In-Floor Heating for a Shop & Greenhouse - Considerations ?

[PandDLong]

I am in the process of putting up a multi-use building - Building a shop / shed / barn / greenhouse

It will have a shop area about 28' x 30' that will be insulated with a finished interior and a concrete slab for the floor. I want to be able to heat it but only from time-to-time when I am working on a project (or repairs). I am thinking it is likely to be for a few days at a time every 2-4 weeks and then I can let it revert to being unheated. I have an oversized attached garage that I keep heated and above freezing all winter where I store all the various products and items that can't freeze.

I will also have an attached 8' x 16' greenhouse lean-to that will have a concrete floor. The greenhouse is a season extender rather than being in use all year. My frost-free period is mid-May to early-September so adding a couple months on each end makes a big difference.

My contractor recommended I install piping for in-floor heating and the slab will be insulated properly for it. I gasped a bit when I got estimates for a natural gas boiler and installation so I am not convinced I will go that route, but if I don't add the pipe now, I can't do it later. So I am going ahead with the piping - the cost of the pipe isn't much and I am going to lay it myself.

Now I realize, I need to make a couple decisions just to be in-floor heat ready - where will the boiler go and where will it vent? I am a bit challenged as I can't find a local place where I can go in and see what a full setup looks like and the space it needs on the wall.


For those with in-floor heating:

1. Any specific considerations I should make for boiler location?

2. Do you recommend in-floor heat and would you do it again?

3. If it is gas or propane, is it vertically vented or just out the wall or out the wall and then vertical?


Any recommended dos/don'ts for laying the pipe?

For those that have the piping for in-floor heat but don't use it - why not?


Thanks for your collective wisdom!


Michael

 

[Jims1025R]

I have done in floor heating in both my attached [to house] garage, and my separate workshop. I am very happy with both systems, but yes, the boilers are expensive! My heating expert made the design recommendations for me, and I did the work laying the pipe. There are many considerations. I don't claim to be expert at it, but it seems that I have avoided mistakes which could have been made - both systems work excellently.

I like the insulation which is like Lego, the pipe snaps in. For my garage, I stapled the pipe to plain insulation - more layout, and requires two people - Lego insulation much better result. It also keeps the pipe safe when you walk on it (the concrete floor guys are casual about this!). You're supposed to protect the pipe from sunlight, so I sewed up protective "socks" from old tarps for the pipe which would remain exposed after the floor was poured (I also used the same pipe for compressed air outlets around the shop).

Use plastic rebar chairs to keep the rebar off the pipe, and in the middle of the poured slab. The rebar also keeps the pipe down, so it does not pop up during pouring, you don't want the pipe near the upper surface of the poured slab, in case you drill a hole for something in the slab later.

If the floor could be left unheated for any period, use glycol in the system. I just use water, but I never let it freeze. When I first "started" the garage floor, it was just at freezing, and the floor water froze a little in one corner. I had to use a heat gun on the floor to get it flowing, and it worked.

Arrange your loop terminations neatly where they come out to the boiler, you'll be happy you made the effort later. Make sure your gas line is coming to the same place as the loops come out of the floor! I put in a lot of in floor conduit for electrical, and one for a gas line. My boiler is in the enter of the workshop, mounted to a center pillar, as that worked better for my arrangement. But I expect that most boilers are placed on a convenient wall. My air and exhaust go straight up, out a roof chimney.

The floor holds heat really well, and is nice when you're going to lie on it to work under a machine! I would do this for every floor I would ever pour!

 

[Rustyiron]

In floor radiant shines for steady comfort but for your infrequent use, explore other means.
With radiant you'll need hours to heat up your shops slab and everything in it only to shut it down. It's arguable that leaving a radiant system with a well insulated building "on" for the season at a much lower temperature your fuel use could be similar "spot heating a couple of days every 2 weeks. Insulation is everything regardless of how you heat in terms of economy.

 

[PandDLong]

In floor radiant shines for steady comfort but for your infrequent use, explore other means.
With radiant you'll need hours to heat up your shops slab and everything in it only to shut it down. It's arguable that leaving a radiant system with a well insulated building "on" for the season at a much lower temperature your fuel use could be similar "spot heating a couple of days every 2 weeks. Insulation is everything regardless of how you heat in terms of economy.

That's a good point - i have heard that once it is warm, keeping it a low temperature takes little energy. So it may be less energy to heat and keep at a low temp than cycling hot/cold. May take a bit of experimentation to find the right balance.

For my immediate and intermittent needs, a simple blower may be a cheap solution. Perhaps I will do that while I debate the merits of buying the boiler.

