I had a conversation with an insulation contractor. They install the fiberglass BIB, L-77 from Owens Corning. It is installed at 2.25 psf density (should that be pcf?) that they verify with some sort of handheld equipment to measure the installed density. They use a mesh on the stud, overpack then make it flush with the studs. Installer said for a 2x6 wall it would reach a value of R24. I have 1" of ISO on exterior, and I wanted to install 1-2" cc spray foam then fill the rest with wet spray or dense packed cellulose.

How does this compare to a wet spray cellulose? Installer said with the wet spray the the value would be R23 for the 2x6 wall. I thought there was something about convective loops and radiant heat that made a difference in cellulose vs. fiberglass? The density number seems high for the BIB they install. Installer said the cost is about the same between the two installs, one is cleaner but need to put up mesh, the other messier, but no mesh.

So if costs are similar, R-values are very similar, then how do you choose? I have been set on finding a cellulose contractor that does wet spray or dense pack because I read very good things about cellulose. But after the talk about the L-77 BIB, I am now wondering if it would be ok to go with BIB?

Thanks,

BG

excellent question, I'm interested in the responses. When we built our house I asked similar questions & got some curious responses. Specifically, one insulation contractor said they won't use cellulose "because it settles", but promoted their BIB system. I'm still confused how one product, blown to a specific density, will settle, but the other won't.

The thing I find interesting in your post is the comment about costs. I've always heard that dense-packed cellulose was cheaper.

In my area we have seen an increase in cellulose costs. Combine that with how messy and dusty it is, most contractors are now charging the same for BIB or cellulose. And if you ask them, most will prefer the BIB in both walls and attic since it blows faster and cleaner. It also comes packaged far more compressed so their truck size is smaller.
I read somewhere that the convection loops you refer to are greatly reduced and practically eliminated with the highly packed modern fiberglass installs. Dana1 will comment I am sure, and he will post all of the fun insulation facts.
I have spec'd the BIB on a few projects now. However I have no baseline comparison of performance vs wet spray cellulose. I have never spec'd it on a project yet other then loose in attics.
With that being said, I will probably still choose cellulose to blow in my attics of my own new home most likely since it is a fully vented attic, however using ICF for the walls.

I believe it is the owens corning that is dense packed. BSC says that air tightness is similar between dense pack fiberglasss and cellulose so it becomes a wash. The densty is what stops the convection. Cellulose has borates that will keep the insects out and buffers moisture. I think cellulose is the way to go in a vented attic.

The key to either of them is creating an air tight enclosure.

Jerkylips - this contractor said he'll do either, but it was very obvious that he prefered the BIB over the cellulose. He did even mention that the wet-spray could settle at the top a half an inch if he drywallers get too rough with the walls. He did not know what density the cellulose is installed at, since he said he went by the manuf. instructions. He did say he could do a core test if requested. The BIB he said was att 2.8, and I thought I read somewhere that BIB packed over 2 pcf would perform as good as dense pack cellulose.

Izerac - I really do not have a way to know how dense pack or wet spray cellulose is going for around here. So far I've only found one contractor that does wet spray, and one that does the dense pack. Only the wet spray guy has called me back. Everyone else I spoke with said loose blow into the walls, which I don't want. I saw one installation that did what they called a BIB. This was my first experience with the term.
To me it looked like they were taking batts of pink fiberglass, running it through a machine that ground it up and made cotton ball sized balls of fiberglass and loose blown into the wall through a hole in sheets of poly installed on the walls. I didn't see how that could be better than using batts.
With my 1" of ISO on the exterior of the house, I'm concerned about having any poly in my walls, specially since I would like a skim coat of 2 lb foam before filling the rest with insulation.

Roberth, the BIB system that the contractor described was from owens corning, and the density he quoted seemed very high. I happen to know someone who used their BIB in their home, so I plan on visiting and taking a look at the insulation since it is not covered in the mechanical room just yet and is it visible.

I have not seen the quote yet, but I'm curious to see how much different or close the BIB will be with the cellulose. If they are really close, what criteria can I base to do the pros and cons of each and choose for the walls?

In the attic I will go with cellulose over the skim coat of foam, and will most likely be DIY to blow it in, since we have limited budget and I'm sure the flash and fill on the walls will be spendy enough.

