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

[Raspy]

Here are some pix of my project.

 

[mx842]

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

Cool...My plan was to place an in slab temp sensor somewhere in the middle of the big 32x40 floor to control the temp for the whole floor. The small rooms that I have added to the sides of the main shop floor are all open and if it does get a little cooler in these areas it is no big deal as they are mostly storage. I will have a lathe and mill on one side but the machine shop area is mostly open to the main floor area with to big 8'x8' case openings at each end. I do plan on having a small office area but I can add a small heater if needed in there which I have plenty of but I don't think it will be needed.

But having said that by all means fire away with any suggestions because if they are not helpful to me maybe someone else is thinking about the same thing and would appreciate the info.

 

[Raspy]

Floor sensors are generally good when you have a radiant system inside a forced sir system. Such as a radiant kitchen in a house with forced air. Or, if you have a shop that is hard to heat, but want a nice inviting floor. Excellent for working at a lathe, for instance.

But floor sensing will not accurately control the environment because it knows nothing about the air temp and other heat sources.

You could use a floor sensor in the shop and wall thermostats in the living spaces or bedrooms and have better results.

Always choose a setback thermostat and plan to use it as a timer and air sensor both. I'll go into that more if needed.

If you have a very high ceiling, plan on a paddle fan or equal to overcome the stratified heat. This problem is also dealt with by using the thermostats as timers and having a relatively high BTU input to the slab. In other words, blasting the slab for a short period to greet you when you get up, but not long enough to heat the whole house and waste energy by heating upper layers of air.

These are all well proven strategies that I'm touching on to whet your interest and steer you. More info as needed.

 

[wedge40]

Here are some pix of my project.

No insulation under the slab?

Wedge

 

[Raspy]

Wedge,

No insulation under the slab.

The house is on a slight slope and the inside of the footings and stem walls are insulated with 2" Blue Board down 3 to 5 feet.

It sits on decomposing granite ground with 1 to 5 feet of 1 1/2 inch rock (depending on which side of the house) , then a compacted layer of sand.

The heat is held back about 1 1/2' from the outside.

Underslab insulation only slows the heating of the ground under the house. That ground becomes additional mass. Without air movement or water under there, there is no loss to the surroundings straight down. Just mass that absorbs at a slightly faster rate than if if was insulated.

I also was interested in having the maximum stability of the slab and leery of supporting the slab on insulation that would deteriorate and crush down over time.

For someone that wants underslab insulation, the best way I've seen is to use void forming. Or just insulate the first two feet in around the perimeter, below the slab, and let it form a bridge from the footing to the uninsulated area.

This is designed as an 8" slab that is used as partial solar storage. I plan to supplement the heat with wood because I like wood heat so much and have a lot of oak and pinion available.

The slab energy source will be oil primarily. I've found that a low grade heat in the slab, to make it "invisible" to the touch, and a nice fire to add ambiance, is about as good as it gets.

With this system I can leave the Garage cold until I want to work on a project, the Pantry always cold, the Guest Bedroom cold until guests arrive, the Master Bedroom warm in the morning and cool at night and the Great Room/Kitchen very warm all evening. The boiler waste heat will heat the Laundry Room and, partially, the Garage. All of this control comes very simply with setback thermostats and manifold balancing valves. It also means very little loss because only the zones being used are warm and the floor is never hotter than necessary.

 

[crbr]

Thanks for the pictures

 

[SPIKER]

Wedge,

No insulation under the slab.

The house is on a slight slope and the inside of the footings and stem walls are insulated with 2" Blue Board down 3 to 5 feet.

It sits on decomposing granite ground with 1 to 5 feet of 1 1/2 inch rock (depending on which side of the house) , then a compacted layer of sand.

The heat is held back about 1 1/2' from the outside.

Underslab insulation only slows the heating of the ground under the house. That ground becomes additional mass. Without air movement or water under there, there is no loss to the surroundings straight down. Just mass that absorbs at a slightly faster rate than if if was insulated.

I also was interested in having the maximum stability of the slab and leery of supporting the slab on insulation that would deteriorate and crush down over time.

For someone that wants underslab insulation, the best way I've seen is to use void forming. Or just insulate the first two feet in around the perimeter, below the slab, and let it form a bridge from the footing to the uninsulated area.

This is designed as an 8" slab that is used as partial solar storage. I plan to supplement the heat with wood because I like wood heat so much and have a lot of oak and pinion available.

The slab energy source will be oil primarily. I've found that a low grade heat in the slab, to make it "invisible" to the touch, and a nice fire to add ambiance, is about as good as it gets.

