Tag Archives: ceiling insulation

Insulation, Insulation, Insulation

The Pole Barn Guru discusses the always popular ceiling insulation, vapor barriers with insulation, and closed cell spray foam insulation.

DEAR POLE BARN GURU: I read your article on unvented roofs. My building has a vapor barrier installed. I am at the point of insulation and plan on doing closed cell spray foam. What would be better spraying the roof deck or the attic floor/ top side of the ceiling. I was thinking spraying the roof deck and then doing blown in insulation above the ceiling to get my r value. I thought having the entire building done in closed cell would make for the tightest building. BRAD in FLANAGAN

DEAR BRAD: If you have a condensation control barrier (having a thermal break, not just a vapor barrier) of some kind between roof steel and framing, then there would be no need to closed cell spray foam underside of roof deck, unless you are going to use this as your only insulation.  Insulating ceiling line creates a dead attic space above, so it will need to be ventilated (either eave and ridge or gable vents). Closed cell spray foam will give you a very air tight building, applied properly.

DEAR POLE BARN GURU: Built pole barn installed 1-2 inch thermal sheathing in outside installed 8 inch batt would you install vapor barrier on inside been told I have two vapor barriers answers. JIM in HARTFORD

DEAR JIM: You are going to have insulation sandwiched between two vapor barriers, however air leakage into the cavity is a greater issue than through a vapor barrier. Goal is to keep insulation and wall framing dry. As long as you adequately seal all of the air leakage pathways you would not need an interior vapor barrier. In other words – if you install an electrical outlet or switch box, seal it, seal around any door or window openings.

DEAR POLE BARN GURU: What do you feel is best insulation system for pole buildings building we got is 162 x 72 wood structure built on foundation wall columns on 6 ft on center girts nailed to outside of columns and also inside corrugated metal we installed 1/2 poly iso insulation and 8 inch batts in wall spray foamed  base to seal air leaks and plugged holes on top with 3 inch iso between columns and foamed around window frames poly iso has foil face and we taped seams wanted to install poly vapor barrier on inside but was told that I would have two vapor barriers which is bad what do you recommend? JIM in HARTFORD

DEAR JIM: My recommendation would be two inches of closed cell spray foam on inside of steel siding. Install another set of girts on inside of columns to support interior wall finish material. Fill wall cavity with BIBs (https://www.hansenpolebuildings.com/2011/11/bibs/). Glue two inches of closed cell foam insulation board on inside of girts, sealing around any penetrations. Glue interior finish material to inside of insulation board.

 

 

 

 

Uplift Concerns, Retro-fitting Insulation, and High Water Tables

This week the Pole Barn Guru answers questions about uplift concerns, retro-fitting insulation, and setting posts in high water tables.

DEAR POLE BARN GURU: I am adding an open overhang to the gable end of my 40×80 pole barn. I bought 36’ trusses and will lower them to fit under the existing gable going out 16’. Since the underside is unfinished should I worry about wind uplift? SCOTT in SHERIDAN

DEAR SCOTT: Regardless of whether your addition will be open, enclosed, or somewhere in between uplift should always be a consideration. Ideally the original EOR (Engineer of Record) who designed your 40′ x 80′ building would be consulted, not only because of a potential uplift issue, but also due to what affect open carport will have upon existing building. You may be placing wind shear issues upon endwall closest to addition and these will need to be addressed, as well as if endwall column footings will be adequate to support added weight (not just dead load, but also potential weight of a snowfall). An issue of drifting needs to be reviewed also, as snow could build up upon carport roof against existing endwall.

If original EOR proves unavailable (or nonexistent), you should enlist services of a competent RDP (Registered Engineer or Architect) qualified to review your existing building, as well as your intended work.

DEAR POLE BARN GURU: Need your suggestions on any improvements I can make. Below is a sketch of my current building roof insulation. Basically I tried to seal off the cathedral ceiling using the bottom of the purlins to hang 4” Dow board sealed with aluminum tape. I did purchase the radiant reflective barrier that was installed per instructions between the roof purlins and the steel roof panels. I live in Michigan. 

I love my two pole buildings I purchased from you guys. Just need some help on insulating the roof on my last building. Nothing is wrong. Just concerned about the un-vented dead air space. JOHN in SAGINAW

 

DEAR JOHN: Always glad to hear back from happy building owners! As long as the cavity was dry when it was sealed up, and the Dow board is sufficiently well sealed there is a chance you will not have problems. The only guaranteed solutions involve having to take down the insulation board and make provision for airflow from eave intake to ridge exhaust by drilling holes through all of the purlins.

