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Compressing Batt Insulation.

 
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Old 02-05-2011, 10:37 AM   #1
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Compressing Batt Insulation.


Ive heard both sides that you can comprees r-38 down to 10 inches and it maintains r-value or use r-30 and add r-19 to it. I thought compressing batts lessings the r-value. Made me scratch my head. These guys are trying to get 38 in 10 inch bays with out using high density r-38 batts.
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Old 02-05-2011, 11:42 AM   #2
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Re: Compressing Batt Insulation.


This is GREAT question, and I'm glad that someone asked this sooner then later.

Correct, it will in fact lose the R-value when compressed. When the batt is fluffed that is where it is at it's peak in R-value. Compressing it will restrict it and decrease the R-value, also it will/can make for some trouble when it comes to apply the drywall. More is not always better in many casing when insulating.. A proper fit, and application in insulation will yield best results, not more.. Less can be more in many cases. A correct installation is what is key, not trying to go above standards to expect best results.
If they are trying to achieve the greatest R-value inch per inch with the space at hand, there is much more options in insulation applications to concider. Different materials for one is a great place to start. With different products that have a specific designed goal, these are the things that needed to be weight out in an instant such as this.. Why not an R-30 foiled faced Batt?
Have I stressed how much I love Foil/FSK faced insulation products?!?!??!

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Old 02-05-2011, 03:35 PM   #3
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Re: Compressing Batt Insulation.


I also wanted to stress here that you can use Regular R-38 in 10", with-out using R-38c, and still work out fine. Keep in mind when I refer to compressing, I'm talking about really smushing the B'Jesus out of the dang thing. It's really only a 2" differ, so no real harm will be done.. Also if the area is vented that may be a factor there, and interfere with the vent by crushing and restricting the air flow. It's really situations like trying to stick R-19 in a 2x4 that is the no brain'ers when compressing is a issue. lol
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Old 02-05-2011, 04:04 PM   #4
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Re: Compressing Batt Insulation.


R-values applied to batt insulation really are not meaningful, especially in lightweight construction in the real world.

The R-value is just a short term lab measurement of the maximum short term insulation value under ideal conditions (for advertising purposes) with no infiltration or studs that reduce the WALL insulation down to realistic performance levels. I don't think the real wall test values are available to the public for obvious reasons. Any moisture or dust in the batts will dramatically reduce the insulation more than compression.
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Old 02-05-2011, 04:16 PM   #5
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Re: Compressing Batt Insulation.


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Originally Posted by concretemasonry View Post
R-values applied to batt insulation really are not meaningful, especially in lightweight construction in the real world.

The R-value is just a short term lab measurement of the maximum short term insulation value under ideal conditions (for advertising purposes)
w-w-w-what?
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Old 02-05-2011, 04:43 PM   #6
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Re: Compressing Batt Insulation.


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Originally Posted by concretemasonry View Post
R-values applied to batt insulation really are not meaningful
Well, then someone better notify the Department of Energy!
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Old 02-05-2011, 04:52 PM   #7
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Re: Compressing Batt Insulation.


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Originally Posted by cork-guy View Post
Well, then someone better notify the Department of Energy!
Yeah buddy, cause I need to get a new cert. cause mine just went out the window... I been lied to all this time...
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Old 02-05-2011, 05:03 PM   #8
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Re: Compressing Batt Insulation.


Only one "w"would be enough to show your lack of total thermal properties for a structure as opposed to a myopic view of a small detail, where infiltration may be as important as the quality of insulation.

Have you ever seem guarded hot-box tests run? - How about long term dynamic tests which are usually not revealed publicly in the U.S.?
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Old 02-05-2011, 05:45 PM   #9
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by cork-guy View Post
Well, then someone better notify the Department of Energy!
Quote:
Originally Posted by Crawl-Dog View Post
Yeah buddy, cause I need to get a new cert. cause mine just went out the window... I been lied to all this time...
So, what you are saying is that you are relying on a government run agency to tell you the truth.....

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Old 02-05-2011, 05:51 PM   #10
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by concretemasonry View Post
Only one "w"would be enough to show your lack of total thermal properties for a structure as opposed to a myopic view of a small detail, where infiltration may be as important as the quality of insulation.

Have you ever seem guarded hot-box tests run? - How about long term dynamic tests which are usually not revealed publicly in the U.S.?
Have you? If so please elaborate on the exact ramifications of these test.

