Donald Gares <[email protected]> wrote in message news:<[email protected]>...
> [email protected] wrote:
> > In a 2x6 wall is the any advantage to stuuffing 2 4in r12
> > batts instead of the single 6in batts or does the compression
> > just reduce the effectiveness?
> > I ask because I have several bales of the four inch stuff.
> Your hunch is correct, do NOT stuff in two 4" R12 batts because the
> compression will defeat the purpose.
Two 4" R-12 layers of fiberglass compressed into a 2x6 stud space will
provide less than R-24 insulation value but still more than the R-19
of 6" batt because for fiberglass the insulation value per inch
increases with density, up to a point, so you'll probably end up with
R-20 or R21. None of this implies that you should compress fiberglass
if you don't have to because you'll get more insulation value by
leaving it as fluffy and thick as possible then.
Actually it would offer less insulation than one 6" batt. It looses
value when compressed.
--
Joseph E. Meehan
26 + 6 = 1 It's Irish Math
<[email protected]> wrote in message
news:[email protected]...
> In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts instead of
> the single 6in batts or does the compression just reduce the
effectiveness?
> I ask because I have several bales of the four inch stuff.
>
> JJ Thanks
[email protected] wrote:
> In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts instead of
> the single 6in batts or does the compression just reduce the effectiveness?
> I ask because I have several bales of the four inch stuff.
>
> JJ Thanks
Your hunch is correct, do NOT stuff in two 4" R12 batts because the
compression will defeat the purpose.
Don
--
Donald Gares - Broker/Owner
Creative Farm and Home Realty
Keosauqua, IA - Licensed IA & MO
http://www.crsales.com
On Sat, 27 Sep 2003 17:33:09 -0500, "Nate Weber" <[email protected]>
wrote:
>
>"Yaofeng" <[email protected]> wrote in message
>news:[email protected]...
>> Donald Gares <[email protected]> wrote in message
>news:<[email protected]>...
>> > [email protected] wrote:
>> > > In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts
>instead of
>> > > the single 6in batts or does the compression just reduce the
>effectiveness?
>> > > I ask because I have several bales of the four inch stuff.
>> > >
>> > > JJ Thanks
>> >
>> > Your hunch is correct, do NOT stuff in two 4" R12 batts because the
>> > compression will defeat the purpose.
>> >
>> > Don
>>
>> I disagree. Two R12 compressed is better than one R19. he fiber
>> glass is denser. You do need to watch out if the batt is lined to
>> puncture sufficient number of holes on the outer layer.
>
>I want to see you compress that extra 2 inches of insulation when your
>hanging the drywall.
>
No problem, my walls are plywood not drywall
"Joseph Meehan" <[email protected]> wrote in message news:<[email protected]>...
> Believe what you want. What I presented is based on the empirical
> information I have seen. Note that actual results will depend on many
> factors so in some cases compression may cause some increase in others some
> decrease and it will also depend on the amount of compression.
>
> --
> Joseph E. Meehan
>
> 26 + 6 = 1 It's Irish Math
>
> Mr. M, I believe you are more nearly correct than what's his face. However, Journal of Light Construction says a slight compression of U.S. glass t fiber insulation does increase R value. I was told this at a seminar on house construction a couple of years ago and asked the magazine for proof. The did not give what I would call proof, but quoted - as I remember - building researchers.
Tom Baker
On Fri, 26 Sep 2003 10:35:40 -0700, jjfros wrote:
> In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts instead of
> the single 6in batts or does the compression just reduce the effectiveness?
> I ask because I have several bales of the four inch stuff.
>
> JJ Thanks
The fiberglass batts I've used will pull apart into 2 layers. If yours
does, you could use one and a half 4" batts. Just make sure to remove the
vapor barrier from the half that it's attached to.
-Doug
Not quite true. A fraction of the insulating value is lost as you
compress it, but you will still likely have more insulating value than
you would have with only the 6" batt. I looked this up on one of the
manufacturers web sites because I wanted to put 6" insulation into a
cavity made of 2x4s. As I recall the compression caused a loss of 20%
over what it would have been in a 6" cavity, but 6" insulation offers
almost twice the insulating value as 3.5", so it was still a large
improvement. You are correct that at some point if you keep compressing
the insulation you totally defeat the purpose, but he is only
compressing it about 25%.
Donald Gares wrote:
> [email protected] wrote:
>
>> In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts
>> instead of
>> the single 6in batts or does the compression just reduce the
>> effectiveness?
>> I ask because I have several bales of the four inch stuff.
>>
>> JJ Thanks
>
>
> Your hunch is correct, do NOT stuff in two 4" R12 batts because the
> compression will defeat the purpose.
>
> Don
This is not necessarily true.
You are increasing the thickness substantially and not compressing the batts
to a level that the r value per inch is compromised. Insulation
manufacturers make thinner higher R-value batts for cathedral ceilings by
INCREASING the density of the insulation.
The density of typical fiberglass insulation is driven by the minimum amount
of fiberglass necessary to reach a certain rating (this allows it to be most
economical). It is not the optimum density. You can pay more and get denser
better performing insulation.
I would say that the thing to be careful about would be the presence of a
vapor barrier in the middle of the insulation, but then again, if it has a
vapor barrier on the outer or inner face, then it shouldn't make much
difference there either.
-Jack
"Joseph Meehan" <[email protected]> wrote in message
news:[email protected]...
> Actually it would offer less insulation than one 6" batt. It looses
> value when compressed.
>
> --
> Joseph E. Meehan
>
> 26 + 6 = 1 It's Irish Math
>
>
> <[email protected]> wrote in message
> news:[email protected]...
