Installing Radiant in my garage, I have a bunch of ? head is spinning

JoeG

Hi, I am putting up a 28 X 28 Garage, first floor will have 10 Ft ceilings, the Second floor is just for storage and will have 8 Ft Ceilings, The first floor ceiling will be insulated.



I am getting a 1000 Ft roll of 1/2 In tubing and will be putting down the insulating tarp below it.



I am not adding the actual heat source yet, prob will do that next year but want to get the pipes run now.



I won't have a full time water source out thee for a while I can reach it with a hose to charge the system.



What kind of heater should I use? I have choice of electric and LP, I am unsure if I should use a 40 or 50 Gal water heater or a Instant Heater Elec or LP?



Thoughts? Thanks



P.S is Radiant even the way to go, I plan to keep the heat around 50 Deg I don't want to spend a fortune to heat the place, Just want to keep stuff from freezing.



If I was going to be out there for a while how long would it take to raise from 50 Deg to say 65 ot 70? if out side temp say was around 30 Deg.

Zman

Suggestion

First of all "insultarp" is not a very good product for radiant. The r-values advertised are not true r-values. I my area it is not allowed by code.Use rigid insulation.



I don't think your garage is a very good candidate for in floor radiant. The install cost is going to be quite high and you won't be able to just turn up the temp to work on that one project. Given your lack of available water and the potential for freezing, I would reconsider.



The least expensive solution would be electric fan coil heaters, although they are more expensive to run.

A gas fired heater, like the Modine "hot dog" would also be a good choice.



Carl

JoeG

Cost

I was thinking of doing four loops, I want a heat source that I can keep

the temp up enough to keep things from freezing all winter long, I also

don't want to spend a ton of money to heat it. If I need temp up quick I

can always get a salmander or something like that for a quick heat

boost.



 I am looking at a total cost of about $2,000 to do the job.

Zman

Why?

Why do you want to put radiant in a garage? I don't see any advantages.

I don't think you could buy the parts to do the job "wrong" with your budget. You certainly can't do a quality install.

JMO

Carl

JoeG

Price

That Price is just, for the Insulation,Tube and install that doesn't include the Manifold or fiting's or the Heater.



I figured that it would keep the building at about 50 Deg and do it cheaper per month then other heat sources. Am I wrong about this?



I know the up front cost will be more but I don't want a very expensive monthly bill.

Zman

I see

A nice infloor system with a high efficiency boiler will use less fuel than other options. It will also react very slowly, and have high install costs. A less expensive infloor system with a hotwater heater or electric boiler will not offer any savings in efficiency. Look at the efficiency ratings on the appliances. I love infloor heat but would not install it in your application, even if money was no object.

Carl

JoeG

Why

How come you would not in my application, Everyone that has it in there garage that I have talked to loves it. Can you go into some detail as to why. and what you suggest and why. Thanks

Zman

Lag time

I also like to keep my garage around 40- 50 degrees.It costs very little to keep an insulated building at this temp. If I am working on evening or weekend projects, I turn it up to 65. You cannot do this with infloor. It would take a day or more and it would likely overshoot your target. Most people I know with infloor garages end up keeping the temps higher, thus using more energy. Unless it is a full time workplace or you are trying to melt snow off vehicles You are going to spend 2 or 3 times the money for infloor, then fire up a salamander? I don't see the logic.

Just my opinion,

Carl

JoeG

Freezeing

I want to keep the building's contents from freezing, I don't need to work in a t shirt. I just figured this would be the cheapest way to go.



Am I wrong in my thought, do you think it would be better to use a over head blower type heater to keep it at a constant none freeze state?

SWEI

insulate, insulate, insulate

Under the slab, in the walls, and of course the ceiling/roof.  Spend more on insulation and less on the heating system -- you'll thank yourself later.

STEVEusaPA

a few thoughts....

1.  If your not gonna run any loops to the driveway for ice melt, or use the same boiler to heat a swimming pool in spring/fall, I would forget the radiant....and I love radiant. 

2. Based on what you say your needs are...I would put in a mini split.  You get heat and AC.

JoeG

Mini Split

How much am I looking to spend on a mini split and what type of gas do they run or is it elec? You guys are teh onlys I have heard talk Neg about radiant for my situation.

Gordy

Negative about radiant

Personally I think concrete with out radiant is a shame in a controlled envelope. Snow melt is a rich mans waste of energy.



