Heated floors?

[myxpykalix]

Do any of you have heated floors in your shops? Are they electric or solar hot water? If electric what is the operating cost?

[dlcw]

My 40' x 80' shop is radiant floor heating. Wouldn't trade it for anything. I have 16' ceilings at the peak and I couldn't justify sending a bunch of heat that high up since my head will never get up there (other then to change light bulbs once in a while.

I put all the tubing in myself over 3" pink panels. The concert is 4" thick with fiberglass reinforcement in it to make it unnecessary to have rebar.

I keep my floor thermostat set at about 72 degrees and I am VERY comfortable even when we are having a temperature streak in the negative numbers to single digits for for highs 10 days to 2 weeks.

Since out electric is $.038 per kilowatt hour, I went with a 100amp on demand boiler. The other option was propane but when we ran the numbers electric was about half the cost of propane.

We have a 800 sq ft appt in the shop so we use a water heater, electric drying, electric oven/stove, plus other appliances and when I combine that with all the power tools, central dust collection, CNC, etc. with the radiant floor system, my monthly electric bill is around $245/mth. When I shut the radiant system off in the summer my bill drops to about $85/mth. Not bad considering I'm heating a 3200 sq ft building with 16' peaked ceilings.

[gene]

Don
What type of ceilings and insulation do you have?

[myxpykalix]

Don,
What i don't understand is how, if your shop air is cold, tools, and other things how does heating your floor make other things warm? Or when you walk in your feet might be warm but when you touch stuff it's all cold?

I understand that heat rises and you have a on demand system so i assume you turn the heat off to the shop when not in use right? If so how long does it take to get the shop warm enough to work in?

[scottp55]

Jack, entire house is hydronic radiant(2800 ft tubing) run off indirect propane boiler.Wouldn't trade for anything. Water going to tubing is controlled by external temperature probe and an algorithm to control the mixing valve for the water temp going to the tubing. Water going to tube NEVER goes above 80F. So floor never feels warm to bare feet. 6" slab/tubing stapled to 2" blue foam(so it's at the bottom-away from the coring/expansion cut every 12'). It is not a fast on/off type heat. When I started working in shop(12x24x8') I just cracked the shop valve(200' tubing) and shop never goes below 50F even in the 0F we just had. But I do open the adjoining fire door to the house when I'm working and within an hour it's 65F. With valve closed the thermal mass of the concrete alone it Never got below 45F ever in 18 years. 12"insul in 2x12 rafters, 6" in walls in shop.
Jack, it's radiant(think a giant 85F woodstove). It heats ALL the objects in the room in a straight line from the floor. THEY warm up which heats the room air. Lost power 3 days in sub zeroF 5 yrs ago and in those 3 days house only went down 10 degrees. It takes a long time for the heat to come up-BUT it takes a long time for the heat to go down also. The heat you put in today, will mostly still be there tomorrow. Put thermal breaks in so slab doesn't touch foundation.
You can also set it up to run COLD water(AC) but you want to make sure you run either a de-humidifier OR keep the water above the condensation temp or you'll have "Dew" on your floor and mold problems.

[gpinard]

