In floor heating vs. radiant vs. forced air in shop??

[patrick_g]

Supply parameters and line diameter?

Egon the line from the first stage reg at the tanks is 3/4 inch and about 50 ft long run to where it branches to two existing 2nd stage regs. Third will be similar (not a separate run from the 1st stage but tapped into where the input to one of the other regs is. The regs are all 3/4 in and 3/4 out. My plumber is also an HVAC sales and installation company so I have no qualms relying on his experience and knowledge. He did fine on all the rest of the house.


Now as regards in-slab heat. It is terrific, a real luxury and maybe somewhat of an extravagance depending on your usage pattern. For infrequently occupied spaces it is an expensive energy wasting system. For often occupied spaces it is cost effective and deliriously comfortable.

It does not lend itself well to areas with rapid shifting temp swings as the thermal mass is so great you can't track the rapid change in demand and will end up under or overheating the space. That said, I love mine but I also have forced air available in same spaces so I can ease up on the slab heat and supplement with warm air and not get the massive over and under heat situations we'd otherwise experience with our wild temp swings. Record in these parts was 80F temp swing in less than 24 hours. Not the typical situation, of course, but an example of when the in-slab system is totally unable to come close to being able to track the outside temp.

If you are in an area where it gets and stays cold with only minor temp fluctuations for considerable periods of time, in-slab is a fantastic choice.

Pat

 

[BradB]

All of the above is good input, hot water radiant floor heat is great from my experience. Plan to incorporate an outdoor wood/coal boiler some day when we can afford an efficient one.

 

[Redneck in training]

I have in floor heat in my 2000sq Ft Basement and in my 1000 sq ft shop. It is heated by an outdoor wood furnace and propane back up. If I built another building, I would do it the same. If you buy the correct Pex tubing, It is not bothered by Concrete. I have a dozen friends who have the same and none have had a leak. I drive my 30hp Tractor on the floor and never have an issue. Plus the floor dries in no time when its 65 degrees. You can run your lines yourself and save some labor but I am a believer in the floor heat method. Like someone stated earlier, It was -25 outside my Garage door and my floor was +65.

MM.

The selection oif PEX depends onthe type of heat source. You can use standard PEX for heat pump but for any kind of boiler you should use PEX with Oxygen barrier to prevent corossion. Do not buy cheap components. One of the best are Rehau.

 

[steveoutdoorrec]

For a slab that size you might want to build in expansion joints so that as the heat comes up it won't crack and leave a place where the tubing might get cut if the slab shifts.

The camp where I work has a dinning hall about twice the size of your planned shop that is heated with radiant heat. The floor is made up of slabs about 9 feet on a side with an inch of silicon between. This is the most comfortable building that size I've ever been in. The ridge is about 30 feet high but the heat stays close to the floor. Wish the camp shop was heated this way.

 

[jdmar]

jgrreed....
So have you decided what to use?
I opened this string up for two reasons.
1) I saw the picture of your dogs...what an amazing view from the porch!
2) I was talking with my fire chief a few days ago. They have radiant in their one station. When they need to drill into the floor they just use their thermal imaging camera and can clearly see the tubing placement. This is one complaint of radiant...not being able to drill safely into the floor after it is poured. But I imagine a local fire station would be happy to help. They are generally very helpfull and supportive of their community. Mine said they would be happy to come out (for me less than one mile) if I needed to verify line placement!
Just an idea I thought I'd pass on...
Peter

 

[jgrreed]

jgrreed....
So have you decided what to use?
I opened this string up for two reasons.
1) I saw the picture of your dogs...what an amazing view from the porch!
2) I was talking with my fire chief a few days ago. They have radiant in their one station. When they need to drill into the floor they just use their thermal imaging camera and can clearly see the tubing placement. This is one complaint of radiant...not being able to drill safely into the floor after it is poured. But I imagine a local fire station would be happy to help. They are generally very helpfull and supportive of their community. Mine said they would be happy to come out (for me less than one mile) if I needed to verify line placement!
Just an idea I thought I'd pass on...
Peter

Hi,

I think I'm going to at minimum lay the PEX lines in the slab. My plumber's trying to talk me out of it, but I've heard too many good things not to.

Great idea on the thermal camera!! Thanks for the compliment on the view as well!!

-Jer.

 

[Redneck in training]

Hi,

I think I'm going to at minimum lay the PEX lines in the slab. My plumber's trying to talk me out of it, but I've heard too many good things not to.

Great idea on the thermal camera!! Thanks for the compliment on the view as well!!

-Jer.

Use PEX with oxygen barrier. It isn't required (but preferred) for geothermal because of low temperatures. It is required for any other source such as any king of boiler to prevent corrosion of ferrous materials.

 

[patrick_g]

Pictures and accurately located datum points are useful too. My finish carpenters drilled a hole to mount a newel post and hit a PEX line dead center. We had to use a small jack hammer to dig out the area, insert a double ended mail barb fitting to fix the leak, and then patch the concrete.

You can put something like a colored piece of plastic (plastic coffee stir stick in the concrete with a little sticking out above the surface to use as land marks to give reference points to PEX locations. This will let you take measurements after the concrete is poured.

Just curious...why should a plumber not want you to put PEX in the slab????????

Pat

 

[2manyrocks]

Great idea about the thermal imaging. I thought any tubing would tend to move during the pour so you can't really end up knowing exactly where it lies.

 

[DRL]

You don't even have to get as high tech as thermal imaging. I've used a IR temp gun to read the temps and find the pex. Move the IR gun slow with the trigger pulled and watch the temp, when it peaks and starts back down you have crossed the line. This method works best if you let the slab cool for a couple of days then turn the heat back on, there will be more temp difference at the tube.

DRL