Retrofitting Insulation for a Milking Parlor
Reader CALEB in SLEEPY EYE writes:
“Hello! So many questions! We have a simple 20 by 30 pole shed we are looking to retrofit into a cow milking parlor on one half and a general purpose/milk equipment cleaning area on the other half. We’ll pour concrete, insulate, and then install steel on the entire interior. We’ll also be removing the current sliding doors, framing in those openings, and adding man doors/windows (I’m hoping that will be fine to frame in on the slab and won’t have frost heave issues?) Currently, the exterior is just metal on wood, no WRB, no soffit or gable vents. The rafters do not seem very substantial and about 8 feet apart, so we are hoping to have a local design build figure out how we can beef them up to support insulation and steel ceiling (unless that’s something you guys can do?). My main questions at this point are with the insulation. I realize this is the age old question, but my hours of research have still left questions. I am hoping to insulate without rigid or spray foam because of price and difficulty of future repairs with spray foam. With foam board, there’s no more drying to the exterior and I would prefer that since this will be a substantial amount of humidity produced in this environment during milking equipment cleanings. Without using foam, it seems I would have to remove steel and install WRB if I hope to have a good air seal, correct? Once there’s a WRB, can I then just use 2×6 walls with fiberglass or mineral wool batts, or insulation blankets? Then vapor barrier, and then steel? This seems to still allow drying to the exterior which I would think to be a good thing. On cold days, will moisture that does make its way into the wall cavity still condense on the WRB? Or does it go through the WRB and condense on the back of the steel? I ask this to try and figure out how much it matters if I do fiberglass or mineral wool batts. As for the ceiling, after adding gable vents, would I be fine with just blow in fiberglass on top of the new flat steel ceiling? I am not sure how to address the condensation on the current roof steel without pulling all that up and adding the reflective insulation you mention in other posts, or spray foaming. I suppose all of that above could be summed up in the questions, what would be the best way to insulate a bare bones Minnesota pole shed without foam? And, if you think foam would make more sense to add, what would be the best way?
Thank you.”
By the time you get done retrofitting this building, you could start from scratch and build a new building for less. And – it would be exactly as it should be, not sort of like.
Assuming you are dead set upon utilizing this building….please read on.
Before pouring concrete for your slab, excavate between columns and install minimum R-10 rigid insulation at least two feet down and two feet out around entire perimeter. This will assist in mitigation of potential frost heaves. Under slab should have same insulation from wall-to-wall with a minimum 10mil vapor barrier on top of insulation and beneath concrete.
Walls – remove wall steel and place a well-sealed omni-directional WRB between framing and siding. Add 2×6 girts bookshelf style between columns flush to inside of posts. These girts will both provide an insulation cavity and will also serve as framing to support your interior liner steel panels. Then place R-30 Rockwool batt insulation between wall girts. This wall assembly will dry to building exterior. Moisture passing through your wall, should pass through WRB and may condense on inside of wall steel, leading to it either evaporating or running down inside of wall steel and out through bottom of siding.
At a 20′ span, roof trusses do not have to look very substantial in order to be strong enough to carry a decent amount of load. With specific information on how those trusses are built, we may be able to run them on our truss design software to determine if they would be adequate to support a ceiling load. We would typically have wanted to have raised heel trusses, so full depth of insulation can run from wall-to-wall.
Roof is going to pose some challenges, as there is no provision to prevent condensation from appearing on underside of steel roofing. If it were my own, I would have two inches of closed cell spray foam applied directly to underside of roof steel. Add gable and ridge vents. Then blow in R-60 fiberglass above a steel liner panel ceiling.
You may find it necessary to mechanically dehumidify – there is just no way to guarantee you will not have issues with excess humidity, given how you intend to use building.