I applaud you for your observation on my three "W's", that represent my lack of understanding in field that I specializes in particular of Convection, Conduction and Radiation transfer. At this point you are highlighting the principles of infiltration and quality by implicating my lack of awareness in mentions above ( Themal Properties ).

At this time you have brought it to the forums attention of these so called TEST that have been conducted. Can you provide us with some backing of this event that took place, besides just what is now considered hearsay.

What you are projecting holds little to no weight, and is meaningless in the entire post!

Next.....
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Old 02-05-2011, 05:52 PM   #11
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by concretemasonry View Post
R-values applied to batt insulation really are not meaningful, especially in lightweight construction in the real world.

The R-value is just a short term lab measurement of the maximum short term insulation value under ideal conditions (for advertising purposes) with no infiltration or studs that reduce the WALL insulation down to realistic performance levels. I don't think the real wall test values are available to the public for obvious reasons. Any moisture or dust in the batts will dramatically reduce the insulation more than compression.
You guys don't agree with this?

I've seen testing that shows an R-19 2x6 batt wall is actually in reality a measurable R-12 due to just thermal bridging of the studs alone.

I've also seen that R values are based on perfect installs, and most real world installs are far from perfect and R values are 10% lower just for that.
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Old 02-05-2011, 05:52 PM   #12
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by CookeCarpentry View Post
So, what you are saying is that you are relying on a government run agency to tell you the truth.....

Honest Abe would tell me, wouldn't he?
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Old 02-05-2011, 06:01 PM   #13
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by Mike Finley View Post
You guys don't agree with this?

I've seen testing that shows an R-19 2x6 batt wall is actually in reality a measurable R-12 due to just thermal bridging of the studs alone.

I've also seen that R values are based on perfect installs, and most real world installs are far from perfect and R values are 10% lower just for that.
I seen reads on a few insulation company's ( no names ), that at one time were lacking in Department of Energy's standards, and were rectified soon after by the Environmental Energy Technologies dept.
Each year they will hold test and expose weak points and find better and new ways to improve energy and spending. What would fly 5 years ago, would hit the fan today!

However, I'm yet to see any test or reads/results that state that what is being used today by company's I know and/or work with use products that lack where these imputation stand.
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Old 02-05-2011, 07:11 PM   #14
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Re: Compressing Batt Insulation.


I think a few people need to go back to class based on their shocked attitudes...

A 2x6 wall - studs 24" OC Grade 3 Install, has an effective R-Value of 13.88 (no counting drywall, sheathing 12.88)
2x4 - same as above using R13 - (Level 3) 10.3 eff R (Level 2) 11.1R (Level 1) 11.8R

Level 3 is the default rating given to all FG jobs, unless physically verified that they did a better job than that - Best I have given out is a 2 for a rating

Next the slightly over sized r19 (1/4 on side & 1/2 in depth) batts per the manufacturers & other testing only equate to an r18 when installed with regular 2x6's

As for the degradation of FG and loose fill products - do you really need a refresher lesson based on what happens to those materials insulative qualities when their is air leakage, water intrusion, or they are installed incorrectly?

As an FYI, contractors are getting smarter about the games played and building science as shown above by Mike, Mark & Dick - might be good to remember when you are brought in for an estimate or quote - try pulling crap or not knowning your trade can cause you a contract
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Old 02-05-2011, 07:29 PM   #15
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by SLSTech View Post
I think a few people need to go back to class based on their shocked attitudes...

A 2x6 wall - studs 24" OC Grade 3 Install, has an effective R-Value of 13.88 (no counting drywall, sheathing 12.88)
2x4 - same as above using R13 - (Level 3) 10.3 eff R (Level 2) 11.1R (Level 1) 11.8R

Level 3 is the default rating given to all FG jobs, unless physically verified that they did a better job than that - Best I have given out is a 2 for a rating

Next the slightly over sized r19 (1/4 on side & 1/2 in depth) batts per the manufacturers & other testing only equate to an r18 when installed with regular 2x6's

As for the degradation of FG and loose fill products - do you really need a refresher lesson based on what happens to those materials insulative qualities when their is air leakage, water intrusion, or they are installed incorrectly?

As an FYI, contractors are getting smarter about the games played and building science as shown above by Mike, Mark & Dick - might be good to remember when you are brought in for an estimate or quote - try pulling crap or not knowning your trade can cause you a contract
I have read/seen similar statements, and also seen where R-19 was told to be true at R-10.5. In which the statements where made, none could provide the manufacture of these. Reads just inducated that a test was made on such and such, and these where the conclusions.
I'm yet to see any solid base, or have anyone for that matter show me before, and even today bring me any spread sheet of adobe read that has specs on these test of products that I use or been using.

