In floor advise

[jtsboss]

Ok guys, so when I built my 40x40, 5yrs ago- at the very last minute I decided I would run pex line for floor heat hooked up at a later time. I didn't have much know how then and this is what was done. A vapor barrier was put down then 2in 4x8 sheets of the white styrofoam. Then wire, pex and concrete. Knowing what I know now about radiant floor heat systems should I just scrap that dream and go with a different way to heat the building? I didn't use the correct foam board and it didn't get a foam border. It has treated 2x10s around the base. I just don't know if it's worth the cost for the rest of the setup if it won't heat worth a darn.
Thoughts?
Oh and what brought this on was I can get a really good deal on a 2 post lift. I would need to drill into the slab and would probably damage the pex line.
If you all think its still worth it I will pass on the lift.
Thanks
JT

 

[DarrenF]

do get the lift, and do use the in floor heat. First, hook up the heat, then map the loops using a thermal imager. They can be had for a decent price, or rented. Google locating infloor pex. you will be able to locate your anchors to miss the pex.

 

[Firebrick43]

Is the eps you use 15psi rated? If so and you have good drainage it will be fine. Xps is blown with freon which gives it a higher r value new but as time goes on it looses it and after 10-15 years the r value is pretty close to eps. 15psi density eps is pretty damn good. Most of your icf foams are a high density eps.

Cheap low density eps can have issues but it shouldn't have been placed under a slab due to weight as well.

Perimeter insulation would have been nice but it's not the end of the would yet. The wood is r2 at least. If you want to you could use a pick and spade and still place a 2' piece on the perimeter.

As Darren said you can have someone use thermal imaging to locate the pipes. Just make sure their equipment is not cheap junk and they actually know how to operate it correctly.

 

[Randy in Maine]

It would also be nice to know just how thick the concrete is under the proposed lift area and how strong that concrete is.

 

[finn]

Unless you are going to heat the building 24/7, skip the radiant heat and go with a simple hanging heater.

75k btu should be adequate, and they are priced under $500! Less the flue.

If you eventually find that you are using the shop more, you can do the radiant installation, but keep the hanging heater in any event.

 

[jtsboss]

Unless you are going to heat the building 24/7, skip the radiant heat and go with a simple hanging heater.

75k btu should be adequate, and they are priced under $500! Less the flue.

If you eventually find that you are using the shop more, you can do the radiant installation, but keep the hanging heater in any event.

15' ceilings 75k btu should be ok your saying?

Ok, Well the slab is also 6 inch in the front where my 3 bays are and 8 in the back where my motor home sits. I guess I might look into heating the air for now and if i'm in there all the time do the floor heat. I think Ill go for the 4 post lift until I get the unit up and running so I can see the runs.
Thanks for everyone's help!
JT

 

[finn]

I’ve got a 75k unit in each of two different buildings.

The first is in a 32’ x54’ garage with 10’ and 12’ ceilings. The Ute heater brings the temp up quite quickly, but Itransition to wood if I’ Going to be there for a while. The building has tubes in the floor but I never connected to a liquid media heat source, since the building isn’t heated full time.

The second building does have radiant in floor heat, but I only use the boiler to maintain about 42 degrees, and bring the shop to working temperature with the hanging heater. The work area in that shop is 32’x75’, with 16’ ceilings.

Both of my buildings have 2”x6” studded walls, insulated with bats, and bats/blown ceiling insulation.

Both have 6” slabs.

Letting the slab get really cold in the first building makes the hanging heater cycle frequently. I try to keep the building around 42 degrees after a sub zero night.

 

[Randy in Maine]

Suggestion...call the local heating contractor and have him get you some hot water to your floor. Do the mapping of the tubing using the imaging machine. Buy the lift and install it as the manufacturer tells you to. I would get a little boiler to run it.

Hard to get better or cheaper heat that with radiant heat. I keep my "room temp" out there to about 55º. Keep the tools from rusting and the paint from freezing. I turn mine on about Thanksgiving.

 

[jtsboss]

Suggestion...call the local heating contractor and have him get you some hot water to your floor. Do the mapping of the tubing using the imaging machine. Buy the lift and install it as the manufacturer tells you to. I would get a little boiler to run it.