DEAR POLE BARN GURU: I recently moved into a house with a 40×30 pole barn (wood post and wood trusses) with a metal exterior. The building has a reflective foil radiant barrier between the metal and wood structure. It is extremely hot in the summer and cold in the winter. I want to insulate and cannot afford spray foam. I also don’t have the ability to remove the walls to remove the foil barrier that way. I do have some Silvercote insulation that has an attached vapor barrier. It is just a fiberglass roll insulation that has an attached vapor barrier to it. It is sold around here for use as insulation in metal buildings. I was given enough to insulate the whole shop from someone that had left overs. I would like to install this insulation to help with temps in the shop. I have tried to research to get an answer on the best way to go about this. The shop builder said just put it up but I feel that would create a double vapor barrier. Is my best route to cut the foil radiant barrier out and then install the fiberglass insulation with vapor barrier facing the interior of the building? This would basically take the foil barrier out and install the fiberglass against the metal with the attached face vapor barrier to the inside of the building. I want to make sure I do it right. Thank you. DAVID in OKLAHOMA CITY 
DEAR DAVID: If you are dead set on using this Silvercote insulation then you should cut out any foil radiant barrier. You never want to have a double vapor barrier situation as any trapped moisture will have no method of escaping. Downside of this is you do not have a Weather Resistant Barrier (aka housewrap) between framing and siding. An option to consider would be to resell your metal building insulation, then use unfaced Rockwool batt insulation, as it is unaffected by moisture.
DEAR POLE BARN GURU: I plan to build a 28×48 metal pole barn, concrete floor, 12′ eave with 8/12 pitch. Barn will have 6 3×4 windows, and two 10×10 roll doors, one roll door on each gable end. For now, the roof will be insulated with 3in closed cell foam. I plan to insulate the walls down the road with rigid foam board. The building will not have A/C. Question: Do I need vents or exhaust fan in the gable ends of the roof with the high heat/humidity of Alabama? There will be no ridge vent or soffit vents. I may not have the building open every day, either. Thank you. JASON in MONTGOMERY 
DEAR POLE BARN GURU: I live on an acre within the city limits of Victoria, MN does the code allow pole barns as a detached garage? MARK in VICTORIA 
HOLLY: We can provide 19 pieces of 3′ net width coverage by 3 feet tall polycarbonate panels, as well as steel “z” flashing needed for your transition from polycarbonate to steel siding and appropriate screws to attach. Along with this, you will get a Chapter from our Construction Manual to detail installation. To save on delivery costs, we can have these all available for you at our Browns Valley, MN facility. Please reach out to Materials@HansenPoleBuildings.com for pricing.
DEAR POLE BARN GURU: Have residential well, need a small building has this been done? CHRIS in ELMGROVE 
Thank you for your kind words, they are much appreciated. Provided your client will not be doing closed cell spray foam on walls, use house wrap between girts and wall steel. For his roof, housewrap is totally incorrect, as it allows moisture to pass through and become trapped between wrap and roof steel – potentially causing premature degradation. If your client is not closed cell spray foaming directly to roof steel, then order your roof metal with an Integral Condensation Control factory applied (Dripstop, Condenstop or similar) 
DEAR POLE BARN GURU: Hi Mike, I built a 32’X40’X12′ pole building, (Shop) I used 1 1/2″ foam board on the inside walls, (on the inside of the girts) I can’t decide how I should insulate the underside of the roof. I have had a couple Spray Foam guy’s quote it , that’s pricy. Of course, the best R Value etc. at the most reasonable price is what I am looking for. In some of your post you have mentioned Rockwool that has gotten my attention. I see they make it up to R30. One thing that sticks in my mind is, my builder suggested not to use an insulation that will give insects a place to live. What would be your suggestion for underside of Roof insulation. Thank you. JIM in SPRING HILL 
DEAR POLE BARN GURU: What screw is best for installing metal panels on the ceiling to wood trusses. MICHAEL in WENTZVILLE 
“Wet insulation of any stripe is bad. But cellulose is hygroscopic. It’s able to soak and hold liquid water. Undetected leaks can wet cellulose causing it to sag within framing cavities. Water leaks can compress the blanket of fiber and in extreme cases, can create a void space, degrading its thermal value. Another concern is that chemicals used to protect cellulose from fire make it potentially corrosive in wet environments. Tests conducted by the Oak Ridge National Laboratory show chemical treatments used to treat cellulose can cause metal fasteners, plumbing pipes and electrical wires to corrode if left in contact with wet, treated cellulose insulation for extended periods of time. “
