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Hydronic Heating Systems - (cement floor heating)

Dusty

Dusty

(Bill)
Premium Member
Simple questions as it relates to cement floor heating systems, there may be a member out there with such an animal, and no I'm not going to install one.

1. Are they efficient with or without ceiling fans?
2. Do ceiling fans help more especially during our western cold winters?
3. Do they help reduce the amount of moisture in damp like climates?
 
Well I don't have in floor heating myself but I'm going to open my pie hole anyhow....I do have family members that have that style of heating both in domestic and shop situations.

Ceiling fans help circulate hot air from above no matter what style of heating system is in place. Hot air naturally rises, and because of that fact the in-floor heating is in an ideal spot to make use of that natural phenomenon.

I can not see how in floor heating would affect air moisture content any different than say water register style heating. If the excess moisture is coming from inside then that is a problem that can/needs to be fixed. If the excess moisture is coming from outside then dehumidifiers inside I believe are the most common solution. Any sort of flame combustion will take up air moisture with it. My natural gas furnace emits water vapor in the exhaust that freezes at the chimney exit. In my climate when we are heating our homes the air is usually pretty dry. The colder it is outside the dryer the air. (There was a real good explanation on this forum somewhere about relative humidity) .
I suspect your temperate climate has significant outdoor relative humidity all year and thus when it is cold/cool outside it makes it feel so much colder and damp.
 
Hi @Dusty : I have installed and have several in floor heating systems- my shop is in floor heating.

1. Yes, absolutely- no fan required and really not advised as you want the heat at the floor in your work space - not up and away.

Design is that you keep the heat low and about head height. You are warm and tools are warm. Fans ruin that dynamic.

2. Should not need a ceiling fan at all. Use of one will push and cycle heat up and out of the comfort zone.

3. Radiant heat “theoretically” will not dry things out or change the humidity , however, keeping the shop warm and the floor warm, will help to drive moisture out as the moisture will evaporate. Proper venting to allow the moisture to exit is needed.

If there are plans to heat the floor that is routinely wet - not going to help


Radiant floor in my shop will keep ambient temps at 65° F and humidity around 35% in the winter.

Reducing moisture is through -de-humidifiers that essentially cool the air, allow moisture to precipitate out and re-introduce the air.
 
I have boiler fed radiant heating in my house, 1700 sq ft with no overhead fans. Some of the house has 13 foot ceilings, some of it 9. I wouldn't want to live in a house without it. In the winter the floor is warm. We walk around barefoot and the thermostat is set at 16C. We wear shoes or slippers in the summertime as the floor is cold and the house is cool. We do have an air exchange system that runs intermittently to keep fresh air coming in to keep things from getting stale.
The kennel is 5800 sq ft with two 5 ton geothermal systems running the in floor heat. No air exchange system other than tails wagging and dogs going in and out and in and out and in and out and....... Perfect for dogs as the floor is warm and melts any snow they track in very quickly. Given that the relative humidity in the winter around here is really low the water evaporates quite quickly. We can wash the floor and have it be dry in minutes.
In-floor heating is perfect if you want the building to maintain a set temperature for constant use. It sucks for on demand heating as it is very slow to respond. The boiler in my house has failed a couple of times and even if it is minus 30 it takes days for the house to cool down and us to notice because of the large thermal mass of the floor, (the walls of my house are ICF and brick). It also takes days to heat up again. On those days in the shoulder seasons when we get 30 degree swings in temperature the house is either too hot during the day or too cold at night but that is a small price to pay and easily tempered with window control.
I have an overhead radiant heater in the shop, 1800 sq ft with 13 foot ceiling and am almost always either chilly or too hot but doing a re-pour of the floor would have been cost prohibitive. If I leave the shop heat turned on for a few days it is quite comfortable as it heats up all the various things in the shop and not just the air.
If you do in floor heating it is critical to do proper under-slab insulation. A portion of the kennel, 2400 sq ft has no slab insulation and is a bear to heat. 1000 sq ft has that foil bubble foil wrap under the slab and is just as bad. CMHC had recommended it at the time but then changed it's mind and said it was not effective in that application. I may as well have lined the forms with 20$ bills. 2400 sq feet of it was done with the proper styro insulation complete with the corrugated ribbing to manage heaving and the channels to accept the radiant tubing. It is night and day difference heating the three difference portions of the kennel. A couple of years ago we hydrodug a channel along the foundation of the poorly insulated parts and dropped in 4 ft of vertical styrofoam. That helped a lot.
 
