Gas and Oil Home Heating Furnaces - Lazy job of hooking of supply ducts!

I've own house for about 1 year and still finding things to fix. In the attic where the main trunk of the A/C-Heating runs, then connect to the flexable insulant ducts,but coming up the walls is a flat metal duct with rounded corners. There is no adaptor, someone just stretch flexable duct around the flat metal duct and wrap duct tape around it. And of acourse after about 14 years stuff starting to fall off. Wanting to fix it right. I like to find a adaptor to that would go onto the flat metal duct coming up the walls, convert it into round duct, so flexable could be attach. I all I have found at lowes/homedepot as been square. Does anyone know where I can get adaptor to fix this?

Thanks

Hello: Online2

If the part your searching for isn't found in the mass marketing giant retail stores, try shopping at your local heating agents retail stores.

Also consider the fact that such a part {adaptor} might not even exist.

The fact that the rectangular metal ducting has rounded corners may be to prevent tearing of the round stretchable flex ducting....when it's forced over the rectangular metal ducting.......:D.....????

Could be an experiment to prove rectangle ducting can fit into rounded flex ducting.....??????......as long as there is ducting tape handy??????.....:)

Side Note:
Duct tape is WONDERFUL stuff..... it can hold ANYTHING together.....EXCEPT:

>>>>>>>>>>"PEACE TREATIES"<<<<<<<<<<<

The fixture you need is commonly called a square to round. If you say it real fast the hvac community will accept you. Just take the dimensions of the two ducts the rectangle and the diameter of the round one and how much room you can spare between them and go to a sheet metal usually a hvac company and have them make a square to round transition fitting for you. they'll charge 50 bucks for 20 minutes of work,2 dollars worth of metal and 20 years of know how.

if it a standard size, 3 1/4 by 10, 12 or 14, it is called a "stack boot", and available at most supply houses.