Does spun fiberglass have the same R Value as blown in pink fiberlass?
Does the big white fluffy stuff have the same R Value as the pink, blown in fiberglass insulation? I have heard it is less affective than R2.8.
Asked by Kellye Markowski | Mar 16
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Kellye,
Please be more specific. What brands are you talking about?
As I'm sure you know, the color has nothing to do with it (except as an indicator of a particular manufacturer). Both fiberglass batts and blown-in-place fiberglass vary in R-value depending on its density; the denser the product, the higher the R-value per inch. So called "high-R" batts have a higher R-value per inch than conventional batts (because they are denser).
If you are blowing spray-in-place fiberglass into a wall cavity, it can be blown at low density or high density.
Standard, low-density fiberglass batts offer around R-3.14/inch. Loose-fill attic fiberglass has about R2.2/inch. High-density batts or semi-rigid board and blown-in fiberglass now offers as much as R3.8-4.2/inch.
White and fluffy can also describe Johns Manville's "Spider" microfilament insulation which has the same R-value, 3.6 per inch, as some open cell spray foam products and cellulose and can be damp sprayed in 6" walls or blown through mesh in thicker walls. As with all new products, the pricing is volatile so multiple quotes are essential.
http://www.greenbuildingadvisor.com/community/forum/green-products-and-m...
See also http://www.greenbuildingadvisor.com/product-guide/prod/jm-spider-custom-... Great stuff, no flame retarder chemicals such as tris or BPDE which may be present in some spray foam components, no formaldehyde, you can snake wires through it, no waste is shaved off to go to the landfill, it's just swept up, returned to the hopper and comes back to be sprayed into the walls again. No worries about staining finished concrete floors the trimming crew cutting phone and speaker cables. won't hold water, support fire or feed bugs. I've been using it in all my homes for a couple of years now. I like it a lot better than spray foam in a well-built wall.
(Our homes are generally under 2.0 ACH-50 so we don't need the air sealing in our walls from spray foam and we are in North Carolina with a reversing vapor drive so our walls dry both directions. I don't work for Johns Manville and I pay regular competitive prices for all products I use in my homes. I just get enthusiastic about the things that make my job easier.)
Michael,
What about mice? I've yet to see the fiberglass product that does not quickly become a haven for rodents, with all their foul leavings and catacombed thermal layer.
Robert, Maybe it's the galvanized termite shields and sealed crawls we use down here. We sometimes get mice in the crawlspaces but very rarely in the walls and attics. Maybe southern mice are just less industrious than the yankee variety.
I have no idea who the manufacturer was or the density. How do you determine the density in existing blown in insulation in an attic? The home was built in 1987 in Missouri.
Attic loose-fill fiberglass is nearly worthless as an insulator, both because it's R-value is quite low and it does not prevent air exfiltration.
Top it off with blown cellulose for higher R-value (3.6/inch) and much better air control. If you can seal any openings from the conditioned space below with spray foam first, you will further reduce exfiltration.
Michael,
Why does the JM Spider spec sheet claim up to R-23 in 2x6 walls?
Wouldn't that make the the R-value 4.18 per inch?http://www.specjm.com/files/pdf/bid0060_SpiderDataSMech.pdf
Brett,
Those numbers do seem surprising. It's possible to get up to R-4.2/inch for semi-rigid fiberglass boards (foundation drain boards), but that's at considerably higher density.
Would blown fiberglass of this kind be an R 2.8 or less per inch?
Kellye,
Which kind are you now referring to? And are you talking about loose fill in an attic or dense-packed in a wall or other closed cavity?
Michael... I have been studying R-value on and off for the last two winter down times.. Here's the deal on marketed R-values... Every manufacturer tosses out the highest R number possible, and they do this by claiming entire built up wall and all dead air near the wall.
So... if you take in this example .... R-23 minus 3.6X5.5"=19.8 the remainder is R-3.2=your wood sheathing,sheetrock, siding,and both inside and outside close to wall air layer.
Remember that all marketing.... is spun... like WMD in Iraq... and 9/11=Saddam
aj
ADKJAC,
Advertised R-values are regulated by the FTC R-value rule. Manufacturer's cannot just "toss out" a number to make their product look better. However, it's the responsibility of the user to understand what the tested R-value means and how the framing system and installation will effect the whole wall performance.
