Layered fiberglass batt different R value than loose fill ?

**Gene South** · 07-02-2009, 02:38 PM

I was wondering if Layered fiberglass batt has a different R value than loose fill fiberglass? I am in the field and cannot check my reference material. Wondering if anyone knows ? I was thinking that since batt layers are more uniform and contained, they may provide a higher R value than loose fill ? Anyone know ?

Gene

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**Jerry Peck** · 07-02-2009, 05:34 PM

Yes, loose fill has a lower R-value per inch than batts, at least from the insulation I have seen.

Also loose fill insulation settles and the R-value is given based on placement depth, not settled depth (as I recall).

The R-value varies depending on the manufacturer, not all loose fill fiberglass insulation has the same R-value. Most loose fill insulation is rated on square feet per bag, which is translated into depth, but it is really the amount of insulation (number of bags) spread out over a specified square foot area.

I would measure the depth, take a photo of the depth, and do so at the lowest areas and at the highest areas, which will show inconsistency in application and document with photo the lowest thickness encountered.

I would report the thickness, not the R-value, unless you know the brand of insulation and their depth for R-value, and even then it may have been 'stretched out' and blown lightly to the minimum depth without using the proper number of bags for that area, resulting in less R-value than the depth would indicate.

**Jerry Peck** · 07-02-2009, 05:52 PM

This is why there is no way of knowing what the R-value is for a given number of inches of loose fill fiberglass without knowing the manufacturer and the number of bags/square foot coverage: ColoradoENERGY.org - R-Value Table

R-Value Table
- Fiberglass Blown (Attic) R/Inch = 2.2 to 4.3

That is a pretty darn big spread in R-value per inch.

**Gene South** · 07-03-2009, 04:48 AM

Jerry, thanks for your always knowable input.

Happy 4th.

Gene

gary gramling · 07-03-2009, 08:53 AM

For my sake, please advise as to why we would comment on the R factor of insulation? I understand why we report on the presence or absence of insulation; as well as whether it may have been installed properly.

In my experience, blown insulation compresses over time, batts do not. As the blown insulation compresses, voids are created at the top, thereby eliminating the R factor in those areas. And, the loss of air pockets in the bottom portions of the wall, as the compression continues, greatly reduces the effective R in the bottom portions of the wall. If you are using an infrared camera, you should pick this up; but, without the camera, we would probably never actually observe this. The presence of blown insulation in the attic could lead us to surmise the rest; but, our inspections should not, I believe, be based on surmise.

So, in the presence of blown insulation that appeared to provide complete area coverage; and, which was relatively even in depth, would you say anymore?
Gary

**Jerry Peck** · 07-03-2009, 10:48 AM

Gary,

If you inspected a house and found blown in loose fill fiberglass insulation in the attic which was 1" deep, what you you say about it?

gary gramling · 07-03-2009, 08:06 PM

Jerry,
I would note the presence of blown insulation of approximately 1 1/2" in depth; and, comment that it was, in my opinion, insufficient to provide any meaningfull insulating capability. Assuming it was an older house, I would then recommend that an insulation contractor be retained to bring the insulation up to a level sufficient to reduce heat loss. But, I would not attempt to measure, calculate, nor guess the existing R factor.

If the house was relatively new, I would recommend contacting the builder and call to his attention a probable code violation for the builder to fix. In California, it might qualify as a latent defect which would extend the builder's liability to ten years from NOC.
Gary

gary gramling · 07-03-2009, 08:08 PM

Correction. I would note that the depth was approximately 1" in depth.

**Jerry Peck** · 07-03-2009, 08:16 PM

Originally Posted by gary gramling

For my sake, please advise as to why we would comment on the R factor of insulation? I understand why we report on the presence or absence of insulation; as well as whether it may have been installed properly.

So, in the presence of blown insulation that appeared to provide complete area coverage; and, which was relatively even in depth, would you say anymore?

Originally Posted by gary gramling

I would note the presence of blown insulation of approximately 1 1/2" in depth; and, comment that it was, in my opinion, insufficient to provide any meaningfull insulating capability.

Yet just above you said you would check only for the presence of, complete coverage of, and relatively even depth of, the blown loose fill insulation - and it is all nice and even at 1" deep.

Now you are adding something else, "insufficient to provide any meaningfull insulating capability".

Okay, based on what standard do you make that call?

Based on R-value, or lack thereof? Based on what standard specifying what R-value as being "sufficient to provide" a meaningful insulating capability?

See where you are heading? Right toward answering your own question - because if you do not you are doing your client a disservice, and you could potentially end up insulating the house for them in a worst case scenario.

gary gramling · 07-03-2009, 08:53 PM

Jerry,
By identifying the presence of the insulation, evenly distributed, at a uniform depth of approximately 1"; and, recommending that a qualified insultion contractor examine the situation further, to determine whether additional insulation is appropriate, I have, in my opinion, properly advised the client as to a probable defect without attempting to ascertain the existing R rating.
Remember, the question was whether we needed to state an R factor for blown insulation, which I believe is beyond the scope of a proper inspection.
Gary

**Jerry Peck** · 07-04-2009, 06:33 AM

Originally Posted by gary gramling

Remember, the question was whether we needed to state an R factor for blown insulation, which I believe is beyond the scope of a proper inspection.

The question was as stated below, with your ending statement which changed the discussion from the question to your statement.

Originally Posted by gary gramling

For my sake, please advise as to why we would comment on the R factor of insulation? I understand why we report on the presence or absence of insulation; as well as whether it may have been installed properly.

I had already answered the question in the posts above by stating that it is next to impossible to determine the R-value of blown in loose fill unless you know the manufacturer and how many bags per how many square feet are stated on the bags. Being as we do not know that, and the R-value of blown in loose fill insulation varies from 2.2 to 4.3 per inch, there is no reliable way to guess at that R-value.

Which left us discussing your statement: "I understand why we report on the presence or absence of insulation; as well as whether it may have been installed properly" and I stated we should be reporting more than that, we should be reporting the depth of blown in loose fill, and not just one depth, but the thickest and thinnest depths, and even the depth of most of it (many attics will have thin areas, thick areas, and areas which are between and which are likely the greater area. All that said, though, if there is 30" in part of the attic and 3" in other areas, the 30" is wasted as the heat is going through the thinnest areas - regardless how thick the thickest areas are.