In process of rewiring an 80 year old colonial that i live in. House will also be resided before the snow flies, (I hope). House has no insulation in walls and had only 2″ of old rock wool randomly strewn about in attic floor. I have 2 quotes from reputable local companies that are fairly close in price. One is for blown in cellulose the other is for a blown in fiberglasss product. Boston area.
Framing is 2X4 walls w/ 2X8 in attic floor. Is there a long term advantage of one material over the other assuming R values are comparable? should I lay a 4mil or 6 mil vapor barrier in the attic floor before running wires?
Thanks for your thoughts.
Replies
I don't think there is going to be much of a diffrerence if the products are installed properly. I would be worried about the long run settling of the product. Which product will stay longer. To these I have no advice. Ask the contractors, or wait for more postings here.
cellulose.... fiberglass insulation is next to uselessMike Smith Rhode Island : Design / Build / Repair / Restore
I agree with Mike Smith but I would choose foam. there are several advantages to foam that cellulose doesn't have. Among them is it will make the house more rigid and less squeeks
Ah, finally! My mission is complete!
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
DanH
What, because given a choice between poor and terrible I selected poor? Didn't I still recommend foam?
Just for the record, I think SIP's are the best, ICF's a close second, foam sprayed stick built a distant third, celluliose a poor fourth and fiberglas a near worthless 5th.
See http://forums.prospero.com/tp-breaktime/messages?msg=80501.13
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Hi,
I would go with the cellulose.
It has a higher R value per inch, especially in the loose fill form.
http://coloradoenergy.org/procorner/stuff/r-values.htm
Fiberglass also loses effectivness as the outside temperature drops due to convection currents forming in the insulation. In this ORNL test, FG loses half of its R value in cold conditions, while cellulose is unaffectd:
http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html
Another side by side comparison test:
http://www.builditsolar.com/Projects/Conservation/Insulation/Colorado.pdf
Cellulose also has less embedded energy, so its a bit easier on the planet.
Gary
Thanks Gary, great links.
info here helped me to make a good choice and may even save mea few hundred clams! Thanks again.
What is embedded energy?
there are certain hidden energy costs to bring a product from a raw material to a conumer product use
IE: it takes energy to gather the raw material, process it and transport it
FG has a higher embedded energy cost than cellulose
much like Ethanol has a high embedded energy costMike Smith Rhode Island : Design / Build / Repair / Restore
I though it had something to do with Viagra.
DP
Fiberglass needs to be enclosed to be effective. If they're just going to blow a layer of fiberglass into the attic, it will not perform very well at all (though it's performance won't be quite so bad in the walls).
Cellulose has another advantage in older, drafty homes in that it also provides a significant air infiltration barrier, cutting down on drafts, and on air leakage into the attic.
Besides which, fiberglass is itchy.
The only place where fiberglass would be preferred (IMO) is if you have significant water leakage issues (roof, around windows, etc). Cellulose will absorb water and hold it whereas fiberglass will let it run through (and hopefully out somewhere). But a house that leaks like that probably isn't worth insulating anyway.
It definitely is a good idea to put plastic in the attic, UNDER the insulation. But also make an effort to seal around pipe and wire penetrations, etc.
I'd leave out adding any plastic to the attic "floor".
It will be a pain to scoop up all that loose original insulation. Efforts are best spent airsealing all the penetrations to the attic plane i.e. foamseal all the holes for wiring; close off any chases from chimney (must use non-combustible materials in many cases); box around any recessed lighting cans not rated for insulation contact; air seal the wall to ceiling drywall area; etc etc.
<start of argument to follow>
If you use a good PVA primer and then two coats of good latex paint you will not need to add any plastic sheeting in the ceiling with cellulose insulation.
</start of argument to follow>
Yeah, if a VERY GOOD job is done at sealing all penetrations, including studwalls, then probably the twelve coats of oil paint already on the ceiling will suffice. It may pay to at least put plastic over the backs of ceiling electrical boxes, though, extending a few feet in all directions. There are several other ways to deal with electrical boxes, though no "ideal" way.(Which brings up a good point: All knob-and-tube wiring must be replaced before adding insulation.)
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Nah, 12 coats of oil paint are not required. PVA and 2 coats of latex ceiling paint.
"It may pay to at least put plastic over the backs of ceiling electrical boxes, though, extending a few feet in all directions"
Whatever for? If, and an unlikely if ... any airborne water vapor gets by the caulking and foaming (and airsealed box) over the back surface of any ceiling fixture electrical boxes.... you want to trap it behind some plastic sheeting so it can get on the backside porous paper of the drywall ceiling? Not a good idea.
