Insulation experts - need some help!

[jeff5295]

Hey guys, I need some insulation advice from some experts.

I have a wood-framed, metal sided, pole-barn building. It’s 36 x 56 and 13’ 6” from floor to bottoms of trusses. Open trusses (no ceiling). I have about 2” of closed cell spray foam on walls and underside of roof.

For heat I have radiant floor with propane water heater. It works fine until we get down around single digit temps (F). Lately it’s been struggling to keep up. Before someone tells me that my water heater won’t work to heat a shop of that size, I have experience with this in another shop and had excellent results. The difference being traditional insulation vs spray foam. The old shop had a ceiling with blown-in fiberglass and R19 fiberglass on walls. The heater rarely ran.

I’m convinced my heat is working properly, but I’m losing too much heat from the insulation. I thought 2” foam would be adequate as it worked great this summer when using AC. Looks like I was wrong. Probably should’ve used more foam, but thought I’d give it a shot knowing I can add more insulation later at a much lower cost than foam. The 2” gave me a well sealed building so any other insulation should work great (no air infiltration).

So I’m now looking to add more insulation. I’ll probably add fiberglass batts to the walls, but I’m looking for advice on the underside of the roof. I’m thinking the best might be to add 2” or 3” foam board with foil facing (to help deflect radiant heat). This would be fairly easy as I could screw it to the exposed 2X4 girts. That stuff is fairly pricy though and I would like to consider some alternatives.

What about that foil-faced bubblewrap? I’ll have a couple inches of airgap between the girts and the foil should help with the radiant heat.

If this or the foil-faced foam is the solution, would there be any decrease in effectiveness if I add ribbed steel over the insulation to finish it off? I know the bubble wrap needs and air gap to work properly, but does it need air on both sides?

Any other suggestions? If I could find something that would provide insulation and a finished “ceiling” all in one, that would be ideal.

Would bubble wrap be something to consider on my walls instead of fiberglass as well? I’ll have about a 4” air gap on the walls if I went that route.

Sorry for the long post. Hope someone can provide some good advice. If someone would rather speak than type, I'd be happy to call. Just PM me your number.

Thanks!

 

[galwaytt]

Can you access PIR or XPS-backed plasterboard ? Becoming the norm around here - this would give you a plasterboard for finish suitable for taping/jointing, and insualtion, in one go. It's fixed with drywall screws, so just put is straight over your existing structure. Insualation backing is available in range of thicknesses from 25mm to 100mm iirc, around here.........

 

[galwaytt]

..this is the type used around here: http://www.xtratherm.com/products/literature/xttlmf.pdf

 

[walrus]

Bubble wrap is a joke, I wouldn't use it unless you'd like to continue to throw your money away

 

[jeff5295]

Thanks for the replies. I don't really want to use anything that will require mudding, tapping, painting, etc on a ceiling. Too much work/mess. If I can't find an insulation that will give a suitable finish on it's own, I'll cover it with ribbed steel. I haven't seen xtratherm around here, but depending on price it might be worth looking at.

Actually, foil faced bubble wrap (when used properly) works quite well. I agree that under a slab it doesn't work, but with proper airspace it works. Just don't know if it's going to be enough.

 

[walrus]

Actually, foil faced bubble wrap (when used properly) works quite well. I agree that under a slab it doesn't work, but with proper airspace it works. Just don't know if it's going to be enough.

If it works so well, use it.

 

[Jack90210]

Did your old shop have open trusses as well?

Is your slab insulated?

I ask because there might be reasons other than 'insufficient insulation' for your heating problems.

And I'm a big fan of the spray foam. When you say 2", do you mean of closed-cell? Did they use the same stuff on the underside of the roof?

 

[Torque1st]

You can get white plastic faced fiberglass batt insulation. I see it all the time in metal buildings. It needs some protection from physical damage on the lower walls. OSB etc will work OK to cover it. Forget the bubble foil.

The 2 inch foam @ R7 per inch would only be about R14 if I remember right.

