txav8r's new barn construction (RV but could be boat)

[Bruce]

Guys, I'm in the commercial roofing business and want to clear up your R-Value claims. Spray Polyurethane Foam is a closed cell version of a very common roofing insulation in commercial roofing called Polyisocyanurate. Both use urethane resin and Isocyanate mixed in a 50/50 ratio. The max R-Value of Polyisocyanurate or ISO is an R-5 per inch. It is the most efficient roofing insulation per inch in the industry right now. EPS or Expanded Polystyrene has an R-4/inch. I sell EPS as part of a LWIC system for roofing. LWIC = Light weight insulating concrete.

Do you use spray on polyisocyanurate?

What would the cost be to coat the outside of a 30x40x14 Quonset hut building in 1 or 2 inches and apply whatever roofing product is required to protect the polyisocyanurate?

Thanks

 

[Murf'n'surf]

Maybe you should look into just ventilation for the hot season? Roof fan with air intakes low to the ground.

 

[Julian]

Actually, the barn is tight, and those big doors are insulated steel and do have an R value, although I don’t know what it is. Even the entryway walk door is insulated. The R Value of the foam is R7. It is about an inch and a half. It is thickernin the ceiling as it was ajoce them and harder to layer evenly, so when finished they told me it ended up thicker. And the quantity of product used figured to be more. Be that as it may, the heat loss or gain rate in the building is good, but it doesn’t prevent it from dropping to freezing in long stretches below freezing. Nor does it keep the inside from climbing in the summer eventually. My big issue, is that once the temps climb by late afternoon in a day over 100F outside, in the 90’s inside, and then at night, the temp falls outside, but don’t drop much inside and the humidity is trapped in the building. So I need to condition the air. The question is, could I get a inside temp window of 40 to 80 year round out of a smaller split, or do I need to get the 3 ton?

I'm curious to understand why you want to air condition a garage? Do you piss off your wife that much that you have to spend that much time out there???? LOL Are you using the garage for something other than storing the RV? If you are doing car maintenance....wouldn't it be better to AC a smaller space?

 

[txav8r]

@Julian , these motor coaches are expensive! With expensive components, appliances, and furniture. Hsveing all that in an oven, and then below freezing, is just not a long term life expectancy. The conditioned space would allow the coach to be less affected by extremes. Let’s see, a good comparison is a boat meticulously maintained but kept outside in the sun vs a boat meticulously maintained but kept indoors. And conditioned indoor space goes beyond that. So that is the logic.

 

[BigN8]

Do you use spray on polyisocyanurate?

What would the cost be to coat the outside of a 30x40x14 Quonset hut building in 1 or 2 inches and apply whatever roofing product is required to protect the polyisocyanurate?

Thanks

It's been a while since I was a contractor and priced these systems. Back in the early 2000's I think we charged about $2.50/sqft for 2" Polyurethane foam and coating. I'm sure it's more now. You project would be more because they are working on a steeper slope. Keep in mind foaming the outside will have less than desirable curb appeal. The foam telegraphs whatever you spray it on. And there is a huge spectrum of guys who can spray foam good and bad. If it were me I would spray a white elastomeric acrylic roofing coating on the outside, install some vents, and spray the polyurethane foam on the underside of the roof. The white coating will knock down much of the heat on it's own. White is the most reflective color you can use on a roof. Aluminum coating is not that great, it actually gets pretty hot, just like the chrome moulding on the outside of your car door in the summer. If you've ever rolled down your window and placed your arm on the frame you'll know what I'm talking about.

 

[txav8r]

@BigN8 I hear the logic here. But what I don’t get is they use foil on every product made to create a radiant barrier. So why would a galvanized steel barn not be as reflective? I assumed the metal would be very reflective and the foam would slow heat loss and transfer a bunch.

 

[zipper]

Maybe you should look into just ventilation for the hot season? Roof fan with air intakes low to the ground.

