I use cedar or pine 1x6x7 fencing boards. You can get them at lowes for as little as $1.20 each. Depending on where you live, this could work.
Im in the south where we have mild winters so i dont worry about drafts as much as someone in colder climates.
Thank you for all your suggestions. I have a plan, just got to see if it will work. If all goes well, I will save the $130 I had allocated for the wood.