 

[little d]

you answered your own question in your first post "The old shop had a ceiling with blown-in fiberglass and R19 fiberglass on walls. The heater rarely ran." ill bet ya a dollar to a donut that if ya crawled up into your rafters you'd be warm as hell!
i see 2 fixes for ya. 1 put in ceiling fans to pull the heat out of the rafters, or 2 put in a ceiling. ive put in tin ceilings, quick and easy! as far as your walls, id wait untill ya fixed your ceiling first, id be suprised if ya needed any thing else.

 

[jeff5295]

Did your old shop have open trusses as well?

Is your slab insulated?

I ask because there might be reasons other than 'insufficient insulation' for your heating problems.

And I'm a big fan of the spray foam. When you say 2", do you mean of closed-cell? Did they use the same stuff on the underside of the roof?

I have 2” closed cell foam on walls and underside of roof. It looks to be a bit thinner than 2” on several areas on the roof though, which isn’t helping. The slab is properly insulated under and on sides of slab with rigid foam, just like my old shop. I also have thermo-breaks at OH door footer, same as old shop.

After doing a little more research and talking to an engineer at work, it sounds like the foil facing would work great for radiant heat, but covering it with steel would negate the radiant properties of the foil, so it’s probably not worth the added expense.

 

[jeff5295]

you answered your own question in your first post "The old shop had a ceiling with blown-in fiberglass and R19 fiberglass on walls. The heater rarely ran." ill bet ya a dollar to a donut that if ya crawled up into your rafters you'd be warm as hell!
i see 2 fixes for ya. 1 put in ceiling fans to pull the heat out of the rafters, or 2 put in a ceiling. ive put in tin ceilings, quick and easy! as far as your walls, id wait untill ya fixed your ceiling first, id be suprised if ya needed any thing else.

Actually, no. I have a loft in the shop and the temp there is the same as ground level. I’ve checked temps on the ceiling and walls with a temp gun and find the ceiling is maybe a degree or two cooler than the walls. The north wall and ceiling are a little cooler yet. With radiant heat, I’m not heating the air so it’s not collecting at the ceiling. Ceiling fans don’t help with radiant heat. Had them in my last shop and only could use them in summer. My problem is losing heat out the ceiling, not having it collect there.

I went with the open trusses because the previous owner built it as a cold storage shed. There are no soffit or ridge vents. Plus, the height to the bottom of the truss isn’t quite high enough for a second floor, so my loft area (along my back wall) has your head above the bottom cord of the truss when standing on the loft.

So adding a flat ceiling isn’t an option, just need more insulation. I’m leaning towards using 2” or 3” rigid foam on the girts. I’ll have about a 1”-2” air gap between the spray foam and the rigid foam, which I believe should also provide some insulating benefits.

I considered the white faced rolls of insulation, but think it’s kind of sloppy looking as it would tend to sag a bit and have wrinkles. I’d just like something a little cleaner looking.

If I go with rigid foam, I could probably paint it white before I hang it and later add ribbed steel to really finish it off nicely, but the budget won’t allow both right now.

I believe I have a good start with the spray foam, but just need a little extra for these cooler temps. When we were around 20-30F, it was fine and the shop held 58 degrees easily. Since we’ve dropped to around zero for the last few weeks, it’s been struggling and running longer. I took a chance on using only 2” knowing there were cheaper ways to add more if it wasn’t enough.

 

[Torque1st]

Ceiling fans don’t help with radiant heat. Had them in my last shop and only could use them in summer. My problem is losing heat out the ceiling, not having it collect there.

The warm air rises from the heated slab and collects up high. This has two major effects. First, the warm air up high is not keeping you and the thermostat warm. Second, the warm air increases the temperature differential across the roof insulation which causes more heat loss. Ceiling fans do help with both problems.

The engineer is correct in that the reflective foil will help reflect some of the infrared radiation back down. Unfortunately the effectiveness of the foil diminishes greatly with time due to corrosion and particulates in the form of dust and soot generated by things like welding or smoking.

The white plastic faced fiberglass bats do sag and they do have wrinkles but they are cost effective which is why they are widely used. Engineers and architects have worked on this problem for many years and the faced fiberglass is the most cost effective solution.