The point being made is that unless this is going to be a garage where you are going to work all the time thus maintain a temp that is going to be worth having a nice radiant floor setup. It's more beneficial to have some heat that can bring temps up faster than radiant can in concrete. Radiant floors take time to bring aspace up to a desired temp. So going from say 50 to 65 takes some planning ahead to work out in the garage for a brief time, and then turn the heat back down.



Concrete is mass which takes time to heat.





For a budget of 2000 dollars you can't do radiant right in a 28x28 garage. Tubing, insulation, manifolds, heat source, and plumbing will be way over that if you could even do it all yourself.



You could do it in stages though. Insulate the slab 2" xps. put the tubing in the concrete in loops of 200'. Then wait until you can afford a decent boiler.



Gordy

JoeG

Confusion

Guys, I know I can't do the whole thing for two grand, What I am saying is the floor will be poured in two weeks, for under two grand I can Insulate and put the tubing in, 4 loops.



What I want to do is keep the stuff I store out there from freezing and get a salmander or somthing like that to bring it up to temp fast if it is cold in there and I want to work.



I want the radiant to keep stuff from freezing and keep the garage and a constant temp of around 50 DEG. I do not need it to go from 50 to 80 in a few Min, just nice constant temps above freezing and I want to be able to maintain a above freezing temp for the least amount of money and I thought radiant would be the way to go maybe I am wrong.



It seems like I may not be explaining it right.

Gordy

Understand

That a lot of people think that you can throw a bunch of tubing in concrete, add a heat source say a water heater, viola radiant simple, and cheap. Only to be disappointed with the outcome, and deem radiant heat a poor choice. Because certain expectations are not met which radiant may not be capable of. Radiant heat installation is a science to work efficiently.



So everyone must be thorough when answering questions. No one knows the knowledge, or abilities of posters asking question about radiant heat.





Yes it will work for what you want it to do. .



A mini split is electric, and can provide heating, and cooling.





Gordy

Zman

Thorough

Gordy makes a good point that we all need to be more thorough when posting.It can also be a problem with clients

For the reasons previously described, If it were my garage, I would do the following;

Insulate the structure well

Install a quality insulated garage door and windows

Install a heater like this one http://www.grainger.com/Grainger/DAYTON-Electric-Utility-Heater-3UG73?Pid=search   on a low temp thermostat

Save a bunch of money



If you want a future infloor option, install your 1/2" tubing in 4 loops of about 200 feet. 12 inch spacing should work fine. It will perform best with 2" ridged insulation underneath and should be suspended so it is centered in the slab.



It is rare for the guys on here to try to talk people out of radiant. It is a great product, maybe not for your application.



Carl

JoeG

Heat

The guys installing the radiant said they would space it 12 " apart  and there would be four loops I think about 250 ' each run,



I am not trying to be a pain in the rear I just want to make the right choice, so you think that installing that elec heater will be cheaper to run keeping the garage at a steady 50 Deg all winter? Like I have said I am not looking to go into the garage and crank the heat and think it is summer in there, I just want the paints and stuff not freeze, I can get a second heater that runs on kero or something for the quick heat blasts if I need it.



I want to learn and I am listening to what your saying, But you guys are going against everything I have heard and read and I am not saying your wrong and that is why I am posting here to hear it from the pros.

Zman

Heat

4 loops at 250 will work fine. They will probably end up closer together than 12", not a bad thing.I don't like to see loops longer than that as it begins to effect flow rates.

The electric vs. propane question would require some more info. Post your cost per gallon and KW and I can tell you.I am fairly sure price difference will be slight.

Carl

JoeG

Zman

What I mean is what would be cheaper to run to keep garage above freezeing the radiant or the hanging blower heater? I know they make the hanging ones in Elec and gas.

Zman

Rates

Radiant is not inherently more or less efficient than convective. A BTU of energy that moves from fuel to water to slab to air, Is no different than one that goes directly from fuel to air. You tend to "feel" warmer with radiant allowing the actual room temp to be lowered.



In your application if you assume the efficiency of the appliance is the same ie an 80% efficient gas fan unit compared to an 80% gas hot water boiler. The overall efficiency should be pretty close. I would expect the radiant would be slightly less efficient due to the tendency of high mass slabs to overshoot the target temp.It is just hard to stop the heat gain momentum as the outdoor temp warms. The heat has been applied to the slab an want to warm the air whether you need it or not.



The same would be true for electric.



To compare propane to electric, post your local rates.



Carl

JoeG

So

So you are saying that say I used a Propane hanging heater that is 80% and a Propane Water heater that is 80%, I would spend about the same to keep the garage at a constant temp all winter long, even with doors being opened to go in and out and what not, i just figured the Hanging would kick on more often. and this is at 50 Deg set temp..