With this system I can leave the Garage cold until I want to work on a project, the Pantry always cold, the Guest Bedroom cold until guests arrive, the Master Bedroom warm in the morning and cool at night and the Great Room/Kitchen very warm all evening. The boiler waste heat will heat the Laundry Room and, partially, the Garage. All of this control comes very simply with setback thermostats and manifold balancing valves. It also means very little loss because only the zones being used are warm and the floor is never hotter than necessary.

John:

what you have there is a home with heating, the person posting to is building a pole barn like mine for working in and keeping warm enough to do something in it.

My barn has heating tubes laid out well and at 280' per loop so making tight bends like yours will kill water flow very bad for in-floor heating systems. This was a mistake made by my co-worker who did his barn used nice tight bends like yours his flow cant get up as the 250 spools he put in were OK but many tight bends killed the flow rate. as far as too little loops I followed a radiant contractors recommendation as far as keeping 6" apart from loop to loop at the perimeter of the slab and farther apart on the interior of the slab. Under the lean-too is for ice melting only and will not be run ever unless I decide to enclose it and even then only part of it.

I have the center beams with tubes moved away from there center beams of the building slab with tubes wider apart in those areas. Reason for this was due to adding anchors later for holding equipment to the BARN floor. Where cars or tractor will be parked I also moved the tubes apart some as I later plan (cost permitting) install a maintenance trench down that section of floor. I had planned on installing slab penetration protection for the tubes but a combination of a wall going there and time constraints I didnt get to it. Where they exit they are well protected against the interior wall should be flush once it is dry-walled.

I also would not think about doing radiant flooring without first installing insulation under all of my floor in Ohio here due to water tables, and ground temps. the ground will pull heat out of a slab like crazy here and is mostly clay stays wet and can frost down to 40" pretty quick. With the Rebar on your slab it pretty much overkill for a home floor I have seen heavy factory floors with less steel in them! My slab is 5~6" thick 6KPSI mix with fiber mesh in it on top of the 6x6 10GA mesh the tube is tied to.


Remember not everything is a one size fits all budgets building plans (usage) has a lot to do with it. Mine will be warm all the time but probably not 70 degrees as that is too warm anyhow. exterior walls are almost 8" and will be heavily insulated. (my next step) planning on some 2+" of CLOSED CELL spray foam once I can save up the $ and then a layer of fiberglass between stud walls and either sheet rock or maybe plywood interior walls on 1st floor. It is being setup for car repair and some equipment mechanical work...

Mark

 

[Raspy]

John:

what you have there is a home with heating, the person posting to is building a pole barn like mine for working in and keeping warm enough to do something in it.

My barn has heating tubes laid out well and at 280' per loop so making tight bends like yours will kill water flow very bad for in-floor heating systems. This was a mistake made by my co-worker who did his barn used nice tight bends like yours his flow cant get up as the 250 spools he put in were OK but many tight bends killed the flow rate. as far as too little loops I followed a radiant contractors recommendation as far as keeping 6" apart from loop to loop at the perimeter of the slab and farther apart on the interior of the slab. Under the lean-too is for ice melting only and will not be run ever unless I decide to enclose it and even then only part of it.

I have the center beams with tubes moved away from there center beams of the building slab with tubes wider apart in those areas. Reason for this was due to adding anchors later for holding equipment to the BARN floor. Where cars or tractor will be parked I also moved the tubes apart some as I later plan (cost permitting) install a maintenance trench down that section of floor. I had planned on installing slab penetration protection for the tubes but a combination of a wall going there and time constraints I didnt get to it. Where they exit they are well protected against the interior wall should be flush once it is dry-walled.

I also would not think about doing radiant flooring without first installing insulation under all of my floor in Ohio here due to water tables, and ground temps. the ground will pull heat out of a slab like crazy here and is mostly clay stays wet and can frost down to 40" pretty quick. With the Rebar on your slab it pretty much overkill for a home floor I have seen heavy factory floors with less steel in them! My slab is 5~6" thick 6KPSI mix with fiber mesh in it on top of the 6x6 10GA mesh the tube is tied to.


Remember not everything is a one size fits all budgets building plans (usage) has a lot to do with it. Mine will be warm all the time but probably not 70 degrees as that is too warm anyhow. exterior walls are almost 8" and will be heavily insulated. (my next step) planning on some 2+" of CLOSED CELL spray foam once I can save up the $ and then a layer of fiberglass between stud walls and either sheet rock or maybe plywood interior walls on 1st floor. It is being setup for car repair and some equipment mechanical work...

