Monday, January 9, 2012

Basement HVAC Cold Air Return Installation

Basement HVAC Cold Air Return Installation TOTAL INVESTMENT:    $50
TIME:                                 2 hours
DIFFICULTY                     Easy
NET RESULT                     +6 degrees to basement temp (average)

Well.  Here it goes.  My first blog post on the house.  Let me say that the HVAC setup on a Ball home isn't the best.  The house has an upstairs, main level, and a basement.  The upstairs system has one return (right under the furnace), which makes it pretty loud.  If you shut the bedroom doors, the system doesn't breathe at all.  If I get a pile of money or get very brave, the upstairs may get a post in the blog.  This post is about the basement system, which heats/cools the main level and basement.  We had the home surveyed by a professional before we moved in.  Fixed the critical stuff, but left some items for later.  Much later in my case.  We've lived here for 6.5 years (longest house I've had so far), so I finally decided that the basement was waaaay too cold.  I'm talking we were in sleeping bags to watch a movie. I think one time I could actually see my breath. 

I broke out the home survey which read, "NO RETURN FOUND BEING DRAWN FROM BASEMENT - MAY LEAD TO COOLER CONDITIONS DOWN THERE".  That wasn't much to go on, so we had a couple of companies come out to do a quote.  I never got the pricetag on either one after repeated calls, and I think I figured out why.  It's easy. 

After an hour surfing on YouTube and 2 trips to Lowe's, I had the parts for the job:
  • Vent cover, Boot, 6" Metal duct, Elbow
Next, I needed some tools:
  • Skill Saw, Razor knife, Duct tape, Sharpie, Drill, Tin Snips
Next, I needed some courage:
  • 750ml Makers Mark, Ice, Plastic cup, Mexican Coke (for after the drill, saw, tin snips, and razor knife)
The steps were simple.
  1. Turn off furnace.
  2. Find a good place in the basement wall to install the intake vent.  Cut a hole in your drywall for the vent boot very close to the floor.  The cold air hangs out by the floor, so the closer the better.  I drew lines for the cutout on the drywall and drilled starter holes for the Skill saw.  This step makes a drywall mess.
  3. Find a good place to cut a hole in the return air duct.  Make sure you cut the hole BEFORE the filter, so you get filtered air going through the furnace.  Trace the elbow with a sharpie and cut out.  I was able to cut mine easily with a razor knife.
  4. Install the elbow in the return air duct.  Install the boot in the wall.  Measure the distance to run the metal duct between the elbow and the boot.  Say a few choice words.  Measure again.  Pray.  Cut the metal duct with tin snips a little longer that what you think.  Test fit.  More choice words.  Cut again to the right size.  Assemble the metal duct and try to slide into elbow and boot.  More words. 
  5. Bourbon break.  Hey, the sharp items and power tools are put away!
  6. Wiggle, push, more choice words, wiggle, and finally it's together in one piece.  Tape up good with duct tape, so it doesn't leak. 
  7. Install vent cover.
  8. Turn funace back on.  Test airflow by putting a piece of paper over the grill to make sure it's sucking in air.
    Grill Pic.  Mine has a switch to control airlfow. 
    Note the proximity to the floor.

I was pretty lucky.  The return air duct was fairly close to the wall.  The metal duct was only about 12" long, but it was pretty tight on the right hand side.  If I were doing this again, I would cut out about an inch of the stud and move the boot over to the right.

    Entire furnace.  Note that I've got duct tape sealing the filter
    in place.  Every  home I've bought needed tape.  Without the tape, the system does not breathe properly, and unfiltered air is going through the furnace.

My last mod to the basement, the electric heater. 
Note the timer, so the heater only runs when we need it.

I really couldn't believe the results.  Last year, the basement was 58-62 degrees with the heater running.  This year, I've seen 64-70 degrees, with an average temp of 67.  Airflow out the upstairs vents has also improved.  One side effect that I wasn't expecting is that my upstairs feels warmer.  After scratching my head, pondering the result over a bourbon, and consulting my dad, my thoughts are that a warmer basement makes a warmer house.  If there's no insulation under the main level floor, it only makes sense that cold basement air will make a cold floor in the space above.  Cool!!!

If you don't have one of these, you need one.  Install is cheap and easy.  I also hear that summertime cooling will be more energy efficient by pushing some of the cooler basement air upstairs.
You may also enjoy an article I wrote about attic insulation.  Click here to read.


  1. I have been to your blog before. The more I visit, the more I keep coming back! ;-)
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  2. This is a great article I am glad I came across it. I am currently finishing my basement and it has been a long process. I really want to make sure that the climate is controlled so I decided to install a system that can perform a Dehumidification service. My kids will be playing down their a lot and I do not want mold to form. However, I do not know if I need a furnace since the air is usually at room temperature in my basement. Thanks for the great information though!

  3. I'm seeing a lot of counter info on the web stating that a return duct in the basement could create negative pressure and cause a potential back draft situation flooding the house with CO. Just FYI. Might want to make sure you have a CO detector down there I guess. But I'd be cautious about promoting this as a solution.

    1. CO and natural gas detector is plugged in about 15 feet from the furnace, and has never chirped except for the yearly test. IMO, the cold air return is necessary for your house to breathe properly (and so you don't freeze in the winter).

  4. Great Post..... thanks for sharing this information I have gain more important knowledge about Basement HVAC Cold Air Return Installation. I am really appreciate for this. Visit my page also Cheap Heat Pumps Auckland

  5. I like the courage part, the most! Could go in to defuse a bomb with that!

  6. You do realize that you should NOT use duct tape for sealing HVAC connections. You need to use the silver foil tape. In about a year your duct tape will be dry and deteriorated.

    1. Good point. Heat isn't the issue but drying out is.

  7. Good job, very impressive. When I was moving to my new house I decided to make things better before I move in. I called They are qualified and expirienced to do their job well. Now I don't worry about my A/C system.

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