I'm at the thinking about heating stage of my barn build...

[AKwelder]

if you want a simple system, try this, it works. I have installed several dozen of these.

1- Get a small efficient boiler, we use Monitor fuel oil fired units, but most of the boiler manufactures have small good units. You might look at the gold series by Burnham, they come in gas or fuel oil. The most practical thing is that it must be able to have VERY cold return temps. We refer to this as a condensing boiler.

2- Look at the TACO mixing block, this unit has both pumps and the controls already installed. But it will be a sticker shock until you check the price of each component.

3- install 1/2 inch PEX tubing loops in the floor, if you have a single room in shop you don't need any Zones. The mixing block will do the job with a single thermostat.

4- When you install the manifolds make the first loop branching off the system the last loop in. This looks opposite from what i said. this means that the supply and return attach to opposite side of the manifold when the loops are paired together. This will balance the pump and flow through the floor


We heat small shops here in Alaska and only burn 200 gallons a year, for way up here it is very impressive.

As for an ice melt system, just leave a extra loop, later you can hook it up, in extreme cold we have to use another pump to flow the Glycol.

You can find most of the information at the site heatinghelp.com

 

[mx842]

if you want a simple system, try this, it works. I have installed several dozen of these.

1- Get a small efficient boiler, we use Monitor fuel oil fired units, but most of the boiler manufactures have small good units. You might look at the gold series by Burnham, they come in gas or fuel oil. The most practical thing is that it must be able to have VERY cold return temps. We refer to this as a condensing boiler.

2- Look at the TACO mixing block, this unit has both pumps and the controls already installed. But it will be a sticker shock until you check the price of each component.

3- install 1/2 inch PEX tubing loops in the floor, if you have a single room in shop you don't need any Zones. The mixing block will do the job with a single thermostat.

4- When you install the manifolds make the first loop branching off the system the last loop in. This looks opposite from what i said. this means that the supply and return attach to opposite side of the manifold when the loops are paired together. This will balance the pump and flow through the floor


We heat small shops here in Alaska and only burn 200 gallons a year, for way up here it is very impressive.

As for an ice melt system, just leave a extra loop, later you can hook it up, in extreme cold we have to use another pump to flow the Glycol.

You can find most of the information at the site heatinghelp.com

Thanks for the link, I'll check it out. We don't have winters here like you do up there that's for sure. I don't know how much of what I have written in this thread but let me add here that in the short term I will run this system off of a 50 gal water heater. I want one out there anyway so it won't be a total loss when I buy it. Once I get in the building where I can work I plan on building a simple wood fired outside boiler stove to run the system on.

The whole thing now is getting my floors poured so I can at least start putting my stuff to work with in there. Right now all I am concerned with is making sure all the piping and anything else that needs to be laid out is put in the right place before I pour concrete. I have to do the floor in two pours because of funding but I can do that easy enough because of the way I have laid out my piping detail.

I want to use only one zone and I should be able to do that without any problems even though there will be several different rooms that are attached to the main portion of the building. I feel like it should not be a problem because even though there are several different rooms they will all be basically open. All of the rooms accept the office space will have large case openings where one whole wall will be open to the main floor. The office area will have a door on it but I backed off the tube in the center of this area and just ran tubing around the two outside walls. This room will also house the manifold and hot water heater so that room will probably stay pretty cozy without much added pipe.

As I said before I will probably make room for another zone or two before I pour concrete for the ice melt area in front of the building and the small 8X10 entrance patio where I will put my 3' door to enter the building by. I also have a small dog kennel I want to put in the back of the building but this extra stuff is a ways off because I want to get my boiler on line before get to this point.

Right now I just need to know how much pump I will need to circulate the water through the roughly 2000+ feet of 1/2" pipe and do it effectively.

 

[northpolefolks]

I heated my shop with in-floor, in fact the whole house too for that matter.

Make sure you put loops of no more than 250-300 feet of pex at a time. I put four inches of blue board under my slab and used foam insulated form blocks for my foundation walls. If you already have your foundation in line the outside with foam, 2" will help drastically.

When you run your loops near your garage door make sure you hold them back about a foot from the where the door seal will touch the slab. There will always be a transition point between the cold and heat. If this transition is between the slab and door seal frost will form on the outside of the seal and over time it will effect the seals ability to remain flexible and actually seal out the cold air.