 

[jeff5295]

The warm air rises from the heated slab and collects up high. This has two major effects. First, the warm air up high is not keeping you and the thermostat warm. Second, the warm air increases the temperature differential across the roof insulation which causes more heat loss. Ceiling fans do help with both problems.

I follow your logic. Maybe I'm not understanding totally, but it doesn't appear to directly apply to my situation. I have no warm air up high. I've checked temps and it's not any warmer at the roof than it is near the floor. With no warm air up high, I don't see how blowing the ceiling air back down would help. Seems like it would feel cooler as I would now have relatively cool air blowing around. If the air isn't warm at the ceiling, the temp differential isn't any greater. I've verified temps all over the shop with a temp gun. My old shop wasn't warm at the ceiling either. As I understand it, that is the nature of radiant floor heat.

I'll price out the white faced bats vs foam board and see what looks more attractive.

Thanks for the help.

 

[Torque1st]

I've verified temps all over the shop with a temp gun. My old shop wasn't warm at the ceiling either. As I understand it, that is the nature of radiant floor heat.

Use a regular digital thermometer. It has been my experience that those temp guns **** big time...

Floor heat is part radiant, part convection. Both forms heat the objects in the room and heat the air. Warm air rises.

 

[jeff5295]

Use a regular digital thermometer. It has been my experience that those temp guns **** big time...

Floor heat is part radiant, part convection. Both forms heat the objects in the room and heat the air. Warm air rises.

I assume you mean just a regular household thermometer, like the indoor/outdoor type? I can do that. I have noticed the temp gun can't accurately read temps of bare metal objects, but it seems failry accurate comparing to the digital thermostat that's running the radiant heat. I can tell you it doesn't feel any warmer up near the ceiling though, so I'm thinking the temp gun is fairly close. I'm willing to give it a try.

I'll probably just steal the one from our living room and move it to the shop for a few days.

I decided to turn the heat down for a while until I resolve this. I'll be busy this week and won't get a chance to work in the shop anyway. I set it at 43 last night and when I went down this afternoon, it was 44.5 and nothing was running. The manifolds were cool, so I don't think it had been running in quite some time. Seems to be holding that temp OK, so I think I'm not too far off on my ideal insulation since I'm only shooting for 58. We're finally seeing double digit temps, so that will help as well.

I'll set up the thermometer tonight and report back tomorrow.

 

[jeff5295]

Here's a quick update. I moved our indoor/outdoor thermometer down to the shop. I mounted the outdoor sensor near the ceiling (not at the peak, as I can't reach that high without scaffold or scissors lift). The base unit is about 6' off the floor. I let the temps stabilize and it appears there is about a 1 degree (F) difference, with the ceiling being cooler. This corresponds with the temps I read with my temp gun.

What I didn't think to do was place the outdoor sensor near the base unit to see if they read the same. I will do that to check for accuracy tomorrow.

The unit has a high/low memory. I reset it so tomorrow I can see how warm and cold it was at both locations through a 24 hour cycle.

I'll let you know what I find tomorrow.

 

[Torque1st]

II have noticed the temp gun can't accurately read temps of bare metal objects, but it seems failry accurate comparing to the digital thermostat that's running the radiant heat.

Different surfaces and objects have different emissivities. An infrared temp sensor has to be calibrated to the surface it is reading. They are useful to measure process temps and differences after they have been calibrated.

When you are actually in a heating cycle you will notice a temperature gradient.

 

[RobSmith]

Bubble wrap is a joke, I wouldn't use it unless you'd like to continue to throw your money away

Wasn't bubble wrap developed for stress relief ? (and at the same time annoy the **** out of someone else)

 

[walrus]

Use a regular digital thermometer. It has been my experience that those temp guns **** big time...

Floor heat is part radiant, part convection. Both forms heat the objects in the room and heat the air. Warm air rises.