Thanks.

typcailly the BIB or dense pack cellulose is installed behind a tightly stretched fine netting, not polly. It is breathable, and will not be affected by the exterior foam. BIB is better then batts because it can fill in around all of the areas and gaps batts leave. It packs the walls just the same as cellulose, it just has some slightly different properties.

There is a nice comparison of dense pack fiberglass versus cellulose at:
http://www.mnshi.umn.edu/kb/scale/i...epack.html

The BIB installations that I have seen in new construction are as Izerarc has described, with a mesh that looks sort of like a light, stretchy, burlap bag stapled to the studs and the insulation blown in.  In this subdivision, BIB seems to be used in place of the wet cellulose that they used previously in new construction. 

If life-cycle reuse of materials is important to you, then cellulose is the winner over fiberglass.  Cellulose buffers moisture much better than fiberglass, if that is important in your climate.  Thermal performance appears to be similar, and hopefully the dense-pack fiberglass will perform better than fiberglass batts at low temperatures, but I have not seen test results.  The decision might be influenced by whom you can find to do the job.  I expect either would work well.

From a heat loss point of view, above ~R15 or so in a 2x6 framing it hardly matters what the center-cavity R-value is, since the R-value of the thermally bridging

At a 20% framing fraction with lowly R15 center-cavity R the whole-wall R (old-school rock wool or something) is ~R12. Bumping up the center-cavity to R24 only yields R15 for whole-wal- the difference in performance is like adding another 1/2" of iso.

If the framing fraction is 25% the differences are even smaller. (R11.5 whole-wall compared to R14)

The difference between even R23 and R24 center cavity is academic- nearly inconsequential from a thermal point of view, so whichever is cheaper is fine.

From a wintertime condensation point of view with R5.6 (derated for cold climate) iso on the exterior and R6 or more of ccSPF on inner surface of the sheathing, the condensing hours at the fiber/foam interface are few no matter which product you use, and the sheathing would be well protected from wintertime interior moisture drives in any lower-48 climate zone (but not necessarily in central AK.)

At sufficiently high density the convective losses of performance of any fiber insulation becomes inconsequential, but with cellulose even the lowest density is almost always "good enough. With the new-school fiberglass blowing wools only the higher-density installations are air-retardent enough to eliminate that issue, but that may be less of an issue here than in some other applications. L-77 is specified to be R21 @ 1.3 lbs density in 2x6 framing, and R24 at 1.8bls+, but that's under ASTM C518 test conditions. In a real-world cold climate the 1.3 lbs goods will likely underperform spec at the average winter temps by quite a bit, if it were the only insulation, whereas the dense-packed R will be fairly stable over a far greater range.

But with ~R12 of sheathing, siding, and foam to the exterior those losses in performance are dramatically lower than they would be a no-exterior-foam stackup. It'll still be somewhat outside of ASTM C 518 conditions for delta-T, but not nearly as much as it would be without the exterior R. You might consider going with low-density 1lb Spider (wet-sprayed to activate it's adhesive, to keep it from settling) in your stackup, but I suspect the wet-sprayed cellulose would likely be cheaper. With L-77, dense-packing would still be required to eliminate settling.

Exterior R also protects low density cellulose from settling, since the settling of cellulose is a function of it's density plus seasonal humidity cycling, which is a function of the average winter-temp of the cold side of the cellulose. (The colder the winter, the more moisture is buffered, the higher density is required to eliminate creepage related to the hygroscopic expansion/contraction of the fibers.) With R12 on the exterior and R15-16 (4.5" of cellulose) and minimal condensing hours, the amount of moisture buffered by the cellulose will be miniscule compared to a no-exterior-foam stackup where it might otherwise need to be ~3.5lbs density to eliminate settling completely. Wet-sprayed also helps the settling issue by locking it all in with adhesive.

With either material, do NOT install an interior vapor retarder- it's not necessary, and creates a moisture trap.

BTW: Note the air-retardency curves for both Spider and cellulose on the bottom left, p.2. 

Yes, 1.8lb Spider is about as air-retardent as 3.5lb cellulose (both are dense-pack densities), but it doesn't take much imagination to infer from those curves that 2.5lb "two hole method dry blow" cellulose is more air-retardent than 1.0lb or 1.3lb Spider. 

And yes, according to the data, at 2.2lbs Spider is tighter than 3.5lbs cellulose but even if there WASN'T going to be a flash-foam air seal in this application, the practical difference between "nearly nothing" and "2/3 of nearly nothing", is also merely academic, when "2x nearly nothing" is already sufficient to prevent loss of performance due to convection.

