Questions about radiant floor heating

[fatjay]

This is all fairly new to me but I've done a lot of reading and want to make sure I have what I need. If any of my understandings are wrong, please let me know.

Structure is 24'x44' with 8" walls, the idea was to run 4 runs per circuit putting me at 32 runs with 8" spacing, which would be 8 circuits.

This is the tubing I was looking at. I figure 2 spools of that will put me at 500' to spare: https://www.pexuniverse.com/bpr1210-1-2-x-1000ft-oxygen-barrier-pex-tubing


The manifold would be something like this to bring it together: https://www.pexuniverse.com/ssm208-steel-radiant-heat-manifold#

I need a pump and a water heater. I want it to be electric, something like those instant hot water job's. As far as I know that's all the components of it.

 

[78SC4X4]

FJ - There's a bit more to it than that. I don't understand what the walls have to do with it and why you are going for 8" spacing. What kind of floor are you installing this in? (slab or joist)

 

[fatjay]

Poured 6" concrete slab with insulation. The walls help me determine the actual area of the slab, 44' is 42'8", 24' is 22'8" on the inside. Everything on the internet I was able to find said recommended spacing is 8", or down to 4" when the circumstances are not good.

 

[78SC4X4]

You want to install the insulation around the perimeter and under the slab. A typical layout is 12" spacing. So you need about 1000' of tubing. Keep the runs at about 250' each. You'll only need 4 runs in a single zone. Poke around in this forum, you'll find lots of folks that have used this approach.

 

[fatjay]

This is going to be a multi-floor garage and I want to be able to heat the upstairs as well (on a separate circuit) in the future if the need arises. There is perimeter insulation as well as under slab insulation.

 

[SGKent]

we had it in San Mateo when I was a kid. Hated it. I like forced air. You'll want to filter the air in the house anyway, so you might as well condition it too while moving it around to filter it. I also had radiant ceiling and floor heat in San Diego and it was too expensive to operate.

See if any of your neighbors with similar homes have it and what it costs them to operate VS other forms of conditioning/heating.

Be sure you document where everything is in case you need to nail or screw something down someday. Expensive repair if you hit it accidentally.

 

[yeldogt]

Are both areas/ levels 6" slabs ?

I'm confused about the terms as well. What are runs ? I guess a circuit is a loop on the manifold?

Radiant design can be tailored to the building or just done for coverage depending on intended use. There are many piping strategies ..... have you done a heat load?

I never do 12" -- always less. Lower water temp and faster response -- PEX is cheap.

 

[BD1]

You only want to do this once. Contact a local heating contractors for estimates and engineering. Everyone has opinions, yes they work. But are they efficient ?
I did this with copper tube in the old days. Today's plastic tube is great. Pay a few bucks and have it enginneered.


Sent from my iPhone using Tapatalk

 

[bimmer1980]

You'll need to do a bit more reading...... A few other things come to mind that you will need.... Air separator, expansion tank, etc.

Good luck with electric. That will be expensive to operate over time......

I would recommend natural gas if you have it available.

I'm pretty happy with my natural gas boiler for my garage. My brother was trying to run electric heat in our other shop in SD and it was $400 per month in electric. I had a high of about $120 per month. Most months are $75 to $100, pending on the temp I set it at and the degree days.......

Lots of variables here.....

 

[Randy in Maine]

Unless you get your electricity for free, you may want to find a better way to heat the water. I ran my 1/2 O2 barrier pex about 12" on center and it is fine. Even if you miss a few areas (like under or near your lifts) it is also fine. Mine is very comfortable and cheap to heat.

You are essentially heating a rock just as the cavemen did, so it is really not all that difficult. Don't overthink it. Paying a pro to set it up would be cheap money well spent.

 

[tdkkart]

24 x 44= 1056sq/ft, unless you live in the arctic, 1ft of tubing/sqft is more than sufficient. So 1100 feet of tubing, with a max of approx. 300ft per loop gives you 4 loops of just under 300ft each.
2nd floor can be done the same, off the same control circuitry and a priority based setup so it's not trying to heat both levels at the same time.

Use a 4 loop manifold downstairs, and another upstairs.

