thickness of insulation

[shaune]

You don't have to tell me too much about insulating and vapour barriers as i am Canadian......but you do have to tell about the thickness of insulation. here is my question.
I have several bags of R 20, cut the bags open and the insulation "swells up" to thickness except this stuff (white batts) didn't. I have batts of pink batts that are R 20 and 6 inches thick, these white batts are also R 20 but in some places are 6 inches thick and other spots they are still compressed to 4 inches. They have been sitting out of the bag for several weeks....haven't swollen any. Are they still going to give me a R 20 value ?????

 

[seamusmcfadden]

Johns Manville vs Owens Corning?

 

[Shocker]

Give it some time?

 

[shaune]

It's already been 3 weeks

 

[sillyhillbilly]

It's already been 3 weeks

that sounds like a no to me, should be minutes not weeks

 

[notme_76]

ive never seen white? what brand? was it on sale by any chance ;-) and any insulation that i compressed at all will not have the same rvalue...

 

[z28snksknr]

Sure you didn't open a bag of rags instead?

I would return the stuff, especially if it has an inconsistent thickness.

 

[toolchaser]

The white may be Johns Manville Formaldehyde Free but it should fluff out. Is it compressed at the fold line?

 

[shaune]

No it compressed all over. I think i will use in the walls and go buy the usual pink R20 for the ceiling.

 

[jklingel]

Is it Corning's SoftTouch.... or something like that.... made out of cotton? Whatever, if it has a LOT of irregularities, I'd see about returning it. Compressed in no way will have the R of fluffy; that may not be critical, but if you paid for R20, then they should sell R20. In the 4 houses we've done, any of the fiberglass batt brand have a few compressed pieces, but nothing to worry about. They are minimal enough that we just re-fluffed them, sort of, and went to bed.

 

[redsky49]

All batt insulating materials have a nominal production thickness.

For example, an R-19 fibrous batt will typically range from 5.5" to 6.5" depending on the manufacturing methods, density, etc. Manufacturers will state the nominal thickness of their products on either the backing material (for faced products) or on the wrapping of the blanket (for unfaced batts). Slight variations from the published thickness are to be expected and should not be a cause for concern.

There are numerous factors that affect the performance of insulating batts. As a matter of fact, the actual thickness of the individual insulating fiber makes a difference (smaller being better), as does the physical arrangement of the fibers, not just the overall thickness of the batt.

In my experience, the compression of the insulating material makes little to no difference, unless the compression exceeds 20% of the uncompressed thickness. I cannot state this as scientific fact, as I cannot put my finger on the published data here at my desk. You will however, find this to be a typical standard in the construction industry.

In any case, the insulating batt is only part of a planned insulating assembly, and is just one of many considerations that should be carefully examined prior to installation. Vapor barriers, air spaces, reflectivity, direction of heat flow, etc. should all be taken into account in determining insulating capabilities.

If your exterior wall assemblies meet the required transmission factor with this material, I would go ahead and install it. My guess is that a much higher performing material will be required for the ceiling, depending on your climatic requirements. Under no circumstances should you use less than required by local codes and standards for new construction.

As always, offered only as opinion