Thanks Dana1. I still have not received the bids. I am not so sure that cellulose will be much cheaper than the BIB, since very few contractors here in my area seem to actually do the dense pack or wet spray, but quite a few are doing the BIB fiberglass. I have not priced the spider version, but I doubt it would be cheaper than the L-77 or cellulose. Only one company seems to have it around my town.

At least now I have some comfort that either dense pack cellulose, or the l-77 bib would perform ok for my stack-up, and it will come down to price/comfort with the contractor.

I noticed the literature talks about 1.8lbs+ for the spider. This contractor claims they install the L-77 at 2.25 lbs, and verify with a handheld meter. So I'm assuming higher density is better for the fiberglass BIB.

Thanks

The lit for L-77 also talks about 1.8lbs (and 1.3lbs & 1.5lbs), and also "...up to 2.50..." , so 2.25 lbs is good. Higher density means it won't settle, and won't convect much within the fiberglass layer. With any of them there is a density above which the R-value starts to fall, but that's never specified in the product datasheets.

Thanks Dana1! I finally have a quote from the foam guy and 1 dense pack guy. Still waiting on a couple of more, including the BIB one. I wish bids came back faster, but they never seem to. Maybe 'cause I'm not a builder... or maybe they are very busy.

I did have one guy ask why don't I just foam the whole wall? But I'd think that would be even more expensive than what I'm asking for. Any comments?

Posted By Boontucky-girl on 03 May 2012 09:59 PM
Thanks Dana1! I finally have a quote from the foam guy and 1 dense pack guy. Still waiting on a couple of more, including the BIB one. I wish bids came back faster, but they never seem to. Maybe 'cause I'm not a builder... or maybe they are very busy.

I did have one guy ask why don't I just foam the whole wall? But I'd think that would be even more expensive than what I'm asking for. Any comments?

Closed cell foam is going to cost a buck a square foot for every inch of depth, and they can't do a complete fill since planing it flush with the studs would be extremely labor intensive.  In addition to being more expensive, it adds less than R2 to the whole assembly due to the thermal bridging of the studs. It also lowers the permeance of the insulation layer to the point that in conjunction with the exterior foil-faced iso, there is no path for moisture to get out of the sheathing- no matter how it gets in, it becomes trapped there.

As if that wasn't bad enough, the HFC245fa blowing agent most commonly used would increase lifecycle greenhouse gas emissions of the assembly well beyond that of the energy-source emissions it was offsetting.  This is true for almost any depth beyond 2"/R13

Closed cell foam (and XPS) isn't very green as insulation, but is worth considering for it's superior air-sealing qualities, and for adjusting the permeance at a given point in the stackup for condensation control.  The first inch of cc foam on the interior of the sheathing is enough for an air seal & condensation/moisture control at the sheathing, and still sufficiently vapor-open to have a drying path to the interior.

EPS and polyiso use pentane for a blowing agent, which is orders of magnitude more benign.

With open cell foam spray foam it varies with vendor, but most have a net lifecycle greenhouse benefit even at R40 or more.

one thing to consider besides the wall is the attic and roof. How are you planning on sealing that up?
I have pondered this area, and want to do a vented attic as I feel they are the best way to go (no hvac, not even ductwork in attic).
I think I have settled on a 1-2" open cell "attic seal" on top of the gyp and over everything else. I have been working very closely with my insulating contractor has he too has a passion of extreme efficiency and shares the goals for this project that I do. He has never done one as efficient as mine, so he is excited. After the attic seal, then he will blow cellulose or fiberglass on top of it. I am leaning more towards cellulose in the attic and fiberglass (BIB) in the walls (double stud). The attic seal eliminates air tight drywall and should make things easier to tighten the entire thing up. For can lights, he said they wrap the can in batts and then spray the batts to create an entirely enclosed shell.
I think a lot of focus is placed on walls, but the roof sealing is just as important (many argue more).

Posted By lzerarc on 10 May 2012 10:25 AM
...snip...
The attic seal eliminates air tight drywall and should make things easier to tighten the entire thing up. For can lights, he said they wrap the can in batts and then spray the batts to create an entirely enclosed shell.
...snip...

Have you considered track lighting instead of cannister lights?  That way you are not poking holes in your primary air and thermal barrier, you retain full insulation depth at all point in your attic, you are not creating hot spots in the cannisters, and there is more flexibility in directing light where you want it.

