I currently have a WaterFurnace Envision 5 series 5 ton unit that was installed when we built our home in 2009. It has two zones. Due to current code, one cannot put heat or cool into a garage and have the same returns come into the house due to the possibility of Co2 entering the house. With that said, I use a pellet stove to heat my garage, using approx 3 tons of pellets per heating season, average of about $600-800 each season. This adds up over the years, maybe I should be investing in some type of geothermal for the garage? Is there an application that can use my existing vertical ground loop and/or my existing 5 series to work for the attached garage without having returns into the home?
You can't use the existing heat pump. No way around those codes that I can think of. You could use the loops, assuming you have the capacity for the extra btu's for the garage. A console unit or such plumbed in parallel would do the work for you. From experience, the garage is a big use of btu's - even when temps are kept low. It has a good volume % compared to the rest of the house (typically). So you don't likely have the extra capacity in your ground loops. We do a fair % of garages/shops in our work. They are almost always radiant slab.
Thanks, makes sense. I would've done a radiant slab when we built but it just wasn't in the budget at the time.