Any miniscule amount of airborne water vapor that very unlikley gets up into the attic cellulose would be absorbed harmlessly into the cellulose. And then it will simply eventually diffuse into the cold dry air of the attic and out the vents. We're talking extremely slight chance of an even smaller amount of water vapor. It would be much less than the humidty in the air that makes it way from the soffit vents and out the ridge vent on a Summer's day. Cellulose is a very forgiving buffer for any humidity/vapor. It will store some harmlessly and the give it up when the air is drier.
My point about the twelve coats of oil is that they're already there.Ceiling fixture boxes are difficult to seal and can be a major air leak if not sealed. The plastic can do a good job of sealing under some circumstances (instead of caulk/foam/et al). It won't "trap moisture".I personally don't like foaming electrical boxes, especially from the back side, since the foam is hard to control and can make a mess of the wiring,
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
It won't trap moisture that cannot get there in the first place.
But let's say some moisture escapes teh caulking sealing etc. Why won't the plastic trap the moisture that hits it? Is this magic plastic?
If the plastic is under the insulation it will be at essentially room temperature. No condensation will occur.(And the purpose of using the plastic there is not for a vapor barrier so much as an infiltration barrier. I suppose you could use a piece of Tyvec if you're that worried about condensation.)
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
So then the plastic really is not necessary if no moisture will condense on it.
I wouldn't use Tyvek either. I don't worry about.
Like I said, the point was to prevent air infiltration. You can use the other techniques -- caulking/foaming, etc -- but they're apt to be more hit-and-miss.
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Here is where I get to open a can of worms.... oh well!
The two may appear similar in insulating and fire resistance values. There might even be lab tests to support any figures added. Yet, I disagree with these figures.
The paper (cellulose) products are far less uniform, and subject to quality control problems that mineral fibers do not have to deal with. That simply must be the case, where the one product has additives to make it less flammable, or less likely to rot, while the other product is inherently mold and fire resistant.
Given a choice, I'd opt for the mineral every time.
Ah, there's one in every crowd!(Now all we need is for someone to come in and say the OP would be stupid to use anything other than foam.)
Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
Edited 10/25/2006 3:11 pm by DanH
yeah, well , your mudder wears combat bootsMike Smith Rhode Island : Design / Build / Repair / Restore
When you say you would use mineral everytime are you talking glass or mineral fibre?
If your talking glass well ya, Your mudder wears army boots. ;-)
But mineral fibre thats a whole different story. I have mineral fibre batts in all my walls int/ext for a number of reason. Best fire resistance of them all hands down best or close to the best sound control . Great moisture resistance. No nasty glass fibers to clog your lungs. and on and on(cellulose still might have it on infiltration but I don't know for sure and in the walls there are other ways to control infiltration). Blown in Mineral fibre seems to be somewhat elusive, up here at least. As I said I am not sure of its infitration qualities but its got to be better than glass. I'm so surprised glass still dominates the market.
My attic ended up getting R50 cellulose. I would never blow glass. I have yet to see an indepenant study that tells me fiberglass is a great choice when considering all the variables and other options available.
brian... i might be making this up... but my recollection is that mineral fiber insulation was / is a by-product of making steel.... something to do with slag.... or perhaps coke ovens
but you know me... what i don't know , i make up.... i'm irish , ya no ?
what is the slang term for "mineral fiber" ? the name escapes me
working in attics with mineral fiber was never one of my joyous recollections.. some of those fibers were just like little knives
anyways.... my point is that something has changed in US mfr'g and that is the reason for the relative disappearance of mineral fiber...
but hey, whadda i no ?Mike Smith Rhode Island : Design / Build / Repair / Restore
"but hey, whadda i no ?"Not much.That is diesel, not Diesel Pig.
The studies list here have to do with "convential" FG.Does anyone know about BIBS (blow in bat system). That is for walls and uses either a glue or it is blow behind a mesh. Much like cels.Also last year I worked in an attic that had a white, soft cotteny like blown insulation.I know that there is a cotton insultion, but it is recycled stuff. And this was pure white. I don't know, but for some reason I have the impression that it was the same fiber used in BIBS.
"what is the slang term for "mineral fiber" ? the name escapes me "
Slag wool? Mineral wool?
rock wool..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
rock wool... that's it !
ain't that a by-product of something ?Mike Smith Rhode Island : Design / Build / Repair / Restore
http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11540
The term "mineral wool" typically refers to two types of insulation material:
Rock wool - a man-made material consisting of natural minerals like basalt or diabase.
