BLOW-IN-BLANKET SYSTEM PROS AND CONS
I have been researching insulation systems and talking to people in the business. I think I understand the principles of thermodynamics, vapor barriers, ventilation, air intrusion, etc. However, I am amazed at the number of claims and approaches that people are advocating. I am curious about what people here think about the BIBS approach to insulating.
My interest in this topic is for cold climate applications. Here are a couple of questions I have about it:
1) Does this system always use a flash coat of spray foam on the inside of the wall sheathing or roof deck as an air infiltration barrier, or is that not an intregal part of the system?
2) As an alternative to the flash coat of foam, could a person use an air barrier house wrap outside of the sheathing?
3) How does an installer know that he or she is installing the fibergalss at the proper density? I did learn of one method of controlling the density, but I would like to hear what others think about this issue.
Replies
CONTROLLING DENSITY
Well, okay I guess there is not a lot of ideas about how to check density when blowing in fiberglass blankets. The only method that I have seen is where the installer cuts out a certain square footage of a sample of the blown blanket after the job is done, and then weighs that sample as a check on proper density.
But how accurate can that be? The more glass the installer blows in, the higher his cost, so he would have an interest in being on the light side. And if the installer cuts out the test sample, he knows ahead of time where he will take that sample. So he can blow heavy in the area of the intended sample.
And if the sample were light, the installer would have to assume that it represented the whole job. So he would have to go back and blow more glass into every cell. If the installer is confronted with that requirement, he might be inclined to take a few more samples before re-shooting every cell. Then what if he takes a total of four samples, and they vary widely?
Calculations
and a good hand at blowing.
You do a wall-8x10, (for example) 80 sf in relation to the poundage of the bale of insulation used. Lbs per SF of wall.
Well, the guy is starting with an empty machine. He loads it with the material before he can shoot it into your attic.
You can figure out the cubic area of a specific portion of the job. You know how weight in material SHOULD be applied up there.
After he blows that section, measure out what's left in the hopper.
If the bale weighs 50lbs to begin with, and there should be 20lbs in your sample section at proper density, there better not be 40lbs of material left in the hopper!
CONTROLLING DENSITY
I can see how the solution would be to know the proper weight of a given section, and then blow in a measured weight of material that matches the intended weight of the section. Maybe that is what most installers do.
However, the reason I asked how it is done is that I watched a demonstration video in which they seemed to be controlling density by the hand-feel of the finished cell. And then then when they finished the job, they would cut out a sample section and weigh the material to check the density. Apparently, they would assume that the sample would be representative of the entire job.
But another thing occurs to me. Wouldn't it be possible for the density to vary quite a bit within each cell? There appears to be a fair amount of technique involved in the blowing process and moving the nozzle around as the cell fills. I can imagine that a flaw in the technique would get repeated over and over, so that each cell might be over dense in the lower area and too light in the upper area, for example.
Wouldn't it be possible for the density to vary quite a bit.....
Sure it could.
And the world might end tonight.
You do alot of thinking about a subject, and that is good.
But, sometimes you have to come to a conclusion and a decision. Base it on the best available information and don't keep beating a dead horse.
Your stomach will feel all the better for it.
Best of luck.
Looking for the best way
Well, I don't know about beating a dead horse, but I am always looking for better ways to build things. So I ask questions about the way people are doing things. Right now, the focus of what I am doing is superinsulation. And I don't think there are two people who agree on any aspect of it, especially when you throw in the issues of vapor and air barriers, ventilation, etc. Vendors are pushing their products based on some of the most outlandish claims. And regulators are staying up late just churning out a blizzard of new regulations for the subject. There is a lot of misinformation on this topic.
For instance, I am very familiar with building a vaulted ceiling with a vapor barrier and cold-side ventilation.
Here is an article that claims that the best way to insulate a cathedral ceiling is with dense blown cellulous, no vapor barrier, and no ventilation:
http://www.applegateinsulation.com/Product-Info/Technical-Pages/249234.aspx
He claims that the way vapor gets into walls is by being carried by air currents from the interior, and entering through cracks. My understanding is that vapor gets into walls because vapor always wants to move from regions of high vapor pressure to lower vapor pressure, and the interior of the walls are cooler than the room they surround, so they have a lower vapor pressure than the room. So my understanding is that the movement of vapor does not depend on the vapor being transported by air currents.
He says that dense blown cellulose will not allow air movement, so air cannot transport vapor into the cellulose filled ceiling cavity. I believe that the cellulose may be made dense enough to stop air movement, but vapor will nevertheless flow right into it and through it as the vapor seeks a lower vapor pressure region.