I should add that I can envision that in a few years, when I move to semi-retirement - and beyond - I would spend more time in the shop. Perhaps I make in-floor heat ready now and install the boiler when I begin to use the shop on a more frequent basis (or I find a bargain).

Michael

 

[PandDLong]

I have done in floor heating in both my attached [to house] garage, and my separate workshop. I am very happy with both systems, but yes, the boilers are expensive! My heating expert made the design recommendations for me, and I did the work laying the pipe. There are many considerations. I don't claim to be expert at it, but it seems that I have avoided mistakes which could have been made - both systems work excellently.

I like the insulation which is like Lego, the pipe snaps in. For my garage, I stapled the pipe to plain insulation - more layout, and requires two people - Lego insulation much better result. It also keeps the pipe safe when you walk on it (the concrete floor guys are casual about this!). You're supposed to protect the pipe from sunlight, so I sewed up protective "socks" from old tarps for the pipe which would remain exposed after the floor was poured (I also used the same pipe for compressed air outlets around the shop).

Use plastic rebar chairs to keep the rebar off the pipe, and in the middle of the poured slab. The rebar also keeps the pipe down, so it does not pop up during pouring, you don't want the pipe near the upper surface of the poured slab, in case you drill a hole for something in the slab later.

If the floor could be left unheated for any period, use glycol in the system. I just use water, but I never let it freeze. When I first "started" the garage floor, it was just at freezing, and the floor water froze a little in one corner. I had to use a heat gun on the floor to get it flowing, and it worked.

Arrange your loop terminations neatly where they come out to the boiler, you'll be happy you made the effort later. Make sure your gas line is coming to the same place as the loops come out of the floor! I put in a lot of in floor conduit for electrical, and one for a gas line. My boiler is in the enter of the workshop, mounted to a center pillar, as that worked better for my arrangement. But I expect that most boilers are placed on a convenient wall. My air and exhaust go straight up, out a roof chimney.

The floor holds heat really well, and is nice when you're going to lie on it to work under a machine! I would do this for every floor I would ever pour!

Super useful post and pictures - thanks so much.

I definitely like the advantages of the "Lego" - I will definitely look into getting that. Is it a thin sheet which sits on top of your slab insulation or does it replace some of the slab insulation (I am currently planning for 3" of insulation under the slab)?

I like the look and advantage of the conduit sweeps and verticals where your pipe comes up to the boiler area. The only in-floor heating system I have seen roughed-in just had exposed pipe coming up the wall.

I hadn't thought of conduit for the gas line - I have been wrestling with the fact that the logical entry for the gas line is on my south wall but the logical place for the boiler is on the north - conduit across the floor seems like an elegant solution.

That's a busy floor. Do you have an "after" picture - particularly of your boiler setup?

Michael

 

[Jims1025R]

You can zoom into the middle of this photo, and see the boiler (white) on the pillar wall, the wood stove is behind it (for quick heating!). The boiler plumbing is quite something, you'll need someone familiar to do that.

 

[Rustyiron]

Keep in mind that all an in slab radiant system needs is around 110* +/-. A simple job for even a regular hot water heater.
My design guy suggested a "Bock" hwh that has a separate supply (from domestic hw) for radiant heating. My choice of fuel was oil and this is used up until we fire our (indoor) wood boiler.
Imo the white "coffee cup" (Lego) foam is very convenient for the installer but severely lacks in actual insulation value compared to the blue or pink foam. Stick with your proposed 3" that will reward you forever despite the grumblings of the installer.

 

[PandDLong]

Keep in mind that all an in slab radiant system needs is around 110* +/-. A simple job for even a regular hot water heater.
My design guy suggested a "Bock" hwh that has a separate supply (from domestic hw) for radiant heating. My choice of fuel was oil and this is used up until we fire our (indoor) wood boiler.
Imo the white "coffee cup" (Lego) foam is very convenient for the installer but severely lacks in actual insulation value compared to the blue or pink foam. Stick with your proposed 3" that will reward you forever despite the grumblings of the installer.

A HWH certainly has a different price point.


Since I am the installer I guess I will need to keep the grumbling to a minimum

 

[newbury]

Since I am the installer I guess I will need to keep the grumbling to a minimum

That happens a lot with me. Generally the guy ordering the installation (Me) dreams up things to improve the process overnight, then Me, Myself, and I talk it over in the morning and come up with a plan.

 

[MAX-24-Dean]

I heat a 24' x 32' shop with two 1500 watt electric heaters. R30 in the walls, R60 in the ceilngs. The 5 1/2" Concrete slab has 6" of closed cell foam under it. The thermal mass of the concrete keeps the Temps above 55° F for several days. The heat is only on if the Sun is shining. Solar is only source of power.
If the temps get below 10° F, I have to supplement the electric with a 12,000 btu propane heater.