Hi, I also have radiant heat. About 4500 sq ft on 3 floors. Basement workshop 4” concrete on 2” insulation, tubing attached to 6x6 wire mesh at mid slab, 2 upper floors of living space 1 ½” concrete topping slab on wood structure. The thermal mass on the living floors is less at 1 ½” thick so it reacts a little quicker than Scott describes, but still takes a couple of days to heat up or cool off. Mine is an heating oil fired boiler, not as economical as when I made the decision to use oil in 2001, but still reasonable for the sq ft. To do it again I might change the source but not radiant, it is wonderful. The best way I have found to describe it, is heat is a non-issue, you come in the space and are comfortable.
Radiant heat is a little different animal to understand, I can add to Scott’s description a little. On a cloudy day when the sun pops out and shines on you, you feel the warmth, and yet the air temp has not changed. The sun is radiating energy to you. In the grocery store in front of the freezer case, if you measured the air temperature you might find it to be a couple of degrees less than in other areas of the store, not enough to explain the cold you feel in front of the case. You have become the radiator and are providing heat to the colder object. When the mass of your building and the objects in it are at a compatible temp with your body, you are comfortable. One common misconception is that heat rises. This is not true. Heated AIR rises. In a forced air system, over temp air is pumped into the space warming you and objects as it races UP, displacing air that has cooled from the ceiling. This creates a lot of air circulation and movement. Radiant heat does heat the air but only up to the temp of the surrounding objects, there is a lot less air movement in radiant, the ceiling and roof are cooler. In my home we have a big window wall, this is an area of greater heat loss. In the winter as you approach the windows, you would become the radiator, so the radiant panel (the area of tubing in the concrete topping slab) is run at higher temp, the panel in front of the windows delivers more energy to counter act the area of greater heat loss, so it remains a neutral environment for the occupant. Think the check out at Home Depot, with the roll up door open in the winter, look up and see the gas fired long 4” tube glowing orange above the checkouts. A radiant source delivering energy directly to you in spite of the greater heat loss.
Dan Holohan is the author of an excellent book on the subject, “Hydronic Radiant Heating, A practical guide for the non-engineer installer”

[steve_g]

Jack…
Just to add to the caveat expressed by others…
I remember with great fondness laying on our radiant heated floor and playing with my trains… My parents hated it as the house was always catching up to the cold, or grossly over heated as millions of BTU’s of stored energy in the slab dissipated. When I built their new house, we used perimeter hydronic radiators that they were very happy with.

SG

[gpinard]

We also experienced what Steve described. In days that the outside temperature had a larger swing, the system could not react quickly enough to the falling outside temp, so the house temp would cool off. The system is calling for and delivering heat. Then as the outside temp rises and the house has been calling for heat, it ends up overshooting the mark. For us it was not a big deal, we noticed it, but it was not uncomfortable. On days with not so large of temperature swing we did not even notice it. Whether it is cold or warmer is not the issue, only the change in outside temp thru the day.
About 4 years ago I upgraded the controls for the boiler to a computer based (Scott’s algorithm) control. The new control eliminated the problem and paid for itself in fuel savings that year. I think now the simplest computerized controls take care of this problem.

[dlcw]

Don
What type of ceilings and insulation do you have?

My shop building is constructed using structured insulated panels (SIPS). The eve walls are R-30 and the gable end walls are R-36. The ceiling has 30" of insulation giving it an estimated R value of around 64+. The SIPS make the building virtually air tight.

I have to keep windows open a crack to keep air circulation. Some day I might add a air handler to move the air around but the down side would be introducing moving air around (moving dust everywhere).

[dlcw]

Don,
What i don't understand is how, if your shop air is cold, tools, and other things how does heating your floor make other things warm? Or when you walk in your feet might be warm but when you touch stuff it's all cold?

I understand that heat rises and you have a on demand system so i assume you turn the heat off to the shop when not in use right? If so how long does it take to get the shop warm enough to work in?

The shop air up to head level is warm thus making all the machines warm (reduce or eliminate rust potential). Anything above head level does not need to be heated.

The heat stays on all winter. It takes a lot more energy to heat things up then to keep things at a constant heat level. Since I also have my "apartment" in the shop building, I keep the thermometer set and don't vary it. When it starts to warm up in the spring, I back the thermostat down a few degrees. It takes more then 24 hours for the slab to change 1 degree up or down in temperature. Remember, I'm not heating air. I'm heating a massive concrete slab which radiates the heat from it. We can have 5 to 7 day power outages and the temp in the shop building stays comfortable even in the coldest temperatures.

At some point I will think about a backup electrical generator in the case of longer black outs like what happened in 1997 when there were places without power for 6 to 8 weeks in the dead of winter after a huge ice storm took the power distribution grid apart.