Hard to get better or cheaper heat that with radiant heat. I keep my "room temp" out there to about 55º. Keep the tools from rusting and the paint from freezing. I turn mine on about Thanksgiving.

Randy, do you have any of the glycol in your system or just water? I see your in Main. Im in Ohio. I think once you turned it on you would have to keep it on right?

 

[79rallysport]

From a comfort perspective...my feeling is that 55-60*F of in-floor radiant heat is equivalent to about 60-65*F of convection air heat.

In-floor heat requires less BTU's input to maintain a comfortable environment. However, it doesn't recover nearly as fast as convection air form a hanging heater.

So its going to be your call. What do you want more? Constant heat with higher systematic efficiency, or intermittent blasts up to temp quickly but with lower efficiency.

 

[yeldogt]

Have you done a heat loss calculation? How many loops and are they equal length?

Radiant is the best ... you don't need a complicated system. NG available?

 

[Randy in Maine]

I do not run glycol in my 3 zone radiant floor heating system. That being said, I also do not lose power for days at a time when it is -20º.

I can also get my system to work (if I needed to) using a little generator or even my camping battery. The condensing boiler has a little power vent and the circulator pump just moves 120º warm water around.

That being said, my shop was built to use as little energy as possible to heat it. R-40 or better and just about windproof everywhere. I use the 21 cubic yards of concrete in my 6" slab as a 42 ton thermal mass to retain heat. I wish my house was that tight.

If I were to leave for the winter, I would probably want to run some glycol in there. When I turn it on it takes a little while to come up to the 55º air temp. I just leave it there until April so nothing freezes.

 

[Thumper68]

I use my shop just about everyday so keeping the in floor up to temp, 62 degrees, is way more efficient and comfortable than cycling the temp up and down.

 

[jtsboss]

Have you done a heat loss calculation? How many loops and are they equal length?

Radiant is the best ... you don't need a complicated system. NG available?

no heat loss calc yet but not worried since I over insulate everything. I went down and looked I have 5 loops. They were all the same length and I put one tube all the way to the center thinking I had to snake a temperature wire down for a thermostat. I don't even have a manifold.
No NG but I have LP that the house runs on. I was thinking of tapping into that or getting the shop its own. The company here does not charge for them as long as they are being used. My last fill was 1.21$ gallon.

 

[Randy in Maine]

I run my garage warmth off my house propane Baxi boiler through a 3/4" pex, but it is only about a 60 foot run to there (and another 60 feet back).

 

[jtsboss]

I found a great deal , IMO anyway on a 150$ unit Here are the specs on it. Think its good or to small?
https://www.flickr.com/photos/159071148@N06/shares/LNRSN6

 

[Randy in Maine]

I don't know if that is an on demand hot water heater or a boiler. Whatever...

My suggestion would be to get a local qualified heater guy over there to do a calculation to see just how many BTUs you really need and suggest something that will work for you long term. Have him hook it up complete with the manifolds and burp the air out of the system and the balance it.

Getting it to work correctly right off the bat will greatly achieve your satisfaction goals.

 

[kj_mustang]

You also need to know the calculation of total gpm for the system. For that heater that you posted, you should figure on the lowest number 2.6 gpm supply so your system would need to require that or less.

 

[finn]

You'll need to plumb a primary and secondary loop with a low flow heater like that.

 

[jtsboss]

So my dad is doing some work on his house and has giving me a 50 gallon Rheem electric high efficiency HW tank. Thing is almost new. He was saying I should hook this up and see how things ran in the building. Worth a shot? Free can't be bad. These are expensive tanks.

 

[Hoops1]

i have been running a 40 gallon electric water heater in my 26X28 for 10 or so years now with very little fixing

the pump is on a thermostat

and before anyone shoots me for using electric its about all we got in this area just about everyone heats with electric i do have a propane fireplace

 

[yeldogt]

It's all a question of the BTU capacity of the WH and what is the BTU needed for the building ... also, the only thing that can make an electric WH "high efficiency" is the insulation. You need to do a simple calculation so you know what BTU is needed.

Your loops are equal length - you don't need a very complex set up -- CU pipe - some valves/ expansion tank/ air vent -- circulator .. bunch of fittings.

