Maximize Your Home's Efficiency This Summer
By Frank Wickstead, owner and partner of Alair Buckhead
As you experience another hot summer, are you considering the best home efficiency upgrades, such as replacing or upgrading your HVAC equipment or windows? Before you make that big expense, be sure to check your building envelope (air sealing and duct sealing).
Most states in the US have adopted the 2015 IECC (International Energy Conservation Code), which says that a building envelope (the barrier between conditioned and unconditioned space, inside and outside) in a new home can only experience five air changes per hour (ACH) under an amount of pressure equal to five times what a home would typically experience on a cold day or under a strong breeze.
You might be surprised to know that the average home experiences around 20 air changes per hour. Imagine that! Five to 20+ times an hour, your home’s heated or cooled air is being replaced and re-heated or re-cooled. This is why “job one” of home efficiency and keeping your home comfortable is air sealing or decreasing the number of air changes per hour.
Despite how it sounds, air sealing isn’t that complicated. Numerous DOE/EPA/HUD/CDC studies have proven that it offers the highest ROI (return on investment) of any other efficiency-related home improvement.
Tech Talk
The International Energy Conservation Code (IECC) is a building code created by the International Code Council in 2000. It is a model code adopted by many states and municipal governments in the US for the establishment of minimum design and construction requirements for energy efficiency. Several states have adopted the updated 2021 IECC. The IECC is in use or adopted in 48 states, the District of Columbia, Puerto Rico and the U.S. Virgin Islands.
Your Best ROI Isn’t Replacing Windows
Speaking of ROI, what efficiency-focused upgrades perform the worst? Window replacement. Window manufacturers are great marketers, but they will not lower your energy cost or make a noticeable difference to your comfort on their own.
The best practice for air sealing is to use a blower door to pressurize your home. The blower door is also what provides your home’s measured ACH, so your before and after results will be quantified. Make sure you see at least a 30% improvement. If you test in at 20 ACH, then you should test out at 14 ACH or better to see a noticeable improvement.
Tech Talk
Air changes per hour (ACH) is the measure of the air volume added to or removed from a space in one hour, divided by the volume of the space.
Don’t Duck Out on Checking Your Ductwork
Is it duct tape or duck tape? While both terms are used interchangeably, neither should be used on ducts! After checking out your building envelope, focus on your ductwork or ducts — that is, the tubes in the attic or crawl space that move conditioned air around your home. While the 2015 IECC says a new home’s ducts should only have 6% total leakage, in my experience working on older homes in the Atlanta market, it’s more likely to be 70% leakage. That means that 6-70% of the air you are paying to heat and cool is potentially blowing into your attic or crawl space. Depending on the condition of your ducts, they may need to be replaced rather than sealed.
The process of measuring and quantifying duct sealing is done with a duct blaster. The same consultant that tests your building envelope can test your ducts. You can also have your HVAC tech test and seal your ducts. If your tech hasn’t heard of a duct blaster or mastic, run! Mastic is the only way to properly seal ducts. What is duct tape for? Probably everything except your ducts. The goal with ducts is as close to 0% leakage as possible. You should expect at least a 50% improvement; if your ducts had 30% leakage, expect 15% or better.
After you’ve addressed your building envelope and ducts, it’s time to consider insulation and HVAC upgrades—but never before.
Most utilities offer rebates for the BPI assessment, envelope sealing, and duct sealing (in addition to other improvements). If you are a Georgia Power customer, visit Georgia Power Rebates and Discounts. Are these rebates offered out of the kindness of their hearts? No. It is a Public Service Commission-mandated program that you fund! So take that money back and get comfortable year-round.
Average Air Changes per Hour (ACH) in Homes vs. IECC Standards
| ACH Level | Description | Notes |
|---|---|---|
| 20+ | Average Home | Many homes experience high ACH due to leaks in building envelopes. |
| 10-20 | Typical Older Homes | Homes with moderate air leakage. |
| 5-10 | Better Sealed Homes | Homes with some air sealing, closer to IECC standards. |
| ≤5 | IECC Standard | New homes should meet or exceed this standard for energy efficiency. |
Key Points:
- Homes with high ACH (20+) may benefit significantly from air sealing to improve efficiency.
- Meeting or exceeding IECC standards (≤5 ACH) can lead to substantial energy savings and increased comfort.
- A blower door test can accurately measure your home’s ACH and guide improvement efforts.
Frank Wickstead brings a wealth of expertise to the table as a Professor of Practice at Georgia Tech’s College of Design, School of Building Construction, and as the owner and partner of Alair Buckhead. With his deep knowledge of building construction and sustainable design, Frank is dedicated to helping homeowners achieve the highest standards of home efficiency.