Isn't one of the benefits of radiant heat in a slab that the heat stays low and doesn't collect at the ceiling? Its not warming the air but the stuff in the room. That's the selling point I hear all over Maine anyway. I have no experience with it but I will once I get it set up in my shop

 

[jeff5295]

Isn't one of the benefits of radiant heat in a slab that the heat stays low and doesn't collect at the ceiling? Its not warming the air but the stuff in the room. That's the selling point I hear all over Maine anyway. I have no experience with it but I will once I get it set up in my shop

This is true, both in theory and in my experience building two radiant slab shops. When heating the air as in a traditional furnace, you have to overheat the air to compensate for the hot air rising away from the work area. Radiant works just the opposite. The floor is the warmest part and it gets cooler as you go up (not much). The slab would only be marginally warmer than the thermostat setting. The air being warmed is just a byproduct of warming the objects.

Here's what I've found from my temp experiment. I measured at about 6' off the floor and about 1' below the roof insulation, about 1/3 the way up the incline of the roof on the south side of the building (the highest point I could reach). This is using a digital thermometer with indoor/outdoor readings. The outdoor sensor was placed high and the base unit (indoor) was the lower one. Thermostat set at 43 and test was over a 24 hour period.

Currently - UP 42.6 - DOWN 43.3

Max - UP 47.8 - DOWN 46.8 (It was a sunny day. No windows on that side of the building, but I get some solar gain)

MIN - UP 42.4 - DOWN 42.4

I belive this confirms that heat is not collecting at the roof and that ceiling fans would hurt more than they help in my case. I've never seen anyone use ceiling fans in a radiant floor situation.

I belive this also tells me that my heat is slowly escaping through the insulation (both walls and roof). I still have snow on the roof, so I don't think I'm losing a lot. I guess I'm coming to the conclusion that I need more insulation, but probably not a huge amount more. I'm leaning towards adding (in addition to the existing 2" spray foam) either 2" rigid foam under the roof or the white faced batts. On the walls, probaby unfaced batts which will get covered. I can get 7 1/2' wide rolls that fit perfectly between the 6x6 post at 8' OC spacing.

I should note that the systems isn't running much with the 43 thermostat setting. I prefer to keep it 58 in there, but that's when it was running a lot so I turned it down until I resolve the issue. It could sustain 58 when the outside temps were in the upper 20s or higher. It's when we got around 0 to teens when I started having problems. I think just a little more insulation should do the trick.

Anyone have thoughts/comments on my findings?

 

[trailwart]

in my barn my trusses are 48 on center. i am gonna run drywall corner bead at the bottom of each truss and set 4x8 sheets of foam insulation there. im wondering if your issue is not what the temp is high and low or heat loss, im wondering if its the amount of air(volume) being heated. if all the air above the bottom of the trusses was taken out of the heat eqaution, i think you would be fine.

 

[trailwart]

seems like some people have issues with the water heaters in 0 degree temps. seems like it comes down to recovery time, water is not staying in tank long enough to get heated back up, basically circulating cold water. would be interesting to see what the water temp is that is flowing back into the slab once the system has been running a while in 0 degree weather.

 

[Possum]

Even if the temp remains the same from the top to bottom, you are still trying to heat approximately 6050 extra cubic feet of area compared to your last barn if it was similar in size. I guessed a 4:12 pitch on the roof. Not to mention 2 inches or less of spray in foam is probably not near the R value of the fiberglass you had in the previous barn.

 

[little d]

Jeff,

on radiant heat. think of a wood stove, its brick lined, ya build a fire in it, and after the bricks warm up, they radiate the heat out into the room for hours after the fire goes out. if ya take out the brick, build a fire, it radiates for a while, but shortly after the fire goes out the stove cools down. this is how a floor radiant heat system works, ya warm up the concrete, and it radiates it into the room. being its in the floor, you get warmth from the floor up, but, and this is a scientific fact, heat rises, don't take my word for it, check it out.
OK i looked at your temp readings, this is the highest they have got? you have probes with your heating system. either not enough circulation, not enough coverage, or not enough temp. i would get a heat, and flow gage. if ya got the temp, and the flow, then id say you don't have enough "loops" in your floor. possom and thrust are right, with your ceiling open your heating a lot more area, again, don't take my word for it, call a hvac shop and ask, good luck, little d.

