Radiant heat or not

[raspy]

Yes I think where you live makes a difference. Here in the great white north you need insulation. I would also like to say I think I am correct on if your system isn't pressurized and is open to the atmosphere o2 barrier is a waste of money as your system will keep picking up oxygen from the air. Most outdoor wood stoves are this way. If your system is pressurized it is isolated from the atmosphere. and only the initial oxygen will react with the iron parts of your systen.

Dagny,

Please do some research on what "oxygen permeation" means. It has nothing to do with being open to the atmosphere or being pressurized. It's oxygen molecules permeating through non-metalic tubing from the atmosphere to the water in the system. System pressure has nothing to do with it. This occurs on closed loop systems and leads to rusting of iron parts. When there is an oxygen barrier, this cannot occur and iron parts can be used.

Non oxygen barrier tubing can be used with iron parts if a good corrosion inhibitor is used. This will coat the surface of the iron, aluminum and copper parts in such a way that the oxygen in the system cannot interact with the metal.

"Pressurized" does not have anything to do with corrosion or oxgen in the system. Better terms might be "open loop" or "closed loop". My closed loop solar and my closed loop radiant system are not open to the atmosphere and they are not pressurized. Sometimes they are under a slight vacuum and sometimes they may have a slight pressure increase above atmospheric, but they are not set at normal hydronic pressure of 12 PSI and they are not open loop.

The solar system is subject to possible corrosion because it has non-oxygen barrier, non-metalic tubing and iron in the heat exchangers and pump. But it has a corrosion inhibitor. It also has about 20 gallons of air (at normal atmospheric pressure) that can supply a lot of oxygen for corrosion. No problems with corrosion in the system.

The radiant system is closed loop with a non-diaphragm expansion tank in the attic that has about 3 gallons of air to stabilize the pressure. It uses 3/4" PEX throughout the floor with an oxygen barrier and corrosion inhibitor. No problems with corrosion.

 

[86turbodsl]

im far from an expert, but it seems like the insulation would break down over time. seems like the whole point of having a good base is for the slab to rest on? and I believe blue ridge priced me out a package with non 02 pex

The insulation will support the foam just fine. Most foams used under slabs are rated at 25psi. One square inch of concrete 4" thick weighs less than 1 pound. I figured out once that my foam under my slab will support millions of pounds of concrete with no issues.

 

[Randy in Maine]

You only get one chance to do this right.

Well compacted fill.
6 mil Vapor barrier.
2" foam
1/2" O2 barrier pex attatched to the foam or 6x6 woven wire using clips or ties.
4-6" of concrete. (I used 6" of fiber 4000psi crete in mine 8" under the lift post area). If you feel the need for rebar, use it.

You need to cut stress joints after the concrete is poured. All concrete cracks as it dries, you are just controlling where that happens.

 

[raspy]

You only get one chance to do this right.

You need to cut stress joints after the concrete is poured. All concrete cracks as it dries, you are just controlling where that happens.

Just don't cut the joints with a saw. Use a grooved float tool while finishing. You really don't know where the tube is after the pour. It can be very near the top if the wire mesh springs up or a clip breaks.

 

[Radix2]

You only get one chance to do this right.

Well compacted fill.
6 mil Vapor barrier.
2" foam
1/2" O2 barrier pex attatched to the foam or 6x6 woven wire using clips or ties.
4-6" of concrete. (I used 6" of fiber 4000psi crete in mine 8" under the lift post area). If you feel the need for rebar, use it.

You need to cut stress joints after the concrete is poured. All concrete cracks as it dries, you are just controlling where that happens.

+1

As far as anything floating up, you can place your welded wire mesh on top of the pex. It also keeps the wire from just laying on the bottom.

 

[Radix2]

Insulation prevents heat loss, or slows it. Can you explain where the heat loss is underneath a slab? Not the edges, not the walls or the ceiling. Underneath the slab when it is on dry ground?

What is the mechanism and where does it go? I can see the dirt adding to the mass that must be heated, to a certain extent, but is that energy lost? To where?

Additional mass isn't necessarily a bad thing as it stabilizes the temp. This increases the comfort and reduces system cycling. But it could reduce response time from a cold start.

I'm not telling people not to use it, I'm saying use it where it will produce a benefit, or where the benefit outweighs the negatives.

