Where are your ducts located? (I’m not talking about ‘getting your ducks in a row’!)
Home builders in our metro Atlanta region continue to build houses with the HVAC system in a vented attic. The location of the system is a primary reason our cooling systems struggle to keep us comfortable in the hot, humid months.
Many years ago I made this statement to an uncomfortable, frustrated homeowner, “Your AC system would perform better if it was sitting in your front yard! ...Put it under a big shade tree, and it is especially true.”
Speaking of shade - if you have a large tree that provides your roof with afternoon & evening shade, consider yourself blessed. In the average home, that afternoon shade has the same effect as another ton of AC capacity! And it’s FREE.
(More on the positive & negative effects of environmental conditions and shingle colors in a future blog article.)
Most cooling systems found in homes in our region, are fixed-capacity, central, ducted systems. A fixed, 3-ton system cycles on and off throughout the day, typically three-to-five times per hour.
If that system is in a vented attic, you have several negative unintended consequences. Usually around midday, - the system may run continuously, never shutting down until the late evening hours. And, from our phone calls - these set-ups aren’t keeping Atlanta families cool and comfortable.
The typical remedy from many HVAC companies is something like this:
Make sure the system is properly charged (service call).
When that doesn’t work, a larger system is recommended, (call this a “change out”). Replace your two-ton system with a 2.5 or 3 ton system.
However, if the existing hvac in the attic still has good years of service left, why replace it with a bigger system? Questions need to be answered:
If you’re enlarging my cooling capacity, don’t my ducts need to be larger, to accommodate the added airflow?
Shouldn’t we test and evaluate the duct system, to see if the sizing matches the equipment, and if the Supply vs Return airflow is balanced; that it’s not leaking 35% of airflow into the vented attic, or needing more improvement (like more duct insulation or more efficient design)?
Can we redesign the duct system, for more efficient airflow; getting more airflow into the higher-priority rooms? Remember, the longer your cold air is in the duct system, the warmer it gets. Once it passes through the cooling unit, you want that airflow inserted into the living space as quickly as possible.
If you’d like to save the money of an expensive change-out, approach this from a different direction: Seal and Insulate your attic, using SPRAY FOAM Insulation.
The Instant Shade Tree
Notice the immediate benefits of sealing and insulating your attic with spray foam insulation:
Your attic temperatures rarely (if ever) exceed the temperature of the living space directly below the attic, by more than 15 degrees. Remember, the typical vented attic in our region hits 140 degrees midday.
Are your ducts leaking 35% of the air they are carrying? Instead of losing that cold air to the atmosphere, now you are capturing it and benefiting from it. Remember, your attic is sealed and insulated. (You should consider sealing those ducts, because the leakage contributes toward hot/cold zones, stale air, poor indoor air quality, etc).
Remember the “free 1 ton of added AC capacity” that scientists tell us a strategically located shade tree provides? Well, your spray foam insulation is an “Instant Shade Tree”, and your current system could perform as if you had an additional 1 ton of AC capacity! (Here’s another truth: In a vented attic, with leaky ducts, a 13 SEER AC can actually be performing at 9.8 SEER efficiency.) Why change-out to a 17 SEER high-performance AC, only to hook it up to a set of 20 year old ducts, to locate it in that inferno-like attic, where the actual performance may only be 13 SEER?
Have you noticed that the first few minutes after your AC kicks on, the airflow is actually hot, gradually turning warm, before it gets cool? The AC is absorbing the stored heat in your system, and passing it into your home. That heat is added to the cooling load, and the system has to overcome this hurdle every cycle. However, when your attic is sealed and insulated with spray foam, this hurdle goes disappears! You shorten this cycle to less than a minute, and the initial airflow temp is only mildly warmer than your indoor temperatures!
With a sealed attic, you dramatically slow the dreaded “stack effect”. The stack effect is why your home suffers from dust, humidity, hot & cold zones, drafts, and more.
Indoor air quality is demonstrably improved with the sealed attic.
And there’s more ...
Bottom line: Until the residential building code requires builders to locate hvac systems inside the conditioned space, the benefits of a sealed and insulated attic with spray foam insulation will almost always be a wiser, more informed decision than to change-out and enlarge an AC system, when located in a vented attic, and that otherwise is performing as designed.
Are you ready for the benefits of an Instant Shade Tree, with Improved Indoor Air Quality? Consider sealing and insulating your attic with Spray Foam Insulation!
Got questions? Call Bob in the office at 404-538-9168 or email him at Bob@Birdinsulation.com