Just took a quick walk thru of a neighbors new home with him.
Two questions I need to ask.
What do any of you know about dense pack fiber glass blown in the stud bays?
Have you ever heard it said that the glues used in f/g or cellulose blown in this way acts as a vapor barrier?
Dave
Replies
dave.. you've got to define your terms..
dens-pak cellulose, i know about.. there are no glues used..
i've never heard of dens-pack fiberglass blown-in.. i've used high density batts..
are you talking about wet-pack cellulose ?..
i've heard the glue may have some vapor barrier characteristics.. but cellulose ( dens-pack & wet-pack ) is a great air barrier anyway
Mike Smith Rhode Island : Design / Build / Repair / Restore
Ok Mike, wet pack it is. The HO said the contractor called it dense pack, but it was sprayed in f/g. I started a google search, but didn't have time to refine and finish it. I figure this sight gives a more honest assesment of products than any website full of sales hype anyway.
So what do you know about wet pack f/g?
There is a BIBS system for FG.
I think that is called blowin in blank system.
Here is one link.
http://www.eere.energy.gov/consumerinfo/refbriefs/ee6.html
A quick google, looks like -blow in blanket system- will get you closer hits than BIBS.
Thanks Bill.
Dave
Not long ago, I had a cathedral attic space blown with dens pack chopped fibreglas. Similar to denscells in use but slightly more expensive. Less problems with moisture or settleing supposedly. Materials slightly more expensive - 3% I think it was.
I'm very happy with it. On an 84° day, you can be at least 10-15° cooler inside.
Excellence is its own reward!
c'mon, piffen.. what's this ?
<<<Similar to denscells in use but slightly more expensive. Less problems with moisture or settleing supposedly>>>>
first, by DEFINITION.. denspak is installed at greater than settled density.. so it is impossible for it to have settling problems..
2d, cellulose will flow better than glass, so it will have LESS void potential
3d, since cells can absorb, and then release, moisture, whereas glass CANNOT, the moisture problems are GREATER with glass than cellulose
don't make me come over there...Mike Smith Rhode Island : Design / Build / Repair / Restore
OKL, I won't argue the voids and packing issues but how is it better for it to be able to absorb moisture than to not be able to absorb it in the first place????? It's great that it can eventually dry out but I like that the fibreglass doesn't take it on in the first place.
Maybe I am wrong but I been told that the chopped fibreglas is a less hospitable place for molds to form and I've seen places with blown cellulose that started to rot quickly after insulation. That make the chopped fibreglas my winner..
Excellence is its own reward!
here's the skinny.. take it or leave it..
cellulose can absorb moisture.. it can absorb it and hold it until it reaches the saturation point..
there are many instances during the year when a house may have excess moisture moving from In -to- Out or Out-to-In...
if the cellulose can hold that moisture nothing will happen until the conditions change.. as teh interior / exterior gets dryer, the cellulose will give up its moisture and return the wall system to a stable condition
fiberglass , on the other hand, has next to zero absorption potential.. and the fibers themselves are IDEALl condensing surfaces.. so a little moisture in the wall, hitting a fiber that is below the dew point will CONDENSE.. these droplets will congeal.. and drip to the nearest horizontal surface.. .. over a period of time.. that horizontal surface will rot from the continuing water condensing off the glass..
cellulose is just like any other product made of wood.. if it is wet, has the proper temperature, and the right amount of oxygen , it will promote mold and fungus..
the solution is not to use fiberglass, but rather . to not let the cellulose get wet ( notice , i did not say moist.. or damp.. ) the problem , of course is what level of moisture will the cellulose efficiently handle ? a lot more than fiberglass..
and of course .. if either wall system is WET, we're both in troubleMike Smith Rhode Island : Design / Build / Repair / Restore
Good points made by both you and piffin.
We have beat this vp/moisture/dew point thing to death in the past. What surprised me was the lack of vp and the explanation of why it wasn't there.
The sprayed in blanket f/g or celulose with out some type of vapor retarding membrane would present more of problems, IMO, than either with one. The explanation given the HO, that the glue forms the vp seems way off base. The link that Bill Hartman provided says the glue can easily be clean up with water. It did not say if that was immediate clean up or after it had fully cured. There in lies a potential problem. I have a mental picture of a gooey mass of f/g and glue forming inside the wall cavity where interior or exterior moisture has infiltrate and reached the dew point. Of course with no vp it will dry to the inside and maybe not cause mold or rot. but what about the cohesiveness of the system? Will it settle? Will it retain enough moisture to ruin the R-value of the f/g?
I haven't run across this system in any of my remodel or repair jobs, so I haven't seen how it performs over the long haul. I have pulled out enough water ruined f/g over the years to make me leary of that type of sales hype.
Dave
Dave,
The moisture barrier is installed to stop the movement of wet air into the wall cavity. For the air to move into a space, there must be a void into which in can move. If the cavity is densely packed enough (with something) the air can't move into it because there are no voids, which makes an additional moisture barrier redundant.
If the insulation is exposed to moisture, and it is more hydroscopic than the wood, it the moisture will bind with the insulation and the wood won't get wet. Cellulose is supposed to be more hydroscopic than fiberglass and the wood framing. See how much water a piece of glass can aborb compared to a newspaper. If water gets into a FG insulated wall, it goes directly to the wood, since the FG has very poor water absorption qualities.
This is the theory and the science behind this, anyway.
Results may be different in your area. Void where prohibited by disbelievers and poor installations.
Theory and science are fine, but I was looking at real world. I am not knocking this builder, he does generally good work. The basement of this house is getting a drop ceiling and has 9' wall (8'8" finished). The dw was hung to 8'. I did not see any foam or fire stopping at top plate penetration, etc. Same thing with rim joist penetration.
Science says heat moves toward the cold side of the wall. In the winter that is warm air moving into the wall cavity above that dw. In the summer it means warm humid air moving into the wall cavity toward the air conditioned inside of the home. Maybe the whole thing is packed dense enough to retard gross air movement, but it seem to me the only way to achieve that level would be with foam, not f/g.
Explain where I am wrong with this thinking.
Dave
Dave,
I can't speak towards the firestops, nor have I seen df fg or read any research done on it. I have used df cellulose and there is plenty of research literature about it. If it is installed properly, to acceptable density, there will not be significant enough air moving into it to load it with enough moisture to be a problem. It has also been demonstrated to retard the spread of fire, not that it can be used in lieu of firestops. Since air moves through traditional fg, it does none of these things. Dense pack fg may.
Attached are a couple of photos of some wet-applied dp cellulose.
Ooops, looks like one uploaded twice.
I know you all went to church today but you shouldn't be saying that dense packed cellulose is capable of being considered a serious vapour barrier.
It will wick moisture like a common piece of celery and will take just as long to dry out.
Gabe
I've never seen celery wick water Willy! Are you saying to practice safe insulation and use a condom?.
Excellence is its own reward!
Don't you remember the old elementy school science experiment where you put the stalk in a glass of water with some food color in it.
I guess I missed a good one, Eh?.
Excellence is its own reward!
In honor of Gabe here is a link for the experiment from the Curious Canuck.
http://curiouscanuck.iscapenetwork.com/external?title=Soaking+It+Up&url=http://www.ed.gov/pubs/parents/Science/celery.html&ID=616
But I am not too sure of the site, one of the other experiments is titled "Exploring Density: Teachers".
But not to worry the site really get it's information from the US Dept of Ed so it can be "trusted' <G>.
I'm sure there are some teachers unhappy with that topic title.
;).
Excellence is its own reward!
No Piffin, I'm saying dense cels ain't sexy unless you wrap it in a condom because it's no FG.
I'm a foam man so this chatter about fg or dense cels being a vb is NFG to me.
stay safe
Gabe
My favorite insulation is blown foam where the budget supports installing it.
With either cells or chopped fiber I use vapour bar but I see Mikes point. With dnes cells, the dew point is eliminated for all practical purposes, which eliminates the condensation. He lets the moisture keep moving on through without stopping to visit, like the sherriff in the old western town does with the bad hombre`s..
Excellence is its own reward!
I used the blown in fiberglass in a house I built a couple of years ago, and am happy with it.
One of the selling points that I liked was that they used less water when they blew it in compared to cellulose.
I've just learned about his illness. Let's hope it's nothing trivial [Irvin S. Cobb]
i've never done wet-pack.. but the guys that do it tell me the spray equip. has evolved to where they are using almost no water... the drying time is much better..
both glass and cellulose
i still like regal-wall... like g. la londe showed me here..
we staple up the insul-mesh.......
apply the latex glue...
and blow dens-pak cellsMike Smith Rhode Island : Design / Build / Repair / Restore
"apply the latex glue."
Where does the glue go?
The 2nd picture is the guy's hand is not clear.
Is this what happens? You stapple up a plastic mesh. Then at the stud roll the glue over the mesh and on the surface of the stud.
bill.. the latex glue pentrates the mesh .... the glue prevents the cells from getting under the mesh and bulging it out
Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike, how about installation- time wise cel vrs fg batts for the same identical space ........... trying get a handle on it.
no comparison, jc... batts might take one day.. regal wall two.... but there is also no comparison in the performance..
wanna save money .... ? or heat and comfort?Mike Smith Rhode Island : Design / Build / Repair / Restore
Dave. I don' know if you have gone through http://www.buildingscience.com or not.
They have some recommend construction practices for about 5 different climates for insulation, waterproofing, and mositure control.
Also the books go into much more details and show more of the way.