Make sure you take alot of pictures of your pex before you pour your concrete. Have your pex laid on wire mesh and tied to it so that you can measure, using the photos, to where the loops are. Usually the mesh is on 6" centers. This comes in really handy when you decide to concrete anchor a drill, press or lathe down the road so that you don't hit a loop.

Expansion Joints are a good idea. Every 200 square feet is a good estimate for joints. You don't need to have a full depth joint if you don't want. Lay your 1/2" rebar mesh in front of your door entry and where you expect the heaviest loads. When you pour your mud use a good trowel and "cut" your joint in about 1/2 the depth of the slab. Make sure that if you pour concrete in your door entry and it is sitting on top of your foundation wall that there is no rebar coming up out of your foundation wall into your slab. If you do have bar coming out of your foundation wall into your slab you will get cracks in your slab as it tries to move but can't.

Just a few ideas.

 

[mx842]

I heated my shop with in-floor, in fact the whole house too for that matter.

Make sure you put loops of no more than 250-300 feet of pex at a time. I put four inches of blue board under my slab and used foam insulated form blocks for my foundation walls. If you already have your foundation in line the outside with foam, 2" will help drastically.

When you run your loops near your garage door make sure you hold them back about a foot from the where the door seal will touch the slab. There will always be a transition point between the cold and heat. If this transition is between the slab and door seal frost will form on the outside of the seal and over time it will effect the seals ability to remain flexible and actually seal out the cold air.

Make sure you take alot of pictures of your pex before you pour your concrete. Have your pex laid on wire mesh and tied to it so that you can measure, using the photos, to where the loops are. Usually the mesh is on 6" centers. This comes in really handy when you decide to concrete anchor a drill, press or lathe down the road so that you don't hit a loop.

Expansion Joints are a good idea. Every 200 square feet is a good estimate for joints. You don't need to have a full depth joint if you don't want. Lay your 1/2" rebar mesh in front of your door entry and where you expect the heaviest loads. When you pour your mud use a good trowel and "cut" your joint in about 1/2 the depth of the slab. Make sure that if you pour concrete in your door entry and it is sitting on top of your foundation wall that there is no rebar coming up out of your foundation wall into your slab. If you do have bar coming out of your foundation wall into your slab you will get cracks in your slab as it tries to move but can't.

Just a few ideas.

Thanks, I had not thought about the rebar and foundation thing but then this is a pole barn and doesn't really have a foundation like regular stick built structures do. Although mine is sitting on built up piers and I had at one time thought about drilling them to put short stubs of rebar in them to tie the two together. But it was just a thought and I never have given it much thought one way or another. I'm not doubting what you are saying but what about monolithic pours where you pour the slab and foundation all at the same time? I don't know how many building pads I have graded over the years that used this kind of system.

As I said in an earlier post I have to pour this in two sections so I will do the back half first and will have all the loops routed to a closet that will be 1 foot past the half way point on a side wall so that when I run my tube everything that is under the first half will come up in a wall and out of the way while I am getting the second pour ready.

The way I drew it up is that I will have 4 loops in each half that are all between 240 and 255 feet. I know that will change a little when I go to lay them out but I still should be able to keep them all to around right at 250'. I didn't want to push the 300' limit and the way the floor plan is laid out the loops of 250' +/- actually worked out better, at least on paper anyway.

I am still up in the air about what door I am going to use for the big entrance door. At first it was going to be a sliding door then I found these rollup doors that roll up in a drum like they put on storage units which would work very well with the trolly beam I have that ends at the middle of the door. A regular garage door wouldn't work because the door would be in the way when it was open and I couldn't use my hoist to unload stuff.

Those rollup doors are priced fairly well and to be honest I don't know if I could build a sliding door for what I could buy one of those for. The reason I brought this up for is because of what you were saying about the frost forming at the entrance way. My building faces in a southern direction and gets full sun all day so that will help some. If I did a sliding door this wouldn't be as much of a problem because no matter how well they are built they are not all that tight anyway but either way there will be a break at the door that will divide the two areas. I plan on using a 2x8 as an expansion joint to divide the floor from the apron and I can still put some foam board cut at an angle at the top on the outside of this joint to stop any frosting from being a problem.

We don't have that bad of winters around here like they do up north and I plan on using the ground as a heat sink to help hold my heat longer. I plan on using 2" foam board all around the perimeter out to 8' and leave the center open. I also plan on putting the 2" foam board all around the outside wall edges down to about 18" and I think I will be good.