Do you have Hanging gas heaters you recommend? I am unsure of the rates off the top of my head, propane depends on how much you use for the rate, I use it now for hotwater and coking.

Zman

You got it!

That is what I am saying. When you open the door with radiant you get a call for heat just like with the fan coil, you loose the same amount of energy. Look at the efficiency ratings of the heat source. A domestic water heater will be in the 70's (don't do radiant with this) a mod con boiler will be in the 90's (these are pretty expensive for garage boiler).



A modine "hot dawg" is 80% efficient. They work quite well.



The electric option will be a less expensive install. Your local rates will determine the payback. Propane prices can be hard to pin down. I comes down to the average price. Propane prices are historically lowest in August, I always top off then.



Carl

JoeG

Can you

Zman can you point to some diffirent heater options that you think would be good for me.

SWEI

depending on rates

and your climate, and how long of an ROI you are willing to tolerate, a heat pump might make sense for this.  Perhaps a mini-split with two heads?

JoeG

Can you Guys

Can you guys post some links of heaters you suggest.

SWEI

more info needed

Need your heat loss and outdoor design temp.

JoeG

Ill try

Not sure how I would figure out my heat loss for you, Building is 28 X 28 10 Ft ceiling first floor and 8 foot second floor, the second floor is 16 x 28 x 8. Second floor unsure if Ill have separate heater or try and heat off first floor. Ill have 3 Windows down stairs double hung new 28 x 53. 1 16 Ft door in front and one entry door on the side with a hay type door for second floor unsure exact size at this time.





Winter temps average 20 to 30 Deg with single digits at time overnite.

SWEI

heat loss

Is a number based on the ASHRAE winter design temp (which you can look up online, use the 97.5% one and not the 99% one) along with the desired interior temperature (say 50F for a garage) and the building envelope U-value.



http://www.greenbuildingadvisor.com/blogs/dept/musings/how-perform-heat-loss-calculation-part-1 will get you started.  There are plenty of online tools and spreadsheets to help.

JoeG

Lost

I read though that article and now I see why I am not in the heating and cooling business, I have no idea what my heat loss is.

Gordy

Found

Your garage with 2x4 walls insulated r25 ceiling couple doors windows ect is right around 31000 btus if its -9 design day in your area at 60 degrees indoor temp.



4 loops at 200' plus leaders to the manifold at 12" centers. If you bought 1000 foot roll tighten up to 8" centers infron of the garage doors for about 4' in.

JoeG

2x6

Going to have 2x6 walls. Thanks for helping figuring that out.

Zman

Little High??

I am having trouble with the heat loss of 31,000 on a 784' garage. I know it is difficult to do a loss calc with the info provided. I think it is likely 1/2 that.

As for the heater recommendations, I have used dayton electric fan coils and modine "hot dawg" with good results.

I don't mean to critique Gordy (He consistently provides good advice) I just can't get my head around 40 BTU/ft in a garage.

Carl

Gordy

Zman

Your right, and so do I. I just through some provided info into heat loss explorer 2 , and that's what it spit out. That program seems to hit high on garages for some reason. But on the other hand we do not know doors window numbers, and garage door types.





Gordy

RobG

Radiant in garage

No matter how you heat your garage, insulation and air sealing are the key to saving energy (and the cheapest way with the highest ROI). Insulating under the slab should be done whether or not you do radiant. That said, why not install the tubing. You only get one chance, once the slab is poured, that's it! You can install an electric heater until you can afford to finish the radiant properly or you can keep on using the electric if you find that it suits your needs. In the big picture a 1000ft roll of O2 barrier pex should not break the bank.

Just my opinion,

Rob

JoeG

Tube

I am going to put it in even if I don't use it, I am stuck on Insulation now, You guys seem to say the foam, I called around to some different contractors around here and some heating warehouses and they all seem to use the tarp.

SWEI

please read this thread

http://www.heatinghelp.com/forum-thread/142427/What-kind-of-insulation-do-you-guys-recommend-How-is-the-tarp-stuff

Gordy

Save the tarp

For covering boat,firewood,old car, duck blind, etc. use 2" xps.

JoeG

Insulation

The insulation is there to keep the heat from going into the ground correct? 

Gordy

Correct

You want the heat to go to the garage not in to the ground

JoeG

Heat

I Didn't word that last question right, yes I know it is to keep heat up but is it there to do anything else like keep moisture down, I am guessing with foam I would still use a vapor barrier.

Zman

Yes

You would