October 27, 2016

Heat loss from recessed lighting.

Have you ever experienced drafty rooms, uneven temperatures between rooms, cold floors, ice dams, insects, or rodents? I doubt you will answer “no” to all of these questions.

A relatively easy solution to fixing these issues is air sealing. Air sealing sounds pretty straightforward and, for the most part, it is. Almost everyone has come across weather stripping kits for doors or windows at their local big-box store. You also understand the logic of door sweeps and caulking around windows. What you may not realize is that filling holes around doors and windows is only a very small percentage of what air sealing entails.

In my last blog, I talked about what stack effect is and the desire to control or reduce the effect. That’s where our activities should begin. Air leakage has a negative effect on insulation performance, moisture migration, energy usage, occupant health, and more.

Where should air sealing occur?

To be most effective, air sealing activities should focus on holes, penetrations, and bypass areas at the lowest and highest parts in a house (typically in the basement and attic). Warm air rises and will escape through any means possible. This can, and does, happen inside wall cavities as well. With air sealing, the devil really is in the details. Some important areas to concentrate on (but certainly not all) are:

  • Attic bypasses (wire penetrations, chimneys, etc.)
  • Interior dropped soffits
  • Recessed lights
  • Basement/crawl space bypasses (have a look under where your toilet/shower is)
  • Ductwork
  • Band joists

Why should I air seal when I can just install new windows?

Everyone loves the fresh look of new windows. Replacing those old single hung, single pane, hard-to-clean windows adds a nice touch to a home. You can typically spend around $4,000 to $8,000, or more, depending on how many windows you replace and with what you replace them. Sure, they save energy, but unless you’re completely missing a window, the typical payback in terms of reduced energy use is about 20 years (assuming $6,000 and a reduction in energy use of $302 per year). So, in 20 years, you will have saved as much money as they cost.

Windows are not a bad thing, don’t get me wrong, but if energy savings, comfort, and health are your goals – don’t start with windows.

In comparison, the average cost associated with air sealing (alone – no insulation) is around $800 for a typical home. A typical 1,500 square foot home with 8-foot ceilings can have a leakage rate of 3,500 Cubic Feet per Minute* (CFM) 50. Achieving a 30% reduction in air leakage is an easily met target. That reduces the leakage rate to 2,450 CFM50. Controlling air leakage in this home has an 8-year payback, and comfort benefits will be noticed the same day. A good air sealing crew with blower door-assisted air sealing could probably realize a 40-50% reduction in air leakage.

Can air sealing make a house “too tight?”

Air sealing activities can potentially adversely affect the venting of combustion appliances by changing the way pressures interact in the house. That’s why it’s important that combustion safety testing be performed whenever air sealing activities are applied.

By air sealing, you may also end up trapping indoor pollutants such as radon or carbon monoxide, and other bad characters, in your home. This is commonly referred to as making a house “too tight.” But there are steps to take to make the house work for you, not against you. Many times, it is necessary to add mechanical ventilation to ensure a safe and comfortable environment. This is a good thing that controls your heating and cooling losses and where your fresh air comes from. (We will explore this concept in another post).

The take-away

All factors considered, saving 30% in your annual fuel bill is not only reasonable, it’s been happening for years for thousands of families in the private and public sector. Why not contact a BPI GoldStar Contractor today to have your house evaluated? Your house, your wallet, and your health will thank you.

*CFM – measures how many cubic feet of air pass by a stationary point in one minute.

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Matt Anderson

Matt’s background is in residential, commercial, and industrial construction. He worked at BPI for over 15 years and has provided home performance analyses on numerous residential projects.