I have in floor heating in my garage/shop also. The only fans I use are for dust control or fume ventilation. I usually keep the temperature set to around 16 - 17C which is perfect for working. The nice thing is that unlike forced air heating, the temperature gradient is warmer from the floor and cooler as you go up. This makes for much greater comfort as the heat is not above you. I also find it makes standing and working on the concrete floor far less tiring as it is not cold and sucking the heat from your feet. My garage does not have any humidity issues with this system. The floor does dry pretty quick when it does get wet, but our climate is so dry in winter it has little effect on the humidity level inside.
 
BMW, I thought about it when my garage was being built back in the 90's. I had a clear idea of all the advantages but kind of chickened out as the knowledge base (meaning contractors & suppliers & maybe how the costs were shaping up) was a bit skinny at the time. Just curious though - did you zone off certain areas of the either for individual heat control or for flow reasons? What fluid is being circulated? Is the heat source gas fired or electric element? What kind of footprint is involved with the pump equipment? Did you have to increase the pad thickness or do anything substantially different than a typical garage? Would placing heavy machines (say our biggest typical home shop mill or lathe) present any considerations?
 
Are you ready @PeterT : lets begin

My shop is 750 SqFt (roughly) and I have it divided into 3 zones. Rule of thumb for 1/2" pex tubing is tube space is every 12". A 750 sqFt floor will need roughly 750 feet of tubing. For Flow reasons you want to keep each zone or loop (some zones can have more than 1 loop) under about 300 feet in length for 1/2" tube. You can go like 500 with 3/4 tube and 200 with 3/8" tube (in general). Glycol or water as a fluid for the heating medium have different viscosity and thus you can pump water easier so to speak. My manifold has 3 x 250 foot "zones" - however, I just run the shop as a whole. I am circulating Ethylene glycol as there is no chance of it cross contaminating - the heating unit is a simple "on demand" hot gas fired water heater mounted to the shop wall.

  • Ethylene glycol. A historically popular and very effective anti-freezing agent, modern HVAC experts try to avoid using ethylene glycol because of its toxicity. Nonetheless, it is commonly implemented in industrial settings where strict regulation prevents any chance of it seeping into drinking water.
  • Propylene Glycol. A more modern compound, propylene glycol is an effective anti-freeze agent generally recognized as safe by the FDA. HVAC experts use this anti-freeze compound in residential and commercial settings. Propylene glycol is also the preferred anti-freeze for industrial food processing applications.
You can circulate straight water if you don't have freezing concerns. My house is just water as the on demand also does the hot water for our domestic use and I do not want any cross contamination from a failed check valve etc and freezing is not a huge issue - could be if we lost heat for more than a couple days - but I am not concerned

Fluid temp is kept at 100 Deg F for the system. There is one pump and it is pretty small and I have a thermostat and a control box. My system is "open" so I have a header tank secured to the attic floor joists with make up fluid. The tank is an old travel trailer water tank - fit between the joists perfectly.

The thermostat is mid shop and about 4 feet off the ground and set for 60 deg. or 70 if I am painting something.

Pad thickness is 5" as is normal with 6x 6 wire mesh reinforcement that also has the tubing zip tied to it at the 12" spacing. Under the cement floor is 2" thick R10 dense foam board and under that is a vapour barrier 6 mil poly. The foundation is a 4 foot ICF frost wall so there is a 2-1/4 thermal break at the foundation.

The only thing you would need to reinforce for the floor is if you were going to be using a power hammer or something of that kind.

It is cheap to heat the shop - maybe $15 a month and that is tagged into the house heat.

The whole system occupies maybe a half sheet of plywood with the header tank being in the ceiling.