In my opinion, this article contains several points of misinformation in its claims of the alleged disadvantages of vapor barriers and cold-side ventilation.
Yeah, pretty much everyone who expounds on this topic is wrong. Except me.
Going by feel is a method that someone experienced might use to verify the section just blow is correct. Calculating the weight blown in to a particular cubic space is a way of veryifying a hundred individual hand pressings. They each have their place.
On measure looks at the moment, the other looks at an average.
What I have observed
is that good blown-in installers just do it by feel. They do it day after day, house after house, thousands of cubic feet per week. They know that if they under-install it will settle. They know that if they over-install it will piss off the drywaller. Hopefully you are using a good outfit where the guys get manufacturer training on the material and equipment.
My experience is that blown-in FG jobs seem to perform better than FG batt jobs on the blower door test. This is hardly a scientific observation and it could easily relate to the fact that the blown-in company does a good job on the other details too.
I would consider this BIBS system for a superinsulated house. And I agree that a good installer could probably control the density. But with so much committment to extreme insulation thickness, I want the density control to be an exact science. So I would be nervous about picking one installer for one job and gambling on him getting it right.
But on the plus side, blowing in fiberglass would fill the gaps between the double studs and in the triangles of the scissors trusses. For using batts, those gaps need to be delt with as separate issues.
Batts
hardly make sense if you can get a good blown-in installer.
Practically speaking, the best you can do is to keep a tally of bales installed along with cubic footage of area completed, and compare to the manufacturer's specs.
What if the guy had to spread 30 bales and has 10 left over... how do you know those 10 are spread to the correct spots?
That's why I advocate checking a smaller section first, just to make sure his method of measure (Pressing the pillow) is good, then checking the number of bags used vs expected can proceed.
Controlling Density
I do not know what various blowing machines are capable of. But if you have a cell that is supposed to have say 25 lbs. in it, I would want a machine that I could set to blow 25 lbs. And as the machine blows the 25 lbs., I would like it to show the progress of that blow over time, and have it automatically stop blowing when it reaches the 25 lb. limit. That way, I could adjust my filling technique to the progress of the 25 lb. blow. Then I would feel the blanket and shoot a little more in here or there if it felt like it needed it. With all of that, I think the density could be properly controlled.
Wanting Too Much??
If I were building one house after another, and if I had an installer whom I was convinced did a good job, and no customer ever complained, I would rely on the "seat-of-pants" density control.
But if I am building my own house once, there is no way that I am going to take the installer's word for it that he did the job right. This is especially true for insulation density measure and uniformity, considering that I would have no way of knowing whether it is right or wrong. And if it is wrong, not only did I not get what I paid for, but I would also be paying for the mistake as long as I heated the house.
Well, sometimes, no matter how big a temper tantrum you throw, you don't get what you want.
You have to take a risk. The only thing sure in life is that you don't get out alive.
Well no, I don't have to take any risk because I can use fiberglass batts and rolls that come with factory-controlled density. Eventually, however, the fiberglass blowing industry will have machines that monitor the density just as I described.
Good
then that's all settled.
Discussions like this ........
bring back to mind all sorts of memories of jobs past.
Engineer or not, thinking through something as important as your home so you just might get it right, is a good thing.
But, at some point in time decisions must be made. And you will live with them.
Educating yourself on all this stuff in a short time is difficult. And education is a give and take proposition. Coming into a discussion with the answer already stuck deep in your mind does not lend itself too readily to education. Taking all the information in and postulating the best answer is something we should all strive for. Being bullheaded, set in your ways or just plain closed minded on good information, is something to avoid.
But this isn't from a rocket scientist-just a dumb carpenter..........
who's oftentimes told what to do by minds much brighter.
No, sound's like an engineering manager. They always want a "documented, repeatable process" when much of what we do is seat-of-the-pants.
BIBS Pros and Cons
There are two systems, BIBS®, and BIBS HP®. Both are registered trademarked.
BIBS® is a trademarked system that is installed by only certified BIBS® dealers who have gone through the BIBS® classroom and field training program.
The original BIBS® uses only dry fiberglass products made by CertainTeed, Johns Manville and Knauf. Their products are blown behind a Blow In Blanket System® fabric to the correct density, ranging from 1.8-2.3 lbs per cubic foot.
BIBS HP® (Hybrid system) uses between 1/2" and 1" of closed cell foam manufactured by tested manufacturers, then once cured, the BIBS HP® fabric is installed over the front of the stud cavity and approved fiberglass products are then dense-packed to the correct density, completing the application.