 

[northpolefolks]

Monolithic pours are very popular. They are easier, time saving and cost saving. The down side is that without expansion joints at consistent intervals there will be expansion and contraction cracks. Also, the heat in your slab will "chase" down the footer into the ground.

You can use the ground as a heat sink, however when it comes to heat loss you can only store so much heat below a slab before the heat leaches below your footing and it subject to the cold that penetrated under your footing. The cold penetrates under at a decreasing angel. If you flipped a house upside down the roof line would be similar to the heat line, close to the slab at the edges and farther away in the middle.

If you choose to use the ground as a heat sink I would lay 12"-36" of blue board at the base of your footer extending away from the footer parrallel to the ground surface (we do this commonly) Similar to an apron look. This will require the frost and cold to stay a total of 2-6' back from the center of your slab and will give you a huge benefit in heat loss. Instead of the edges of yours slab feeling "cold" the will be far from it. You may not be in real cold country but if you ever lose power and the ability to heat you will stay warmer for days longer that without it.

I have built quite a few homes and commercial building up in this "cold" country. My personal home, in 20 degree weather, loses 1 degree in 24 hours with no penetrations opened or heat added. My slab is 5" thick in the house and 6" thick in the garage. The slab itself is the main heat "sink". If you have a good price on concrete you can always add an inch or two to the thickness and your retention value will skyrocket.

Either way is sounds like your well on your way to a great shop. Putting the thought into it that you are will serve you well for a lifetime. Heated slabs are a little more work, but the sweat equity and the winter benefits are 10 fold. In today's world when you find someone putting in floor heat in their shop it is usually a sign of the whole buildings quality as far as attention to detail.

Let me know how the finish product goes for you. I am putting up a 40x60 shop next summer and can always use new ideas.

 

[Raspy]

mx,

By all means, you should go with radiant heat.

I'm currently building my own home in northern Nevada at 5000 feet elevation. The living space is 48 X 60 and all on an 8 inch slab. All with radiant.

I poured the perimeter footing to 24 inches below grade and insulated inside it with 2" Blue Board. Vertical reinforcement rods are #3 bar on 12" centers bent over to tie to the slab. The entire slab area has 12" OC bars both ways and 3/4" radiant PEX tied to it on 12" centers. Hold all PEX lines back a foot or so from inside the perimeter walls to reduce heat loss.

Be sure you run the radiant piping in a uniform way with no more than 12" OC spacing. 9" is better for faster recovery and more even heat. Tie the tubing to the rebar with rebar ties. No casual routing here and there with non defined spacing! You'll regret it later. Size your boiler to 25 BTU/ sq ft or more for your heat load. Less os OK with a lot of thermostats, more is better for extremely cold climates or fewer thermostats.

Use oxygen barrier PEX tubing ONLY. Period. No rubber hose or other stuff.

Set up loops to allow thermostats to match the house, such as one thermostat for master bedroom, one for kitchen and general living area, one for second bedroom or group of bedrooms and one for garage. A thermostat can run any number of loops. Arrange the loops to match the room layout, in other words, bedroom loops serve only the bedroom and not the bedroom and living room. Loops should enter and leave each room through doors and not under walls. All tubes should pass through PVC electrical conduits as they enter or exit the slab. This protects them and defines the bend radius.

The system should be a closed loop design. Don't run it as a loop of fresh water on your plumbing system! I never use the pex-al-pex stuff and have no corrosion issues. Once again, the best choice is simply barrier PEX for a number of reasons.

I've seen over and over where people held off on radiant for some reason and were very sorry afterward. It is the absolute best heating system there is. Silent, comfortable, efficient and easily tied to solar if you want to. Just last week my friend invited me over to help him figure out a way to heat his hangar. The floor is very cold and he is building an airplane. He has had two incidents with carbon monoxide poisoning from propane systems and just can't get it comfortable in there. The only solution I could see was a thin slab radiant over what he already has. It would have been so easy to incorporate it during the original construction.

A few general guidelines like these make a very nice system.

 

[mx842]

mx,

By all means, you should go with radiant heat.

I'm currently building my own home in northern Nevada at 5000 feet elevation. The living space is 48 X 60 and all on an 8 inch slab. All with radiant.