If the water heater is not enough BTU's .... guess you could set it all up and use another electric heater to raise the temp. My radiant can heat my house -- but I warm the floors and use a ducted system to maintain a temp.

Personally -- with gas available -- that's the way I would go unless you have very cheap electric ... if your electric is cheap you can use an electric boiler -- they are also very reasonable and can be purchased with the correct BTU output ... remember .. electric need a lot of amps ... do you have the capacity for electric.

 

[jtsboss]

Hoops1, I only have electric also. LP take is about 120ft. but my house runs off it. I at least want to try this since its in the floor and the tank will be free. Thanks for the reply

Yeldogt, CU Pipe? I do not have NG available. My shop is on its own service meter since it was the first thing I built on the homestead. I will google the BTU of the building, and compare to the water heater. I am looking for my bill to see what the KW/hr costs. Maybe someone can fill me in on how it works since I'm alittle confused on how i get billed for electric used.

 

[jtsboss]

So I looked at my bill, Generation and Transmission fee is 0.08 KWH and a distribution charge of 0.03 KWH How does this stack up?

 

[yeldogt]

It's about 1/2 of what I pay.

my quick math

if you have a typical it's 9000w WH (2x 4500 element) you will need a 40amp (37.5) circuit . 9000w is about 30000btu's.

when you need 30000 BTUs the unit will never stop.

running for 1 hour is 9x11 = .99


The CU pipe and fitting are to set up the system -- you still need the pumps and tank ..etc..

 

[jtsboss]

It's about 1/2 of what I pay.

my quick math

if you have a typical it's 9000w WH (2x 4500 element) you will need a 40amp (37.5) circuit . 9000w is about 30000btu's.

when you need 30000 BTUs the unit will never stop.

running for 1 hour is 9x11 = .99


The CU pipe and fitting are to set up the system -- you still need the pumps and tank ..etc..

Interesting. The BTU Calculator, what do you normally look at for desired temp increase?

 

[jtsboss]

So i'll just post the question what size of unit do I need for 40x40x15? with normal insulation? I keep getting conflicting numbers.

 

[yeldogt]

Don't understand your question .... I was just trying to show you the cost to run an average WH for 1 hour using the rate you provided.

Also -- when using an electric WH for heat the term " high efficient" is irrelevant, New energy standards increased the insulation required on newer models. If you place a WH in a cold basement -- the extra insulation keeps the water inside warmer .. so it saves energy. If you are using a WH for heat and the WH is in the room you are heating .. any heat lost is going into the room -- there is no difference.

Without doing a proper load on your building .. no one can help you. It's all a guess.

Electric water heaters have two elements that work together to heat the water -- I gave a typical example .. look at the plate on the heater ..... it will tell you. A typical 40g gas has a 26-30k Btu burner. That's the output ... you can get high output models -- that's what I used when I did the floor warming ... 90k burner. it's got to heat the water and warm the floors remember.

Think how long it takes a WT to heat a full cold tank of water. You are asking it to heat the water in the tank ... and the water in the pex .. and the slab. You can't use a WH to heat a shop from cold. You have to maintain close to the temp you want -- if the slab is warm and the water in the tank hot you have the hot water in the tank to bring the slab up a tiny bit.

High mass radiant heat is not designed to be turned off and on -- it designed to stay on. Concrete slabs are high mass.

A proper heat loss will give you the BTU's you need and take into account your local climate -- you can figure out your yearly average costs -- plugging in various delta points.

 

[yeldogt]

So i'll just post the question what size of unit do I need for 40x40x15? with normal insulation? I keep getting conflicting numbers.

I have an extremely well insulted SIP building .. about your size with a 40k 80% propane cabinet heater.. Three insulated windows -- one door. The twin carriage doors are 6" thick (8x8 opening). I maintain the temp around 65 when I'm using it often and a bit lower when I'm not.

My places with radiant floors I turn on once it gets cold .. and don't turn them off until it starts to get warm.

 

[jtsboss]

Good points. Thanks for the reply.
How much propane do you go through in a winter on you cabinet if I could ask?
Do you use NG at your other locations?
Thanks again a big help