PEX tubing size

[slowTA]

I'm almost ready to buy my supplies to heat my 32x50x12 pole building. It will be insulated with R19 batts in the walls, blown in R30 for the ceiling, and R10 Foamular250 under the slab.

I have quotes from a few PEX supply houses (in order of cheaper to most expensive):
6 loops of 1/2", 12" spacing
3 loops of 5/8", 13" spacing
8 loops of 1/2", 8" spacing
4 loops of 5/8", 10" spacing

Some notes from the last guy I talked to. The smaller tube is easier to work with, tighter spacing and larger diameter means the water temp can be lower to keep the floor at my desired temp.

I won't keep the garage that warm in the winter, maybe 50ish if I know I'll be out there for a while otherwise I'll be happy with just above freezing for the few days we get below zero in North Jersey.

Also, he said to figure on an average of 1 staple every 1.5 feet. But in reality you staple every 2 feet in straight parts and 3 or 4 in the bends.

So what diameter PEX and how many loops would everyone recommend? The price difference is about $350.

 

[Bondo]

Ayuh,..... I'd go with the 1/2" tubin' in as many loops as you want,.....

I won't keep the garage that warm in the winter, maybe 50ish if I know I'll be out there for a while otherwise I'll be happy with just above freezing for the few days we get below zero in North Jersey.

The problem with that is,.... You stand a chance of spot freezin' the tubes,.....
Unless you run antifreeze, rather than water,....

 

[brewchief]

Radiant infloor heat doesn't have a quick recovery time, if you plan on keeping it just above freezing and then turning it up when you are working you may be very disappointed. I fired a friends floor up with temps in the 30s indoors and it took 2 or 3 days to bring up to temp, that's with 1/2" tube at 8" spacing in most of the room(there are 3 4'x8' section that are recessed for snowmobile lifts with no tube).


Sent from my SM-G965U using Tapatalk

 

[klassenl]

When I worked with my dad on projects like this the designers always told us 1/2 tubing with 12" spacing. Coincidentally this works out to 1 foot of pipe for every square foot of floor

 

[slowTA]

I should have phrased that differently. I want to keep the floor set at a steady temp, but if it dips when it is ridiculously cold I wouldn't mind too much. But then that means the system is lagging and probably running all the time!

My issue with the 1/2" tube is that it needs to be closer together which makes drilling into the floor annoying. That said I'm trying to future proof everything and I have a 4 post lift that I never bolted down in my previous garage...

 

[Bondo]

My issue with the 1/2" tube is that it needs to be closer together which makes drilling into the floor annoying.

Ayuh,..... A point, 'n shoot thermometer will tell ya where you can drill,... or not,....

 

[finn]

Point and shoot didn’t work for me, but an infrared camera attachment for my phone did ok.

 

[yeldogt]

People have a misunderstanding of tubing and its relative ability to transfer heat to a slab -- I have done many slabs w/tile using 3/8 tubing -- it will work just as well as any other tubing. The difference: 3/8 tubing will need to be done with shorter loops .. the ability of it to transfer heat to a slab is not the issue.

1/2 inch tubing is commonly specified because it happens to fit many parameters -- because of this ... it's the most common. Most common = cheapest. Why use 3/8 when 1/2 is cheaper and allows for more length per loop .. as long as it fits the specification for spacing and height.

Same with using 5/8 -- 5/8 is not better .. it's different. One also has to think of the water -- how hot does the boiler need to make water to start out cold in a 5/8 tubing for 300 feet vs a 3/8 one over 200?

The OP does not say if he is using NG -- but if he is the cost to maintain 50 degrees in NJ at constant temp with a proper insulated and sealed building will not be that expensive.

5/8 is typically specified for larger commercial buildings where constant temp is desired -- large boilers pushing larger volumes out to the slab.

No question you should do the 8" spacing -- this will allow for faster response. Do you have any areas where you will always be working?

The neat thing about radiant -- you have control of the floor. Most people have a space where they will be working -- or maybe two spaces. It's very easy to serpintine an extra loop in that area ... or to make the loop by the main doors closer together to make a heat curtain to stop drafts. Most people just lay out a static floor even though that's not how they the space.

Think about where you want heat -- and where you just need it warm.

It takes quite a long time for 12" spacing to heat a slab ..... I sometimes do 6" when I'm trying for a low temp output.

If you want lower operating costs ..... more tubing and more insulation.

People make the mistake when retrofitting to go with 5/8 tubing under a floor -- when it's just the opposite .. 3/8 spaced close together.

 

[purplezr2]

I'm almost ready to buy my supplies to heat my 32x50x12 pole building. It will be insulated with R19 batts in the walls, blown in R30 for the ceiling, and R10 Foamular250 under the slab.

I have quotes from a few PEX supply houses (in order of cheaper to most expensive):
6 loops of 1/2", 12" spacing
3 loops of 5/8", 13" spacing
8 loops of 1/2", 8" spacing
4 loops of 5/8", 10" spacing

Some notes from the last guy I talked to. The smaller tube is easier to work with, tighter spacing and larger diameter means the water temp can be lower to keep the floor at my desired temp.

I won't keep the garage that warm in the winter, maybe 50ish if I know I'll be out there for a while otherwise I'll be happy with just above freezing for the few days we get below zero in North Jersey.