 

[buddyboy]

3 variables you need to work with

one is the amount of BTUs your heater can produce
two is the cubic feet you're trying to heat
three is your heat loss

you need:

a) bigger heater (faster recovering time)
b) smaller cubic feet to heat (block off ceiling)
c) more insulation (to stop loss)

 

[jeff5295]

this is a scientific fact, heat rises, don't take my word for it, check it out.
OK i looked at your temp readings, this is the highest they have got?

I see what you're saying, but your statement isn't technically correct. It's a common misconception that heat rises. It does not. Heat goes to cold, wherever that may be. Hot air rises, but I'm not directly heating the air. If I was directly heating the air, I would see higher temps near the ceiling. The studies I've seen for radiant floors show just the opposite. The warmest temps are near the floor and the higher you go, the cooler it is, but only by a couple degrees max.

I agree that the air is being heated slightly as result of the floor giving off heat, but to nowhere near the extent of forced air heating system.

The temp readings are after I turned the thermostat down to 43. They're not the highest temps the building has seen this winter. I think they are about what I expected considering I was only attempting to heat to 43 for this test. They dropped a bit overnight and went over the thermostat setting during the day. They hovered right around the thermostat setting and the system did not run excessively.

The problem is when I'm trying to achieve a higher temp. For instance, when I had it at 50, it kept up fine during the day, but struggled during the dark hours. It boils down to the temp difference between outdoor and indoor. It got down to -10F the night of the test. This would be a 53 (-10 plus 43) degree difference and it worked fine for that amount. When I'm shooting for 58 and it's -10 outside, that's a 68 degree difference and it couldn't keep up.

I think that tells me I'm close, but losing too much heat thru the insulation when shooting for that higher temp differential. If it couldn't keep up at the 53 deg difference, I'd be thinking something more serious is wrong.

 

[trailwart]

question, what is the highest floor temp that you have been able to achieve during the coldest days. if you cant get the slab over 70, then i think you dont have an insulation issue. the system i think from what you described is not up to snuff. if the thing is runnin all the time, you are just circulating cold water, water goin back in the tank is probly floor temp, water going out is most likely with in a few degrees, but not enough to gain.

 

[jeff5295]

3 variables you need to work with

one is the amount of BTUs your heater can produce
two is the cubic feet you're trying to heat
three is your heat loss

you need:

a) bigger heater (faster recovering time)
b) smaller cubic feet to heat (block off ceiling)
c) more insulation (to stop loss)

Blocking off the ceiling isn't an option as there are not soffit or ridge vents. I'm also not 100% sure the trusses would accept the additional weight of ceiling and insulation. The previous owner did not build it with the intention of finishing off the inside. If I had built it myself, there would be a lot of things done different.

I agree that I need more insulation. Checking floor temps on different areas of the slab show the perimeter is 3-8 degrees cooler than the center. The north wall area is cooler than the south. I think this confirms that heat is escaping through the walls (also ceiling) and it make sense that the north area is cooler because it never sees sun this time of year.

I agree that the interior volume has an effect on heating, but not nearly as much as if I were doing a forced air heat system where all the heat would go to the ceiling. My temps prove my heat is not collecting at the ceiling.

The 2" of foam was a calculated risk and also a bit of an experiment. I at least a completely sealed building (the only air infiltration I have is a slight draft on a few areas around the OH door seal. Need to tweak the track adjustments and hopefully tighten that up a bit). Having the building sealed will greatly improve the performance of any additional insulation I add. If I had it to do over, I probably would have just done about 1/2" to 1" of foam and backed it up with something else. Lesson learned. Don't know until you try it, right?

It's actually warming up around here (we went above freezing for the first time in about 4 weeks yesterday) so I may be OK with what I have for the rest of the season, but I know I need to do something before it gets really cold again. I'm going to try bringing the temp back up a little since it is warming up a bit.

The confusing part about this is that I saw a huge performance increase when I used the AC unit over the summer. It's the same unit I removed from the last shop. Just a 220V window unit framed into the wall. In the old shop (with R19 walls and R38 low ceiling) it could barely drop temp a degree or two. It removed a lot of humidity and made it much more comfortable, but really didn't drop temps.