What the Dept of Energy's specs are, to the PERFORMANCE specs are, there will be a fine line and will most deff vary.

Also, where Dick is refering I think is the specs on the true wall, 2x4/2x6 as they would hold an rvalue of 5-7. The highest R-value in the wall would be infact the insulation, not the wall itself.. When a builder stresses that he builds a R-19 or R-21 wall, sounds nice and all, but you have the thermal brakes and such. 14% of that wall is infact R-7
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Old 02-05-2011, 07:41 PM   #16
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Re: Compressing Batt Insulation.


As an FYI - those are not statements but the exact numbers taken from the rating and modeling software to obtain a HERS score. The HERS score is used and recognized by DOE and EPA for ENERGY STAR (and a crapload of other studies), which in turn is recognized and used by USGBC, NAHB Green, Earth Craft, MN Green Star, and most every other "green" program out there.

Now if you want to play with the numbers yourself to reach the eff. R value - you can play the U & R value game and calculate out what the effective walls value is when you add in windows, doors, siding, the studs, etc... The math doesn't lie
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Old 02-05-2011, 08:06 PM   #17
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Re: Compressing Batt Insulation.


Quote:
Originally Posted by SLSTech View Post
As an FYI - those are not statements but the exact numbers taken from the rating and modeling software to obtain a HERS score. The HERS score is used and recognized by DOE and EPA for ENERGY STAR (and a crapload of other studies), which in turn is recognized and used by USGBC, NAHB Green, Earth Craft, MN Green Star, and most every other "green" program out there.

Now if you want to play with the numbers yourself to reach the eff. R value - you can play the U & R value game and calculate out what the effective walls value is when you add in windows, doors, siding, the studs, etc... The math doesn't lie
I seen Renewable energy systems "HERS" reads back in 06,and a few others, but do you have anything of these studies that are UPDATED on specs as of now? Not reads of 06/07, but FINAL report of lets say residential and FINAL analysis for Energy Star and the REM "Rate Consumption Estimations "report from these Green programs.

Also, to add the windows and doors ext into the exp I was giving is a post of it's own, I was giving an exp on just the framed wall alone.
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Old 02-05-2011, 10:35 PM   #18
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Re: Compressing Batt Insulation.


Ok I am confused - what is there to update? Do you understand how to find the effective R value for a wall assembly? Do you understand the different grading levels & how the compaction & other defects will cut down on the effective R value? While this is a 2007 document, it should help explain many of these items - http://archive.resnet.us/conference/...nspections.pdf

As for the losses caused by convective currents forming inside a batt, wind washing, etc... I don't have any of those handy but you should be able to find some at BuildingScience.com where they have examined other structures and the problems found - As you know, the field is completely different than a lab, as nothing is ever the same - but the issues found in the field can help the guys in the lab come up with better systems

As a FYI, the figures above don't bother accounting for other losses or issues, this gets addressed mainly with the Blower Door Test where we test to see how leaky the structure is. As for the windows & doors - those are calculated for in other screens - so the numbers above are just for the wall itself.
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Old 02-05-2011, 10:55 PM   #19
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Re: Compressing Batt Insulation.


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Do you understand how to find the effective R value for a wall assembly? Do you understand the different grading levels & how the compaction & other defects will cut down on the effective R value?.
Ok, where is the wall assembly commentcoming from? now your talking about exterior and interior and everything in-between.
Do you fully understand these concepts I must ask?
we went from compressed batts, to untrue R-value, to YOUR engineers point of view. What point are you trying to make?

Your link stressed and had photos of poor insulation applications, who and where does that effect me? and any point I was making?
I don't know what you read, or what specs you think you have before you but your taking this topic down a highway that is unrelated to any of the post prior.
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Old 02-05-2011, 10:57 PM   #20
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Re: Compressing Batt Insulation.


Are not all or any ratings on products based off of "perfect Installs"

so when did we start rating things on imperfect installs??? You need a standard of something to even rate it!

Everything you guys just said about this insulation I could say about thin-set, "hey did you know if you install this wrong it wont work".....G T F O of town...seriously

Now Im not a very smart man (Flame shield on) But I would say that the dude who is certified in the field would know what hes talking about.

Even if the rating isnt an exact rating, its still a basis to gauge basic insulating needs in specific areas.

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