With spring around the corner, are you considering a new home improvement project, such as replacing or upgrading your HVAC equipment? Before you take on that big expense, be sure to check your air seals and duct seals.
Most states in the US have adopted 2015 IECC (International Energy Conservation Code), which states that a building envelope (i.e., the barrier between conditioned and unconditioned space) in a new home can only experience five air changes per hour (ACH) under an amount of pressure equal to 5x of what a home would typically experience on a cold day or under a strong breeze.
Would you be surprised to know that a home experiences about 20 air changes per hour? Imagine that! Five to 20 times an hour, the heated or cooled air in your home 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, it isn’t that complicated. Actually, it has been proven in many studies as offering the highest return on investment (ROI) of any other efficiency-related home improvement.
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.
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 the 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.
What’s the Best ACH for Your Home?
Generally, the tighter the home’s “envelope” that keeps the ACH number low, the better. But a too-tightly sealed home might make you wonder about indoor air quality — and that’s something to check into.
Consider hiring a trained Building Analyst from The Building Performance Institute (BPI) to test your home and offer a prescription for improvement, including a minimum-safe ACH number.
The BPI is a nonprofit that’s in the business of decreasing energy costs and increasing comfort. After the analyst’s evaluation, BPI can create a custom work order designed to make your home more comfortable. From there, I’d recommend you work with an independent consultant. If your consultant works for an HVAC company, the work order will always be HVAC-heavy. If they work for an insulation firm, the work order will always be insulation-heavy. (A strange coincidence? If only that was the case.)
If you would like to go for 0 ACH, you will need to install mechanical ventilation that brings in both departiculated (removes allergens, etc.) and dehumidified (removes moisture) air.
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
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 2015 IECC says a new home’s ducts should only have 6% total leakage, in my experience working on older homes, 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 to measure and quantify duct sealing is 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 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 your building envelope and ducts are handled, then it’s time to consider insulation and HVAC upgrades — but never, never before.
Need Help with a Major Home Improvement Project?
At Jones Pierce Structures, we enjoy helping our clients bring to life the improvements that will make their home more energy-safe, comfortable and enjoyable — and we do this year-round, not just in the spring!
Reach out to me if you’d like more information … and here’s hoping spring gets here soon!