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wonderworm 06-24-2008 03:46 PM

Tapping into AC Vent for Room Addition
The previous owners added on a 160sqft sunroom to the living room. To me it serves no purpose so I want to go through the ceiling and tap into one of the home AC vents to provide central AC to this room addition and then add wood flooring and make it a study/xtra bedroom.

Before I hack into the ceiling of the sunroom and break through the wall into the house, I am hoping to get some ideas/advice.
-The sunroom is insulated with it's own insulated crawl space.
-I'm assuming the brick exterior wall is still separating the rooms so I will need to know the best way to break a hole through to the living room for the flex AC duct to travel in.
-I need to lay duct about 9ft to get to the corner of the sunroom with a vent, or about 15ft to run the duct all the way to the center of the room. Not sure if it matters if the duct is near a corner for such a small room.

Any ideas on what tools and supplies I will need and the best way to do this?
Here's the view from the living area to the sunroom.
Here's the view of the closest corner of the sunroom and where I may place the AC register.
And here you can see the entire sunroom that I want to air condition.

wonderworm 06-25-2008 06:04 PM

Has anyone ever did a project similar to this? Advice?

Termite 06-25-2008 11:26 PM

Hi Wonderworm. Welcome to the site.

You should place the AC/heat vent as close as possible to the exterior walls as possible. I'd aim for the outermost wall. It is best to have it near fenestration (doors and windows) to be most effective.

Any chance of using under-floor space (crawlspace) if there is any? Better to have it in the floor. If the ceiling/attic are the only options, that'll work.

You can remove enough brick from the exterior wall to allow passage of the flex duct. Don't remove brick under the ridge beam or other openings if you can avoid it. As long as you're 4 or 5 feet away from loads like that, the bricks will easily span a small opening. Use a hammer drill and a masonry bit to drill a series of closely spaced holes in the general shape of the hole you want to cut. It will take a lot of holes, but they'll allow you to chisel out the opening without boogering adjacent bricks and mortar joints.

One thing to consider. Your home's HVAC duct system is a designed system. Depending on the size and length of the ducts, the number of duct openings, and the tonnage of the AC unit, adding an opening in the sunroom may negatively affect the static pressure in the ducts. No way for us to tell online. It takes a pro looking at it to size the system. There's a chance that it'll benefit from an additional opening as well. Take close note of the velocity of the air you get from other HVAC duct openings in the house before doing this work. Sometimes another opening and length of new duct will totally kill the static pressure in that trunk, which may feed several openings...Sometimes not.

If possible, it would be good to install a return air vent to balance the supply and return to that room. Leaving the door open will more or less take care of this. With the doors all closed off from the house, I imagine that the heating/cooling performance will be lessened.

Insulated flex duct is pretty handy stuff. Avoid tight turns. The less turns, the better the performace. Every 90 degree turn cuts the velocity in half, more or less. Support the flex duct so it doesn't sag. Nice straight runs are best. Also, don't compress or kink the duct.

Your sunroom attic may not be insulated. I would plan on doing this if you want the space to be livable.

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