Basement HVAC

I hope this is in the correct section. I am required to add HVAC to my basement in order to pass inspection. In the attached diagram, I drew the current supply lines (blue) for the main floor that run between the joist in the basement from the main supply run. I also added the return line (black) coming from the main floor as well.
I am thinking about adding 2 possibly up to 4 new registers with at least one new line (red) and extending/attaching to one of the existing lines. My thinking is attaching to the existing supply to add a line and supply the bedroom. Add a new line from the main to supply the living area. I am also possibly thinking about adding a 2nd register for the living area that attaches to the main. With this second line to the living area, I am thinking about adding a register to the office. However, because computers will be there, not sure how much I want to add a register there.
Finally, I want to add one (possibly) 2 return lines to the basement (green) between the studs. I was reading that one 6inch line should handle up to 1500sq/ft no problem. So, this is where I don't know if I really need a second one or not.
Is this a good plan? Anything I should change?

 

There have been several members that have posted about needing additional ductwork to pass inspection. It turned out that the ductwork was required to be installed by an HVAC contractor and inspected.

Check and make sure you can do the work and don't need to have it done by a company.

 

Lines to a basement would not be shared with existing lines, just like 2nd floor lines are not shared with 1st floor. vents.

One vent in each with a common return will work.

 

Some municipalities perform work on their own home that would otherwise require a licensed professional. It is important to take out the permits and list yourself as the person/contractor doing the work. That way there is no paperwork snafu that causes trouble later. Of course it is totally on you to know and follow the codes. Inspectors are not your teacher and don't have the time to hold your hand or tell you how to do a job. They are usually nice people if you don't waste their time.

 

I have the option to hire a company or I can also do it myself. Of course, making sure that it is done correctly.

Yes, I have the required permits needed. I did ask a couple of questions about the HVAC, but the inspector did not give me any info. Instead just told me to go to a professional.

As far as the return goes, it sounds like a 6" would be sufficient.

I guess I will have to find the best way to run the new lines especially to the bedroom since it would have to go across below the joists (from the image, joists go top to bottom).

 

A lot depends on how this is going to be used.

Basements dont need A/C as they are naturally around 60 so all you really need is a little heat. A small mini split electric heat would work back there in the bedroom and then no duct needed.

 

The bedroom will be for guests. So, unless we have any, it will not be used. What we will be using the most is the living area mainly for entertainment/movie purposes.

I definitely was thinking about an electric heater, although I know it would require a dedicated circuit, but will be a lot better/easier to install than running a whole new supply line.