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Floor Heat in shops


AKwelder

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Starting a topic on floor heat to avoid derailing another topic. 
 First of all, knowing what your heat load is by doing a heat loss calculation for your building in your area with the proper design temperature makes a huge difference.  Oversized equipment wastes money and is inefficient. I believe that the majority of boilers are oversized, and keeping a huge boiler hot costs money.  Here we can plan on 30  BTU per sq/ft for a modern insulated shop with limited door use, to 50 BTU per sq/ft for a modern building where they are opening overhead doors a lot and moving equipment in and out.  

Floor heat works in slabs, here we first insulate the slab, under and around the edges.  They claim you can lose 40% of your BTU’s thru a slab.  So insulate the slab and you direct the heat into the building

the size of the PEX and length of runs affects a lot,  we normally run 3/4 PEX 1 foot on center. We have a lot of heating need here in Alaska.  No run over 300 feet with 250 foot being better for us. There are several ways to run the zones of PEX,  some like a single zone on the perimeter, some make the loop go out on 2 foot centers and return in the middle making 1 foot on center overall (I think this is best). Newest school of thought is to put the PEX in the middle of the slab and some are zip tying it to the bottom of the rebar. Easiest is to staple it to the foam insulation, and it seems to work just fine.  There are thousands of systems like this working here.

To pipe the system there are as many ways as there are to build a shop. All of them seem to work, some better than most.  What I prefer is to make a loop.  This loop has two manifolds that collect all the zones, supply and return. I pipe the two together so the last supply in is the first return out.  This balances the system so you find equal flow, or mostly so, without expensive equipment.  
 

a pump needs to circulate the fluid in the floor, the 250 foot PEX has a lot of head loss so a pump with the correct pump head is needed. This means a bigger pump like a taco 0013 or 0011, a large head circulator with enough GPM to push thru all the zones 

 

with the manifold built in a loop and circulating fluid in the floor, you need heat.  There many ways to do this.  I prefer a primary/secondary loop system when I pipe from a boiler. This consists of one loop coming out of the boiler with a pump, and going back into the boiler. The primary loop. We discussed the secondary loop above, so now we place two small lines with closely spaced tees that allow hot water to be injected into the floor loop.  
 

this is an example of what I am trying to describe 
 

A3A5B1FA-2ECA-43F4-919B-CC07802C49B7.jpeg.48342670bdac154ac7b0154d3d5f5b22.jpeg
 

the loads at the top of the chart could be unit heaters if you want to have a another heat option. 
 

controls are a lot about this, here we run an outdoor reset.  What this does is it runs warmer water in the floor to make up for colder outside weather.  The pump that injects hot water into floor manifold can be purchased with these controls and that will help avoid unneeded heat use for warmer weather.

 

in the picture above the primary loop can run at any temperature the boiler needs to be efficient. One method is to run a outdoor reset on a propane boiler that is a condensing boiler. This allows the boiler to run at a very low temp and therefore become ultra efficient.  They have found that for every degree below about 135* F the boiler becomes more efficient by a number I can’t recall

 

lets stop here and let me ponder

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We have a 50x60' shop and a has 6 loops of PEX.. without looking at it I think it's probably 1/2" PEX through the floor

You can probably see the direction of the loops in these pictures. I tried to highlight the way they are run in the one 

IMG_20200223_033642.jpg

IMG_20200222_195113003.jpg

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Its not my preferred heating system here because of 1st , much higher cost , 2nd, limited seasonal use  maybe in far northern states it would makes more sense My priority building my shop was more space  good quality doors and lots of insulation then finding a good reliable heating system I went with radiant propane heaters best heating source around here for your buck for my 42x63 morton building

IMG_20150517_114509940_HDR.jpg

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This is the heat pumps for my house. Mixing valve (on the left) has a pump on the outside woodstove that runs 24-7 . These pumps are for different zones 

IMG_20200223_070441034.jpg

IMG_20200223_070355297.jpg

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The in floor heat is the best heat in my opinion . When I built my shop I was in to big of a hurry to get it done and a tube heater was 1000.00 . Well I can tell you I have kicked my self everyday since that I didn’t do it . The tube heaters work really good but having the heat coming up from the floor is the best and parking trucks in the shop wash bay over night there all dried off in the morning . In the work shop area the floor is always warm , oh and in the spring you won’t get the floor sweat going on for days .

Make sure you put central air in the shop , I know most folks will tell you not to waist the money but I will tell you on those 90 degree days it sure is nice if your working in there all day . You keep the doors shut and only open them like you do in the winter it works out great .There are some guys around here taking a Thermo King off a semi trailer and and setting them away from the shop on there own cement pad and run duct work into the building , Those units run very cheap and you can just run it on those really hot days .