I poured the perimeter footing to 24 inches below grade and insulated inside it with 2" Blue Board. Vertical reinforcement rods are #3 bar on 12" centers bent over to tie to the slab. The entire slab area has 12" OC bars both ways and 3/4" radiant PEX tied to it on 12" centers. Hold all PEX lines back a foot or so from inside the perimeter walls to reduce heat loss.

Be sure you run the radiant piping in a uniform way with no more than 12" OC spacing. 9" is better for faster recovery and more even heat. Tie the tubing to the rebar with rebar ties. No casual routing here and there with non defined spacing! You'll regret it later. Size your boiler to 25 BTU/ sq ft or more for your heat load. Less os OK with a lot of thermostats, more is better for extremely cold climates or fewer thermostats.

Use oxygen barrier PEX tubing ONLY. Period. No rubber hose or other stuff.

Set up loops to allow thermostats to match the house, such as one thermostat for master bedroom, one for kitchen and general living area, one for second bedroom or group of bedrooms and one for garage. A thermostat can run any number of loops. Arrange the loops to match the room layout, in other words, bedroom loops serve only the bedroom and not the bedroom and living room. Loops should enter and leave each room through doors and not under walls. All tubes should pass through PVC electrical conduits as they enter or exit the slab. This protects them and defines the bend radius.

The system should be a closed loop design. Don't run it as a loop of fresh water on your plumbing system! I never use the pex-al-pex stuff and have no corrosion issues. Once again, the best choice is simply barrier PEX for a number of reasons.

I've seen over and over where people held off on radiant for some reason and were very sorry afterward. It is the absolute best heating system there is. Silent, comfortable, efficient and easily tied to solar if you want to. Just last week my friend invited me over to help him figure out a way to heat his hangar. The floor is very cold and he is building an airplane. He has had two incidents with carbon monoxide poisoning from propane systems and just can't get it comfortable in there. The only solution I could see was a thin slab radiant over what he already has. It would have been so easy to incorporate it during the original construction.

A few general guidelines like these make a very nice system.

Lot's of good advice thanks. When I built my house I was thinking about putting it on a slab but decided against it and back then I never would have even thought about in floor heat. My garage floor is concrete and OH! How I wish I had installed in floor heating in there. I don't have any heat in the garage now and it is well insulated but it still gets cold enough in there to freeze water if you leave a pan full on the floor close to the big door. Believe me I have been considering doing a built up slab on top of what is there so it is more comfortable in that area. I also have plans later on to install it under at least my ground floor in the house. I have always had a problem in the back part of the house where it is always cooler, almost too cool when it really gets cold out. The front living area is wide open to the roof and we have a big stone fireplace with an insert in it that keeps that area nice and toasty but I can't get that heat to the back part of the house because it all goes up but it does make it nice for the upstairs bedrooms. If I ever get around to it I plan on doing at the very least that back half of the house on the ground floor and probably the great room as well.

But for now I have to finish my pole barn shop so I can get back to work. My biggest problem now, is the lack of funds and I have been doing what I can when I have the money to do it. That is partly the reason I have to pour the floor in 2 pours. Normally I would do that in 1 pour but with the added cost of the heated floor that will take a big chunk of my budget but it will be worth it when it's done.

One thing that bothers me about getting information off sites like this and that is conflicting information that sometimes gets passed around. Don't take this wrong and I truly hope that northpolefolks doesn稚 take offense by this either but an example of this is shown right here in this thread. And as I said please, don稚 take this as I am calling either party out on this because I知 not, it痴 just that sometimes it can become a little confusing especially to those that don稚 really know what they are up against.

It has to do with what you said about tying the foundation to the slab with rebar. And again I知 not saying one way or another is the one and only way to do this. I hadn稚 really thought about it much and have seen it done both ways with success. The thing about concrete is that it is going to crack in places no matter what you do and is the reason you either cut joints in after it has had time to harden or place mechanical joints in the slab while it is being poured to at least control where the cracks will form.

When I started my building I decided not to go the more traditional route and put my 6x6 post in holes with concrete around them. I built my piers on 24 bases below the frost line and then came up to grade level and I attached my post to the top of these piers with connectors I made in my garage. It was my plan to drill holes in these piers and insert ｽ rebar in 3 or 4 places that would stick out 6 to 8 so that when I poured my slab it was all tied in. After what northpolefolks said what he did about not tying in the slab it made me think and I almost abandoned the idea.