 

 

DEAR POLE BARN GURU: Mike can you please tell me what is the proper way to set posts in holes that have water. High water table. Thanks much I enjoy your blog. PATRICK

DEAR PATRICK: Back when I was a contractor we would run into this situation occasionally. Our solution then was to stand columns in holes, brace them and then backfill with pre-mix concrete with very little water in it. Concrete weight would displace water in hole. It did take a significant amount of concrete, however it was only about $30 a yard then.

How I would do it now – I would use sonotubes equal to or larger in diameter than what was specified by engineer. Cut tubes to depth of hole length, then cover one end of tube with six ml black visqueen (read about visqueen history here: https://www.hansenpolebuildings.com/2013/07/moisture-barrier/ ) sealed tightly around sides of tube. Place tube in hole with covered end down (this will take some work, as tube will want to float like a boat). Once sonotube has been placed, backfill around outside with compactable material – compacting no more than every six inches. Then stand column in tube, brace it and backfill with pre-mix concrete as engineer specified.

 

Post Frame Antiperspirant- Ventilation Frustration

This is a sad story I hear all too often from pole (post frame) building owners who have buildings which were not properly designed for future uses, especially when it comes to insulation and ventilation.

Reader JASON in TENINO writes:

Hi Pole Barn Guru,

I recently purchased a new house and it came with a 40×60 shop. This past year I’ve experienced terrible slab sweating every time there is a change in humidity. Now that it’s summer I would like to prevent the sweating from occurring again. What are my best options on a limited budget? I’ve looked into using a penetrating concrete sealer, but I don’t think that addresses the underlying condensation problem.

As far as I can tell the shop has no ventilation of any kind (ridge/gable/soffit). And I’m noticing black mold starting to develop in the insulation below the roof. And I’m not sure if any sort of vapor barrier was placed before the slab was poured.

In the future I would like to insulate and heat the shop, but for now, I’d be happy if I can stop my condensation problems.

Thank you for your help!!!

DEAR JASON:

Yep – you have a problem on your hands. I can pretty much guarantee there is no vapor barrier under your concrete floor, which is a shame someone cheaped out. Vapor barriers are so inexpensive.

Taking care of first things first, let’s get the floor sealed. Here is the information you will need: https://www.hansenpolebuildings.com/2012/07/concrete-sealer/.

Secondly – get rid of the mold. Mix in the ratio of one cup bleach per gallon of water and use a hand pump sprayer to saturate all moldy surfaces. You can also use a scrub brush to remove the existing mold.

Third – I am going to leap ahead to your future plans, as they will impact your solutions now. I am not a gambling man, but I would put money on your shop’s trusses not having been designed to support the weight of a ceiling. This means if you want to eventually insulate and heat the building, you will have to insulate above the bottom chord of the trusses and up the roof line. On the walls, you can frame in either with a stud wall or with bookshelf girts to create a method to support insulation, with either batts or BIBs (Blow in Blanket) insulation being the most cost efficient and effective for your investment dollars.

Insulating the roof, not so easy, as the only really practical solution will be to use closed cell spray foam between the roof purlins. You will want to consult with an installer to get their opinion as to whether the metal building insulation under the roof steel will have to be removed prior to spraying.

If you are going to spray foam, then you do not want to use a ridge vent, as the foam would cover it.

Here is my best advice (provided you have the space on your property) – use your existing building only for cold storage. Since you do not have vented sidewall overhangs to create an air intake, the only solution for ventilation is to use large vents in each endwall. At a bare minimum, you should have at least 576 square inches on net free flowing vent in each end – located in the top half of the gables. You may need to add power vents, in order to adequately move the moisture out of the building.

When your budget allows for some climate controlled space, construct a new building which is properly designed to be able to be energy efficient.

Here is a short list of features which you should include:

Underslab vapor barrier
Pex tubing in slab for in floor heat
Perimeter slab insulation (rigid foam)
Bookshelf wall girts to create an insulation cavity
Housewrap between wall girts and siding
Vented sidewall overhangs
Ceiling loaded trusses with ceiling joists
Raised heel trusses to allow full insulation depth from wall to wall
Blow in R-45 to 60 of ceiling insulation
Reflective radiant barrier between purlins and roof steel

Good luck and let me know how things turn out!

Mike the Pole Barn Guru

How To Add Insulation Between Purlins

If you happen to be considering building a pole building in a part of the country where sidewall columns MUST (it is a mindset, not a structural requirement) be every eight feet and trusses MUST be every two or four feet, then it is time to take a leap of faith out of the very small box!

Read more on truss spacing here: https://www.hansenpolebuildings.com/blog/2011/06/pole-barn-truss-spacing/

On to the topic at hand…..

insulation roll

Whilst I am a proponent of insulating above flat level ceilings, there are cases where this just isn’t what people have in mind for their new post frame buildings. Whether it is to create dramatic vaulted ceilings, or just to be different, every reason is valid.

