Hydronic floor heating

[bandito]

I am building a detached garage and would like to heat it with a hydronic system. I already have hot and cold water lines running from the house. If anyone has any input to start me in the right direction that would be great. My plumbing knowledge is excellent but I have no experience with hydronic floors. Thanks.

[BudgetSlasher]

A few thoughts from someone who has toyed with the ideas of radiant floor hat conversions a few times.

1) You are likely going to need 2 more lines; one to run hot water, not DWH, to the garage and another to return it to the boiler. Even if you can share DHW with radiant heating, you will still need a return path to the boiler.

2) What exactly are you heating? The entire garage, the attic work space? Will the hydronic be embedded in the concrete slab of the garage or the anchored to the floor of a work space above the garage? Either way insulate insulate insulate, concrete wicks heat to soil with nearly 0 r-value.

3) I think MMM has a blog post where he DIY'ed radiant heat, you might want to go back and read it, if you can find it.

4) What will your heat source be? If it is a new boiler simply place it in the garage (assuming it will be above freezing at all times). If it is the existing boiler, do you have a heat load calculation for both your house and the new garage; you could need more BTU than the boiler can provide.

5) I have to ask, why heat the garage? When I had vehicles that needed warmth in colder climate (think diesel) I used a plug in block warmer with a timer rather than heating the garage. If you are thinking of heating a work space . . . radiant floors, as I understand them, are not terribly responsive, meaning you couldn't keep the space just above freezing until you heat out to the workshop and then dial the heat up. Heating an entire garage constantly is going to be throwing away purchased air every time a car comes or goes.

6) If you have lots of time there is a youtube channel call pure living for life, where a couple is DIY'ing their house from site prep to timber framing; while they don't set it up as DIY instruction, they do a decent job of giving an overview. They elected to do embedded radiant heat in their basement/garage. It might be worth your time to see what it takes for in concrete heat. 

[Poeirenta]

We did a DIY retrofit of our 1949 house in Seattle. I highly recommend the Radiant Floor Company in Vermont for supplies and technical assistance. www.radiantcompany.com. Their website should help you answer many of those planning questions.

[bandito]

A few thoughts from someone who has toyed with the ideas of radiant floor hat conversions a few times.

1) You are likely going to need 2 more lines; one to run hot water, not DWH, to the garage and another to return it to the boiler. Even if you can share DHW with radiant heating, you will still need a return path to the boiler.

2) What exactly are you heating? The entire garage, the attic work space? Will the hydronic be embedded in the concrete slab of the garage or the anchored to the floor of a work space above the garage? Either way insulate insulate insulate, concrete wicks heat to soil with nearly 0 r-value.

3) I think MMM has a blog post where he DIY'ed radiant heat, you might want to go back and read it, if you can find it.

4) What will your heat source be? If it is a new boiler simply place it in the garage (assuming it will be above freezing at all times). If it is the existing boiler, do you have a heat load calculation for both your house and the new garage; you could need more BTU than the boiler can provide.

5) I have to ask, why heat the garage? When I had vehicles that needed warmth in colder climate (think diesel) I used a plug in block warmer with a timer rather than heating the garage. If you are thinking of heating a work space . . . radiant floors, as I understand them, are not terribly responsive, meaning you couldn't keep the space just above freezing until you heat out to the workshop and then dial the heat up. Heating an entire garage constantly is going to be throwing away purchased air every time a car comes or goes.

6) If you have lots of time there is a youtube channel call pure living for life, where a couple is DIY'ing their house from site prep to timber framing; while they don't set it up as DIY instruction, they do a decent job of giving an overview. They elected to do embedded radiant heat in their basement/garage. It might be worth your time to see what it takes for in concrete heat.

I live in southern Ontario. Winters here can get pretty cold. I like to work in my garage on my car and motorcycles. In the past I did in the freezing cold.

I would also like to do it for the resale of the house.

I'll have a look at the blog.

Thanks

[CatamaranSailor]

Hey Bandito. Radiant floor heating is awesome. I built a system for our last house and we loved it. That being said, there is one thing about RFH that would seriously make my think twice about putting it into a detached garage. It takes forever to heat up your space. It's best if you set the thermostat and simply forget about it. The house then reaches an equilibrium and you don't even think about it...everything (including the towels you dropped on the floor) are warm. To me, this isn't an issue in a house, it's what you want. But in a detached garage? I guess it depends on how much time you're planning on spending out there. If it's more of a man cave retreat, then cool. But if not, you'll be spending $$$ to keep a garage warm 24/7. If not, you can't just flip on the heat. Even the best system will take hours to make the space warm enough to work. You might be better off building a really well insulated shell (2x6, R/19 in the wall, R50 in the ceiling, insulated garage doors) and putting in forced air or a ceiling mounted shop heater. Then your just paying for heat when you are in the space. Just a thought. I will say, I had a friend who was building a new house and he did RFH heating in his garage and driveway. It was on its own zone, but he did leave it on all the time in the winter and it was awesome. Warm garage in the morning and no shoveling the driveway! Enjoy the project!