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Step 21: Ductwork - Install a New Cold Air Return

When the energy efficiency inspector checked out our house, he suggested I add a cold air return in the basement. This improves air circulation throughout the house - in the summer, cool basement air can be pumped to upper levels to help cool the house.

The main cold air return duct passes straight through the workshop area of my renovation. I decided to install a vent in the end of the duct, as far from sources of sawdust as possible. Before enclosing the duct in a soffit (described later), I did the following:

First, measure the area where you want the vent to be. There are many different sizes of vent covers available, just pick one that first best. With the vent in hand, decide how large the opening in the duct should be. In my case, it was the area in the center, not the outside edges! Transfer those dimensions to the duct using a permanent marker.

You will need to install a small duct that runs just from the edge of the main duct, to the vent (which, in turn, rests on top of the drywall). So that you have something to attach that duct onto, you'll be cutting tabs into the main duct. Inside the rectangle you drew on the duct, draw a smaller one about 1" smaller on each side. Then, draw lines between each of the four corners.

With the drill, cut a hole on each of the corners of the inner rectangle. Then, with the shears or nibbly cutter (whichever works best for you), cut out the smaller inner rectangle. Then, cut along the diagonal lines that link the corners of the two rectangles. Fold the tabs outwards as neatly as possible, and try for a clean 90 degree bend.

Cut a small piece of sheet metal to act as a bridge between the hole in the main duct, and the vent. It should be made to fit tightly around the outside of the tabs, and wrap all the way around. You may want to leave this step until you're ready to install the drywall.

Now, go off and install the soffit around the ductwork as described later in this instructable. When it comes time to drywall the section where the vent will be, transfer the dimensions of the vent opening to the drywall surface. Then, cut out the opening. Fit the drywall in place, and slide the small piece of ducting you made earlier into place. Everything should line up properly. Screw on the drywall.

Using aluminum tape, attach the tabs to the inside of the small piece of ducting. Try to keep the tape as smooth as possible, and be sure to seal up any air gaps. Finally, attach the vent cover on top of the vent hole.
Hi..what laser level were you using? I've been looking for one that wont cost a fortune.
Extremely helpful! Hat off to you!
Looks nice! I was wondering how your floor is holding up after a few years. I've been doing some research on waterproofing my basement and I have not seen anyone else use that type of vapor barrier...just other (and much more expensive) options that I am hoping to avoid. Have you had any problems with moisture seeping through or causing problems underneath the flooring?
No moisture or mold issues as far as I can tell. But, we have a relatively dry basement. Before starting on a basement flooring project I'd suggest doing a moisture test - tape a 1 square meter piece of plastic to the floor and let it sit for a week or two. If no water condenses under the plastic in that time, then you're good to go!
Good to know, thanks! I just found out during the inspection that the house I'm buying has already been waterproofed, so at least that part is already taken care of :) Will still do a moisture test regardless.
Most likely, those are spaced like that (the staggered pieces between the studs) as a fire block. This is code in some areas. It prevents, or at the very least slows the spread of fire up the interior of the wall. Homes built without these in an exterior wall may find their attic on fire before they even know there is a fire in the wall.
Think I'd be wearing steel toe cap boots during the demolition. Nails through the instep are not nice....<br />
Agreed.&nbsp; And for most of the renovation, I did!&nbsp; Many of the pictures taken here were, *ahem*, posed a little...&nbsp; ;)<br />
Beautiful work, and a stunningly complete 'ible<br /> Well done. <br /> Steve<br />
Thanks.<br /> <br /> I have plans to do a bathroom this summer.&nbsp; Hopefully I'll find the time to do it!<br />
&nbsp;Did you have to use anything to hold the foamboards in place while the PL300 was curing or are they light enough not to require that? (The user manual that comes with it says you need to use some type of a fastener to keep things under pressure until cured. ) Also, how long did it take in your case to dry?<br /> <br />
Nothing in particular.&nbsp; I stuck the boards down, pulled them off for a minute or two, then stuck them back on as per instructions.&nbsp; After that, they stuck all by themselves quite nicely.&nbsp; The foam boards aren't heavy at all, and PL300 is very, very sticky.<br /> <br /> I'm not sure how long they took to dry.&nbsp; Unused glue squeezed from the tube and left in the open air took about a day to get rock hard.<br />
&nbsp;What would happen if/when adhesive eventually fails? Would &nbsp;you rely on the studs holding the foam and things remaining airtight?
Presumably the adhesive is intended to be permanent.&nbsp; But, in the unlikely event that it does fail, the second layer of insulation pasted on top, plus the tape, plus the studs on top should hold it in place.<br />
I love Roxul too, I'm planning to use it for my basement reno, as well.<br /> but dude, Roxul isn't fiberglass -- it's mineral fiber, so it doens't make you as itchy as fiberglass though.&nbsp; You still need the breathing / eye protection like you describe. :D<br />
Yeah, someone informed me of my mistake on a different step.&nbsp; Whoops!&nbsp; But, it doesn't really matter which you use; either fiberglass or mineral fiber (aka rock wool) will work here.<br />
Have you noticed a significant change in your energy bill from the fiberglass insulation? I'm debating on whether or not it's necessary with the foam panels...I am on a very limited budget...<br />
Hard to say how much more of a difference the fiberglass makes, since it was installed at the same time as the foam.&nbsp; The top of the wall feels *slightly* warmer than the bottom, but that may be because heat rises.<br /> <br /> Think about it this way:&nbsp; a basement renovation is something you're likely to do once.&nbsp; It'll cost a few hundred more to pack in more insulation, but in the long run it's worth doing really well.&nbsp; The foam panels will likely give you your minimum R-value to meet code, but I'm a fan of exceeding code where possible.<br />
amazing instructable!!
Thanks!
Thanks very much for putting this together. It has given me the confidence to attempt this huge task myself.
No problem! Breaking it into smaller parts, taking time to think things through, and asking lots of questions (and asking for help!) will help you get through it. Oh, and one other thing: Don't lose your momentum. Always do something every day, and don't do anything else until it's done. Make sure that everyone else in the household understands this as well.
That is excellent advise! I will definitely follow it. Thanks again! Eric

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Bio: By day, Jeff is the Jack of All Robots at Clearpath Robotics. By night, a mad scientist / hacker / artist / industrial designer wannabe!
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