I'll second the motion, and further comment...

Down-lighting (particularly narrow or point sources, such as recessed can lights) in adds both glare and shadow, making for lower visual efficacy at any ambient lux intensity. Using high-efficiency indirect lighting sources such as cove & valence lighting or cabinent-top uplighting reduces glare, enhancing visual acuity even when mixed with some down lighting.

Glare == bright spots in the field of view that are many dB above the average intensity in that view. Glare causes pupils to constrict, lower the ability of the eye to discriminate contrast in what you're looking at.

Combine that with shadows being cast by your hands over what you might be working with/looking at make recess lights one of the least effective and least efficient ways to light up room, from a functional point of view. It takes higher ambient luminosity to achieve the same visual acuity as when mixed with (or solely) lit with up-lighting. Mixing it with up-lighting decreases the contrast between the down-light and the surrounding ceiling lowering glare, and lowers the contrast of the shadow edges, filling in behind the shadows.

Yet the "sea of cans" across the ceiling popularized in the 1950s remains popular, despite it's drawbacks. While it's far better than the naked bulb in the center of the room plus a few wall-sconces that was the standard in the 1920s-1940s, there are better methods, now long established, but less implemented in homes than in commercial spaces.

cans would be used (possibly) as spot lighting typically, or limited to only the kitchen, no other spaces. I have not dug much into other lighting options for the kitchen yet, however I have considered some sort of decorative track lighting instead in the kitchen with a majority of my task lighting being picked up under the cabients. I am currently not intending on using cove/crown lighting on the cabients.
I am open to any lighting ideas however.

On kitchen under-cabinet lighting you get better light distribution and more light over the working space if you place the fixture at the forward edge of the cabinet, directing it back to the wall, using the wall-wash effect as the light diffuser. This places the fixture closer to the work so the absolute light intensity is improved, and the wall reflected light fills in the shadow. Most under cabinet lights are not installed this way, with most typical being places at the back of the cabinet abutting the wall, which maximizes glare and provides less light to the space in front of the cabinet, cutting into absolute efficacy.

Cabinet-top uplighting works best when there's at least 18" between the top of the cabinet and the ceiling, or on cathedralized ceilings where the ceiling-wash effect is broadly spaced. Even 65-100watts of 90-100lm/W T8 or T5 no-glare uplighting generally works better than 90-120W of 50-60lm/W CFL or LED down lighting cans, despite the efficiency losses of the uplighting being absorbed by the ceiling. A roughly 50/50 power mix of T8 or T5 uplighting and CFL or LED R30 cans works better than either alone, with the uplighting cutting the glare factor of the can lights.

B-Ky:

a)
Nothing but fantastic results have been realized in trying/ more frequently still using wet-packed-Cellulose for new homes since 1993, and retrofits packed -  "guaranteed not to settle, performance -transferable to the next home owner" in writing on contracts since 1989.

b) more adjustments to heat loss calculations and related ground loop-sizing came into a final alignment in 1996 after reviewing a couple dozen applications of cellulose to new home HVAC systemic studies. The results lead to contracting in new construction to producing contracts that included (then-to~ 2006) "With other than wet packed cellulose insulation, please add 3/4-1"ton" to the ground loop and 1/2 ton to the GT/AirHP 'size'  " , - in writing, and on every contract from 1994 also,  by a premiere competitor - a very well known Water-Furnace(WF) contractor. [2.1/2- to then 5-"ton" systems]   --- DANA "the meters ...up close" (hah!) are the temperature readings at a loop, refrg gauges in the HI-eff ranges, and that extra KWH meter on many installations.

c) As you see written in many posts, guarantees were ONLY b/c installers were contracted to performance specs, and really did a nice job.

1989-1991 HVAC Systems sales involved usual construction improvements in Res and Comm. When going back to one wall of a home in a bathroom remodel 2 years later, we found not one fraction of an inch of 'settling' had occurred, as a bathroom mid-high recessed wall cabinet was pulled away for a newer one to go in its place.
CELLULOSE STAYED TIGHT IN PLACE.
 (Cabinet pulled , leaving a solid rectangular space where one could push at the cellulose, dry-packed) ...  took a picture, and used that in many future discussions in contract sales.

Later cold-wall-warm-wall testing was checked at a few jobs with the then very expensive infra-red readers,  to check settling. No settling found in 3 years later on those retrofit/ nor new dry packed-cellulose: It was installed with adjusted 2nd air-pressurizing blower in the hands of the well trained insulator.

