heating cost. floor vs. air

[Dave Maxwell]

I use ti pay 450 a month just for house

[jack stand]

Originally Posted by Dave Maxwell

Looks like in floor radiant is the thing for me over the long run. Have a forced air unit now I can use until I get all the parts for the in floor.

I DIY all my radiant. Had a radiant design co. do the design work, they provided detailed working drawings that were simple to follow. The materials that go in the slab are pretty cheap, even if you were to not complete the system right away or ever. You're bldg. would be ready for radiant for ever! In a shop, I would not be concerned as much with the professional design as I would if there were living space involved, like I have. There are free heat loss programs on the internet for figuring those numbers into your design and lots of tube spacing/legnth of "loops" etc. info out there as well. I kinda figured when I was questioning myself about the radiant decision, that what money I spent extra on any radiant cost was way offset by the fact that I would have not been able to install the alternate (conventional) heat my self, and would have paid for that labor any way.

[Dave Maxwell]

OK now insulation. I have been looking at the stuff designed for metal buildings. To get a decent r value it is 8 inches thick. I have 2x6 walls. Can it be compressed or does that diminish it capacity? Also the rolled under slab blankets. Are they any good. Big price difference. 600 compared to 3000 for foam board

[sneezer41]

under slab, foam only, everything else is bs

[Highbeam]

The R-value for batts is uncompressed unless specified clearly. It is the dead air space between the fibers that gives you the R-value. If you squish it you squish teh dead air space and lose R-value.

[Dave Maxwell]

Was afraid of that. Trying to get good r value in my walls. What is a good value. Maybe I am wanting to much

[Dave Maxwell]

Reflectix insulation any good?

[jvitez]

Insulation works by trapping air. It's the air that's the actual insulator. DO NOT COMPRESS INSULATION! The air pockets are compressed, reducing the R-value of what you just paid for.

What I used for my 2x6 walls is Roxul.

http://www.roxul.com/residential/pro...l+comfortbatt™

It's mineral wool, R22 vs R20 for a 2x6 wall, is waterproof, fireproof, dusty to install but no fibreglass itch! For your more moderate climate, R40 ceiling and R20-22 walls would be reasonable, but if you float the note, put 1.5 inches of foam board (extruded or expanded polystyrene, XPS or EPS) over the whole outside wall sheathing. It will act as a thermal break so the stud don't lose or gain heat via conduction. The more you insulate, the cheaper the heating cost for a permanently conditioned structure.

[jack stand]

Check out this place http://www.insulationdepot.com/ I have bought from them a few times. They had a warehouse within my reasonable travel distance and picked it up my self. I believe in foam over a "batt" type insulation, but it is expensive. This link makes foam affordable. I have 2x6 walls with a 2x6 purlin to screw the (exterior) metal to. One layer of 1 1/2" polyiso between the purlins on the outside of the stud wall, then a vertical layer in the stud bay, leaving enough room for 3 5/8 fg to complete the wall. Roughly 3" iso @ r-6+ per inch = r 18, and the fg. at r-13, it is at least a r-24 wall. I sealed all the edges of the ridgid foam with the foam gun to eliminate air flow (very important,especially with all "batt" type insulation. If money were no object, I would have had it spray foamed full cavity.
I also like jvitez ideas above.

[JakeKohl]

Originally Posted by jack stand

My experience is with each is that with the tall ceiling height, all of your hot air rises up against it and then is needed to be blown back down with ceiling fans. For economics, I kept the shop at around 60 and that was fine for winter clothing season but when you blow that 60 deg air back down from the tall ceiling, it became more of a cold draft! Not to mention that an Nascar pit team could not get the doors open and closed fast enough to not loose at least an hours's worth of heat (recovery time) and a cold slab on your feet.
Now with radiant, (in a different shop) none of the above problems are an issue, and the same 60ish setting feels much warmer, and just about tee shirt only! It's hard to explain, but with the heat under you and radiating up at you, the same temp's just feel better/warmer. Another efficiency factor that I had not given much thought to before I went with radiant is that when heating with hot air, you're dealing with 180? deg. air (I'm not a hvac guy), but with radiant heat your water temps are only about 110 deg, that's not very hot water to be making heat from! I heat my water with a wood gasification boiler, but have a high efficiency regular oil fired hot water heater as a backup. Your options for boilers and fuels are pretty wide open. The only downside that there might be to radiant slab heat is that it is not going to respond to thermostat adjustments quickly. That mass of 'crete that keeps you warm after the doors were left up for 20 min. takes days to get up to operating temps at the start of the season (ok maybe not days but it depends what temp's you start to warm your slab up from). It is common to put 2" of ridgid foam under a heated slab, and I would suggest that every dollar you spend on insulation on the rest of the bldg. is money well spent. It is said and very true that insulation is the gift that keeps on giving! I love my slab heat!
And the super insulation holds true for any type of heating/cooling system.