Running the same unit in the new shop with spray foam was a night and day difference. I could drop 8-10 degrees within a few hours (I was amazed). I would actually have to turn it down to LOW or completely off because I would start to get cold. I always used HIGH in the old shop. So I was expecting similar results in the heating season. I was cooling a much larger interior volume with the exact same AC unit and seeing much better results.

I should note that I only run the AC on the occasion that it's miserably warm and I HAVE to get something done in the shop. It just gets turned on when absolutely needed.

 

[little d]

lol, ok, good luck.

 

[jeff5295]

question, what is the highest floor temp that you have been able to achieve during the coldest days. if you cant get the slab over 70, then i think you dont have an insulation issue. the system i think from what you described is not up to snuff. if the thing is runnin all the time, you are just circulating cold water, water goin back in the tank is probly floor temp, water going out is most likely with in a few degrees, but not enough to gain.

I've never had the slab over 70, but don't think I need to. I'm only shooting for upper 50's room temp. I've had the center portion of the slab up to around 68 or so to maintain 58 room temp. I didn't check my old shop with a temp gun, but I seriously doubt it ever got to 70 either. It wouldn't even feel warm to the touch. Everyone who came in the shop for the first time would be expecting the floor to be hot, but it wasn't. They'd walk in and say "Wow, it feels nice in here!". Then they'd lean down to touch the floor and were a little puzzled because it wasn't all that warm.

Obviously the old shop had more insulation and retained the heat better. I think that's the key to my whole problem.

You had a question earlier about my return temps. At the coldest days, the return temps would be around 60 or so. Definately an issue, but I think it's one resolved with more insulation to retain the heat in the building. If the heat is not escaping as fast out the walls and ceiling, the slab should remain warmer too, right?

 

[jeff5295]

lol, ok, good luck.

I'm guessing by your comment that you don't think this will work even if I add more insulation?

I'm proving that the system currently can maintain a 53 degree temp (-10 out, 43 in) differential, as-is. It has normal cycles and doesn't run excessivley. Why wouldn't just adding more insulation allow me to increase that temp differential?

 

[trailwart]

here is my train of thought. for what ever temp you want the air to be, the system needs to get it there. i would not focus on the in and out temp difference. simple fact is if you need it 65, the system needs to get 65+ to get the air to where you want it. think of the floor as a heat sink as it can only **** out what is going in. just take a look at the cooling system in a car, radiator is the heat sink cooling down the engines coolant. the t-stat controls flow to speed or slow the water. the faster it goes thru the rad. the less heat that can be taken out, the slower, the more heat that can be taken out. now for your water heater in the barn,with that pump running and pushing water thru the tank, it isnt staying in there long enough to gain heat to transfer to the floor. if you cannot get the water hot enough on the return side you are just wasting money on a system that cannot get you where you want to be. an on demand type tankless heater will probly be the best bet for your issues. you need hot water on the return side, not warm.

 

[trailwart]

when i asked if you had the slab over or up to 70 degrees, it was because the system should be able to if it was demanded to. if it cant, you need to look at the heater side of the system- not insulation.

 

[D.J.]

Well I hate to be the one to state the obvious but you are trying to heat 27,216 cubic feet of area. How big was the old shop? Maybe you should consider the fact that you might need to install a ceiling like the one poster suggested. No, wait I forgot you're heating more than that because seems like I remember you don't have the attic area enclosed, do you. Another 1008 plus cubic feet plus, well wait you didn't say how tall the attic area was to the peak! I would need more info. I think you should feel really good tht it's keeping it 43 degrees in there. Man that seems to me like it's doing more than I'd expect it to when it is -10 outside. Might think about putting up some 2 X 4's and some drywall sheets 12' in length
Just my $.02.
Thanks and I rant again! D.J.

Thanks D.J.
________
WENDIE 99

 

[little d]

jeff, na, I'm just saying i think ya need to talk to a hvac expert, more cubic feet, is still more cubic feet. and your right, more insulation will help, to a certain extent, but if you look at the differences between your old shop and your new one, the one diff that really stands out is the ceiling, but like i said, i think ya need to talk to a expert.
I'm sorry if i cam across as insincere, i meant it, good luck with your prob, little d.

