Help with shopping list - 40X40 Shop

R_and_D

Hey folks,
I've been snooping a bit on here and can't find exactly what I'm looking for so wanted to just ask... I'm hoping someone can give me a good list of what I need to look for in installing a radiant heat floor in my 40X40 shop... Now I've already downloaded the LoopCAD software and have a loop plan for the building but I'm still in the dark on what all I might need based on my overall system plan... So, here is what I'm planning on in the future system...
- 6 loops of 1/2" on 12" spacing with 2.39 USGPM total system flow.
- Solar Panel(s) for heating and water heater/surge tank to suppliment.
- No propane or NG onsite, only electric...
- Also, have considered possibly including a loop to the wood stove I plan to install as well... Thoughts?
- In slab temp OR outside temp controlled system.
- Ability to adjust a zones heat (we will have a 300 sqft apartment within the shop)

I understand and prefer quality and understand that it costs more but I don't want to break the bank... I'll do it in stages if needed over the next few years. I plan on doing the install myself and some specifics on the build... 4" floating slab on compacted red dirt with 1.5in foam insulation underneath. The building itself will be 40x40x14 with an apartment and loft running down the south side... I'm sure there are more details I need to provide but was hoping this will get me started... Thank you in advance for the help!

Dustin

SWEI

2.39 GPM total flow would imply 12-18k heat loss at design conditions. Is that what you got from LoopCAD?

It takes much more than a "loop to the wood stove" to heat water safely and effectively using wood. Start by reading this and come back with questions.

Solar thermal space heating is nontrivial from a design perspective. If you hire a contractor, it will either be quite expensive, be done wrong, or both. If you want to do this yourself, plan on doing quite a bit of technical reading. I'd probably suggest starting with Idronics #12, then maybe #6 and #17.

R_and_D

Yes... 19,700 heat loss. Yes it's from LoopCAD.

Yes, I'm aware that it takes more than just a loop to the wood stove, This would only be to supplement the total system when the apartment is occupied. I'm aware there would be other controls to make sure I'm not over heating the system. Again, I'd build the system around the solar/electrical to keep the building above freezing and supplement with wood heat when occupied and the demand is higher.

Your statements are true and thus the reason I am taking this project myself... I'm a technical person (engineer) so I know with some direction and suggestions on which brands are better than others I should be O.K.

Is there a reputable online dealer to buy from? I've got some time off coming up so wanted to try an get the PEX down and slab poured, the other equipment can come later. Thanks for the link, I'll study up and come back. In the mean time, website for ordering supplies? Also, I've got some circuits that are almost 300ft... Will that be ok? Should I add another loop to bring down the length?

kcopp

You cant get LP/ propane to the site?

R_and_D

I can but it's a bit extra work to get it piped over to the shop. I was hoping I could keep the building at a reasonable temperature (50-60) with solar while vacant and then use other means when occupied.

kcopp

You cant simply move a bottle to the side on the building?

The problem w solar is the time when you need the heat the most is when the sun is out the least.
I like to keep all the systems I install as simple as possible. Install the slab... pay attention to detail and make sure to get the edges insulated w blue board. Then install a decent quality LP boiler or if you must, a LP gas water heater.

I think you will be far ahead on budget.

Where are you located? There may be someone near you to help out w/ the details...

Ironman

Unless you're in a warmer climate, 12.3 btus per sq. ft. sounds too low.

You've got to think worst case scenario when designing. Solar is best case scenario. The sun won't be out when it's 3am at design temp.

SWEI

This is one of those cases where building envelope performance becomes absolutely critical. If you are located in a cold climate and the heat loss calc you provided is accurate, you clearly understand that. Passive solar features in the shop?

R_and_D

I'm in NW Arkansas... I calculated roughly 15BTU/sqft. Load of 23,835 BTU. I agree with the premise that it won't be that effective at 3AM however 80% of the time it will be unoccupied and when someone is there they will be using supplement heat. Wouldn't the heat from the day still maintain some through the night, especially if it's running off a tank? On the subject of circuits, do you think the program is right with loop placement and size?

R_and_D

I was conservative on my building envelope calcs.... The run down goes like this... 1.5 rigid foam board all the way around, possibly using a friend who does foam sealant and spraying a .5 layer of closed cell (still undecided, as it's not cheap) then utilizing R30 batts up top and R19 on the walls. No passive solar design except south facing windows that will catch some sun in the winter but doubtful it will move the needle. Wind is blocked from the north and west (prevailing in winter) and only an insulated roll up door is on that side.

Ironman

Realistically, solar will give about a 30% contribution to space heating, depending upon the number of panels.

Let's say you put in an inordinate number of panels and keep the space 55*. Maybe then you'll get 50%?

The sun is out for about 8 hours during the winter, and no matter how much solar storage you add, you're still gonna get about 8 hours production on sunny days.

Another thing to consider is that a slab is high mass: it takes hours, many hours, to bring it up to temp. You seem to be planning on setback when the shop is not used. This is difficult with the full horsepower of a properly sized boiler; it won't be a reality with the modest input the solar will give.

Am I saying don't use solar? Absolutely not. Just don't expect more than what it can actually do.

hot_rod

I'm in SW Missouri, with about the same size shop. The office on the south side gets a lot of passive and often over-heats on sunny winter days!
Five 4X8 collectors does some of my shop, wood boiler, and LP for weeks when I travel. I have a 500 gallon tank that the wood and solar dump into. The past few nights we have been in the high 20's. If I get the 500 tank to 160F, it carries through the night.

