A house that is not airtight can raise your heating bill by up to 15% per year, and can cause premature deterioration of the house due to humidity and dampness. Doors, windows and cracks and fissures should be properly sealed. Caulking and weather stripping are low-cost remedies to such problems.

Draw up a list of air infiltration sites
If you take the time to detect and list places where outside air infiltrates your home, it will help you effectively solve the problem. The inspection service provided by the Agence de l’efficacité énergétique (AEE) du Québec includes a blower door test that pinpoints and measures air entering from the outside. The test also indicates any leaks to the outside, i.e. warm and humid air leaking out of the house.

Detecting air infiltration
By slowly moving a lit candle, a smoke pen or a thin piece of paper along the edges of the walls, floors and ceilings along the perimeter of the house, you will notice an air leak whenever the object flickers. This simple method will give you a good indication of the work to be carried out. Turning on all exhaust fans (kitchen range hood, dryer, central vacuum cleaner, bathroom exhaust fan) will help locate the leaks more quickly and accurately.

Seal leaks from attic to basement
Air that is leaking to the outside can cause condensation problems and damage the insulation and wood framing of the house. Since air leaks tend to rise upward, start by caulking and sealing the top of the house and rooms with the highest moisture content such as the bathroom.

Caulking requires a clean surface
For best results, the joint to be sealed must be clean. Remove any paint, dust and old putty using a putty knife or screwdriver.

Strategic points to inspect when making a house airtight:

  • attic access hatch (trapdoor) and ceiling voids;
  • entry points for components that run from the ceiling to the attic (wiring,
  • plumbing pipes, ventilation ducts, etc.);
  • doors;
  • exhaust fans (such as kitchen range hoods);
  • letter slots;
  • the joint between the wall sole plate and the end joists at the outer edge o
  • the floors;
  • inlets in exterior walls for conduits, wiring and pipes;
  • the area drain;
  • cracks in the foundation;
  • electrical outlets;
  • windows;
  • chimney.

What can happen if a house is not airtight?
Infiltration of cold, outside air greatly diminishes the comfort of your home and increases your heating costs. As for warm inside air escaping from the house, it is humid air that can create condensation problems inside the envelope. It can damage the insulation, produce mold and cause the wood framing to start rotting.

Air tends to leak through the following weak points in the envelope:

  • the joints where the exterior walls meet the foundations, the floors, the ceilings and the brick wall backing tiers;
  • the joint where the backing tiers meet the insulated ceilings;
  • the joint where a door or window frame meets the exterior wall, and the joint between the glass and the window frame;
  • wherever wires or pipes run through exterior walls and insulated ceilings (ceiling lights, electrical outlets, light switches, exhaust fans, fresh air intakes, plumbing pipes or the main electrical service panel).

How can I detect air leakage?
Hear are two methods for detecting air leaks.

Flicker test
This simple method consists of slowly moving a lit candle, smoke pen or a thin piece of paper along the inside walls at the weak points mentioned above. The flickering flame or smoke, or the trembling sheet of paper, indicates an air leak.

Blower door test
This is a more sophisticated method. A blower door panel is used to create artificial depressurization inside the house so as to simulate high wind conditions. The air penetrates through holes and cracks in the house, which makes it possible to identify the specific points of air infiltration.

What are the rules to follow to ensure an airtight house?
Install the air barrier material in seamless, continuous fashion to prevent any passage of air through the building envelope. A lack of continuity in the air barrier will allow cold air to penetrate the insulation, which will diminish its insulating capacity.

Install the vapour barrier material in continuous fashion on the warm side of the insulating material. The vapour barrier prevents humid air and moisture from penetrating colder zones. Without the barrier, the humidity could cause condensation and mold to form.

Seal the perimeter of any object (ceiling lamp, electrical outlet, light switch, fan, dryer outlet, fresh air intake, electrical entry conduit, plumbing entry pipe, etc.) that runs through either the air barrier membrane or the vapour barrier membrane to ensure their integrity.

When choosing a sealer, keep the specific nature of the site to be caulked or sealed and the climate conditions in mind. Also take into consideration the cost of the sealant, as well as its resistance, adherence, elasticity and ease of installation.

Start by caulking and sealing the interior in order to stop leakage of warm air to the outside. Then continue sealing leaks from the outside to prevent rain water from infiltrating into the exterior walls.

Install weather stripping around doors and windows.

Improving air tightness of foundation walls
A cracked or damaged joint between the concrete foundation walls and the wood framing is often the cause of direct infiltrations which increase heating bills and reduce the comfort of your home. During construction, it is relatively easy and inexpensive to place a compressible sheet under the foundation sill to prevent the entering of cold air from underneath the ground level floor.

It is possible to correct that shortcoming in an existing house, but it calls for careful attention. Start indoors by sealing each joint with foam insulation. If you are doing major repairs to the exterior cladding of the house, seal the cracks between the concrete and the wood with the same type of sealing product before installing the new siding.

Once your house is airtight, it’s time to insulate the top part of the concrete wall and the edge beam to prevent any direct contact between cold air and the wood framing. A range of different materials provides satisfactory results. Glass fibre batt insulation is the easiest to apply. Cut the insulation to the exact size required and place the pieces into position loosely, without packing them too tightly. Cover the insulation with a polyethylene vapour barrier and seal the joints of the membrane with the appropriate adhesive tape. You can also use styrene foam insulation, but it must be covered with a fire-resistant material.

Source: Agence de l’efficacité énergétique du Québec