 

[buddyboy]

you are generating heat in the slab

you are gonna lose that heat to the outside

why are you surprised to see the temp drop (stay the same) the farther away you get from the heat source?

if you can't reduce your cubic feet then you have to increase your heat or stop your loss.

because the ceiling is not hotter that means your heat source is not producing enough heat.

imagine a candle on the floor, take the temp next to the candle, then take the temp on the ceiling... ceiling will be cooler cuz the candle isn't putting out enough heat for that amount of cubic feet.

 

[jeff5295]

you are generating heat in the slab

you are gonna lose that heat to the outside

why are you surprised to see the temp drop (stay the same) the farther away you get from the heat source?

if you can't reduce your cubic feet then you have to increase your heat or stop your loss.

because the ceiling is not hotter that means your heat source is not producing enough heat.

imagine a candle on the floor, take the temp next to the candle, then take the temp on the ceiling... ceiling will be cooler cuz the candle isn't putting out enough heat for that amount of cubic feet.

I'm not suprised it is getting cooler towards the ceiling. I fully expect that with radiant heat (I believe I've expressed that several times). Several people posted saying my problem was that heat was collecting at the ceiling and I need to blow it back down with ceiling fans. I was proving that is not the case and fans are not needed for this system.

 

[jeff5295]

when i asked if you had the slab over or up to 70 degrees, it was because the system should be able to if it was demanded to. if it cant, you need to look at the heater side of the system- not insulation.

I'm sure I could get the slab to 70 if I tried (not at -10 outside though), but it would be warmer than my target temp in the shop. At my old shop I had a water heater with a little less BTU and I turned it all the way down to its lowest setting (just one notch above the VACATION setting. I had minimal heat going in to the slab and it maintained 58 room temp with no problem. Yes it had a lower ceiling than the current shop, but also had a lot of air infiltration (could feel drafts coming from electrical outlets. The old shop was roughly 100 sq ft smaller in flor space and I had just a little less tubing in that one. Pretty equal heating system on both shops, probably a little better at the new one.

 

[jeff5295]

because the ceiling is not hotter that means your heat source is not producing enough heat.QUOTE]

I didn't address this in my earlier post, but I can't agree with that statement. The ceiling was never warm at my old shop. I don't have documented proof, but I've had to get up high to change light bulbs and the ceiling was not noticebly any warmer than the lower areas of the shop. I obviously had sufficient heat source at that shop (much less than the new shop), yet a "cool" ceiling. I don't believe a warm ceiling is the tell-tale sign that a radiant slab is performing properly. Everything I've researched and my personal experience shows just the opposite. The room will be cooler, the higher up you go (unless using forced air heat system).

If the guy that bought my old place wasn't such an a-hole, I'd go back and confirm some temps.

If adding insualtion doesn't cure the problem, I'll post new questions in the Heating section of the forum.

 

[jeff5295]

i would not focus on the in and out temp difference. simple fact is if you need it 65, the system needs to get 65+ to get the air to where you want it.

I dissagree. You have to focus on the inside/outside temp differential. That is the key. It will take the same amount of engery to heat a room to 50 when it's zero outside as it would to heat a room to 80 when it's 30 outside. I agree that you can't make it 80 inside if the heater can't put out more than 80, but mine can put out more than enough when the temp differential isn't as great.

If the in/out temp wasn't an issue, why does the temp inside change when the heat is turned off? If I have no heat and it's zero outside, eventually it's going to be pretty close to zero inside. If it's 60 outside, it's going to be pretty close to 60 inside. There's going to be some difference as insulation will slow the temp changes and it obviously is cooler at night than during the day.

If it wasn't a factor, why does my home furmace run more often when it's colder outside? I keep the thermostat set at the same temp, but it runs less when it's warmer outside than when it's really cold. That is because it has to work harder to overcome the temp differential between in and out temps. If the differtial temps didn't matter, my furnace would run the exact same amount in December as it does in April. That doesn't happen.

If I'm not understanding this properly, someone please correct me.