Checking density is done by cutting a specific area out of the walls at random intervals, taking the product out of the wall and weighing it. Our training requires it to be done after the first 4-5 cavities are done, then again every 800-1,000 sq. ft. of wall area till the job is complete.
You can find out more about BIBS® and BIBS HP® at our website: http://www.bibs.com, or on our new Facebook page at: http://www.facebook.com/pages/Blow-In-Blanket-System/348711258500672?ref=tn_tnmn
Or contact us at
Blow-In-Blanket Systems®
800.525.8992
Thank you
And just to reassure the forum that this just isn't an attempt to place a free ad, could you go further into answering some of the other questions put forth by the original poster.
It would be good to have a member that has experience like yours.
thanks.
BIBS questions
Double post deleted.
I'd just add a titdbit of info to this - doesn't apply to fiberglass, but a friend had his floor joists blown with staple up reinforced poly keeping it in place until sheetrocked, and it amazed me at how it deadened sound and the entire floor system felt more solid - just by cutting down on that hollow floor feeling/sound. I was so impressed it's something I highly recomend to anyone who wants an interior floor upgrade.
edit: this was with cellulose
Years ago my parents had cells blown between the floors for similar reasons.
Just had
a house blown with cellulose. Loose fill attic, dense pack walls, dense pack floor joists. Done mostly by feel with the installer checking bag count periodically. It turned out great, and really isn't complicated at all.
Blown FG goes a bit faster.
BIBS Clarification
Sorry I'm just getting back to you. I've been traveling and have not had addequate computer time to get to this post. I'm more than happy to answer any questions about BIBS and/or BIBS HP. (not to mention this site didn't send me updates that anyone had responded)
I hope no one thinks my original response was opportunistic on behalf of BIBS, but instead an offer from "the horses" mouth on information, myth busting and clarification about the actual system itself.
There are many misconceptions about BIBS, where it originated, who actually owns the trademark, that it's not just a "generic" type of application, what blowing products are approved, what fabric/mesh and netting is approved, what R-factors and densities are acceptable. I'd appreciate the opportunity to discuss each if asked to do so.
Regarding the original questions asked by the poster, KDESIGN:
"1) Does this system always use a flash coat of spray foam on the inside of the wall sheathing or roof deck as an air infiltration barrier, or is that not an intregal part of the system?"
Original BIBS does not include any foam "flash" application in the back of the wall cavity. BIBS HP, on the other hand, does. It can be as little as 1/2", or more. Depending on the budget and local codes requiring it to be of a certain depth to achieve a total "seal" and vapor retarder.
BIBS is not a "roof deck" application, unless it is in a closed cathedral cavity application. If BIBS HP is used, with foam, then codes will need to be strictly followed, such as: do the local regulations require a baffle system against the roof deck BEFORE BIBS/BIBS HP is applied.
"2) As an alternative to the flash coat of foam, could a person use an air barrier house wrap outside of the sheathing?"
Parts of the country require a vapor barrier/retarder on either the inside, or outside (depending on where you are in the country), some don't require it at all, so BIBS does not include a vapor barrier/retarder in it's system simply because it's not required all over the country, or it's required in different places in the wall system in various municipalities. Once can use a retarder/barrier with BIBS, but BIBS cannot dictate where, or if, it's to be used at all. Just like any other insulation application, local codes have to be followed.
"3) How does an installer know that he or she is installing the fibergalss at the proper density? I did learn of one method of controlling the density, but I would like to hear what others think about this issue."
There are density requirements requred for a BIBS installation. Each approved manufacturere, CertainTeed, Johns Manville and Knauf, have printed the correct densities on every bag of approved blowing wool for our system.
When we train a certified contractor, we show them how to do a physical density check, actually measuring the poundage per cubic foot, to make sure their densities are inside the perameters of the original testing. It may seem a little "archaic" but it's the most precise way of making sure densities are on track. And again, once the correct densities are tested and followed, you can compare them to the bag count that is required by the mfg. on the side of the bag of FG blowing wool. If to many bags were used for that job (according to the chart on the bag), then the density is to high, and if the bag count used is less than the chart says, then the densities are to light.
The system was tested for nearly 20 years to get the correct densities in place for the highest R-Factor, no settling, and no bulge that the drywall contractor can't comfortably cover without issue.
Paul Colley
Blow-In-Blanket Systems®
800.525.8992
[email protected]