It is super nice to to have the machines warm to the touch when it is 10 below outside :)
 
PeterT said:
BMW, I thought about it when my garage was being built back in the 90's. I had a clear idea of all the advantages but kind of chickened out as the knowledge base (meaning contractors & suppliers & maybe how the costs were shaping up) was a bit skinny at the time. Just curious though - did you zone off certain areas of the either for individual heat control or for flow reasons? What fluid is being circulated? Is the heat source gas fired or electric element? What kind of footprint is involved with the pump equipment? Did you have to increase the pad thickness or do anything substantially different than a typical garage? Would placing heavy machines (say our biggest typical home shop mill or lathe) present any considerations?
Click to expand...
My system has just a single zone in that there is just a single thermostat controlling it. In the main part of the garage which was the original build, there are four loops in the floor. I added onto the garage several years ago and have three more loops in that area. The multiple loops serves to limit the length of the tubing and thus improve the flow rate. I have manual valves that can be used to balance the flow between the two areas, but they actually run full open with good results based on equal return water temperatures from each area.

I did nothing special with the pad other than using the concrete mesh to help secure the oxyPex tubing prior to pouring the concrete. The only issue is that I dare not ever try to drill any anchors in for fear of hitting a tube. That could be bypassed by either setting anchors during pouring or using thermal imaging to locate lines prior to drilling.

The fluid I'm using is propylene glycol, the heat is a Takagi gas fired on demand water heater that is rated for use as a boiler. I originally set it up with a standard hot water tank, but found it to be less than ideal as it requires a lot of fluid, takes up a lot of space and is not overly efficient. I had to replace the heater once before, so when I did the addition I went to the on demand heater instead. It's worked fine for eight years now other than some icing issues on the fresh air intake in very cold weather. With this system and all the associated plumbing and other components ( expansion tank, air bleeder, pump, etc) it occupies about a four foot wide section of wall in the corner and is less than a foot in depth from the wall.
 
Dusty said:
Simple questions as it relates to cement floor heating systems, there may be a member out there with such an animal, and no I'm not going to install one.

1. Are they efficient with or without ceiling fans?
2. Do ceiling fans help more especially during our western cold winters?
3. Do they help reduce the amount of moisture in damp like climates?
Click to expand...

Reason I posted this thread is I had a neighbor (Art) drop by who believed my attached garage had a heated floor. Unfortunately I don't although I told him I would try to find out more on the topic that being the purpose for this thread. I was impressed with so many positive replies and how they varied, however the very basics we're there along with first hand experience.

Art has an older almost double garage that requires the floor being replaced due to much cracking and heaving (no rebar). So I invited him to come and read the replies to this thread and he was extremely pleased by that. He mentioned that he now had better insight into what can be accomplished in a somewhat limited space.

So there you have it folks, happy campers all around thanks to the kind members that replied. Well done thank you!
 
@Dusty : I can send you a Radiant Floor manual that has all the specifications, flow rate equations and installation parameters for different floors if you would like?
 
Brent H said:
@Dusty : I can send you a Radiant Floor manual that has all the specifications, flow rate equations and installation parameters for different floors if you would like?
Click to expand...

Hey @Brent H, if it were my shop I would jump all over your kind offer. Since it's not my shop floor I shall leave it up to Art although I shall inform him of this. Believe he was going to visit our main library to do some reading before he approaches contractors. Thank you just the same.
 
If he's replacing the floor and is even thinking about the radiant heating, he should at very least put in the tubing. Small extra cost even if he does not utilize it for some time.
 
I have infloor heat in my 36x50x14' shop. Theres 1900 feet of tube in the floor, which is 7-8" thick, 65 yards of concrete. Theres R10 under the floor, and r10 all around the perimeter of the slab, r22 in the walls, and r40-50 in the ceiling. I don't have a proper boiler yet, just a small wood boiler i rigged up. I have a suspended propane heater i use to warm it up, while i'm lighting the fire in the woodstove. Once up to temp i shut the overhead unit off. The little woodstove works good to heat the slab up to 60* or so and its very comfortable to work in. The great thing about it is that there are times when i won't by in the shop for 5 days at -30, and the shop never goes below 5*C, with no heat. The concrete and everything in the shop stores a lot of heat.

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