I'm finishing my basement and need to install an air vent. The problem is...?

Question

I already have existing duct running through the floor joist where I want to add the vent. The existing duct that i need to "splice" runs from the main duct to a vent upstairs. It is 6" flex duct. I want to add into that line a duct facing down from the ceiling into my new finised basement but i need that line to keep going to reach the already existing vent upstairs. All the register boots I find will direct the air straight down but it stops it there. I cant seem to find any type of T register boot. I found a T that I can add the boot to, but all that doesnt fit in the ceiling. What can I do? Thanks for your help!

Answer 1

What is normally used for this application is a Y. However, you really should be running a separate incoming line and return line to the HVAC system. There are a couple of reasons. First is you will drastically affect air flow to the existing register that line is feeding. Secondly, without a return in the space you'll never achieve proper air flow. In addition, your temperature control is on the floor above, instead of in the basement. You should really hire an HVAC tech to advise you on the proper installation for your basement.

Answer 2

Well you could just use the tee and use a round register that will fit into it.

There is a register called an Easy Air Grille (made in Canada) and does not require screws to attach, it just slips in and is held by three tabs.

Keep in mind you are taking away air from the original location and that location may get less than half of the airflow it was intended to get.

An 8" duct could supply the amount of air needed for 2 - 6" ducts.

If it's going to be a problem for that upstairs area I would run a new duct if possible.