Slag wool - a man-made material from blast furnace slag (the scum that forms on the surface of molten metal).
slag wool must be what i'm familiar withMike Smith Rhode Island : Design / Build / Repair / Restore
that's all I know about it...
other than it's nasty stuff and fun to put on TP...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
Mike,I also have heard/read that mineral wool is spun blast furnace slag. I hate the stuff because it shreds my skin in the attics I've encountered it in. Inch for inch, I still think cellulose is better for thermal insulation, especially for non-transmittance of IR.Mineral wool is definitely better than FG for both fire and sound control. Cellulose is, too, and so much less harsh to work with. I also like that the borates in cels repel rodents and bugs.Bill
Throw a fg batt on a bonfire sometime and see what happens. You'll be amazed. Throw on some cellulose to put the fire out.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
my old boss at RI Energy invented the hot penny demo.
he'd take a handful of cellulose and put a penny in the nest,
grab a small torch and heat the penny to cherry red....
try that with FG
Mike Smith Rhode Island : Design / Build / Repair / Restore
"Throw on some cellulose to put the fire out."
LOL! Glad I wasn't drinking something when I read that, I actually laughed out loud. That's a perfect demonstration.
When I had cellulose put in my attic and exterior walls, I had to try the torch test on a hand full.
Humor, like its twin tragedy, is merely an unexpected view of truth.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Andy, you must have heard this other saying about pigs...
Never wrestle with a pig: You both get all dirty, and besides, the pig likes it. -George Bernard Shaw
Your signature quote always makes me think of this one as well.
Are you only talking about blowing insulation in the attic.
Or are you also talking about blowing insultion into the walls?
Walls & Attic floor
Full 2X4 walls, Full 2X8 in attic floor.
This is being done after a complete rewire, bye bye Knob & tube, BX, Paper wrapped romex w/ a ground wire the diameter of a childs hair, and all the bad connections between the 3.
Our 1915 farmhouse in NW CT sounds something like yours, and lacks insul and needs elec upgrade like you had done. Can you give us approx cost on your elec upgrades? Thanks
2 floors, complete rewire 8-10 K This all depends on codes, any upgrades etc.
Insulation est was 2300-2600, walls and attic floor for cellulose or fiberglass.
Google ''airkrete''
Looks very interesting.
what do the plumbers and electricians think of the stuff?
Any clue on cost vs. glass, cellulose or foam? Probably the same or more than foam i would guess.
Thanks again
All the fiberglass bashing (including the links to the scientific studies) here is referring to the conventional fiberglass batts. Blown in Fiberglass systems will perform as well as (if not better than) cellulose and are not susceptible to mold growth as cellulose could be. I am going with blown fiberglass in my home.
doobz... interesting viewpoint..but wrong
BIBs or any form of fiberglass will not perform as well as cellulose
and cellulose will do a BETTER job of not promoting mold or vermin..
the boric additives is the secret to the whole thing .... and the nature of cellulose fibersMike Smith Rhode Island : Design / Build / Repair / Restore
"BIBs or any form of fiberglass will not perform as well as cellulose"How do you know?
Edited 10/26/2006 10:38 am by BillHartmann
gee, bill.... what do you know about BIBS ?
it's just a finer filament than standard fiberglass, a little easier to handle
but certainly still has all of the features and drawbacks of fiberglass
how would i know ? it's my business to know
maybe you can enlighten us ?Mike Smith Rhode Island : Design / Build / Repair / Restore
"maybe you can enlighten us ?"I don't know.That is why I asked."but certainly still has all of the features and drawbacks of fiberglass"What specific do YOU KNOW or have reports on that say that.Until I get something more specific than "you know" it is still an open questions.FACT celulose insulation has caused serious corrosion.Shouldn't you also claim that the celulose insulation that you uses has the "all of the same features and drawbacks of" celulose (that causes corrosion).No, it is a different product.Now the basic problem with fiberglass is that is allows lots or large air spaces and thus will have internal air currents that thus reduces it's effectivenss at colder temps and when used with an exposed surface in attics.Now does the smaller fiber allow it to back so that it only has small scale air pocket, much like cels, and thus performs better (that FG bats) at cold temps and/or in attics?
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FACT celulose insulation has caused serious corrosion.>>>
that's not a fact... that's a selectivley used occurence
bill if you google on cellulose insulation corrosion... the only sites you will find that trumpet this "fact" are the sites created by fiberglass insulation mfrs
here's one..about cellulose mfr'd with AMONIUM SULFATE.... which, when wet , is corrosive
the cellulose we use is mfr'd only with borates... not corrosive
and borates do not promote mold
most of the bad things said about cellulose are by researchers paid by fiberglass insulation mfrs...
the truth is , cellulose is a superior product to any fiberglass product..
vermin cannot live in cellulose
cellulose mfr'd with borates is not corroisve
any insulation that is saturated is a potential source of mold... including fiberglass...
as for BIBS.... it's the same old fiberglass with smaller filaments.... nothing new
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FACT celulose insulation has caused serious corrosion.Mike Smith Rhode Island : Design / Build / Repair / Restore