The challenge is… how to get adequate insulation between purlins into a typically very small area.

With typical “Western” style pole barns, double trusses are placed every 10 to 14 feet with 2×6 or larger roof purlins on edge between the trusses.

Even using high density insulation batts, the R-23 from a 2×6 insulation cavity is only going to be adequate in the deepest South.Ceiling R Values

There ARE solutions….using larger roof purlins being a very simple one. Using high density batts would allow for R-46 in a 2×12 purlin. Or, for increased depth, furring strips could be added to the underside of any sized purlins.

If gypsum wallboard is to be added to the underside of the roof purlins, a deeper purlin is often required to prevent undue deflection from cracking drywall joints.

Oh, I forgot to mention, purlins are best placed 24 inches on center, to fit with the most common insulation width, and insulation between purlins should be unfaced.

Further insulation may be added by the use of high R foam boards placed beneath the purlins; however Code requires them to be covered with a fire barrier on the inhabited side.

For more foam board information: https://www.hansenpolebuildings.com/blog/2012/04/rigid-insulation-boards/ and https://www.hansenpolebuildings.com/blog/2012/04/foam-board/

There IS a challenge, which we have not yet delved into….ventilation is required between the insulation and the roof deck. The roof purlins running the length of the building prohibit airflow, and even if the insulation was not the same thickness as the cavity (depth of the purlin), not enough holes could be drilled through the purlins to allow adequate airflow and not degrade the purlin strength.

The solution: Lay 2x4s flat on top of the purlin, running up the roof. Although these 2×4’s and their connections need to be structurally verified against uplift conditions, in most cases, spaced every four feet will prove adequate. This space will become the “air chase” between vented sidewall overhangs and the vented ridge cap.

On top of this layer of 2×4’s, reflective radiant barriers needs to be placed.  This prevents warm moist air from contacting the underside of the roof steel. Using a product with a tab along one edge with an adhesive pull strip, helps to make sure no air will leak through the vapor barrier. (Go to www.buyreflectiveinsulation.com for reflective radiant barrier information and pricing).

In order to attach the roof steel, yet another layer of flat 2×4 needs to be added. As the previous layer runs from eave to ridge, this layer will be used to attach the roof steel. Spacing of these will be dependent upon the snow and wind loads, but they usually will be no greater than 32 inches on center. Besides affording the ability to attach the purlins to a wide target (the 3-1/2 inch face of the 2×4), the dead air space increases the effectiveness of the reflective radiant barrier.

Ask the Guru: Is Vapor Barrier Required?

For those of you just joining Mike the Pole Barn Guru’s Blog – Mondays are now “Ask the Guru” where you can submit construction and building product questions for Mike to answer in upcoming Monday segments of this blog.  If it is a topic Mike is not well versed in, or a new product he has not yet been exposed to –  he will do “due diligence” in his research and give you his best advice.

Submit questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU:  Finishing & insulating inside pole barn that was here when purchased last year. What are your thoughts on vapor barriers for ceiling between the metal and insulation?

Also in quandary over no over hangs for soffit vents it’s a Mo**on with the gable ends venting where trim meets the ribbed siding, snow blows inside currently and not sure if after I have it closed in it will still do so and get insulation wet (fiberglass). Thanks BLOWING IN, IN OHIO

 

DEAR BLOWING: It is essential to have a vapor barrier between the roof steel and any conditioned area below. In the event there is not a vapor barrier between the roof purlins and the roof steel, there are some options. The best choice, is also the most work.  Remove the roof steel, install a reflective insulation on top of the purlins and reinstall the roof steel, using larger diameter, longer screws than what originally held it in place. Spray foam insulation could be placed on the underside of the roof steel (may be cost prohibitive), or reflective insulation could be installed under the roof purlins, as long as all of the seams are tightly sealed.

Assuming you are placing the fiberglass insulation at ceiling level, there should not be a vapor barrier below it. You want any warm moist air from inside the building to be able to rise into the dead attic space, which must be adequately vented. Venting can be accomplished by a combination of sidewall eave vents and a vented ridge, or by gable endwall vents.

 If snow is coming in under the gable end/rake trim, the screws can be removed from the gable face of the trim, expanding closures can be placed along the edge of where the trim lies, and then reinstall the trim using metal-to-metal stitch screws. The expanding closures should be placed so the lower edge of the closure is just covered by the trim.

 In any case, you want to be certain any fiberglass insulation will not get damp, as it will lose its effectiveness, as well as possibly contributing to decay of any wood members it is in contact with.