Danny

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Depending how your boiler is built I still cannot see how having the water temp over 125 will let the boiler condense. And yes I have not been keeping up with the newer tech from when I was in the HVAC/R  trade. Can someone explain?

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This is a great resource, thx AK, I built my own house 1800 sq ft on slab in 2001 and then  shop 1500 sq ft in 2004 and put radiant in floor in both, we live in central Alberta so have fairly long winters compared to most.

I used dry sand and vapour barrier under the slab for the house and 1 1/2" styrofoam under the shop. I built all my own manifolds and designed my own system one because I'm cheap and I liked to think I had the motivation, skills and intellect to successfully accomplish.

3 things I have learned that I could have improved or done differently, I didn't consider the secondary loops and ran everything off a primary, this is essential for temperature control of all your secondary devices and improves efficiency, a bit more equipment but really essential on a good install. The second is the mass of your slab, it takes a healthy amount of btus to raise or change it's temperature and much less to maintain it, here is where your insulation is so important, I have never installed it but I think if you installed a bypass timer where 5 or 10 mins every hour you circulated glycol when your zone is satisfied and not calling for heat you would burn less fuel overall. Lastly as good of heat as it is you should have a way of bringing in fresh make up air to maintain a healthy space and get rid of humidity, heat recovery units have come a long way here recently.

If you live somewhere in intermittent temperature zones I don't think this is the system for you, in the shoulder seasons spring and fall I will heat with a wood stove until the clan finally complains enough about cold mornings and when I switch to slab I don't go off for the whole winter.

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Is that a special insulation under the concrete? I would have thought the concrete would crush the insulation from the weight. Does the insulation compact over time causing settling? Sorry for hyjacking thread.

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18 minutes ago, MarkG said:

Is that a special insulation under the concrete? I would have thought the concrete would crush the insulation from the weight. Does the insulation compact over time causing settling? Sorry for hyjacking thread.

There’s a similar topic on Agtalk discussing that very subject! It was a day or so ago so it shouldn’t be too hard to find it

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installed several in floor heat.I used 5/8 pex tyed to concrete wire every foot  sand is a good insulater but i found the foil bubble bubble plastic to work real good and ylu can bring it up the sides of the pour easily. i have used a boiler but had to temper the water temperature. In other installations i used a propane hot water heater in the loop. Ak is right on with keeping your loops at 250 ft. I kept the temp about 5  10 degrees warmer than my ambient air temp.set thermostat and dont touch it. The in floor takes a bit to get started but if you get.it going on the last warm days it wont take hours to heat your space up

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1 hour ago, VacDaddyt said:

Depending how your boiler is built I still cannot see how having the water temp over 125 will let the boiler condense. And yes I have not been keeping up with the newer tech from when I was in the HVAC/R  trade. Can someone explain?

The new boilers run as low as 75* but turn up as needed via an outdoor reset sensor. Some of these boilers are built with SS, Aluminum, or other metals to work like this.  When they are heating at a low temp, under 135* +/- they are more efficient.

there are very few diesel/fuel oil boilers that can do this, mainly works with propane & natural gas

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1 hour ago, MarkG said:

Is that a special insulation under the concrete? I would have thought the concrete would crush the insulation from the weight. Does the insulation compact over time causing settling? Sorry for hyjacking thread.

We use the blue foam from Dow Corning or a similar product.  Minimum here is 2 inches of foam and some are going for 4 inches.

we then wrap the slab edge with 2 inches of foam and put on a flashing.  Stop the heat from conducting out from the building

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7 minutes ago, AKwelder said:

The new boilers run as low as 75* but turn up as needed via an outdoor reset sensor. Some of these boilers are built with SS, Aluminum, or other metals to work like this.  When they are heating at a low temp, under 135* +/- they are more efficient.

there are very few diesel/fuel oil boilers that can do this, mainly works with propane & natural gas

This all sounds great and looks like a good way of heating , Now lets hear some costs $$ what can you expect to spend for a complete floor heating system and what monthly costs like electric or gas  running the boiler ?and recirculating pumps 

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4 hours ago, ksfarmdude said:

Its not my preferred heating system here because of 1st , much higher cost , 2nd, limited seasonal use  maybe in far northern states it would makes more sense My priority building my shop was more space  good quality doors and lots of insulation then finding a good reliable heating system I went with radiant propane heaters best heating source around here for your buck for my 42x63 morton building

IMG_20150517_114509940_HDR.jpg

That is a nice looking building. Morton does a good job. Your size is perfect for 1 or 2 men working. I know machinery is getting bigger but your size is ideal.

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10 minutes ago, AKwelder said:

We use the blue foam from Dow Corning or a similar product.  Minimum here is 2 inches of foam and some are going for 4 inches.

we then wrap the slab edge with 2 inches of foam and put on a flashing.  Stop the heat from conducting out from the building

Here they so times insulate the 4 ft down the footing to.