It gets cold in Nevada too. That's why I have 24" of blown in insulation in the attic, and walls full of it. It's why my radiant slab is insulated all around the edge with 2" Blueboard and the heat is held back from the walls inside. It's also why I went to the trouble to install thermal solar to carry the majority of the heating load. Fortunalely, we are almost always sunny.

The typical earth temp near the surface in OH is in the fifties. If you are planning on heating to room type temps, the earth will **** the heat out down to that temp. On the other hand if you just want frost free, then it makes some sense to just insulate the perimeter to protect from freezing winter temps and let the earth warm the interior - esp for large buildings.

The downside is that these cool slab temps are below the dew point a lot of the time and will tend to give a damp slab unless heated in the warm months.

I actually leave my slab at 45 all winter with very little cost, then need to turn it up in the shoulder months just to keep the condensation out.

Radiant is great for dew point control too.

 

[6768rogues]

In 1993 I built my shop and put in a Reznor hanging furnace because radiant had too high an up front cost. Now the kids are grown, we are retired, and we spend our winters in FL. When we go we turn off our water in case a pipe breaks, so it will only leak the water in the pipe and won’t spray till the place floats away. With a radiant hydronic system, I would have to leave the water on for makeup and I would worry about water, boiler, piping, etc. Add to that the fact that the Reznor cost less than 20% of the cost of radiant, there is zero floor space used for equipment and nothing is in a place with potential for damage, and I am very happy that I did not use radiant.
I insulate the walls down to below the frost line and do not insulate under the floor. I have seen instances where insulated floors had frost go under the insulation to heave the floor. The heat going down through the floor is slight.

 

[bobbyjean]

I have radiant in mine, and it’s great heat, but a waste of money if you aren’t out there every day.

A forced air system will be cheaper and works with a setback thermostat to keep the fuel bill under control.
Having lived with both forced air and radiant, I find forced air cheaper to run and the extra comfort of radiant not worth the extra cost.

Do insulate the slab, install glass and position the building to take advantage of radiant energy from the sun, and insulate the ceiling and walls well.

If I heat my other, non radiant, building daily with the wood stove or hanging gas heater, to keep the slab above freezing, it heats up quickly if I want to bring the temperature up.

I ended up installing a hanging heater in the shop with radiant floor heat also.

i went the hanging heater route sized correctly and it's working out well for me-garage looks great

 

[ford33]

Yes radiant heat is very nice but what do you do in the hot summer months?

Do you buy an A/C unit and put it in the window or maybe install a mini-split A/c unit.

You might look at a DIY mini-split heat pump unit. It provides on-demand heating and cooling. The DIY units can be installed by a homeowner and there are many video's online showing how to do it. No special tools required but common sense is needed.

 

[rburke65]

A foot square of 4" concrete weighs about 50 lbs. sitting atop of 15 psi foam, where as that 15psi foam can support 2,000 lbs. plus. I don't think the foam will compress anytime soon.

 

[JamesW84]

You only get one chance to do this right.

Well compacted fill.
6 mil Vapor barrier.
2" foam
1/2" O2 barrier pex attatched to the foam or 6x6 woven wire using clips or ties.
4-6" of concrete. (I used 6" of fiber 4000psi crete in mine 8" under the lift post area). If you feel the need for rebar, use it.

You need to cut stress joints after the concrete is poured. All concrete cracks as it dries, you are just controlling where that happens.

Is 6 Mil thick enough? I'm shopping for mine and I'm looking at 15-20 mil because I read that the 6-10 could get torn and defeat the purpose.

I wanted radiant at first, but since I will only be out there weekends and maybe a night or two during the week, it doesn't make sense for me as far as I can see. When I was getting quotes a couple years ago (mine has been a long time coming), it seems like I remember the concrete guy saying I'd need 6" concrete to have room for rebar and pex. The extra concrete is an added cost.

 

[Randy in Maine]

6 mil poly is fine. Taping the joints is a plus. That is what everyone commonly use.

It is your money and your shop and your opinion is what matters.

