We have a large ranch house with a walk out basement.  We bought the house in foreclosure and the basement, although finished ( perimeter walls, drop ceiling, commercial carpet) is basically a large ~3000 sq/ft room.
I'm in the planning stages of framing it out for (2) bedrooms, gym, bathroom and billiard/bar/entertainment room.
I'm focusing on the 2 bedrooms and gym on the one end for now as we're preparing for the arrival of our 2nd child, and we'll be having a relative from Italy come help us - hence the reason I need to start on the bedrooms first so she has a place to stay.
I'm a bit perplexed about temperature control.  We have 2 furnaces on opposite ends of the house.  Both zones feed both the upstairs and down stairs off the plenum.  
The basement is usually ~10* cooler than upstairs, and I understand why.  
What I'm needing to know is what I should do to heat the basement more consistently/efficiently and closer to the temps we maintain upstairs?  Obviously in the summer, the basement is perfect.  In the winter, it's a bit nippy.  
I was figuring I'd run ducts off the plenum to each room as well as adding an individual electric baseboard or in-wall heater to each room to control heat.  I'm concerned though that the heat generated by the electric heaters will be minimized/eliminated by the returns at the furnace.
Also, not sure if the slab is insulated, but I've read about people insulating the slab with 2" XPS foam boards, and then the sub floor framed ( I saw 2x4's laid flat and the XPS boards laid between the "joists") and the subsequent flooring installed above.
Well, what do you guys think?  Thanks for any advice.





 

You can also use infrared"spot" heaters if the typical electric heaters aren't effective enough at boosting the HVAC heating

So would you support my idea of installing supplemental electric heat in addition to the forced air from the furnace in each room?



 

What do you think about using a mini-split to condition the bedrooms and bath because they'll have doors to isolate those spaces?  The furnaces could still be used to condition the remaining space.  If your bath will have a tile floor you could use an electric heat mat beneath the tile which could be nice.

I think you make a good point about the basement return air pulling heat from the bedrooms and bath.  If you do decide to use the existing forced air to heat those spaces I would undercut the doors rather than having a high air return grill.  That way you'll be pulling the cool air from floor level back to the furnace if those doors remain closed.

Is the stairwell to the first floor open?  In what state do you reside?  Do you have egress from the bedrooms that will satisfy the building code?

Answers in RED



 

I've found that basements are often cold because they are damper than above. Run one or more dehumidifiers and some fans on timers to move the air around and see if things improve. While it's nice in the summer, it shouldn't be that cool.

Not dampness.  I live in one of the driest parts of the country.



 

my folks have supplemental electric baseboard heat in their basement here in CO.  It works great but the electric bills are whoppers.

pretty sure thermal break/ insulation is required on basement walls only to meet code.  ( not sure if your pulling a permit or not).   New houses generally have a thick blanket looking insulation with a plastic vapor barrier on it.  If you don't have that you glue 1/2 inch foam board to the wall then frame a wall out in front of it and insulate between the studs to get the required r value.

Also be sure to float all walls with at least an 1 1/2 inches.

2" insulation is a lot for a floor.   Plus it would mess with your stairs rise and they would fail inspection (if going the permit route)

an easy thermal break for a floor would be something like a dri core product.

If you're getting such a wide swing in temp, I bet it's damper. Being in a drier part of the country has nothing to do with it. If the basement is cooler than above and there is moisture in the air, it will move down. Doesn't mean you're at the point of condensation but get a hygrometer and see what is going on. A dehumidifier and fan is pretty cheap compared to some other fixes.