To be honest I don稚 know what is right or wrong with either tying the two together of to let the slab float. My honest thoughts are that it really shouldn稚 matter if you are pouring on a solid base one way or another especially on a solid wall foundation. However after thinking about it my piers are on 8 centers and with that much distance between them, well I just don稚 know??? That may be a good question for someone to throw out to the peanut gallery to get a better understanding of what is best. Remember I知 not saying either way is right or wrong and mean no offense by what I am writing to either party so please don稚 make this a reason to start a pizzing contest.

 

[mx842]

Monolithic pours are very popular. They are easier, time saving and cost saving. The down side is that without expansion joints at consistent intervals there will be expansion and contraction cracks. Also, the heat in your slab will "chase" down the footer into the ground.

You can use the ground as a heat sink, however when it comes to heat loss you can only store so much heat below a slab before the heat leaches below your footing and it subject to the cold that penetrated under your footing. The cold penetrates under at a decreasing angel. If you flipped a house upside down the roof line would be similar to the heat line, close to the slab at the edges and farther away in the middle.

If you choose to use the ground as a heat sink I would lay 12"-36" of blue board at the base of your footer extending away from the footer parrallel to the ground surface (we do this commonly) Similar to an apron look. This will require the frost and cold to stay a total of 2-6' back from the center of your slab and will give you a huge benefit in heat loss. Instead of the edges of yours slab feeling "cold" the will be far from it. You may not be in real cold country but if you ever lose power and the ability to heat you will stay warmer for days longer that without it.

I have built quite a few homes and commercial building up in this "cold" country. My personal home, in 20 degree weather, loses 1 degree in 24 hours with no penetrations opened or heat added. My slab is 5" thick in the house and 6" thick in the garage. The slab itself is the main heat "sink". If you have a good price on concrete you can always add an inch or two to the thickness and your retention value will skyrocket.

Either way is sounds like your well on your way to a great shop. Putting the thought into it that you are will serve you well for a lifetime. Heated slabs are a little more work, but the sweat equity and the winter benefits are 10 fold. In today's world when you find someone putting in floor heat in their shop it is usually a sign of the whole buildings quality as far as attention to detail.

Let me know how the finish product goes for you. I am putting up a 40x60 shop next summer and can always use new ideas.

I have learned a great deal since I have taken on this project and in a way I'm sort of glad I am an old broke dude that couldn't afford a real barn builder to put my shed up. I wanted to ask you to not take offense to what I said in my last post as it was not meant to stir you or anyone up. It was just an observation I made and was just trying to point out how people can sometimes take things other people write the wrong way.

I'm already wishing I had gone another 20' deeper and 8' wider on the main building. But I have added 10' to each side and 20' to the back so I guess I'm getting there.:laughing: right now I'm waiting for some funds to be loosened up so I can start my floor. I started this barn last winter about this same time and so far I have done just about everything all by myself. It has been hard at times and sometimes I have to do things over and most of the time it's something stupid and could be left alone because no one but me would ever notice but I am my own worst critic......well other than my wife of course. I was coming along pretty good until the hurricane blew over that great big oak tree and it crashed through the left and front wall and twisted the whole thing to where I had to almost rebuild the whole thing. Thank goodness for USAA, they were a little slow at first but have been great through this whole ordeal. Even with all the problems and the cash flow problems I have had to negotiate through all of this I still would do it again almost exactly the same way. I did learn a few things that would cause me to try another way but for the most part I wouldn't change a thing.

 

[northpolefolks]

Lot's of good advice thanks. When I built my house I was thinking about putting it on a slab but decided against it and back then I never would have even thought about in floor heat. My garage floor is concrete and OH! How I wish I had installed in floor heating in there. I don't have any heat in the garage now and it is well insulated but it still gets cold enough in there to freeze water if you leave a pan full on the floor close to the big door. Believe me I have been considering doing a built up slab on top of what is there so it is more comfortable in that area. I also have plans later on to install it under at least my ground floor in the house. I have always had a problem in the back part of the house where it is always cooler, almost too cool when it really gets cold out. The front living area is wide open to the roof and we have a big stone fireplace with an insert in it that keeps that area nice and toasty but I can't get that heat to the back part of the house because it all goes up but it does make it nice for the upstairs bedrooms. If I ever get around to it I plan on doing at the very least that back half of the house on the ground floor and probably the great room as well.

