panels.

2) There is extensive air sealing in each apartment to “compartmentalize” or separate the apartments from each other.

Why is Air Sealing Important?

A little known fact is that without air sealing to stop leaks, insulation doesn’t work very well. Air sealing is as simple as caulking cracks and holes to the outdoors and between apartments. Not air sealing is like only wearing a sweater (insulation) outdoors on a cold day. You’re cold until you put on a wind breaker (air sealing).
Air sealing makes the super insulated shell work. It also reduces the stack effect, the phenomena that causes heat to escape from the top of the building and causes cold air to be drawn into lower apartments.

Air leaks in buildings have a tremendous impact on a building’s energy use, on occupant comfort, on indoor air quality, on effectiveness of mechanical systems, and even on building durability. Air sealing saves energy and stops the spread of odors and pests between apartments. During construction, the effectiveness of air sealing is confirmed using a blower door test.

Air Sealing Checklist – Apartment

During the renovation, each apartment at Castle Square is being air sealed to isolate that apartment from its neighbors and between the apartment and the outdoors. Here’s the air sealing checklist that is being followed at every apartment.

  • Air seal window installation.
  • Caulk steel door frame to drywall; weatherstrip.
  • Replace existing registers. Remove register grilles. Seal from inside of duct to face of drywall with UL #181 mastic tape. Trim tape at face of drywall so that tape will be concealed by register flanges. Add new sleeve/boot to extend room side of finish.
  • If soffit is opened, seal all penetrations. Ensure drywall behind soffit is continuous. Ensure drywall extends to ceiling and seal drywall to ceiling.
  • Seal plumbing, electrical, other penetrations through drywall.
  • Seal demising wall to exterior wall – At intersection of demising wall and exterior wall, remove 2-4″ wide strip of drywall from exterior wall to allow drywall of demising wall to be sealed to the exterior wall (concrete frame or CMU back-up).
  • Air tight electrical boxes throughout or seal each electrical box.
  • Air seal with fire rated foam and insulate hot water pipes in wall shafts. Seal all floor penetrations in shaft.
  • In smaller shaft adjacent to bathroom, add air sealing with fire rated foam where accessible.
  • All heat riser penetration locations to be sealed.
  • Air seal around trickle vents.
  • Air seal around A/C sleeve.
  • Air tight lighting fixtures.
  • Avoid unnecessary penetrations through air barrier. Any unavoidable penetrations of the air barrier by electrical boxes or conduit, plumbing, and other components or services must be made air, smoke, and gas-tight.

Air sealing compartmentalizes each apartment, isolating each apartment, and allowing it to perform as its own little house.

Typical air sealing products include caulking, foam, and tape to seal holes.

AFTER - Plumbing and electrical penetrations will be sealed.

BEFORE - During construction, bathroom and kitchen soffits are opened to find any internal air leaks. Here, a large opening is discovered above the exhaust ductwork. An opening like this results in air movement between the different building floors.

BEFORE - Here’s a closer look at that soffit. When the building was originally constructed, fiberglass insulation was stuffed in the space. Unfortunately, fiberglass insulation is not an air barrier, so air continued to flow. The insulation is discolored, because dirt from moving air was dropped in the insulation over time.

AFTER - During the renovation, any holes inside soffits are air sealed with foam to stop air movement between apartments.

AFTER - During construction, the demising wall is sealed to the exterior wall. At the intersection of demising wall and exterior wall, a 2-4" wide strip of drywall is removed to allow the demising wall drywall to be sealed to the exterior wall (concrete frame or CMU back-up).

BEFORE - Although this looks like a typical duct, when the register is removed, an air leak is discovered.

BEFORE - The duct work does not extend to the drywall. This means that hot air is leaking into the wall cavity, instead of heating the room.

AFTER - During construction, all existing registers are being replaced. Most importantly, a new sleeve or boot is added to extend the duct past the drywall. Then the duct is sealed to the face of the drywall. Now heated air goes to the right place – the living space.

AFTER - Blower door tests are used to verify that air sealing was done correctly during construction.