Where’s the ideal place to locate your HVAC: Crawlspace, Basement, or Attic?

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Where's the ideal place to locate your HVAC: Crawlspace, Basement, or Attic?

I received the phone call from Beau, our operations manager, (he’s also my son). “Dad, we can’t do this duct job, it’s too tight under this house. There’s no way I can give him the quality of craftsmanship that we practice; no way”.

We had agreed to rebuild the duct system for a midtown homeowner. His ducts were in awful shape because they were lying on the ground, and had been neglected for many years by previous owners. In fact, this job had been postponed a week, due to water sitting in the crawlspace… so you know these ducts were in a soggy, wet mess!

I learned that previous contractors had “replaced” the duct system. But all they had actually done was replace what they could access… which was about 20% of the duct system that could be seen from the very small scuttle hole.

Because the crawlspace was so tight, the ducts were lying in ‘trenches & ditches’ dug out by the initial HVAC crew that had installed the central HVAC. Because of the low crawlspace, it meant that the furnace & air handler wouldn’t fit. So there was a package unit installed, sitting in the yard, against the outside of the house.

A “package unit” is an all-in-one HVAC system. Think of a giant AC window unit, only it’s sitting on the ground. Two large “pipes” or ducts extend from the package unit: One is the conditioned SUPPLY air that serves the house with warm or cool air, attaching to the vents in every room. The 2nd duct is the RETURN duct, that attaches to the RETURN air vents, and draws the stale air out of the house, through the filter, and conditions it again, to return to the house as conditioned air, through the SUPPLY duct system.

When Beau called me, we discussed the job, and I said to him,“Son, you’ve got to give this homeowner hope. He needs a plan, a solution to his dilemma.”

Because the house was a ranch (single level), I made a recommendation that I never make!

“Suggest to him, that he consider gutting the current system. Sell the package unit on Craigslist. We’ll install a new system in the attic, and using spray foam, seal and insulate the attic. He’ll save money overall, have dramatically improved comfort and Indoor Air Quality! And he’ll have a system that can be serviced and inspected regularly, as it should be”.

Our homeowner was gleefully satisfied with our recommendation, and is pursuing it now.

So, what is the better location for your HVAC system? The point I’m driving at is this: Best location for Airflow Temperatures, (overall HVAC performance). We see the majority of ranch-style homes with the systems under the floor. It’s either in the basement or crawlspace. And, in my opinion, that’s the best place for it. Basements are wonderful! When kept dry and conditioned, a basement the ideal spot for your HVAC set up.

Crawlspaces are good spots for HVAC systems too. Except when the system is left to the elements, and neglected of regular, systematic maintenance. When I bought my house (ranch), the previous owner left the scuttle door open, and used the 2 ½’ high crawlspace as a doghouse for his dogs! It took me many trips with gloves and trash bags, to clean out my crawlspace. Old furnace filters were everywhere, rocks, cement blocks, toys, (he had sons) and leftover dog bowls had to be cleaned out.

In our area, HVAC systems located in vented attics usually underperform, especially in summer. For multi-story homes, the bedrooms are upstairs, and it’s hard to rest when you can’t get the bedrooms below 80 degrees at bedtime!

For years and years, I’ve used an infrared thermometer to measure airflow temperature coming out of the SUPPLY vents. I’ve done this simple demonstration for 1000’s of homeowners. What I’ve discovered is a revelation:

In summer months, the AC airflow temperatures will be considerably lower (cooler) for systems located in a basement or crawlspace, when compared with HVAC systems located in vented attics. And I’m talking as much or more than 10 degrees!

I’m always explaining to Mr. or Ms. Homeowner, “It’s hard to get the bedrooms to 72 degrees, when the airflow temp is 76 degrees. It’ll never happen, not ever.” And the poor HVAC unit runs and runs and runs…

So, what’s to be done for those multi-story houses with attic-mounted HVAC? Only one thing you can do (without a major demolition of your house to bring the ducts inside the living space): seal and insulate your attic with spray foam.

When you encapsulate an attic with spray foam, you are converting it into an airtight Igloo cooler! Now, your sealed and insulated attic, and your HVAC & duct system is protected from extreme temperatures, like your crawlspace or basement! And YOU WIN… Big Time!

That same AC system that could never cool your bedrooms, now, with a sealed and insulated attic, is providing SUPPLY airflow temperatures on par with the same unit located under a house. And, those bedrooms are a cool 72 degrees at bedtime, even on the hottest day of summer!

Rarely will a sealed, foam-insulated attic deviate more than 15 degrees from the living space temperatures below it. Compare that with the daily 140 degree temperatures found in vented attics!

So, when we have a choice, we prefer HVAC systems located under the house. For HVAC & duct systems located in the attic, sealing and insulating the attic with spray foam insulation is the only way to protect the system from the extreme temperatures we live with here in metro Atlanta.

After all, it’s hard to get cold air from a warm pipe! Would you like to learn more? See these blog posts too:



Got Questions? Call Bob in the office at 404-538-9168 or reach us by email at Bob@Birdinsulation.com We’re here to help!

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