Also note that foam under the slab is not code in several southern states...the termites, though they don't consume it, appear to enjoy living in it. After I ran the heat calcs, I was rather disappointed to learn that I couldn't put foam in the ground under my pad in SC.

[jack stand]

Originally Posted by JakeKohl

Also note that foam under the slab is not code in several southern states...the termites, though they don't consume it, appear to enjoy living in it. After I ran the heat calcs, I was rather disappointed to learn that I couldn't put foam in the ground under my pad in SC.

Will they let you use it if you (bug) treat the soil/gravel etc. before you lay out the foam? A layer of poly is recomended under the foam for a MB, I would think that would keep them out of the foam as well. Interesting.

[Steevo]

Yeah, that 75K BTU Mr Heater I have in my 1000 sq/ft shop maxes out at $45/mo in the coldest months of winter, which is Dec/Jan/Feb/Mar, with Dec and Mar being less than $45/mo. That's keeping it at a nice working temp full time, 24/7.
I can't see ever finding a lower (operating) cost solution that didn't have such a high capital cost that it would not pay back in my lifetime.
Of course, the larger the building, the bigger the difference between heating options, so the OP's 48K cu/ft building might benefit from solutions that would never be cost effective in my 11K cu/ft shop.

[gooned]

so I'm still planing on two unit heaters with a pair of ceiling fans for my "weekend use" 1000sf shop up here in B.C.
I have been told that the cost of keeping the thing warm 24/7 with slab boiler on nat gas would kill me $$$wise. At least with electric I can set it for a min value paint etc will store and just get it hotter when I'm out there.

Keep those comments coming guys

[Dave Maxwell]

That's what worries me. I hear that keeping on floor at 60 24/7 is cheaper than forced air a few nights per week at 70 when needed

[sneezer41]

reflectix is a scam


I would be surprised if foam underslab is actually against code. There is certainly an issue with termites and carpenter ants, but I am sure there is a way around it

[JakeKohl]

Originally Posted by sneezer41

reflectix is a scam


I would be surprised if foam underslab is actually against code. There is certainly an issue with termites and carpenter ants, but I am sure there is a way around it

Exterior foundation foam / soil contact is against code in South Carolina, Florida, Georgia, Alabama, Mississippi, Louisiana, Arkansas, and Texas. You can encapsulate it in concrete and it appears that you might be able to put it under a slab (i.e., not external) - but even that has shown instances of infestation.

5th paragraph down:
http://dow-styrofoam.custhelp.com/ap...-insulation%3F

top of 4th page:
http://www.ornl.gov/sci/roofs+walls/...technology.pdf

footnote on page 8:
http://www.ornl.gov/sci/roofs+walls/...technology.pdf

[Shop Specialties]

You only need 1/3 of the BTU to heat the slab as compared to forced air. Once the slab is hot it takes very little to maintain it especially when the doors are shut.

2 forced air units to only heat 1,000 sq ft ?

[dirttracker18]

Totally worth the extra expense for me to have in floor.

After having it I would not have it any other way. I keep my shop at 55° air temp and it feels much warmer than thay after a few minutes in there. Working on the floor is great and working up high is virtually the same temp as near the floor.

A big plus is opening and closing the service door in winter. A minute after the door is closed it feels the same again, and no wind from a heater blowing crap all over the shop and overheating me while it is on.

Was afraid of that. Trying to get good r value in my walls. What is a good value. Maybe I am wanting to much

It is more important to make sure you seal the place up good. Ensure you do your best to seal everything up well, accoustic sealant at the bottom, plastic boxes around all electrical, tape up all seams, etc.

Snow melts off vehicles faster and melts from the underside, unlike having hanger units which can takes days to warm up under the vehicle.

[Perryk]

Originally Posted by Shop Specialties

You only need 1/3 of the BTU for in-floor as compared to forced air. Overhead radiant tubes are great if you just want heat under them. If you generate waste oil you will have free heat and be eligible for a up to $ 1.80 per square foot Federal tax credit. You want to check to see if there are any state tax credits available for going waste oil. Here in Montana if you go in-floor with a waste oil boiler the tax credit is 25% the cost of the total job.

Interesting theory on the tube heater.....I have been in some big shops using a radiant tube and it felt warm all over...

Waste oil is a serious pain in the ass, it stinks, and is always messy. Plus I looked at the cost of a boiler...$5000+ on top of the pex/manifold/styrofam insulation...thats a $10 000 heating system that requires you to constantly deal with dirty, skunk smelling waste oil?...no thanks.

I know you are into selling, servicing, rebuilding waste oil equipment. Great for a diesel shop, but for the average guy the its not worth the hassle.

[gooned]

Originally Posted by Shop Specialties

2 forced air units to only heat 1,000 sq ft ?

Yeah but only the "construction heater" little 4KW portables, put em on a shelf and you can throw them on the ground if your under something in the winter. By far the cheapest up front cost, and I REALLY doubt in floor heat 24/7 is that cheap to run - I am STILL running the house furnace this year with the cold wet spring here...