Yes, electric heat is expensive, but some people can't seem to grasp that you might not have a choice. AND, electric is very safe, no open flame to deal with around chemicals, dust etc. I heat a 30x40 with a 14KW electric heater, works fine.

 

[That1Guy]

Lots of great advice here Jay. Another thing I would emphasize is that insulation is EVERYTHING!! Money spent up front adding extra insulation will be money saved - multiple times over - down the road. Trust me on this but please dont ask me how I know - lol. Regret is an ugly (and potentially expensive) thing! Far better to err on the side of excess than to cut corners
trying to save a buck. It doesn't work that way. I made much better choices this go around. Lessons learned!


Be careful if you go with that 8" spacing not to make the bends too tight. If you kink that pex, there's no fixing it. You'd have to either patch it - which is a no no! or replace the entire loop. You could get away with it by either having big turns at the ends of the runs or by using some really creative routing that avoids sharp bends.

And I agree with the others that electric, although the only 100% efficient method, is by far the most expensive. I'm running an electric water heater and I'm so afraid of our first electric bill, I'm actually pricing out the cost of running a NG line out to the barn. I originally went electric because A)I was given a brand new (never connected) electric water heater. And B) I don't want to penetrate my walls or ceiling, let alone the roof, for a gas line or an exhaust pipe. But after reading so many nightmare stories about electric bills here, I think I'm going to bite the bullet and run the line and buy either a high efficiency water heater or a micro-boiler. That way I can at least vent it out the wall instead of the roof. If the electric bill is going to be as high as I think it might, I'll be better off spending the money now up front rather than spending far more further down the road. I'm not sure of your electric/gas situation but I'm looking forward to watching your progress and see how things work out for you. Best of luck on this build and please keep us posted.



SGKent - that is the first time I have heard someone who had both systems state a preference for forced air over hydro/radiant. Very interesting. I'd honestly love to hear more details.


*edit*
One other thing Jay, I would suggest that when you pick a manifold, try to order one with an extra circuit or two. Ya never know if you might want to add a loop somewhere or a water/air fan coil. Just a thought.

 

[yeldogt]

Lots of great advice here Jay. Another thing I would emphasize is that insulation is EVERYTHING!! Money spent up front adding extra insulation will be money saved - multiple times over - down the road. Trust me on this but please dont ask me how I know - lol. Regret is an ugly (and potentially expensive) thing! Far better to err on the side of excess than to cut corners
trying to save a buck. It doesn't work that way. I made much better choices this go around. Lessons learned!


Be careful if you go with that 8" spacing not to make the bends too tight. If you kink that pex, there's no fixing it. You'd have to either patch it - which is a no no! or replace the entire loop. You could get away with it by either having big turns at the ends of the runs or by using some really creative routing that avoids sharp bends.

And I agree with the others that electric, although the only 100% efficient method, is by far the most expensive. I'm running an electric water heater and I'm so afraid of our first electric bill, I'm actually pricing out the cost of running a NG line out to the barn. I originally went electric because A)I was given a brand new (never connected) electric water heater. And B) I don't want to penetrate my walls or ceiling, let alone the roof, for a gas line or an exhaust pipe. But after reading so many nightmare stories about electric bills here, I think I'm going to bite the bullet and run the line and buy either a high efficiency water heater or a micro-boiler. That way I can at least vent it out the wall instead of the roof. If the electric bill is going to be as high as I think it might, I'll be better off spending the money now up front rather than spending far more further down the road. I'm not sure of your electric/gas situation but I'm looking forward to watching your progress and see how things work out for you. Best of luck on this build and please keep us posted.



SGKent - that is the first time I have heard someone who had both systems state a preference for forced air over hydro/radiant. Very interesting. I'd honestly love to hear more details.


*edit*
One other thing Jay, I would suggest that when you pick a manifold, try to order one with an extra circuit or two. Ya never know if you might want to add a loop somewhere or a water/air fan coil. Just a thought.

Doing 8" is not a problem ..... you can also do double serpentines to increase piping. Also any kink can be fixed with heat .....

I just installed close to 10k feet of pipe in my new house. Using both 3/8 and 1/2 regular PEX and 1/2 PexAlPex