Since 1993 for hi-eff hvac design-building (for my specifications to retrofits, and wet-spray to new constructs) I think you can find all over KY,  information commiserate with the above posted cellulose commentaries.

d) Pictures of intentionally burned-down corner house frames , for as examples some differences, always showed cellulose, packed, resisted air movement in a fire such that "house" framing in a fire just outlasted fiberglass batt installs. So I think know a more 'packed' fiberglass would be comparable to retarding air movement about that.

skimming through other threads , there are a lot of good details about just using cellulose.
I only in the past 7 years have seen good results with a 1/2-3/4" attempted spray Poly-U --- to seal first, and even batt in 6" after that was pretty good. The cellulose wet spay, alone,  contracts @ $1500+ more than seal+batt.(2011) 

e) Since several thousand heat load studies, it appears wet spray cellulose also has an additional feature:
 Enough money to off-set some additional cellulose costs up front is relative to LESS COSTLY - framing, -enclosing, structural-building that may leave some acceptable-GAPS and/or LOOSER, faster construction on a SMALL PORTION of home building (if reasonable). {just if applicable}   Structural re-enforcing of ceilings under.. is noted by others and Dana in  several other threads for that r(50) + attic of cellulose.

f) Reducing leaks is great, however cellulose it seems does breaths enough also that final results may naturally lead to less erv needs. Some inspectors allow for absolutely no outside-type vapor barrier needed.
- it will be interesting to see comments on that.  -just seen that remarked about over the past 14 years.

x) If your inspectors requires the interior vapor barrier---, as some did 2004-2010, (done here !) - maybe slice it open or off after , ... and you may want to do that as before interior drywall goes up. period. Dana is very right; or you may have a terrarium tantrum.

B-Ky:

a)
Nothing but fantastic results have been realized in trying/ more frequently still using wet-packed-Cellulose for new homes since 1993, and retrofits packed -  "guaranteed not to settle, performance -transferable to the next home owner" in writing on contracts since 1989.

b) more adjustments to heat loss calculations and related ground loop-sizing came into a final alignment in 1996 after reviewing a couple dozen applications of cellulose to new home HVAC systemic studies. The results lead to contracting in new construction to producing contracts that included (then-to~ 2006) "With other than wet packed cellulose insulation, please add 3/4-1"ton" to the ground loop and 1/2 ton to the GT/AirHP 'size'  " , - in writing, and on every contract from 1994 also,  by a premiere competitor - a very well known Water-Furnace(WF) contractor. [2.1/2- to then 5-"ton" systems]   --- DANA "the meters ...up close" (hah!) are the temperature readings at a loop, refrg gauges in the HI-eff ranges, and that extra KWH meter on many installations.

c) As you see written in many posts, guarantees were ONLY b/c installers were contracted to performance specs, and really did a nice job.

1989-1991 HVAC Systems sales involved usual construction improvements in Res and Comm. When going back to one wall of a home in a bathroom remodel 2 years later, we found not one fraction of an inch of 'settling' had occurred, as a bathroom mid-high recessed wall cabinet was pulled away for a newer one to go in its place.
CELLULOSE STAYED TIGHT IN PLACE.
 (Cabinet pulled , leaving a solid rectangular space where one could push at the cellulose, dry-packed) ...  took a picture, and used that in many future discussions in contract sales.

Later cold-wall-warm-wall testing was checked at a few jobs with the then very expensive infra-red readers,  to check settling. No settling found in 3 years later on those retrofit/ nor new dry packed-cellulose: It was installed with adjusted 2nd air-pressurizing blower in the hands of the well trained insulator.

Since 1993 for hi-eff hvac design-building (for my specifications to retrofits, and wet-spray to new constructs) I think you can find all over KY,  information commiserate with the above posted cellulose commentaries.

d) Pictures of intentionally burned-down corner house frames , for as examples some differences, always showed cellulose, packed, resisted air movement in a fire such that "house" framing in a fire just outlasted fiberglass batt installs. So I think know a more 'packed' fiberglass would be comparable to retarding air movement about that.

skimming through other threads , there are a lot of good details about just using cellulose.
I only in the past 7 years have seen good results with a 1/2-3/4" attempted spray Poly-U --- to seal first, and even batt in 6" after that was pretty good. The cellulose wet spay, alone,  contracts here were about  @ $1500+ more than seal+batt.(2011)