Some good advise here. In my experience on my farm and building/operating several commercial greenhouses, removing the accumulated heat load with airflow/ventilation was a necessity. We used louvered thermostatically controlled fans and louvered air exchange intakes down low. I dislike making penetrations in a perfectly good roof, so I suggest mounting on the end wall, both the exhaust fan up high near the peak with the air intakes on the opposite end near the ground and preferably on the north side, if possible. If security is an issue make them small enough so no one can crawl thru. And cover with hardware cloth maybe 1/4" or 1 /2" mesh on the inside. A link to fans https://www.farmtek.com/farm/supplies/cat1a;ft_cooling_fans.html

If it were me I would spray a white elastomeric acrylic roofing coating on the outside, install some vents, and spray the polyurethane foam on the underside of the roof. The white coating will knock down much of the heat on it's own. White is the most reflective color you can use on a roof. Aluminum coating is not that great, it actually gets pretty hot, just like the chrome moulding on the outside of your car door in the summer.

Galvalume gets very hot in summer even in Vermont. The greenhouse frames become hot to touch, very warm, when not ventilated. Find a way to "paint" the roof white. It will need to be cleaned/degreased before application or it may not stick well. The white elastomeric material sounds good as it will expand and contract with temp. changes without cracking. I mean aren't most of the cars in the south white. As far as heat in colder months, I would hang a Modine propane heater and vent to outside. If you want an air conditioned shop to work in, this is not the setup. It will moderate the extreme temp. swings in the coach storage barn and keep a non-winterized water system from freezing unexpectedly. Greenhouses also use evaporative cooling, but you would have to mist your concrete. Good luck

 

[tdonoughue]

Started a reply yesterday, but got distracted (look, a squirrel!). <sigh>

R-7 is good for a door, but wall insulation recommended for your area is twice that (actually, R-13). Your big doors may be that. For the roof it is R-38. So, yes, you have insulation, but I doubt you have the insulation to avoid your 3T unit and go with smaller options. R-values accumulate, so the suggestions above for adding layers just add to the R's (they are linear) and will do better and better.

Would you be looking to control the climate full-time or only during the extremes? For the cold, you can install some gas heaters pretty efficiently. For the hot, you may be able to put a mister on the roof (like down the centerline so water flows to either side) and gable fans to primarily draw off the heat, then close off the fans and use a lesser AC inside to bring the temp down some (like to the 80's). Of course, gable fans when not working don't insulate very well... And that would not be the type of thing you would set and forget, of course.

 

[Julian]

@Julian , these motor coaches are expensive! With expensive components, appliances, and furniture. Hsveing all that in an oven, and then below freezing, is just not a long term life expectancy. The conditioned space would allow the coach to be less affected by extremes. Let’s see, a good comparison is a boat meticulously maintained but kept outside in the sun vs a boat meticulously maintained but kept indoors. And conditioned indoor space goes beyond that. So that is the logic.

Hummmm...actually the comparison is a boat meticulously maintained an kept indoors in airconditioning vs a boat meticulously maintained and kept indoors but not airconditioned. My struggle is with how much damage that temp fluctuation could do? Sun damage I TOTALLY get...and you have that covered. Don't get me wrong, I'd love to have an AC garage, but that isn't cheap. My brother put his HW heater in the garage....its the kind that works as a heat exchanger....so his garage doesn't get HOT....but isn't cool either. I'm just prodding Mel's inner logic (you are analytical like me) to make you ponder the cost vs benefit equation here I'd be figuring out which way the prevailing winds go (mostly) and putting in gable fans to blow from one end to the other. Another idea would be to look into a portable AC unit you could put inside the RV and duct outside as a summer measure when it gets really hot. That way, you'd have the barn insulation AND the RV insulation protecting the cool air inside the RV.....just brainstorming here....or is there a way to hook up the RV's AC to do this....I would think you could????

