Radiant heat in 20x30 garage and 30x45 driveway

rderrick121

Hello, my home has a 20x 30 garage, no insulation and higher ceilings, the driveway is roughly 30x45. There are 4 orange pex loops to the driveway and 3 loops within the garage. I’m looking to add heat to the floor/garage and I’d like to be able to melt the snow in the winter but probably wouldn’t because of the cost. I understand that radiant floor heating is not fast and if I turn the heat on in the garage circuits it will be at least a day before I get any real warmth in the space. Natural gas would likely be the only source of fuel for the boiler unless I could somehow rig up a waste oil system which I think it would be awesome.. I see that this is normally done with a manifold and some sort of boiler however after talking with some friends I found that a traditional boiler wouldn’t work as the temperature difference would be too significant and I’d need a boiler that can be metered like a natural gas cooktop (high for boiling water low for simmering soups and everything else inbetween..)  I am fairly handy and can do my fair share of plumbing. I live in Pennsylvania with the coldest temperatures being around 0f and 20-30f for the other cold months.. is there any cost effective way to do this? Natural gas instant water heater? Oil burner converted to run on waste oil? A traditional NG boiler? I’d hate to not use the 1/2 Installed radiant heating system but after thinking about this for a little while, placing a hanging NG forced air heater on the ceiling seems very easy.. I called around and got estimates for  10-15k which included all the labor and materials to make it so I could heat the space/garage ideally but realistically I’m looking at a couple hundred dollar second hand water heating source and a handful of miscellaneous supplies roughly 1000 dollars as the alternative hanging furnace is about half that. Any insight is greatly appreciated.

Hot_water_fan

 I found that a traditional boiler wouldn’t work as the temperature difference would be too significant and I’d need a boiler that can be metered like a natural gas cooktop (high for boiling water low for simmering soups and everything else inbetween..)

That’s wrong. A modulating boiler would work. So would a boiler that doesn’t modulate. 

is there any cost effective way to do this? 

We can’t answer this, this is a personal question only you can answer. Hydronic systems are usually luxury items. Very few Americans have them, especially newer houses.  

Natural gas instant water heater? Oil burner converted to run on waste oil? A traditional NG boiler?

A traditional cast iron boiler would seem to be the best solution. An “instant water heater” would work IF it’s a boiler. If it’s something from Home Depot designed for showers, no. Not appropriate. Oil is usually a bad option if you already have gas on site. 

I personally think the hanging heater is best. 

PDTech

I have a radiant floor heated shop, about 1200 sq. ft. I believe your first investment for cost and comfort should be getting it well insulated.

rderrick121

Hot_water_fan said:

 I found that a traditional boiler wouldn’t work as the temperature difference would be too significant and I’d need a boiler that can be metered like a natural gas cooktop (high for boiling water low for simmering soups and everything else inbetween..)

That’s wrong. A modulating boiler would work. So would a boiler that doesn’t modulate. 

Hello, how would this work? From what I understand a typical boiler sends water 150-180deg out, if you sent that to a manifold you’d be counting on heat loss in the lines to take it down to a range that’s not significantly higher than the concrete? And isn’t it an issue to heat it up that quickly? 

Hot_water_fan

You’d use a mixing device to ensure the water going to the slab is lower. So the boiler is protected from low return temps and the slab has safe temps going to it. These are installed everyday. 

rderrick121

Hot_water_fan said:

You’d use a mixing device to ensure the water going to the slab is lower. So the boiler is protected from low return temps and the slab has safe temps going to it. These are installed everyday. 

Hi, can you show me an example of one of these mixing devices? 

Hot_water_fan

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_7_NA_Mixing%20in%20hydronic%20systems.pdf

This shows you why and how to do this

Mad Dog_2

Mad Dog_2

Mid picture  left. The Chrome 3 way Valve between the Orange 🍊 handled Ball Valves  That Taco Mixing valve lowers the boiler supply water for a Radiant zone. This is when I was Preggers with Triplets..ha ha 😂 🤣 😆 😄. Trimmed down a Bit....Mad Dog 🐕 

Mad Dog_2

Green knobbed 3 Way valve under the first circulator pump on left.  Mad Dog 🐕 

hot_rod

You may want 100 btu/ sq ft for that snowmelt, so you are looking at around a 150K boiler just for the snowmelt.
What size is the tube in the driveway? How long are the loops. Typically 9" on center for snowmelt, or tighter.

Skip the waste oil idea. They are expensive, messy, maintenance and take a lot more oil that you realize.

If the tube is in the garage floor, that would be my first choice.

If it is a very occasional use, not an everyday work space, a hydronic unit heater is a much faster warm up.