Air sealing attic

One of the most important factors in keeping a healthy energy efficient home is to ensure the entire envelope of your building is air sealed. Much like a balloon, poking holes in your homes building envelope will let air escape.  As heat rises, an area of prime concern is the ceiling vapor barrier, or air sealing attic floor.  Problems can occur within Attics when the warm moisture laden air from your living spaces (cooking, showering, inhabitants, etc.) meets cold air circulating in the attic.  As warm, moist air collects on the underside of the roof freeze-thaw weather actions cause wood rotting and ceiling stains from dripping water.

There are many sources of penetrations in your ceiling or attic floor such as framing voids, ducts, plumbing stacks, bath fans and of course the attic hatch.  Pot lights are common ceiling penetrations that are best sealed with a pre-formed poly boot, fitted over the light by an electrician during   installation.  It is important to note that only IC-rated potlights should be used in Attic spaces so they are safe to be in contact with insulation.  Insulation alone in an attic does not act as vapour barrier to stop living space moisture escaping into the attic. At IDEAL Insulation our attic inspectors check all of these examples of penetrations in your attic floor. We weather-strip and insulate all attic hatches to ensure the least amount of air leakage from this source into your attic.  All identifiable penetrations are sealed in the attic with poly repairs or canned hilti foam if required.

In an attic with an extensively damaged vapour barrier IDEAL can remove your current attic insulation and then install spray foam to the attic floor.  2lb closed cell spray foam is used which contains the required moisture resistant properties.  You can insulate the entire attic floor with spray foam or install loosefill fiberglass insulation over top of the cured foam to reach the desired completed R-value.

Attic air leaks source Fine Homebuilding

Attic air leaks source Fine Homebuilding

Diagram legend

  1. Potlights
  2. Electrical cable penetrations
  3. Access hatch
  4. Gaps near chimneys
  5. Plumbing vent pipe
  6. Unsealed soffit
  7. Utility chases
  8. Duct penetrations





Attic insulation article

Read a great article on the Construction Instruction website discussing some of the same factors we do here on our IDEAL blog.  You can read the full article HERE.    There is also a nice visual representation of Attic insulation factors that you can view HERE.

Highlights include:

– proper vapor barrier seal between living spaces and Attic

– installing Air chutes, or styro-foam baffles, along the perimeter of the Attic space to ensure proper air flow intake from the soffit cavity

– insulating up to and over the external wall plates to ensure full coverage of the Attic floor

– the importance of an R-value of R50 in colder climates


Soffit ventilation

Attic inspections consider 3 major factors:  R-value (measure of thermal resistance) of current insulation, Continuity of ceiling vapor barrier and Ventilation.  Ventilation is evaluated in 2 ways: Intake (usually in through the soffit cavities) and Exhaust (through vents installed high on the roof’s ridges).  Your home’s attic and roof depend on proper ventilation to exhaust heat and moisture from the attic space.  Whenever ventilation is limited, or out of balance between intake and exhaust, issues arise such as condensation.

Most homes draw intake ventilation through the Soffit cavity.  The soffits are the underside of the roof where it overhangs the exterior walls of the building.  Older homes, prior to the 1970’s had soffits made out of sheets of plywood that often had very few or sparse vents cut into them.  The adoption of perforated aluminum soffits came in conjuncture with an understanding of the importance of Attic ventilation that for decades became the standard in new home construction.  Unfortunately all too often in the renovation market contractors install new aluminum soffit over top of existing wooden soffit, greatly limiting air flow.

In cases where Attic intake ventilation is limited due to wooden soffits, aluminum covering wooden soffits or plywood stops installed between the attic and the soffit cavity we must pursue additional measures. These measures may involve attempts to bash out plywood stops from the Attic side.  Not a very effective technique but sometimes successful.  Removing the wooden soffits and replacing with new perforated aluminum soffits.  We can often remove the plywood stops from the outside where access is improved with the existing soffits removed.  The best way to address the intake ventilation issue but surely a costly exercise.

The third is the installation of Lower roof intake vents.  This practice has become much more commonplace in Calgary since it has been adopted by New Construction developments in adherence to local fire regulations.  High density residential construction is no longer permitted to utilize perforated aluminum soffits so they install lower roof intake vents during construction.  In the renovation market we can use the same intake vents to create ventilation in Attics where the soffit cavities are poorly vented.  Intake vents are installed around the perimeter of the roof, or specifically in problem areas, down near the edge of the roof.  Always above the exterior wall plate and preferably above the finished height of the current/new attic insulation.  This allows fresh air to be drawn into the Attic space, above the perimeter of the Attic insulation so it can then cycle through the attic and exhaust up through the vents installed at the ridges.

lower roof intake vents allow for Attic intake ventilation through the lower parts of the roof

lower roof intake vents allow for Attic intake ventilation through the lower parts of the roof