In my case, I am only out there on the weekends also and maybe a day or night during the week, but all of my stuff is out there all of the time winter and summer. No rebar in my 40x28 slab on footers for our 48" frost depths. I did use 4000 psi concrete with the fiber mesh and really no cracking to speak of. Mine is built on really well compacted fill and the "dryer" concrete normally cracks less (according to the concrete guy) with good concrete cutting. Summers here at fairly mild and I do OK with my 2 ceiling fans and 2 Vornado window fans when needed. I run a dehumidifier when it is needed. I don't have AC in the shop or my house as it really is not needed here in Maine at the beach. The midwest or the south is different.

I spilled about 1/2 gallon of gas out there last weekend and once more I am glad I do not have a source of ignition out there (I pump 120º water from my house boiler to warm up the floors. No pilot lights or anything like that in the shop ). I just opened up the doors and windows and to let it air out for a couple of hours and it was OK. My 21 cubic yards of concrete floor = about 42 tons of thermal mass and it stores a lot of BTU so it warmed up nicely after that little event. The pex runs are about 12" OC but don't over think that. Somethings (like a lift post or the air compressor) needs to be epoxy bolted into the floor, so you just don't want any tubing about 3-4' where that happens. Your are essentially heating up a big rock of concrete and it will all equalize itself. I have never noticed hot or cold spot in the floor but I am never out there barefooted to actually feel any either. The cars, the tablesaw, and the paint really don't care about any of that. They all stay nice and warm all winter for as little cost of fuel as I could make it.

 

[kabinenroller]

You only get one chance to do this right.

Well compacted fill.
6 mil Vapor barrier.
2" foam
1/2" O2 barrier pex attatched to the foam or 6x6 woven wire using clips or ties.
4-6" of concrete. (I used 6" of fiber 4000psi crete in mine 8" under the lift post area). If you feel the need for rebar, use it.

You need to cut stress joints after the concrete is poured. All concrete cracks as it dries, you are just controlling where that happens.

YES! I totally agree. In addition to what is stated above I insulted the foundation walls on both sides with 2” and 1” blue board. Mine is stick built 40x60x10 with a vaulted ceiling for the lift. My walls are 2x6 with roll insulation in the walls, 1” foam on the exterior and Tyvac wrap around the vertical perimeter. I installed the tubing on 12” centers and I held it back 2’ from the R-16 overhead door, very seldom do I see melted snow outside the door. Most of the time the snow piles up against the door. I keep the temp at 60 degrees 24/7/365, you should not “play” with the thermostat on a hydronic system.
This method works very well for my application, I doubt if I would do anything different if I was to do it over again.

 

[Jackfre]

On the topic of O2 barrier tubing vs non-barrier tubing, I think it is penny wise and pound foolish to scrimp on this part of the system. Use the best tubing you can get and that is barrier tubing. That is one part of the system that you cannot change. I was recently out on a job where a homeowner self-installed a really nice high efficiency boiler. One year later, I began taking it apart and the boiler was destroyed. It was so gummed up it was incredible. Non barrier tubing and not understanding how the system would work were the result and there was no warranty support. There were all kinds of mistakes, but that was the biggest. As Raspy pointed out, you may be able to do it with non-barrier tubing, but then you are playing chemist all the time. Ph is important in any system and it is required that it be checked and in spec on almost all boilers I am aware of, but don't make a hobby of it. I would never install an open loop system.
If you have the resources and want to do the work for radiant, you will like it, but, look at Dagny's post. I'd chose to spend the money on tools and materials rather than the radiant and I am perfectly comfortable in the shop without radiant.

 

[JamesW84]

6 mil poly is fine. Taping the joints is a plus. That is what everyone commonly use.

It is your money and your shop and your opinion is what matters.

I knew I read somewhere that 6 mil wasn't thick enough. Not to argue, but to provide more information for those interested:

"Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons:

Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.
6-mil plastic often gets damaged during placement of reinforcement and concrete, creating holes that can let a considerable amount of water vapor into the slab."


https://www.concretenetwork.com/vapor-barriers/what-are.html

I doubt most really know the vapor barrier is a problem, they just know their concrete floor is damp, etc and that's just how concrete is.

I'm no expert, I just read that at the above site.

 

[Randy in Maine]

Well I used the 6 mil myself with 2" of foam on top of it and my floors are never wet from upwelling groundwater. I had a really good concrete guy though who supervised the pour.

Try the 10 mil and report back your findings. It is your garage and your money.