But for now I have to finish my pole barn shop so I can get back to work. My biggest problem now, is the lack of funds and I have been doing what I can when I have the money to do it. That is partly the reason I have to pour the floor in 2 pours. Normally I would do that in 1 pour but with the added cost of the heated floor that will take a big chunk of my budget but it will be worth it when it's done.

One thing that bothers me about getting information off sites like this and that is conflicting information that sometimes gets passed around. Don't take this wrong and I truly hope that northpolefolks doesn稚 take offense by this either but an example of this is shown right here in this thread. And as I said please, don稚 take this as I am calling either party out on this because I知 not, it痴 just that sometimes it can become a little confusing especially to those that don稚 really know what they are up against.

It has to do with what you said about tying the foundation to the slab with rebar. And again I知 not saying one way or another is the one and only way to do this. I hadn稚 really thought about it much and have seen it done both ways with success. The thing about concrete is that it is going to crack in places no matter what you do and is the reason you either cut joints in after it has had time to harden or place mechanical joints in the slab while it is being poured to at least control where the cracks will form.

When I started my building I decided not to go the more traditional route and put my 6x6 post in holes with concrete around them. I built my piers on 24 bases below the frost line and then came up to grade level and I attached my post to the top of these piers with connectors I made in my garage. It was my plan to drill holes in these piers and insert ｽ rebar in 3 or 4 places that would stick out 6 to 8 so that when I poured my slab it was all tied in. After what northpolefolks said what he did about not tying in the slab it made me think and I almost abandoned the idea.

To be honest I don稚 know what is right or wrong with either tying the two together of to let the slab float. My honest thoughts are that it really shouldn稚 matter if you are pouring on a solid base one way or another especially on a solid wall foundation. However after thinking about it my piers are on 8 centers and with that much distance between them, well I just don稚 know??? That may be a good question for someone to throw out to the peanut gallery to get a better understanding of what is best. Remember I知 not saying either way is right or wrong and mean no offense by what I am writing to either party so please don稚 make this a reason to start a pizzing contest.

No offense taken. If you tie your slab to your foundation it can not move. You must put expansion joints in or you will have major cracking issues. If your foundation shifts vertically 1/4 inch fron far corner to far corner you will have not just cracks, but elevated cracks which causes issues with creepers, rolling tool boxes, your wife tripping ect.

Your slab, if not tied to the foundations, will not "sinK" as some people say. Make sure you have really good compaction and no soil underneath.

I have poured everything from small 100x10' porches to 35,000sft freezer warehouses and no problems with design like I mentioned. Like driving a tractor, there are more ways to skin a cat, this is just the way I like to do it. Good luck either way.

 

[Raspy]

mx,

There certainly are a lot of ways to do concrete construction and I didn't mean to imply my way was the best or only way to do it. You're right, concrete will crack and you have to deal with it somehow, but as long as you have a good amount of rebar, you don't have to worry about the PEX breaking. I don't like the idea of cutting joints in later because you really don't know how close the tube is too the surface after the pour. During your pour preparation, try to avoid any L shaped pours with inside corners. These WILL crack at the corner. If you must do it that way lay a row of about 6 bars diagonally near the corner.

As I mentioned in my earlier post, a careful tube layout is really important. Uniform spacing specific to the rooms and plenty of tube with 9 or 12 inch spacing in the general areas and 6 to 8 inches in the bathrooms. And extra pass of tubing near the front door and in front of the shower or tub is nice. use the hall to get from the manifold to the bedrooms and don't worry too much about too much tube in that area. Imagine where you will be walking and when. Route the tubing to accommodate your lifestyle. Divide the house into commonly used zones and make those the thermostat zones. Put balancing vales on the manifold so you can regulate the flow to each loop within each zone. This way you can adjust the heat level in each room or turn one room off if needed.

And be sure you have sufficient power in the boiler. I do them with 25 BTU minimum under most circumstances, but with fewer zones you can go higher.
I have some running with about 75 BTU/ft with single thermostats. If you get down to about 10 BTU/ft you'll get very poor response and will have to leave the system running all the time. This leads to inefficiency.

I'll talk to you about thermostat strategies if you wish.

Without wanting to start an argument here, I'd simply point out that the pictures Spiker sent of his layout are a poor example of how to do it. Random looping with no uniform spacing, far too much space or too little tube per square foot and no protection for the tubing where it enters and exits the slab. These will haunt the system later and make the heating uneven. No offense intended, just a good example to learn from.

John