Reader JUSTIN in MONROE writes:
“Hello. Hopefully an easily answered question? I have built a 52×30 post frame, steel siding and roof. Walls have Tyvek between steel and girts. Roof is steel directly on purlins with no barrier of any kind. It has a concrete slab and I plan to periodically heat it during winter months. I’d like to insulate but not sure of best method with my situation and climate. I plan to use R-19 for walls and possibly ceiling. Or blow in for ceiling. Also I have 50% soffit ventilation with 18″ overhang as well as 40 ft of ridge vent. Should I use poly plastic on interior of walls and ceiling? I’m concerned I will create a moisture problem. I’m open to doing things whichever way is best. Things are always easier and cheaper to do it correctly the first time. Any advice would be greatly appreciated. Thanks”
Dear Justin,
I agree things are always best when done correctly the first time around. While it is not always less of an investment, when the long term problems arise and things have to be corrected, it makes it nearly not as fun and cheap becomes expensive. Usually in a quick hurry.
If the roof trusses are not designed for at least a five pounds per square foot bottom chord dead load, you are sunk on adding a ceiling without an engineered truss repair. This would be the place to start, as it will dictate the solution.
I will approach the building as if it is my own and from where it is now.
On the floor – I am hoping you have a vapor barrier beneath the concrete slab. If not, use a high quality sealer on top of the floor.
A penetrating concrete floor sealer is likely the best bet to protect and maintain a concrete floor. These concrete floor sealers penetrate deep into the concrete’s pores coming into contact with the alkali and calcium ions, forming a gel.
This gel expands filling the pores and hairline cracks inside the concrete, turning the concrete into a solid mass. This process will prevent moisture and vapor migration up through the concrete floor, as well as down into it.
Look for a penetrating concrete floor sealer which is water based and says silicate penetrating solution on the specifications. These sealers can be applied with a pump up sprayer.
On the Walls-you did good with the Tyvek. Kudos! If your building has girts flat on the outside of the columns, you can add another set to the inside of the columns. If you have 6×6 columns, your post frame building will now have an 8.5 inches thick insulation cavity. I would use BIBs (read about BIBs here: https://www.hansenpolebuildings.com/2011/11/bibs/) for my wall insulation, and would have a deep enough cavity to get around R-35. There does need to be a vapor barrier on the inside (heated) side of the wall, under the gypsum wallboard.
Roof– the underside of the roof steel needs to be isolated from any warm moist air which would enter the attic. Use closed cell spray foam directly sprayed directly onto the underside of the roof steel. Assuming your building’s roof trusses are strong enough to support a ceiling, blown in insulation is going to be your most economical. Hopefully you (or your builder) had the foresight to order roof trusses with a raised heel so the insulation will remain full thickness from wall to wall. If not you may want to have closed cell spray foam insulation on the “cold” side of the ceiling in the area with a couple of feet from the sidewalls. Make sure to allow a provision for air in the overhangs to not be blocked from venting the attic.
Do not put a vapor barrier between the trusses and the ceiling. You want the warm moist air inside your building to be able to rise into the attic and be vented out through the ridge. And if you are going to insulate your ceiling, R-19 is really not near enough. At a minimum I’d think about R-38 or 45 blown in.
Thank you for allowing me to share some insight into insulation.
Mike the Pole Barn Guru
DEAR POLE BARN GURU: Hello We have an existing pole barn that has an R-7 vapor barrier. The vapor barrier is between the metal and the 2×6 purlins. We would like to insulate the ceiling and maintain the vaulted ceiling look. We are using a 5.5″ wool bat insulation. Can we put the bats in between the purlins in direct contact with the vapor barrier or do we need an air gap between the vapor barrier and the new insulation? If an air gap is needed, how much space is required? Will it need to be vented? SARA in ANACORTES 




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
DEAR POLE BARN GURU: Should the screws for exposed fastener metal panel roofing COMPLETELY penetrate the 1/2″ plywood decking/substrate? STEVE in WARREN
DEAR TIM: Header beam (aka truss carrier) requirements can be determined by a Registered Professional Engineer and are based upon this formula:
DEAR RICK: Code will not allow you to place batt insulation between your purlins unless you have at least an inch of continuous airflow above from eave to ridge. Impossible to do given orientation of roof purlins.


DEAR POLE BARN GURU:
DEAR MARSHALL: Please keep in mind the Reflective Radiant Barrier under your roof steel is a thermal break designed to control condensation from occurring on underside of your roof steel, it is not insulation and has a R value of roughly one (R = 1). If you block off all vents, you may need to mechanically dehumidify your space in order to reduce moisture inside. Alternatively, should you install a ceiling and insulate above it, you would need to appropriately vent dead attic space to prevent roof system mold and mildew.
Although our buildings are designed for an average literate English speaking person to successfully construct their own building (most of them do, and do a wonderful job – because they will read and follow instructions), for those who do need an erector, in many areas we can provide contacts for you to vet.
DISCLAIMER: This is NOT a Hansen Pole Building
This area can be reduced by finishing off the ceiling (with my personal preference being gypsum wallboard) and blowing in insulation above the ceiling – along with having a properly ventilated attic space. To give a rough idea of the volume of space differentials on a 40 foot wide by 60 foot long by 12 eave height building, having the most typical roof slope (4/12), about 25,000 finished cubic foot of area is to be conditioned with the ceiling, as opposed to nearly 34,000 cubic feet otherwise.
Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays. With many questions to answer, please be patient to watch for yours to come up on a future Monday segment. If you want a quick answer, please be sure to answer with a “reply-able” email address.
For starters, keep in mind (by Code) spray foam insulation cannot be left exposed, it has to be covered with inflammable material – like gypsum wallboard. Gypsum Wallboard is not as flexible as steel, so it has deflection criteria which mean upsizing the roof purlins from 2×6 to 2×8, or changing the column spacing to 10’ on center(o.c.). In the end, when I priced it out the change to 10’ o.c. was less costly, adding only about $900.

The skids of steel with Drip Stop applied must be stored prior to use, to prevent moisture from becoming trapped between panels, which may cause staining as well as damage to the panels. This moisture can originate from a variety of sources, such as rain, high humidity or condensation. Panels should be stored in a dry location and installed as quickly as possible after delivery. If this is not possible, panels should be separated from one another to allow for air circulation to prevent panel damage.
While it is true cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for pole buildings of all uses. Today’s “cool roof” pigments allow metal roofing products to be Energy Star rated in dark colors, even black. They aren’t as reflective as whites or light colors, but can still save energy over other paints.