DIY duct sealing that saves on cash

October 9, 2015

Utility bills and uncomfortable rooms are the main issues when your ducts aren't properly sealed. But you don't need a contractor to do it for you. If you're handy around the house, it's a job that you can tackle with these few steps and precautions.

DIY duct sealing that saves on cash

Canadian homes lose up to 20 percent of the air that moves through their duct systems due to leaks, holes and poorly connected ducts.

  • Not only will faulty ducts make it more difficult to keep the house comfortable (no matter how the thermostat is set), but your utility bills will take a bigger bite out of your paycheque.
  • All the more reason, say the home heating and air-conditioning contractors, to hire them to seal your ducts. But the money you spend on having a contractor work on your ducts might offset any savings you'll see in the future.
  • Unless the ducts are hard to reach, chances are you can seal them yourself, saving those contractor fees while making your home more comfortable, more energy efficient and safer.

Here's a step-by-step approach, beginning with a few expert tips for recognizing poorly performing ducts.

Signs of duct problems:

  • High utility bills in summer and winter.
  • Some rooms are difficult to heat and cool.
  • Stuffy rooms never seem to feel comfortable.
  • Little or no air flows from registers.
  • Air filter gets dirty quickly (needs changing more than once a month, which is a sign of leaks in return ducts).
  • Streaks of dust at registers or duct connections.
  • Lack of insulation on ducts in attic or crawl space.
  • Tangled or kinked flexible ducts in your system.

How to seal ducts

  1. Reconnect any disconnected duct.
  2. Seal air leaks using mastic (a gooey, highly effective adhesive that dries to a soft solid) or metal tape. Mastics and tapes should be UL 181 approved. Never use duct tape, which doesn't last nearly as long.
  3. Make sure connections at vents and registers are well-sealed where they meet the floors, walls and ceiling. Use spray foam to seal the gaps.
  4. If your ducts are uninsulated or the insulation is torn or showing gaps, first seal any loose ducts and then add proper insulation.
  5. Insulate attic or crawl-space ducts using material, such as fibreglass batting, rated at least R-6.

Secret weapon: extra insulation

Since heat rises, a good deal of the heat lost by a house is through the attic. So even though your attic is already insulated with batts or loose fill between the joists, it often pays, especially in older homes, to add another layer of insulation.

It doesn't cost a fortune, and it's a job that most homeowners can do themselves, using rolls of fibreglass insulation available at any home centre.

  1. Run the new insulation over the tops of the joists at right angles to the existing insulation. This covers any gaps in the first layer and insulates the heat escape routes created by the joists.
  2. When adding new rolled insulation, work from the eaves toward the centre using a piece of plywood as a platform to kneel on.
  3. You can cut the insulation using heavy-duty scissors.
  4. Three precautions: use unfaced insulation; if it has facing, slash it every few inches so that it won't trap moisture. Don't block vents in the eaves. And don't cover recessed lighting unless it's marked IC (for insulated ceiling).
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