6# vs. 8# insulation

[david s]

Re: 6# vs. 8# insulation

Thickness has everything to do with density because it is the volume part of the equation. The thicker the insulation of a given insulating material will increase the degree of insulation. But I agree with you that the denser a material is then the better it conducts and worse it insulates. Maybe the lighter weight blanket would be more likely to compress under weight and therefore reduce its thickness and consequently its insulation value.

[kebwi]

Re: 6# vs. 8# insulation

Thickness has nothing to do with density. You can purchase blankets in 4#, 6#, and 8#, relatively independent of a variety of thicknesses ranging from 1/4" to 2". For a given thickness, I would imagine that one of the various densities is the best, but I'm not sure which. The higher density blankets are more expensive, but have higher thermal conductivies...which I think means they let more heat through...so that means they are a worse option while at the same time costing more. It doesn't make any sense to me. I wish someone would clarify the matter for us.

[david s]

Re: 6# vs. 8# insulation

Are they both the same thickness ?

[kebwi]

Re: 6# vs. 8# insulation

I realize that 6# means six lbs / cuFt, but I don't think you're right about the intuition that lower density is more insulative. I had the exact same thought you had: more air, better insulation, but everything I have read and otherwise been told tells me otherwise, that 8# is a better insulator than 6#. I have no idea why that's the case, but I think that's what I've been told.

I remain confused on the issue.

[MK1]

Re: 6# vs. 8# insulation

I can't tell you the exact r-values but the #s refer to lbs per cubic foot, density. The lighter stuff (6#) is probably higher in r-value than the 8 as it contains more dead-space.

Mark

[kebwi]

Does it really matter if you use 6# or 8# insulation board for a given thickness? My shopping often turns up 6#. I realize that mathematically the 8# is more insulative, but does that pan out -- would one actually notice a genuine difference in heat-up times? Should we restrict ourselves to 8# for the most part?

Is it actually mathematically linear? Are three inches of 8# exactly as insulative as four layers of 6# or does it not work that way?

[EDIT: When I started this thread, I myself was fairly new to high-temperature insulation and accidentally combined terminology used to describe the density of insulating blankets (#6 and #8) with references to insulating boards. The mistake does not obviate the question, but may lead to further confusion by other newbies. Good luck.]