Radiant Heating - In-Floor, Hot Water

  • Advertise with us

« back to Focus on the Workspace forum

Forum topic by RinBarrett posted 12-06-2016 03:00 PM 1865 views 0 times favorited 22 replies Add to Favorites Watch
View RinBarrett's profile


5 posts in 2478 days

12-06-2016 03:00 PM

Does anyone have experience with heating their shop with in-floor hot water radiant heating? I’m building a new shop in Utah and am considering it. Out here they heat driveways and walkways with it in large commercial applications to help clear snow. So I’m thinking I could use the same technology to bury hot water pipes in my concrete floor and heat the shop that way. I’m thinking it would be a more consistent heat and that it would get rid of the biggest heat sink I have in my shop now, which is the concrete slab sucking the heat back into the ground. I have no idea the cost of operation compared to forced air or other heating methods, but I’m thinking it would be cheaper in the long run. That’s something I need to look into.

Any thoughts?

-- Rin, Draper, UT,

22 replies so far

View ROB_IN_MN's profile


35 posts in 3486 days

#1 posted 12-06-2016 10:22 PM

i have in-floor heat in my shop. It’s awesome, although I’m told it is not the cheapest way to heat a shop.

your foundation will have to be planned out from the start for it. you have to insulate underneath the slap, or like you said, all your heat will be leeched away by the ground.

the install and operating cost is more than traditional heating, but certainly something a non-commercial entity can afford.

keep in mind that the heat buildup and fall off are very long for this type of heat. so, there’s no point in things like programmable thermostats.

View AandCstyle's profile


3306 posts in 3597 days

#2 posted 12-06-2016 11:48 PM

Rin, I have had in-floor radiant in the shop twice. I think it is great; no more cold feet on the concrete floor, no more cold tools, no more condensation on cast iron (maybe not an issue in Utah), etc. By all means put insulation under it and maybe a vapor barrier. I believe that it is more efficient that hot air because it heats things and not air; you don’t end up with all the warmth by the ceiling. Also, you don’t have to be concerned about shop dust getting into your heating system like you would with forced air. On the flip side, there isn’t any duct work for summer cooling. PEX tubing is easy to work, but be careful to not create any kinks in it. HTH

-- Art

View shawnn's profile


156 posts in 2705 days

#3 posted 12-06-2016 11:54 PM

There’s a lot of good info at I insulated my shop floor before pouring and put PEX loops in, still waiting to wall off the woodshop side & cover/insulate ceiling & walls before trying to install a heater.

View gerrym526's profile


331 posts in 5148 days

#4 posted 12-07-2016 12:05 AM

I’m designing my shop, which will be built next year, and researched how it will be heated. I live in northern Idaho, so it gets cold here in the winter.
Here’s what I found doing my research, and what heating unit will be used-
1) Hydronic heating systems are expensive to install and expensive to maintain-you need a furnace, hot water boiler, circulation pumps, manifolds, piping, etc. If one pump fails your looking at $300 for a new one.
2) During spring and fall seasons, when the morning starts out cold (e.g. 40 degrees) but the afternoon warms up quickly (say to 60-70 degrees) your hydronic heating system is out of synch with the temperature. It takes several hours to heat up the concrete slab -you’re cold in the morning to start-and then when it’s putting out heat in the warmer temp in the afternoon-you’re sweating! What you really want is a heating system that warms the shop quickly in the morning when it’s cold, but you can shut off before the afternoon warmer temp arrives-keeping you comfortable.

My heating system in the new shop will be a forced air propane heater (ceiling or wall mounted) with an enclosed combustion chamber to make it explosion/fire proof (Modine makes a model call the Hot Dawg). Simple to install, operate and maintain, and heats the shop fast when you need it on a cold morning. Also much cheaper than a hydronic system by orders of magnitude.

I lived in the Chicago area all my life before moving to Idaho, and the winters there are brutal compared to where I live now. In the Great Lakes, the vast majority of houses and shops are heated with forced air units. Hydronic seems to be way more popular in the West, but personally, I couldn’t see any advantages to it over forced air, especially when it comes to costs.

On a side note, when you pour your next concrete slab floor, research using closed cell foam slabs on top of gravel and a vapor barrier. You’ll find that the “heat sink” problem goes away. And, to get the ultimate in comfort from your floor, I’d put down furring strips covered with OSB flooring-your feet, knees, legs, and back will thank you.

Hope this helps.

-- Gerry

View JAAune's profile


2088 posts in 3657 days

#5 posted 12-07-2016 03:51 AM

I’ve worked in a shop with in-floor boiler heat and now have one with forced air. I’d take the boiler any day. It’s far more comfortable than the on/off hot air system. The forced-air furnace seems to dry out the air a lot more. It also also messes up the airflow around my edge sander (which is in front of the hanging furnace) and blows dust away from the collection port and spreads it around.

The increased efficiency of the boiler should pay off over time. It’s far easier to heat water (a natural conductor) than it is to heat air (a natural insulator) The landlord that owned the boiler-heated building was happy with the cost of his gas bill but I never saw it and can’t compare it to my own heating bill.

-- See my work at

View Picklehead's profile


1055 posts in 3269 days

#6 posted 12-07-2016 05:59 PM

I have radiant hydronic in the floor of my shop. Love it. Leave it set at about 58 year round (in NH). Keeps shop and ALL the tools warm and dry.

