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Air Sealing

The barrier between the inside and outside of a home’s structure is very important to keeping us comfortable, dry, and energy-efficient. This barrier includes windows, doors, walls, ceilings, and the foundation. 

Every home needs fresh air. Your furnace and other appliances need it to burn fuel, and you need it to enjoy a comfortable, moisture-free living space. When air exchange is controlled in the home, it’s called ventilation. But when air seeps uncontrolled through cracks and holes in the home envelope, it’s known as infiltration. 

Ventilation is good, air infiltration is bad 

Air that leaks through the ceiling, walls, foundation, and other areas of the home can waste up to a third of your total home heating and cooling costs. Air infiltration can be driven by a handful of things --wind pushing air through cracks and openings, the natural currents of warm and cool air flow, or appliances pulling air in for their operation. Fortunately, air infiltration is also one of the easiest forms of energy loss to correct. A home energy assessment will be the best way to help you to identify air leaks in your home. The assessor will be able to use a special infrared camera to detect any temperature spikes caused by air movement. 

Here are a few common places that air leaks can happen, and what you can do to correct them: 

In the attic 

  • Weather-strip any hatches and doors leading to the attic to fully separate it from the rest of your indoor space.  

  • Check for any holes in the attic floor that accommodate wires, pipes, ducts, or vents. You can fill these with a good general-purpose caulk or spray foam. 

  • Recessed lights and bathroom fans may create a pathway for air leaks into the attic. You can caulk around them from below with flexible, high-temperature caulk. When you’re done, install an airtight box over the top of any fixtures as well  –not only to stop air leakage, but also to reduce the risk of fire hazard from insulation lying against any wires. When replacing light fixtures, use only air-tight models. 

  • Seal any fireplace chimneys and furnace or water heater flues yourself with metal and red fire-stop caulk, both of which will be available at your local hardware store. 

In the basement  

  • Scan the area where the foundation wall meets the sill plate overhead and fill any cracks with masonry caulk.

  • Insulate the band and rim joist area by spraying with expandable foam. Do not use fiberglass – it will not stop air infiltration, and it is prone to moisture problems like mold and mildew. 

  • As in the attic, seal any hatches, crawl space doors, or chimneys leading to the basement. 

  • Seal the hole where the bathtub drain comes down into the basement ceiling, along with other holes made for plumbing or electrical wiring. 

  • In homes with air ducts, there may be gaps where the ducts pass through ceilings, floors, and walls. Caulk or foam where the two surfaces meet. 

Around the home 

  • Someone with the proper expertise will be able to seal the gaps between the trimming and baseboards around your doors and windows. In the meantime, you can also easily weather-strip your windows and doors yourself. 

  • Don’t forget to head outside to seal your home’s exterior as well! You can caulk around vents, pipe and wire openings, windows, and door frames. 

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