Robert... I am mainly talking about marketed numbers not spec sheets that are a bit farther from reach and may be regulated and such...
That said I am in the middle of reading the Spider specs right now and they do say... r-23... I just haven't drilled down to how the number was arrived at... if you have the info... post it.
aj
OH... and forum numbers... chats online etc... magazine hype...
and green washing... and on and on.
OK... my reading on Spider... sounds interesting... still confusing that their literature states 2 R-values everywhere with no explanation... 2x6 wall R-20 and R-23... someone explain this...
This is really what makes me crazy when researching... coming up on unexplained numbers... and charts that have too little explained making it hard for me to work thru the math and formulas used.
frustrating as all get out.
still... sounds like I may like spider
aj
how does one edit or delete a post????????????????
ADKJAC,
Perhaps if you would read more carefully, you wouldn't be so confused. JM Spider comes in three different forms: Drill & Fill, Blow-In-Blanket, and "Custom" or wet-sprayed. Each has different densities and different R-values. And, like all fibrous insulations, the R-value depends on installed density.
Robert... I wish this I knew how to repost the JM Spider pdfs here... There pdf shows a chart for bibs or blown for a wall and states R-20 and R-23. And after reading dozens of pages... I have circuitously figured out they must be not stating that the insulation can be blown in different densities and therefore have different R-values. Even down to 1lb density that is lower than R-20 but only stated on an installer's page. So now with all the density differences, I have to check bag count and density if I pay for R-23 and the product can be installed to as low as R-12. No fun.
"Johns Manville Spider® Custom Insulation comes in variable thickness levels can fill 2x4 cavities up to an R-15 thermal rating, 2x6 cavities up to R-23" .... key words in this "marketing" is... "up to"
"For example, JM Spider insulation achieves a Sound
Transmission Class (STC) of 43 in an exterior 2x4 wood
framed wall with 1/2" particle board siding, 1/8" pressed
cardboard sheathing and 1/2" gypsum board" IN THIS MARKETING.... SOUND LEVEL INCLUDES ENTIRE WALL SYSTEM...
http://www.specjm.com/files/pdf/spider-builder-value-proposition.pdf READ THIS MARKETING SHEET AND TELL ME WHAT FACTS WERE LEFT OUT... AND HOW SCIENTIFIC THE INFORMATION IS THAT WE ARE MEANT TO BE ABLE TO DISCERN. IT LIKE ALL COMPANIES IS MARKETING SPIN AND IT JUST MAKES IT THAT MUCH HARDER TO COMPARE APPLES TO ALL APPLES... LIKE THEY LEFT OUT CLOSED CELL FOAM TO COMPARE TO AND THEY DERATED THE BLANKET INSULATION BUT NO OTHERS AND THEY DIDN'T EXPLAIN WHETHER THEY ARE VALUING THE ENTIRE WALL THICKNESS AND CLOSE AIR LAYERS AND AT WHAT DELTA T AND THEY DIDN'T DERATE FOR FRAMING AND THEY DIDN'T DERATE FOR 15% WINDOWS IN A WALL...
THE AVERAGE PERSON WHO HERE'S R NUMBERS... R-23 JUST THINKS OK... THAT IS WHAT MY NEW HOME WALL R WILL BE. I AM BUYING R-23, DONE DEAL.
SEEMS WE AS AN INDUSTRY SHOULD BE TELLING THE TRUTH.
My home most likely was marketed as having
R-13 basement R-21 walls R-38 attic
My home built in 1988 most likely has an
R-5 actual whole home value at most.
and after comparing my math to my actual fuel use, that number is close.... Even though my house is 24" oc framed 2x6 with r-21 pink kraft batts in the walls and 12" attic, and foil faced 3.5" 1" off framed from cellar walls, lousey ins at rim joist,.. Cellar ins is kept up from floor 12". it is going to be a major refit to do over this home that no I did not build. I will be redoing it.
Robert, you are one of the best here... my home... cedar claps... seems I should remove siding and do joint ceiling of osb then 2 layers of foam board taped, then sleepers then back with siding? and same with cellar, remove walls, add foam eps and then tight frame back to foam and put back glass, spray foam rim, remove window trim and foam seal,,, remove window possibly to redo weather seal at windows and doors... lot of work... less than a new build... but lot of work. I like the challenge though.
Robert?
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