-- Quote from ebay tool listing: " Has nicks and dings wear and tear dust and dirt rust and pitting but in good working condition"

View Manitario's profile


2818 posts in 4223 days

#7 posted 12-07-2016 06:13 PM

I am going into my 2nd winter with in floor heat; I’ve previously had shops with forced air heat. It is a nice, comfortable heat, and I don’t have to worry about forced air blowing the dust around when I’m doing finishing. It does take a bit of planning during construction and a programmable thermostat; it is slow to heat so you can’t just go out into the shop and turn up the heat and expect it to be warm in 30 min.

-- Sometimes the creative process requires foul language. -- Charles Neil

View DirtyMike's profile


637 posts in 2242 days

#8 posted 12-07-2016 06:16 PM

Nice smallie,Pickle. If your shop has access to the southern sun you should consider a solar boiler. While im sure the upfront cost are not cheap, you would be self sufficient.

View TFA's profile


10 posts in 1939 days

#9 posted 12-07-2016 08:14 PM

in-slab radiant heat is a great option. As many people stated you need 2” sheet of xps insulation and a vapor barrier (6 mil) under the slab to not lose heat to the ground and not take in moisture from the ground. XPS sheets are +/- $1 sq. ft.. you can find the stuff cheaper if you can get it from a salvage place (there’s tons of these places out there with insulation in ‘like new’ condition.) It’s also a good idea to wrap the vapor barrier and insulation up the foundation walls if you’re in a basement condition (vapor barrier should be continuous under the slab and foundation wall).

Also, as many people said I wouldn’t suggest using radiant heat in the slab if you plan on turning the temp up and down based on when you are in the shop.

pex tubing is great for running the radiant heat and it also easily fits into the same clips that are used for rebar so you can clip the pex tubing directly to the rebar making for a really easy installation. You can then pay a plumber to come in and install the pumps and stuff if you need to.

View canadianchips's profile


2632 posts in 4337 days

#10 posted 12-07-2016 08:34 PM

In floor radiant heat !
I have had 3 different shops in Northern Canada. winters are a bit COLD !
First in floor heat was put in IHC dealership in 1970. Back then they used 1 1/2” black water pipe. Huge boiler.
Fortunately he did put in header system. They re still using that heat today.
2nd large floor heat was in Lacombe Alberta. Truck wash. One side had radiant heat (JOKE) the other side had in floor. The employees used to fight over who got to work on in floor heat side. Recovery time was quicker than radiant side.
Technology has significant changed in last few years. Smaller boilers, better zoning valves.
Cost to put radiant heat in floor is MUCH cheaper than forced air.
Hot air rises naturally…..heat the floor and the rest of room stays warm.
ONE note. You can set thermostat 10-15 degrees lower with floor heat .
Im still sitting on fence about insulating floor…....I would insulate 2ft around perimeter…..not sure I would go extra cost of insulating entire floor.

-- "My mission in life - make everyone smile !"

View shampeon's profile


2167 posts in 3523 days

#11 posted 12-07-2016 10:36 PM

I live in an Eichler house, built in the late ‘50s, with radiant heat in the slab. It’s really nice. Luckily our home used copper pipe, unlike a lot of other houses built earlier in the ‘50s that used black water pipe. The black pipe will fail eventually, causing slab leaks. Detecting and fixing slab leaks is expensive, so a lot of owners just cap off the radiant system and install forced air.

We use a smart thermostat (an Ecobee 3) that learns how to most efficiently turn on/off the boiler to maintain the temperature schedule we set.

I’ve also seen electric radiant heat that goes below the subfloor on top of the slab.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

View RinBarrett's profile


5 posts in 2478 days

#12 posted 12-08-2016 01:03 AM

I’ve heard of electric radiant heat. I wonder if it’s more responsive to temperature change than water. One of the issues raised is that turning the heat up and down takes time. I don’t spend that much time in my home shop so turning up the temp when I want to work for a few hours then down after I quit is a good thing.

-- Rin, Draper, UT,

View TFA's profile


10 posts in 1939 days

#13 posted 12-08-2016 01:38 PM

It’s not the water that doesn’t change temperature quickly. It’s the fact that you have to heat up the concrete slab. That slab is 150lbs for every 2-3sq. ft.. It’s a lot of mass to heat up every time you enter the shop.

Another thing that you could do with the radiant is to move the insulation above the slab, then put your radiant on top of the insulation, then lay your sub-floor and finish floor over the radiant. That way each time you turn on the heat you’re only heating up the wood subfloor and finished floor. You can buy plastic sheets that the radiant tube snaps into and sets up a good base for the subfloor. You will still want a vapor barrier under the slab though.

View AandCstyle's profile


3306 posts in 3597 days

#14 posted 12-08-2016 10:24 PM

Rin, electric is the most expensive way to heat. I found that I could set my thermostat at 50° and leave it. That is warm enough when you are working, but not too warm so you are wasting a lot of energy. FWIW

-- Art

View Andre's profile


5010 posts in 3146 days

#15 posted 12-08-2016 11:49 PM

I have a stand alone 600 sq/ft shop 10ft walls with a 8’ x16’ garage door, I’m heating it with a 20 amp. electric boiler, (pulls an average of 8 amps this time of year) with in slab pex tubing. Had to turn the boiler up this week as it is dropping to – 30 deg. C ( F and C meet at -40) at night at the moment. I have 2” H.D. foam below the slab and put 1,5” 24” deep Vertical around perimeter to create a heatsink. Frost/cold travels below grade at 45 degrees. I live north of Edmonton Alberta Canada and does get a little cool this time of the year. Overall the cost is very low, I suspect less than an Hot tub?

-- Lifting one end of the plank.

showing 1 through 15 of 22 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics