What wrong with fiberglass insulation?
So what is the problem using fiberglass insulation? In some of the posts I read a few people won’t use it anymore rather using some sort of blown in or on type of insulation. While the finish product looks good it seems that it is very messy and time consuming and labor intensive to install. Which in my mind translates into a big $$ job for a contractor. After all a tree arborist would rather cut down a huge cottonwood for up to $4500 than a small pine for a few hundred. There is more money to be made.
Granted in renovations, using fiberglass with a paper or foil vapor barrier is difficult to do in odd stud bays due to the cuts and seeming that needs to be done. So using unfaced and applying a poly vapor barrier is the better choice.
In the northeast most new home construction uses fiberglass insulation in all construction.
So the question is what is wrong with fiberglass and a poly vapor barrier?
Thanks,
The Sicilian
Replies
I think the major complaint against fiberglass batts is that they are porous enough that in real world situations you can have enough air movement so that they actually give far less "R" value than standard ratings would indicate. The glass fibers melt pretty readily in a fire, so fiberglass insulation is not as effective as some other insulations in stopping the spread of fire (although they will not contribute to it as some of the foams will). The fibers are suspected of possibly contributing to long cancer, although I have not seen definitive studies on this. And the stuff causes most people, including me, to itch like crazy when they handle it if they aren't fully protected...
I am sure some others will expand on this.
So does and air barrier such as Tyvek on the outside limit air movement thus making fiberglass batts more effective? This is also a standard exterior application on new home and remoldeling construction. The heating season is basically October thru April in the northeast so how many years would it take me to realize a gain in savings using the costly sprayed on or blown on insulation?
Most new or newer home owners would probably pay somewhere in the range of $150 to $300 per month for heating in the most demanded months of Dec. thru March which is acceptable in my opinion.
I need to see the benefits in my pocket. Bottom line is that it is a dollar issue. Forget the R-Value squawk people want to lay on you. What is it gonna cost me and what can I expect to save on my heating bills. One month after it is in nobody can remember what the R-Value is anyways. They remember how much they paid and how much their gas bills are.
If it saves me $300 a year it might take 20 + years to see a gain on investment.
The Sicilian
I'm in the process of adding to the rear of my home and you can see the dirt/dust stain in the edges of the fiber glass. This is in the closed stud bays so there is air movement happening. The gain with spray foam is in the total filling of all the space in the bay, with fiber any bays where the glass has to be cut you going to get "weakness" in insulation. People I know with foam have a house with lower noise levels and lower bills. Payback time is tough to work out, as the variables are many. Foam is an upgrade, I feel, worth the money. Find a local contractor who "does the foam" and ask for 3+ names and address.
Sicilian, you said "If it saves me $300 a year it might take 20 + years to see a gain on investment."
True, if fuel prices stay the same for 20 years. As fuel prices go up year after year, so will your savings.
What insulation slows the spread of fire?
Glass is a poor insulator, period. Fiberglass does two things: traps air in little pockets, and air is a better insulator, and prevents convection currents. Even faced fiberglass is not designed to stop air infiltration, and barriers such as Tyvek work best where there are no windows or doors.
Blown in insulation may fill cavities better (until it settles), but it will not stop air infiltration.
Sprayed-on foam insulation works, as long as it's not being used where it will trap moisture, but which foam? Some outgas nasty vapors, others produce toxic vapors when burning.
Foam is not affected by water, it will not pass air and the correct use of foam will greatly stiffen a wall adding strength.
finally foam panels installed correctly will prevent the transferance of heat from one wall to another.. there is a very convincing video of a bonfire started in the corner of a room that is built using foam panels and the required sheetrock.. 1500 degree flames on one side of the wall with 123 degrees on the other.. after an hour of bonfire..
In my humble opinion think of fiberglas as better than nothing but there are better insulations out there..
Foam is not affected by water, it will not pass air and the correct use of foam will greatly stiffen a wall adding strength.
All true, but if water gets behind the foam, it goes nowhere and rots the wood.
Sprayed foam seals against air infiltration, but as the firefighter said, foam burns, without smoke, and the gases are deadly.
At least paper and wood give off smoke.
everybody here been talking about how insulation burn and nothing about insulation factors, If my house catches on fire, I'm going to be outside not worrying about how the insulation burns
The best employee you can have but you wouldn't want him as a neighbor " He the shifty type"
everybody here been talking about how insulation burn and nothing about insulation factors.
Actually, we're talking about keeping the cold (or heat) outside so you're comfortable. It requires that you consider several factors. The first is air infiltration. If the windows are open, the insulation is doing no good -- and if you don't seal the house well, it amounts to the same thing. The second is moisture movement. Wet insulation doesn't insulate well, causes mold and rot, and if water vapor gets into it and cools/condenses there you have a mess. A good barrier, a good vapor seal, and some flexibility -- so it doen't crack and admit moisture and/or air -- are all important here.
There are lots of kinds of insulation, each with its own particular characteristics. Some are best used in new construction, some (like blown cellulose) are easier to use if the plaster and/or sheetrock is already up. It's a bit more complicated than just R rating -- foil-faced bubblewrap even works in some situations -- but by all means, use as much of whatever you choose as you can.
If my house catches on fire, I'm going to be outside not worrying about how the insulation burns.
I really hope so. But I've studied enough fire protection engineering to know that much of what we have brought into our homes will burn without producing smoke, and gives off toxic fumes that can kill in one breath.
Firefighters now routinely bring their air supply with them when they enter buildings.
As I mentioned back in thread 36888.1 </tp-breaktime/messages?msg=36888.1> you may want to read the articles discussing under what conditions urethane foam will burn. This is written by a foam applicator, but it seems to give both sides:
http://www.monolithic.com/plan_design/fire_hazard/index.html
<http://www.monolithic.com/plan_design/fire_barrier/index.html>
What insulation slows the spread of fire?
I can tell you what I've seen as to being a firefighter, between fiberglass and cellulose(haven't seen any sips)or foam in my city where I work. I have taken a piece of icecenean foam and lit it with a torch. While it did not seem to burn, it did melt, and the smoke to me seemed like it would be very toxic.
The fiberglass tends to melt, the paper backing will burn
The cellulose tends to just singe lightly,a few burn marks here and there,and some light charring if any studs or joist are near it.It doesn't contribute to the fire spread at all.At least from what I have seen.
Working a structure fire with cellulose tends to be lot tougher than fiberglass(from a firefighting standpoint) because it tends to be better at keeping the heat in.It will be hot until we can pull the ceilings down and get rid of the cellulose and vent.
I' building a new house and I;am thankful for the guidance from the good people on this site(Mike Smith for the insulation part) I have chosen cellulose for my insulation type.
Hope this helps. Greg
Cells slows the spred of flames . Ask Mike Smith for a report. He did a study that proved it .
Blown in ,installed properly will not be settling.
On the foam I used Icenene . It will burn but not support flame . It will not add structural strength to the wall. But it will flex with wall movement and stay in place.
Get a copy of this month's FHB and read the article on insulation types.
FG installed correctly will work fine in most climates, but below around 0F the air movement in FG becomes a real factor, reducing its insulation value. At all temps, FG does not inhibit air flow at all, so any air leak in your occupied space will be wasted heat/cooling money - because of this, moisture control issues loom larger (large air flow = larger moisture issues from condensation as warm, moist air meets cool surfaces).
The other types of insulation tend to prevent free air flow, so their insulation values are more stable with temp, and they will tend to prevent the spread of fire by tending to prevent the high pressure, super heated air movement between rooms, thru stud bays and so on. These other types will also tend to minimize moisture condensation issues for the same reasons.
Unfortunately, FG is often poorly installed adding to its shortcomings.
In every type of insulation, if you've got a water leak problem soaking your insulation then it won't matter what type you've got, they will all fail.
I think that it is the ability to stop free air flow/seal leaks and gaps in the building envelope that makes the other types superior to FG.
Hope this helps,
Norm
the answer is in two words - convection and infiltration.
Get a good seal with plastic VB on inside and Tyvek outside and you still have the convection currents within the stud bay. Fibreglas is the blanket of last choice for me. Usually if I am using it, there will be a thermofoil foam in the package too.
My first preference is sray on foam, like Corbond. I have a customer who has a house twice the size of mine who cannot tell that it is winter outside unless he goes out for the paper and mail. He spends less on heating than I do, which is 6-9 notes a year. I don't have a comparative cost/savings analysis for you, but there is also value to be found in the noise reduction. As for fires, If it is going to burn, by time the flames are through the sheet rock the house is going down and the family is out anyway. That is why it is required to be covered.
Try this, Go to the lumberyard and lay your forearm on a piece of fibreglas insulation laid out. Then go do the same with a piece of foam. The difference you feel in heat reflecting back at you will be a great convincer.
Excellence is its own reward!
FG vs cells?
Cells is better at completely filling problem joist bays. Obstructions, around boxes, wiring, etc. Just plain better.
Cells can settle if not blown correctly. FG is hardly ever installed correctly.
Cells are better at minimizing air infiltration.
Cells is better at sound deadening.
Cells is better at handling water vapor. It can hold it when required and give it up when required.
A slow water leak? Who cares, each will reach saturation and you'll have to rip open the wall either way.
You don't neccessarily need a vb when using cells.
R-value comparison? Who cares, they're fairly close. It's the air infiltration that's more important and seems to have more of an effect on comfort.
Radiant gain? Cells can block and absorb, FG is essentially transparent to radiant and passes it on through.
Burn? I'd rather have cells for burn-through protection that FG.
Cost difference is not significant.
Tyvek on the exterior? Not a factor. Tyvek lets moistrure vapor pass through, it's water droplet transimission that it's supposed to prohibit.
FG batts and a ply VB are fine, though again, I've always seen FG installed poorly. especially in detailing around obstructions in bays.
Still, I think cells is better.
So all things being equal, in your opinions what is considered to be a correctly installed FG batt installation?
Or even to this extreme what do you consider to be a bad FG installation?
To start with in old home remoldels with odd stud bays that occasionally appear, unfaced batts with a poly vapor barrier would seem to be the best choice rather than cutting faced batts to odd sizes and having a breach of vb at least on one edge.
What size vb should be used: 4 or 6 mil?
Is unfaced with vb a good choice for ceilings too? What should be used to hold the batts up before the vb is applied?
The Sicilian
fg is bad ... but the best installation is unfaced HIGH DENSITY batts cut slightly oversized so they are friction-fit..
( blown in blanket has possibilities)
then covered with a 6-mil vaporbarrier... with attention to detail..
another approach is the vapor diffusion technique of totally sealing with drywall..
Gene Leger is a big proponent of this..
but we haven't used fiberglass in a long time..
it will just not perform as well as celluloseMike Smith Rhode Island : Design / Build / Repair / Restore
I'm sure you're aware of how FG is supposed to be installed. With 100% of it's faces (all six of them) in full and complete contact with the six faces of the framing bay.
Is it? Hardly ever, and even if the attempt is made, it may be gotten correctly in some or even many of the bays, but not all. Typically, the FG does not come into contact with the vertical corners of the bays. Thus, you end up with air channels and convective lips mentioned previously.
Follow some of the FG installers who attack a house and insulate it. It may look pretty on the inside, but if you poke into the back of a bay, at the sheathing/stud corner, and that's where most of the mistakes occur.
Rim joists? Also friction-fit joist bays. Friction-fit pieces against the rim joist can get dislodged and create gaps and then cold joist bays...or FG batts sag slightly in the center-span of the joist bay, allowing a gap between the top of the batt insulation and the subfloor. You end up with cold bays and cold feet.
When using FG batts, I am in complete agreement with you that unfaced batts and a 6 mil poly vb are the way to go. In a joist bay you really shouldn't need anything to hold them up in the bay.
Friction-fit can work if the framing is standard and pretty. I've not seen jobs where the batts are cut to wrap boxes and blocking, or properly split to wrap wiring. Every little gap in a FG batt installation creates a weak point in the insulation envelope.
Now think blown cells, which get slammed into the framing bay at 88 feet per second and contact and pack against every surface, every nook, every cranny, every obstruction. They envelope and seal against everything. No air channels, no gaps, no leaks.
Framing 19.2" oc for whatever reason? Blown in will work better than batts. Sure you special order get batts to size, but again, getting them installed correctly is another story. Insulating TJIs with the flanges? Cells conform better.
Remodeling an older home with funky, non-standard framing? Blown-in will work better, and cells can omit the need for a vb. A double blessing.
I remember a few years back seeing IR shots of two side-by-side tract houses and a third across the street. All virtually identical. One was carefully insulated with FG batts, one with blown in FG, one with blown in cells. In a heating climate the cells showed best, the blown-in FG showed sceond best, the batts showed the most amount of heat loss/leakage.
In a cooling climate, the cells showed best, by a wide margin. Differences between the two fg houses was negligible. Sound transmission the cells house was quieter. I forget the dB reading, so I don't recall if it was a significant difference or not.
Air infilatration? The cells house was tighter by a wide margin.
I don't know anyone who claims to install FG batts improperly. And everyone also claims to take the time to install them better than everyone else. Even in industry studies, it showed it was very difficult in the field to actually install batts as intended.
Sure cells installations can be screwed up as well. Still a consciencious insulation crew that is trying to do the right thing, or a builder who is trying to truly build well, or a remodeler who wants a quality job, can more easily and more consistently accomplish that with blown-in cells than with FG batts.
Best thing you can do is live in a cells house. You'll notice the difference.
My opinions. Your mileage may vary.
Mongo
Good points, its pretty tough to give you an argument on your assessment. I am left with a couple of thoughts that you may consider:
If you have 3 stud bays side by side one filled with FG batts, one with blown in FG, and the other with blown in cells, like your three house IR example, what would the R-factor be for each bay?
The best you could get with the batt bay is probably R-13, how about the other two?
Now how do you tackle blown in ceilings with open spaces above?
When you pack cells into a bay or FG, if you need to ever fish an electrical run into or through a bay does the blown in material prevent this?
The Sicilian
Using R-values brings up some interesting stuff I learned about while researching an article a few years back. R-values for residential insulation are determined in a lab, in a closed box that allows no air infiltration, at one constant temperature and humidity, all the variables that affect insulation performance controlled -- In other words, in a perfect world. In the real world, R-values aren't very meaningful, even as a base for comparing different insulations. Foam, FG, and cellulose compare quite differently at 10 below zero, 70 above, and 150 above. After doing that research, I insulated my house with polyisocyanurte sheets at the band joists and cellulose everywhere else. It's quiet, comfortable summer and winter, and cheap to heat. Unlike my last house, even though I had it insulated by the best FG installer in the area. Andy Engel, The Former Accidental Moderator