 

[txav8r]

I agree with your analogy @Julian . To a degree. The boat is much better at being all weather than the coach I think. Sure, the coach is designed to be out in the weather, but In time, the sun/freezes/thaw/heat, all take a toll, just like on a boat. Let’s shift the comparison a bit. Let’s compare boats with household systems. Because that’s what I’m dealing with. I have holding tanks, both black, and gray water, fresh water tanks, hot water heater, water distribution, accumulator, water pump, and faucets, not to mention a refrigerator/freezer, that has water and ice in the door. All of these can and will freeze if exposed to freezing conditions. I want to be able to use the coach on a moments notice even in the winter. It takes about 2 to 3 hours to completely winterize the coach. I use air to blow out the lines but I have to drain the tanks and water heater. I forgot the filter last time but it didn’t crack so I was lucky.

Now consider the summer. The building is getting up to outside temps inside over time, and the humidity is going higher than outside, and, the nighttime temp and humidity inside is awful. I could add ventilation but would still face 100+ interior temps. While the coach can handle those temps, in time it takes a toll. And my coach has already had exposure being 10 years old now. So getting anouthe 5-6+
years out of it is the goal. Everytimemitnis exposed to high heat, the wood trim inside tends to come apart if glue is the only component holding it. The stick ups come
Loose too. And that humidity causes mold and mildew. I bought a dehumidifier, and it does dehumidify, but it increases the temp in the process!

I don’t want to throw good money after bad. But I started out just wanting to keep from winterizing. The cost of a hanging gas unit and installation, was told to me to be $4-500. I found no such product that would heat that size barn to even 40F guaranteed, that was less than $1500 installed. Sure, I can do some of the work. But renting a lift again, having to hire a plumber to run the gas line (propane), and costs I just didn’t expect, will not make it much cheaper. Then I stumbled on to a P-TAC unit. And was told I could do this and get a/c too for the $1800 range installed. That turned out to be false as it again needs more tonnage than that dollar amount buys. Then I learned about the mini splits. And while the $1800 quickly jumpers from $1800 to $3600, when it was all said and done, my hvac contractor said I needed the 3 tons and it would cost me about $5200. That’s where @Bruce came forward and said I could buy and install those units myself. He recommended two 18,000 btu units installed at each end. I have some constraints that makes doing that harder than just installing a single 3 ton, 36,000 btu unit on the far end. And, I can buy one complete pretty much for around $2100. So that is more than I originally was told but does twice as much. If I set it to 58 in the winter and 83 in the summer, just arbitrary temps, it wouldn’t run much. When I’m going to be in there, turning it down to 72 summer or up to 72 winter, wouldn’t take a long time because the unit isn’t undersized by much.

As far as the coach having a/c heat pumps, I can run those. But I can’t run them dead of winter and expect to keep all systems from freezing. Because it takes running the propane furnace to keep all the tanks from freezing, and I can’t run those indoors in closed up conditions. Nor would I want to spend the cost to run those propane furnaces full time. Same with running the A/C in the coach. I haven’t had the best of luck with longevity with those Coleman units. And running them indoors causes the barn humidity and temp to increase, causing the a/c’s to work harder.

Kind of a conundrum. I could have never built the barn and let it deteriorate and depreciate, and dictated the need to replace it probably before we were done rving. Wanting to enjoy this with all the best worlds and at a reasonable costs, that’s what I’m after.

 

[txav8r]

Knowing what I know now, I would have done two things different. I would have insulated under the slab and maybe even installed pex in the slab for a radiant floor. Second, I would have put some sort of radiant barrier between that foam and the roof. I hear the conversations about some sort of coating on the roof. I would be interested. Ventilation ideas sound promising, but not sure what good that does in August in north Texas. Regardless, it would be better than the humidity it now has along with temp in August. But winter, I still need to solve.

 

[Julian]

I hadn't thought about all the water tanks and freezing issues! Makes sense!