Tag Archives: wall insulation

When the Pole Building Insulation Problem is Larger Than Imagined

When the Pole Building Insulation Problem is Larger Than Imagined

From questions I have received from loyal readers over the past year, post frame (pole) building insulation is right there at the top of the list for priorities. Sadly, it seems the same concern is not often put forward by those who are designing, providing and constructing post frame buildings – leaving far too many new building owners in a world of hurt.

DISCLAIMER: This is NOT a Hansen Pole Building

Reader KEVIN in WEST CHESTER writes: “When installing my insulation do I stop just short of the vented soffit inside at the top of the wall?”

Well, this is an easy question to answer – the wall insulation needs to not cover the air intake provided from the eave vents, if the thought is for them to be used as a functional vent.

Simple, wasn’t it?

Now we can get into the challenges presented in the photo.

Unless the walls are going to be insulated with closed cell spray foam, there should be a well-sealed building wrap between the wall framing and the wall steel. This allows any moisture which would be trapped in the wall to be able to pass through to the outside world.

Now, onto the big challenge – insulating the roof.

If the idea is to have the vents in the low eave soffit be an air intake, then there needs to be a corresponding air exhaust at the high end of the shed. Along with this there needs to be the ability of unobstructed airflow from the low eave to the high side above the roof insulation. This happens to be a Building Code requirement, not to mention it is designed to prevent mold, mildew and other associated decay issues. As the roof purlins appear to be an impediment to airflow if the cavity is filled – the solution may end up being to have to use closed cell spray insulation under the roof sheathing and do away with the eave ventilation.

Moral of the story – consider insulation and ventilation needs early on in the project, in the planning stages, not after the building shell is already constructed.

Should Poly Plastic Barrier be Used on Interior of Walls and Ceiling?

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,

housewrapI 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

Insulation Dilemma

A reader writes (spelling, grammar errors included):

“When I built my barn I had 2″ insulation bats put between the outside framing and the tin. The side toward the tin is just open insulation. The inside is that heavy with plastic or whatever it is. I built with books shelve perlins on 2′ centers. Thinking it would make it an easy job to just fill those cavities with insulation. 

Where I’m confused is on the vapor barrier. We have a local business that makes insulation. Actually my insulation came from them. They guy there told me to just slice open the white vapor barrier and add insulation then use plastic over the added insulation prior to finishing my walls. So I’m just looking for affirmation that this is the correct way to go. Or other ideas and opinions.

Thanks.”

From the description, I will assume the two inch insulation batts are what is known as Metal Building Insulation. This type of insulation is actually designed to reduce condensation issues in building which have steel roofing and/or siding applied directly over roof purlins or wall girts.

Metal Building Insulation is not an effective insulator, as the fiberglass insulation gets crushed down to nothing every time it crosses a framing member.

This particular building is designed with sidewall framing (girts actually, not purlins which are on a roof) placed bookshelf style to create an insulation cavity. The builder did not do his customer any favors and actually spent his customer’s money unwisely.

Moisture within the walls of a pole building can cause serious problems.  In the colder months, moisture tends to move from the inside to the outside of buildings.  As it passes through the walls, it may condense within them, causing the potential for rot and mildew.  In walls with insulation, the water may condense within the insulation decreasing its R-value.  In the worst case, moisture can actually freeze within the walls, accumulating until a thaw melts it and causes visible damage such as wall or ceiling staining!

A vapor barrier is designed to keep moisture in pole barns from getting inside exterior walls.  Batt and roll insulations usually come with a vapor barrier attached.  However, leakage can occur where the facings meet.  This is especially true if the facings are not stapled to the inside of the wall girts, but instead the insulation is just pressed into place or stapled on the inside of the girt (all too common of a practice with foil faced insulation).  For the best possible vapor barrier, supplement the facing by installing a 4mil or thicker clear plastic sheet over the inside of the entire framed wall before installing any interior finishes (like gypsum wallboard).

Never sandwich the insulation between two vapor barriers. For example, do not install insulation with the vapor barrier facing the climate controlled space and then put plastic sheeting, or some type of vapor barrier, across the outside of the framing. Since some leakage of moisture into the insulation in inevitable, it needs to be able to freely escape from the insulation to the outside world ….. not be trapped inside!

 

Fiberglass Insulation is Boring

Fiberglass insulation is difficult to write about. In my opinion just about everyone knows about this topic or how the product works. There just isn’t much sizzle to the topic. I would hate to work for an advertising agency or public relations firm having to write about this stuff on a weekly or monthly basis! What can you say about fiberglass to excite potential pole building owners or contractors?

I actually started researching fiberglass insulation when questioned by a Building Official as to the amount of weight it would add to a roof system. Fiberglass is a very lightweight material. In this particular case, to obtain an R-factor of 49, it would take 20-1/2 inches of blown in fiberglass. Installed with the proper density, this thickness adds a weight of only .922 pounds per square foot. This means every inch of fiberglass insulation is adding only .045 pounds of weight!

This kind of weight will not overload average ceiling materials. The biggest concern – proper installation of ceiling drywall. Often drywall hangers do not install enough screws in ceilings (note – screws, not nails). A minimum of five screws need to be used across a four foot wide panel. This means one at each edge and then spaced every foot across the panel. It is essential to not tear through the drywall paper, so do not count any screws which do.

I wondered if flow-through ventilation for attics actually sucked air and heat from attic fiberglass insulation (all attic spaces require ventilation, by Building Code). According to the experts, batt insulation does not suffer from convective heat loss. Blown-in fiberglass, however, can suffer minimal heat loss in very cold regions. This loss only begins to happen when attic temperatures drop below freezing.

How about the R-factors of batts vs. blown-in fiberglass insulation? It didn’t surprise me to find out batts are better insulators. The primary reason for this is the tight tolerances found in the manufacturing process. Batts are uniform. The placement and quantity of the glass fibers can be controlled. This is not the case with blown-in fiberglass. The density of the material is controlled by the installer and settings in the machinery used to blow in the fiberglass.

What happens if the roof leaks? Fiberglass attic insulation is not ruined by water. It will retain its R-value once it dries. However, moisture may cause mildew and mold problems, so it is essential to speed the drying process. You may need to set up fans or heat the area, just like drying out carpet.

Wall insulation (and drywall), which is saturated from flood waters must be removed and properly disposed of. Flood waters potentially contain massive amounts of bacteria which will very probably cause a “sick house” if not remediated. Consult with your local health department for proper steps in treating your “sick house”.

While both batt and blow-in fiberglass insulation are made from the same material, they clearly have distinct applications.  Light, relatively easy to install, they perform an important function in your pole building.  Yes, they “fly under the radar” and quite frankly, may be considered “boring” to some of us, but I’d not want to live in minus 40 degree weather without them!