Also, he said to figure on an average of 1 staple every 1.5 feet. But in reality you staple every 2 feet in straight parts and 3 or 4 in the bends.

So what diameter PEX and how many loops would everyone recommend? The price difference is about $350.

I would consider adding a hanging furnace, or adding a water to air heat exchanger

 

[slowTA]

Yeldogt, yes, I will be using natural gas. Thanks for the write up.

Purplezr2, I was thinking that a hot air furnace would be a nice addition. But I don't have to worry about that until later.

 

[yeldogt]

Yeldogt, yes, I will be using natural gas. Thanks for the write up.

Purplezr2, I was thinking that a hot air furnace would be a nice addition. But I don't have to worry about that until later.

depending on the boiler and the actual water temp you need -- you can use a fan coil ... or even radiant panels? I have panels in one room to raise the temp.

it all boils down to desire and costs ... with cheap NG there are many possibilities.

 

[slowTA]

Good idea!

What about he XPS insulation. Are these 2 close enough that it doesn't matter which one I use? Formular250 vs. Kingspan.

https://www.lowes.com/pd/Kingspan-I...d-Polystyrene-Foam-Board-Insulation/999972968

https://www.homedepot.com/p/Owens-Corning-FOAMULAR-250-2-in-x-48-in-x-8-ft-R-10-Scored-Squared-Edge-Insulation-Sheathing-52DD/202085962?keyword=Formular250&searchtype=text&semanticToken=200n000100+>++st%3A%7Bformular250%7D%3Ast+cnn%3A%7B2%3A0%7D+cnr%3A%7B8%3A0%7D+cnb%3A%7B9%3A0%7D+oos%3A%7B0%3A1%7D+tgr%3A%7BNo+stage+info%7D+qu%3A%7Bformular250%7D%3Aqu

 

[slowTA]

Also, I'm considering a 7 loop 1/2" system that keeps me at 10" spacing and is $200 cheaper than the 4 loop 5/8".

 

[yeldogt]

Don't use the 5/8 -- it's not required or cost effective.


You will not regret using the 8 loops and closer 8" spacing.

 

[Flail]

I would consider adding a hanging furnace, or adding a water to air heat exchanger

Anyone have any idea how many btus you could extract with a typical car radiator and a box fan hooked up to tha boiler? Essentially a cheap recycled heat exchanger.

 

[Bondo]

Anyone have any idea how many btus you could extract with a typical car radiator and a box fan hooked up to tha boiler? Essentially a cheap recycled heat exchanger.

Ayuh,..... It depends on the size of the radiator,......

Probably more Btu's than yer boiler puts out,.....

 

[slowTA]

Don't use the 5/8 -- it's not required or cost effective.


You will not regret using the 8 loops and closer 8" spacing.

Only if I need to drill into the floor! The common method to drill into a floor is to drill all the way through so a damaged fastener can be hammered into the ground below and a new fastener inserted.

 

[Handyfarmer]

I think they recommend a special type of pex for in the floor heat, and not the standard box store type, something to do with "oxygen barrier pex".

a quick internet search should give one the information,

whatever you do do it right, a few hundred saved now can be very expensive later, and on in the floor heat insulate under the slap, very hard to heat the earth up,

 

[yeldogt]

Only if I need to drill into the floor! The common method to drill into a floor is to drill all the way through so a damaged fastener can be hammered into the ground below and a new fastener inserted.

Sorry -- don't understand.

I will take a guess -- what you are speaking of .....If you are doing a lift -- you lay the tubing out to stay away Otherwise a simple IR camera tells you where the loops are.

 

[slowTA]

I think they recommend a special type of pex for in the floor heat, and not the standard box store type, something to do with "oxygen barrier pex".

a quick internet search should give one the information,

whatever you do do it right, a few hundred saved now can be very expensive later, and on in the floor heat insulate under the slap, very hard to heat the earth up,

I will be buying a radiant floor kit, so it will have the correct PEX. I plan on doing it the right way, or at least the best way I can figure out right now. Thanks for guiding me in the right direction.

 

[slowTA]

Sorry -- don't understand.

I will take a guess rearing what you are speaking of .....If you are doing a lift -- you lay the tubing out to stay away Otherwise a simple IR camera tells you where the loops are.

I have a 4 post that I don't plan on bolting down because it doesn't need it. However, that doesn't change the fact that I might want a 2 post in the future (doubtful, but you never know) and I have no idea where I would want it to go. Most 2 post lifts have a bolt pattern much bigger than 8". So yes, I'll be able to find it but that doesn't mean it will do me any good.

I'm not too concerned about bolting down smaller stuff like a grinder, drill press, or tubing bender but it would still be nice to do it the right way and larger spacing makes that possible.

 

[yeldogt]

I have a 4 post that I don't plan on bolting down because it doesn't need it. However, that doesn't change the fact that I might want a 2 post in the future (doubtful, but you never know) and I have no idea where I would want it to go. Most 2 post lifts have a bolt pattern much bigger than 8". So yes, I'll be able to find it but that doesn't mean it will do me any good.

I'm not too concerned about bolting down smaller stuff like a grinder, drill press, or tubing bender but it would still be nice to do it the right way and larger spacing makes that possible.

I would pick a few spots and make an educated guess -- look at a few examples and get the specifications. 12" does not get you safety -- some of the plates are large.


You want to floor to perform -- that's why I said you look at the whole space and understand where you need more heat and less.