What heating system to use in my new detached garage/shop?
Hi. I will build a garage/shop in my backyard next summer. It will be a 20'x30' on a structural concrete slab with around R-35 wall and R-40 roof insulation. There will be a south facing wall with a window section of 18' long x 8' high.
I want to take advantage of the passive solar gain with that window section and the concrete slab. But I want to have a radiant floor and I am not sure what to install. I can go with hydronic floor or electric. Hydronic is about 3300$ and the electric, around 2000$.
I will keep the garage at a low temperature (around 12C) and will also have a small wood stove to heat up the space when working in there.
My goal is to use as low electricity as I can because I won't use it everyday and it is detached to the house. I like electric radiant floor because it is cheaper but I also like hydronic because I could try to retrofit other system with it in the future, like passive solar water heater.
What is the best choice? Or are there better options that I didn't think about?
Thank you for your help and keep up the good work!
David
To choose between various under floor radiant heating systems I would first point you to this page here –
Choosing under floor heating hydronic / liquid, electric wires or air heated, which is best?
Some considerations depending on climate – your use of Celsius tells me you are likely in Canada, and if so, are you in an area where you’re at risk of it freezing? I ask because if you are keeping the temperature down at 12C, in the event of a system failure or power outage I just wonder if hydronic tubes freezing is a concern? The amount of sub-slab insulation is also a very big factor in preventing system damage (and frost heave) but also heat loss. see here about how much insulation a basement slab floor needs
If your furnace goes down in your house you will know about it in pretty short order, but for a garage maybe that is not the case if you aren’t in it every day. Just food for thought.
Installing a hydronic system also means getting insulated water lines to the garage, that is another cost /complication/ risk to consider. I just think electric wires has less inherent risks associated with it, and it does not prevent you from pursuing a renewable energy source in the future as you can add solar panels.
The one option I don’t see that you have considered is an insulated raft slab with air heated floors, this solution is extremely well-insulated and removes the risk of leaks, and they are also engineered not to freeze, that may be the most energy efficient system as well as having a lower risk.