Mark

Mark,

Again, no offense intended.

I only based my comments on the pictures you posted with random lines, no clear spacing layout and no sleeves at the entry/exit points.

Fairly tight bends with no kinking has no significant affect on flow rates, but does allow uniform heating and plenty of tubing per square foot. It's good practice.

There are a lot of ways to do things.

Good luck with your system. Try to avoid the myths.

 

[mx842]

Floor sensors are generally good when you have a radiant system inside a forced sir system. Such as a radiant kitchen in a house with forced air. Or, if you have a shop that is hard to heat, but want a nice inviting floor. Excellent for working at a lathe, for instance.

But floor sensing will not accurately control the environment because it knows nothing about the air temp and other heat sources.

You could use a floor sensor in the shop and wall thermostats in the living spaces or bedrooms and have better results.

Always choose a setback thermostat and plan to use it as a timer and air sensor both. I'll go into that more if needed.

If you have a very high ceiling, plan on a paddle fan or equal to overcome the stratified heat. This problem is also dealt with by using the thermostats as timers and having a relatively high BTU input to the slab. In other words, blasting the slab for a short period to greet you when you get up, but not long enough to heat the whole house and waste energy by heating upper layers of air.

These are all well proven strategies that I'm touching on to whet your interest and steer you. More info as needed.

My idea on the floor sensing control is that I don't plan on living in this area and as I said even though I will have a few rooms off to the side my main concern is to keep the floor overall at a constant temp regardless of what the temp is outside. If the air temp falls into the 40's that will not bother me, I just don't want things to freeze on the inside. I have plenty of wood and once I build my stove it will stay lit until the spring comes just like my wood stove does in the house. Yes, sometimes it does get a little warm in the great room but that is what ceiling fans and windows are for.:laughing:

Don't get me wrong please keep the information coming because I love to learn new things and you never know who else may be looking for the same type information.

My ceilings in my shop are 14' and I just finished putting in my blocking for my high bay lights (5 in all) and my ceiling fans. I will have 4 fans in the main 32x40 part and one in the machine shop area and one in the welding equipment room. Hopefully these fans will be enough to keep the air moving around summer and winter and if not I have one of those great big 4'x4' fans on wheels that I can plug in if needed.

One question I do have is about pump sizing. All of this piping, 8 loops of right at 250' each will be all zoned together. How do I figure pump size to get the proper flow? I know I can control the flow somewhat by valves but I want to pump the water through the system not too fast, not too slow with the valves wide open and be able to tweak the system in places if needed. I can not find anywhere what the proper flow rate is through a system like this or how to figure it out. I know it has to be some way to figure this out or does it even matter in a system like this?

 

[Raspy]

mx,

Sounds like you are on the right track to me. Floor sensing, in your case, makes perfect sense.

To install the sensor, bury a 3 foot piece of PEX in the slab with one end sticking out where you can always get to it. Tape the buried end closed with electrical tape and position the buried end half way between two of the heating lines in the slab. If you have 1' spacing the closed end of this tube would be 6" from each loop line, somewhere in the slab. Then slide the thermister down into the tube to the end and have the wires sticking out to connect to your controller. This will allow you to always be able to replace it if needed and it will control the slab well. This sensor can tie into a thermostat with remote sensing capability and the thermostat can mount up on the wall and send a signal to a relay to start the pump. Simple and repairable. Easy to adjust and accurate. The thermostat will display the floor temperature and you can even program it if you wish.

You can simply install an 8 loop manifold and keep your loops at no more than 300' each to stay within reasonable restrictions. Or a 10 loop with 240' each would be fine or better.

Since yours will be able to flow all the time and the recovery rate is not really important, you only need 1 GPM max for each loop and 1/2 GPM would work. I simply go by experience and don't calc each system. Assuming you have 1" copper feeding the manifold and a low restriction boiler or heat exchanger system, you could use TACO 008 cast iron circulator as the smallest size. Another slightly more powerful and possibly easier to get unit would be a Grundfos 15-58, 3 speed pump. If your system has a bit more restriction in the heat exchanger go to a Grundfos 26-64.

Since it will always be able to circulate, and recovery can be slow with no negative affect, you won't need water at over 100 degrees. 120 degrees would give aggressive recovery and 90 would be just about the lowest you could get by with in cold weather with constant flow. You'll be looking for an average floor temp of about 75 degrees from what I can make of your intended use.

The next thing might be plumbing strategies, corrosion resistance or something along those lines.