The shop stays warm from the heat loss from the boiler, so the radiant mainly runs for the 600 sq. ft. of office and apt in the shop.

Stop by if you want to see the system.

Insulation is key, I am spray foamed and some ICF's.

If I had a do over it would be to add more under-slab insulation, I used 1" I would go with 2". I would also tube it at 9", maybe 6" next time for lowest operating temperature and quicker response.

Good seals around overhead garage doors is a big plus, my old door had a lot of infiltration.

Edge insulation can be a funky detail with metal buildings and slab on grades.

I have the metal suppliers break a Z flashing to cover any insulation that sticks out beyond the metal siding. At least 2" around the slab, down 18- 24" It covers the edge of the foam and creates the rat guard with one detail.

R_and_D

This is great information! Also the links provided earlier is great as well. I've forgotten how much I enjoyed thermo in college.
Ok, message heard on the solar. I'm open to changing plans and from what I'm hearing LP is a cheaper more practical method of fuel.
It sounds as if Hot Rod has a similar setup to what I'm looking for, with solar and wood when occupied and LP when traveling? RIght? Also, on the 500 gallon tank... What type of tank did you use? I'd definitely be up for coming to take a look at a real word example.
Bottom line.... I'm an opportunist (buy stuff cheap when available) and technical geek and in this instance I have a lot of time to build the rest of my system... I just want to make sure I've got it sized right for the future and so I know what to purchase when something pops up... Example being a wood stove with hot water circulation take off. Do the calcs look ok below?

P.S. One thing I forgot to mention is that I have access to most everything that would be used in a poultry house (used) so if something comes to mind I can most likely find it.

Zman

The attached spreadsheet will tell you whether you will save money by bringing in propane. Just type in your local rates.

hot_rod

R_and_D said:

This is great information! Also the links provided earlier is great as well. I've forgotten how much I enjoyed thermo in college.
Ok, message heard on the solar. I'm open to changing plans and from what I'm hearing LP is a cheaper more practical method of fuel.
It sounds as if Hot Rod has a similar setup to what I'm looking for, with solar and wood when occupied and LP when traveling? RIght? Also, on the 500 gallon tank... What type of tank did you use? I'd definitely be up for coming to take a look at a real word example.
Bottom line.... I'm an opportunist (buy stuff cheap when available) and technical geek and in this instance I have a lot of time to build the rest of my system... I just want to make sure I've got it sized right for the future and so I know what to purchase when something pops up... Example being a wood stove with hot water circulation take off. Do the calcs look ok below?

P.S. One thing I forgot to mention is that I have access to most everything that would be used in a poultry house (used) so if something comes to mind I can most likely find it.

I do have plenty of scratch and dent stuff. I use LP tanks for the buffers. I have a spare 160 gallon, with legs to mount vertically. Expansion tanks, pumps, controls, misc stuff.

It would take a sizable wood stove to pull much hot water off. I'm sure you have seen those outdoor furnaces as you drive around, you need about that much firebox. The other concern with adding a HX to a wood stove is pulling too much heat, cooling the flue and forming a big, dangerous creosote mess.

With LP at $1.25, it is hardly worth cutting and conditioning firewood

R_and_D

I do have plenty of scratch and dent stuff. I use LP tanks for the buffers. I have a spare 160 gallon, with legs to mount vertically. Expansion tanks, pumps, controls, misc stuff.

It would take a sizable wood stove to pull much hot water off. I'm sure you have seen those outdoor furnaces as you drive around, you need about that much firebox. The other concern with adding a HX to a wood stove is pulling too much heat, cooling the flue and forming a big, dangerous creosote mess.

With LP at $1.25, it is hardly worth cutting and conditioning firewood


Sounds like my kind of system... I realize the problems that can come with a HX on a wood stove and would only use one designed for that purpose, which from what I've seen pulls from the outside down around the firebox and allows the firebox and flu temp to remain high. Essentially you'd be just heating the water instead of air around one portion of the stove...

Once bit twice shy... Where we got it from Anderson's at $0.98 this year, if you recall 2-3 years ago it was over $4 for 6 months. Plus I find cutting and splitting therapeutic in some twisted fashion. I generally keep 3-5 cords on hand.

R_and_D

PM sent to you Hot Rod.

SWEI

Passive solar design is still your best bang for the buck. No moving parts, no maintenance cost, and pays back for the life of the structure.

R_and_D

Agreed on the passive solar and I'll do what I can where existing design permits. I'm using reclaimed and recycled elements so a 100% passive design would be tough but you've got me thinking there are some way to do it down the line... One thing I would like you all to confirm is my thinking around the circuits. PEX is cheap so I'm inclined to put more than minimum and go with the suggestion for 6" spacing... It ups my circuits to 11 which is a bit of added expense in the manifold but I like the idea of it increasing the response time in heating up. It still keeps the flow rate at 2.9 GPM so most of the other equipment stays similar size. This way I can get the slab poured and decide on what I want to do with the actual system down the line.... Thoughts?

SWEI

As long as you keep the loop lengths within a few percent of each other and they're all in the same space, you should not need balancing valves. If you use a compatible fitting system (ProPEX EP, Aquatherm) you can make the manifolds run the length of the slab and bury them in the pour.