Tag Archives: Borax

Cellulose for a Pole Barn Attic

Multiple options are available for insulating attics of post frame (pole barn) attics. Reader NATE in BURNHAM writes:

“Hello! I have been doing some research all evening and I can’t seem to find an answer. I did take the time to read some various forums and blogs regarding this subject to no avail…having said that, here is my question; According to the attached spec sheet for my roof trusses (4ft O.C) spanning my 52Lx28Wx10H pole building, would blown in cellulose insulation at an R38 value combined with 6ml plastic sheeting (vapor barrier) and thin gauge metal ceiling be supported? I do know from the specs that my BCDL is 5psf. Any help on this would be wonderful as I am at a stopping point in finishing my garage. Thank you!”

Mike the Pole Barn Guru advises:

I am going to hopefully change some of your plans here….

Unless your building is where there are 8000 heating degree days or more, you should not have a ceiling vapor barrier (no 6ml plastic sheeting). In Pennsylvania you are well under this requirement (Northern Minnesota would qualify). You do need to have sufficient eave intake and ridge exhaust ventilation to allow warm moist air from inside of your building to be vented out above your insulation. Your total NFVA (Net Free Ventilation Area) must be no less than 699 square inches, with at least 50% and no more than 60% located at the sidewall eaves.

Blown in cellulose weighs roughly 2.5 to 3 pcf (pounds per cubic foot). Blown in cellulose will settle as much as 20% and can take up to two years to do so. Cellulose gives R-3.5 per inch, so your R-38 would be 10.86 inches thick (after settle), so I would plan on no less than 13.5 inches blown in to achieve your R-38. To be safe, I would assume 3.4 psf (pounds per square foot). Besides settling, blown cellulose does have another downside – in order to be fire retardant it is treated with borax or boric acid. Borates can be corrosive to steel in humid or moist environments, so you may want to consider a different insulation type, such as fiberglass. Fiberglass is also lighter weight, coming in at about a pound per cubic foot.

Steel liner panels are most typically 29 gauge steel weighing in around 0.6 psf.

Your five psf BCDL (bottom chord dead load) has to also account, in part, for weight of your trusses and bottom chord bracing, as well as any electrical and light fixtures. Most often this is considered to be a pound per square foot. This is going to put your proposed use of cellulose right at capacity, without any remaining margin for error.

Wood Preservative

What I Learned Today – Wood Preservative

Hansen Pole Buildings’ Designer Rachel had an interesting story today.

She reported, “A builder says he uses Borax around the bottom of the steel.  I thought this was strange and he didn’t say why he was using it.”

Being the naturally curious sort, Rachel started researching on the internet, and this is what she found:

Pressure preservative treated lumber is what most of us recognize as a piece of treated wood. The treating process forces chemicals, under pressure, into the wood fibers – which inhibits decay by making the wood inedible to termites and impervious to mold and decay fungi.

BoraxRachel discovered raw (untreated) lumber can be manually treated with a solution of 10 ounces of 20 Mule Team® Borax dissolved and well mixed into a gallon of water. Once mixed, the Borax solution is to be sprayed onto lumber and a gallon should do about 250 board feet of lumber.

Me, being old enough to remember “Death Valley Days” presented by Ronald Reagan or Dale Robertson and narrated by Merle Haggard – this is the only other thing I associated with 20 Mule Team® Borax.

In doing further research, I found that boric acid of borate treatments kills the protozoa which live in the digestive tracts of termites. Since those protozoa are responsible for digesting the wood a termite eats, their death makes it impossible for termites to garner any nutrition from eating. However, unless borate treatments are applied when a structure is built, they should not be used. Borate treatments applied to established buildings are largely ineffective.

Some wood treating industry experts claim there is a wood preservative which is cost effective, performs well and is environmentally friendly, the “perfect” preservative – borates. The chemical was supposedly so non-toxic, one could drink it.

When CCA (Chromated Copper Arsenate) was generally removed from the marketplace (other than for limited specific uses), chemical companies began a mad dash to develop a binder which could prevent borates from leaching.

Attempts were made to encapsulate the borate in wood using sodium silicate to reduce its exposure to conditions which would leach the borate. Cost considerations to install equipment at the production level and increased treatment costs seem to be some reasons this ‘miracle borate’ did not advance within the industry.

In addition, the industry learned permanently locking borates into wood wasn’t necessarily a good thing. If borates stop migrating, they stop killing the fungi and insects. Borates don’t kill on contact, like spraying on a can of Raid. They act as a drying agent; they dry out the insides of an insect so it can’t eat any more. If borates are fixed permanently in the wood, experience has shown us the wood preservative will not be effective. The borate needs to be mobile in the wood in order for it to be efficacious against decay and termites. It may be possible to develop a semi-fixed borate where the diffusion process is greatly slowed down. So far, no developer of this style of borate wood preservative has opted to commercialize it, however.

While its solubility may prevent borates from becoming an all-purpose super-treatment, the same characteristic of preservative mobility also helps borates diffuse throughout the wood after treatment to effectively serve its protective purpose. The end use of the product is quite specific and limited: a service condition in above-ground applications which is protected from continued exposure to water.

My conclusion – the builder may be doing his “magic” by sprinkling 20 Mule Team® Borax around the base of a completed building, however the reality is, it is “far more show…than go”! Look for proper wood preservative methods by purchasing properly treated wood.