Jet727

I am currently finishing my basement. I am wondering if I need to run new lines from the main trunk line between the joist for heating and air vents. I have seen the saddles that you can cut into the existing runs that are already there for the upstairs and put a vent off one of those. I am just wondering which way is the correct way to do this. Obviously if I can do the saddles and cut into the existing lines this would be much easier but I am worried it might rob alot of the heat for upstairs.

I am finishing off a bedroom, bathroom, and family area, for a total square footage of approx. 1050 sq.ft.

Thanks

Bestheating

Your concern is valid. Let me cite some examples. A typical 6" heat run, has a capacity of 125 to 150 CFM. Your duct system if installed properly, has the terminations located for an even distribution of heat in the home when built. When you splice into one or more of these, you are upsetting this balance. I like to extend the basement warm airs, out to the perimiter of the structure. Sometimes, I will stub them down the outside walls. (Insualte behind them). For you quare footage, you will need a total of 4 to 6 terminations, depending on your geographic location. Make sure to use grills that can be closed, if desired.
Every bit as important, is the installation of return air in a basement. One in each half of the basement should be fine. The reason is two fold. One, the warm airs need this for basic return to the furance. Second, in the summer, you are trying to dehumidify the basement. These will help to get that stagnant air cycled through the a-coil and dryed out a little.
Kind of a short answer for me, I hope it helps.