Tag Archives: closed cell spray foam insulation

When Attic Insulation is Baffling

Proper insulation provisions seem to be one of the least considered items when it comes to post frame (pole building) planning.

Here is a case in point from reader JOHN in BEND:

“We have just built a 32’ x 48’ pole building with commercial GIRT construction, metal siding, 4/12 pitch metal roof, concrete floor, 12 ft ceilings located in the high desert region of central Oregon.  The building will be used as a training center for a sport shooting club, and only occasionally occupied/heated.

We plan to insulate the walls and (flat) ceiling with R19 fiberglass batts and cover both walls & ceiling with 5/8” drywall.  We have some questions/concerns about adequate venting for the attic area above the ceiling.  We had a vent-a-ridge installed along the entire length of the building (48ft which will provide about 5 sq ft of roof ventilation).  We are now installing 4″ round soffit vents to match the 5 sq ft ridge vent to provide airflow.  We had also planned on installing styrofoam soffit/rafter baffles to ensure the fiberglass batts didn’t block the natural airflow from the soffits.  Then we noticed that the purlins run horizontally very near to the soffits.  The styrofoam baffles appear to be designed for vertical facing rafters that will naturally channel air up towards the vents.  Now we are wondering if styrofoam baffles (and our venting scheme in general) will work properly and whether we need to also install gable end vents.

Thanks for the help. We are a volunteer organization and just don’t have the construction expertise.”

From your photo, it appears the ceiling joist closest to the inside of the wall is a 2×6 with airspace above it. If so, your R-19 batt insulation will still have airflow above it. The baffles you invested in should be returned for credit, as they are not applicable for a post frame installation with widely spaced trusses. 

Now your true challenge, R-19 insulation is woefully inadequate for your location. Your attic should have at least R-49 (https://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table) which would be about 16″ of blown in insulation.

Normally I would recommend to clients to have raised heel trusses to allow for full insulation thickness. In your case, I would recommend the area in the three to four feet closest to the sidewalls to be insulated with closed cell spray foam on top of the ceiling, to the thickness of the ceiling joists, then blow in fiberglass for the balance of the attic. Do not use faced batt insulation.

Converting a Pole Barn into a Home

I happen to live in a post-frame home. It was designed to be lived in from day one, so we did not face obstacles in having to convert a pole barn.

Reader DAN in SIDNEY writes:

“I have an existing pole barn that has no current foundation. It looks like 6×6 pt poles right into the ground. I am trying to convert the pole barn into a home and my first task on my list was a foundation. I was told required by code I need a frost protected shallow foundation. My question is what is the best way to add these footers with my poles already in the ground? Do I just pour around it or extend my pour outside the poles a few inches? Thank you for your time.”

Well DAN I will gladly assist with answers to your challenge, however first I might end up bursting your bubble.

Your building itself could very well pose some other challenges. Most often these come from walls not stiff enough (from a deflection standpoint) to prevent cracking of any gypsum wallboard surfaces. This is an area to be looked into by a RDP (Registered Design Professional – architect or engineer) you are going to hire (please nod your head yes).

 

Chances are excellent roof trusses in your building are not designed to support a ceiling load. If you do not have original sealed truss drawings for your building, you will need to contact whomever fabricated them. Every truss should have an ink stamp stating who manufactured them somewhere along their bottom chord.

Gambrel roof pole barnIn many cases it may be possible for an engineered truss repair to be made, to upgrade load carrying capacity of truss bottom chords to a minimum of five psf. I’m sorry to say, this is not free. Truss company’s engineer will need to put his or her license on the line in designing a “fix” for trusses designed for a load other than is now intended.  It’s not same as designing original trusses.  If you think about it, redesigning and augmenting something you have built, is always more time consuming (and brain challenging!) than first time around. His time and expertise are not without a charge.  It’s not usually “much”, like a couple hundred dollars.  Then there is cost of materials to do repairs. This will be final out-of-pocket expense if you are doing truss repairs yourself.  If not, a contractor’s charge must be added.  All totaled, it could run you anywhere from a couple hundred dollars to over a thousand or more.

Siding should probably be removed and reinstalled with a Weather Resistant Barrier underneath, or plan upon using a two inch or thicker flash coat of closed cell spray foam insulation against siding insides.  If a dead attic space has been created, attic area needs to be adequately ventilated to prevent condensation. You can find out more about adequate attic ventilation here: https://www.hansenpolebuildings.com/2012/08/ventilation-blows/.

Once you have decided to survive all of the above, let’s deal with your FPSF (Frost Protected Shallow Foundation). This article: https://www.hansenpolebuildings.com/2019/02/minimizing-excavation-in-post-frame-buildings/ addresses an FPSF scenario for new post-frame construction. In your case you can follow along doing essentially the same thing, although your columns are already in ground.

Ultimately your conversions costs may exceed starting from scratch and erecting a new post frame building designed to be your home from start. If this is your case, please call and discuss with a Hansen Pole Buildings’ Designer at (866)200-9657.

Help Me Insulate My Pole Building

This story is sad, to me. As post frame building “experts” we (an industry collective we) owe it to our clients to educate them at design phase to avoid a situation such as reader ERIC in SPOKANE VALLEY has become happily (or maybe less happy) involved in.

Eric writes:

“I want to start insulating my pole building. 30x40x16, roof layers are metal, synthetic underlayment, osb, 2×8 purlins. My question is, can I leave an air gap between roof and insulation, as I plan on using R19 batting and covering with facing. Has an open ridge vent. Thank you.”

Mike the Pole Barn Guru responds:

Placing batts between purlins is probably not a Top Twenty best answer for several reasons:

If you do not completely fill purlin cavities, Code requires airflow from eave to ridge over top of the insulation. You have no way to achieve this without a major remodel. You don’t even want to go there.

Getting a perfectly sealed vapor barrier under purlins would be nearly impossible to achieve.

You would have to seal the ridge vent (it isn’t working anyhow, because your building does not have an air intake from enclosed vented soffits).

While installing a flat ceiling at truss bottom chord height might appear to be a quick solution, it also is fraught with some perils:

Trusses are probably not designed to support a ceiling load. It might be possible to obtain an engineered repair from the company who produced your building’s trusses.

Ventilation system would need to be addressed for newly created dead attic space.

Closed cell spray foam insulation would need to be added in the area closest to eave sidewalls.

Weighing what you have to start with, my recommendation is to spray three inches of closed cell foam insulation below your roof sheathing. This will provide a greater R value than R19 batts and provides a vapor barrier. You will need to seal off the ridge (foam installer may be able to just spray foam underside).

Also, I notice in your photo what appears to be a total absence of truss web and bottom chord bracing. I’d have to have a copy of your building’s sealed plans, a truss drawing and some more photos to truly discern.

How Could This Have Been Avoided?

Whoever provided this post frame building should have been asking some important questions:

Will you, or anyone who might own this building in future years ever want to climate control (heat, cool or both)?

If yes, what method of roof insulation is being considered? I like insulation over a flat level ceiling personally, as I then no longer pay to heat or cool the attic area. In order to do this right, energy heels (https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/) should be utilized. It also means having adequate attic insulation with soffit vents as intakes and ridge vents as exhaust.

It all could have been so much simpler.