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1 minute ago, dale560 said:

That is a nice looking building. Morton does a good job. Your size is perfect for 1 or 2 men working. I know machinery is getting bigger but your size is ideal.

Thanks  ,this shop building is the morton energy performer style building fully finished inside and insulated was errected in 2012 I actually only work on  tractors and large truck in this one I have another larger building nonheated I work on combines in mostly because those are dirtier and more debri among nasty rodents getting loose

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One thing that has not come up, a floor heat system can be designed to heat to only 40 or 50 degrees, and then you can use a unit heater like shown in the picture in the first post when you want more comfort.  There are also ice melt systems that keep the sidewalk and driveway clean. 
 

 

the number one thing I would do to a slab is insulate it, then put PEX in. You will be surprised how little heat a slab needs from 20 above and up.  

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I used codeboard it is a high density styrofoam and I doubt it squishes much, I guess it depends what type of equipment and floor loads you anticipate, I have a TD18 that is around 16 tons and a grader and the grader that is 12 tons that has more pressure than the dozer per square inch

I can heat the house for one ton of coal every 3 weeks, it was $27 a ton in 2001, soon to be unobtanium...frown I put sand under the slab for the house which is a good insulator but not as good as styrofoam R5 per inch so 4 inches would be R20. I probably could have heated for a ton a month. It doesn't vary that much from cool to -40, at minus 40 it's your building losing it's heat faster or a bigger difference in temperature causing the increased fuel consumption, I would say you might burn 30% more fuel from normal to extreme cold on my setup but like I said once I start heat in Oct-Nov it's on until April

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5 minutes ago, hardtail said:

I used codeboard it is a high density styrofoam and I doubt it squishes much, I guess it depends what type of equipment and floor loads you anticipate, I have a TD18 that is around 17 tons and a grader and the grader that is 12 tons that has more pressure than the dozer per square inch

I can heat the house for one ton of coal every 3 weeks, it was $27 a ton in 2001, soon to be unobtanium...frown

Everyone used to heat with coal down here in North Dakota also but seems to be fading fast. .

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8 minutes ago, ksfarmdude said:

This all sounds great and looks like a good way of heating , Now lets hear some costs $$ what can you expect to spend for a complete floor heating system and what monthly costs like electric or gas  running the boiler ?and recirculating pumps 

Here we almost exclusively run heating oil boilers, we don’t get much gas here, and they truck it in.  We are paying over $3 a gallon for heating oil, and when people build they spend money on insulation. This is a question of what your heating.  One place I did, was 36 x 48, he uses less than 1000 gallons of fuel a year.  His old hose used to burn twice that and was 1/3 the size 

 

 

the circulator cost?  If you pay $10 a month I would suprised

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15 minutes ago, dale560 said:

Here they so times insulate the 4 ft down the footing to.

We also have to run out from the slab or down the footer. In the city they want something like 2 inches out 6 feet, 4 inches out 4 feet, and 6 inches out 2 feet.

 

its all about keep the heat transfer down

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1 minute ago, AKwelder said:

Here we almost exclusively run heating oil boilers, we don’t get much gas here, and they truck it in.  We are paying over $3 a gallon for heating oil, and when people build they spend money on insulation. This is a question of what your heating.  One place I did, was 36 x 48, he uses less than 1000 gallons of fuel a year.  His old hose used to burn twice that and was 1/3 the size 

 

 

the circulator cost?  If you pay $10 a month I would suprised

We heat house here in North Dakota off a electric boiler. Highest electric bill with electricity and heat has been 270. That was with Christmas lights and everything on. Heat costs about 130 a month for 1200 sq ft 1968 model ranch with basement. And recirculating water.  That isn’t avg 12 month that is 130 for the  7 months of heat .

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4 minutes ago, AKwelder said:

Here we almost exclusively run heating oil boilers, we don’t get much gas here, and they truck it in.  We are paying over $3 a gallon for heating oil, and when people build they spend money on insulation. This is a question of what your heating.  One place I did, was 36 x 48, he uses less than 1000 gallons of fuel a year.  His old hose used to burn twice that and was 1/3 the size 

 

 

the circulator cost?  If you pay $10 a month I would suprised

My 42x63 shop on propane uses around 500 gal to heat over the winter and I contract propane in off season , this year was $1.05 gal

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I bought all the material and built all manifolds myself, I would have all the receipts but I'm not going to dig them out, I did all the work for everything, I think I figured out all the plumbing and heating was around 20K for the shop and house, the boiler was 6K in 2000 included in the 20, I never paid myself for any of the labor by comparison all the electrical with fixtures was around 3K but that was before the spike increase in copper.

When I'm quoting 20K for plumbing and heating that's septic all the way to fixtures installed

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