> > In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts instead
of
> > the single 6in batts or does the compression just reduce the
> effectiveness?
> > I ask because I have several bales of the four inch stuff.
> >
> > JJ Thanks
>
>
"Joseph Meehan" <[email protected]> wrote in message news:<[email protected]>...
> "JackD" <[email protected]> wrote in message news:[email protected]...
>>You are increasing the thickness substantially and not
>>compressing the batts to a level that the r value per
>>inch is compromised. Insulation manufacturers make thinner
>>higher R-value batts for cathedral ceilings by INCREASING
>>the density of the insulation.
> You are correct at least in part. It would be difficult to
> make an absolute statement. There are a number of factors
> to consider, and we just don't have enough information.
> Frankly I doubt if there is going to be a serious increase
> or decrease under the conditions noted
What a bunch of pretentious crap on your part. JackD is 100%
right, and you don't seem to have a clue because the R-value/inch
improves even when the density is doubled, as it almost is with
rigid ceiling tiles and was with rigid fiberglass insulation
used in old mid-priced water heaters (cheapest heaters had low
density soft fiberglass, premium-priced had polyurethane foam).
8" of regular fiberglass compressed between 2x6 studs will
give about R-21, compared to R-19 for 6" regular fiberglass.
"Joseph Meehan" <[email protected]> wrote in message news:<[email protected]>...
> Believe what you want. What I presented is based on the
> empirical information I have seen. Note that actual results
> will depend on many factors so in some cases compression may
> cause some increase in others some decrease and it will also
> depend on the amount of compression.
More pretentious crap, and you actually didn't present any
empirical information - because you simply didn't have any.
The fact is that if you mash fiberglass to half its thickness,
which almost nobody is going to do, its insulation value per
inch is going to rise to about R-5 or R-6.
Donald Gares <[email protected]> wrote in message news:<[email protected]>...
> [email protected] wrote:
> > In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts instead of
> > the single 6in batts or does the compression just reduce the effectiveness?
> > I ask because I have several bales of the four inch stuff.
> >
> > JJ Thanks
>
> Your hunch is correct, do NOT stuff in two 4" R12 batts because the
> compression will defeat the purpose.
>
> Don
I disagree. Two R12 compressed is better than one R19. he fiber
glass is denser. You do need to watch out if the batt is lined to
puncture sufficient number of holes on the outer layer.
You are correct at least in part. It would be difficult to make an
absolute statement. There are a number of factors to consider, and we just
don't have enough information. Frankly I doubt if there is going to be a
serious increase or decrease under the conditions noted. What is certain is
that using batts designed for the space will give better insulation and less
problems (no concern about improper vapor barriers) than two smaller batts.
While there are some differences in R values from different materials,
the increase is not necessary result of increased density. In some cases
yes in others just the opposite. The shape, size and distribution of the
fibers is important. Changes in any of those factors would also change the
compression results.
--
Joseph E. Meehan
26 + 6 = 1 It's Irish Math
"JackD" <[email protected]> wrote in message news:[email protected]...
> This is not necessarily true.
> You are increasing the thickness substantially and not compressing the
batts
> to a level that the r value per inch is compromised. Insulation
> manufacturers make thinner higher R-value batts for cathedral ceilings by
> INCREASING the density of the insulation.
>
> The density of typical fiberglass insulation is driven by the minimum
amount
> of fiberglass necessary to reach a certain rating (this allows it to be
most
> economical). It is not the optimum density. You can pay more and get
denser
> better performing insulation.
>
> I would say that the thing to be careful about would be the presence of a
> vapor barrier in the middle of the insulation, but then again, if it has a
> vapor barrier on the outer or inner face, then it shouldn't make much
> difference there either.
>
> -Jack
>
>
> "Joseph Meehan" <[email protected]> wrote in message
> news:[email protected]...
> > Actually it would offer less insulation than one 6" batt. It looses
> > value when compressed.
> >
> > --
> > Joseph E. Meehan
> >
> > 26 + 6 = 1 It's Irish Math
> >
> >
> > <[email protected]> wrote in message
> > news:[email protected]...
> > > In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts
instead
> of
> > > the single 6in batts or does the compression just reduce the
> > effectiveness?
> > > I ask because I have several bales of the four inch stuff.
> > >
> > > JJ Thanks
> >
> >
>
>
"Yaofeng" <[email protected]> wrote in message
news:[email protected]...
> Donald Gares <[email protected]> wrote in message
news:<[email protected]>...
> > [email protected] wrote:
> > > In a 2x6 wall is the any advantage to stuuffing 2 4in r12 batts
instead of
> > > the single 6in batts or does the compression just reduce the
effectiveness?
> > > I ask because I have several bales of the four inch stuff.
> > >
> > > JJ Thanks
> >
> > Your hunch is correct, do NOT stuff in two 4" R12 batts because the
> > compression will defeat the purpose.
> >
> > Don
>
> I disagree. Two R12 compressed is better than one R19. he fiber
> glass is denser. You do need to watch out if the batt is lined to
> puncture sufficient number of holes on the outer layer.
I want to see you compress that extra 2 inches of insulation when your
hanging the drywall.
Nate
---
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.515 / Virus Database: 313 - Release Date: 9/13/03
Believe what you want. What I presented is based on the empirical
information I have seen. Note that actual results will depend on many
factors so in some cases compression may cause some increase in others some
decrease and it will also depend on the amount of compression.
--
Joseph E. Meehan
26 + 6 = 1 It's Irish Math
"Manny" <[email protected]> wrote in message
news:[email protected]...
> "Joseph Meehan" <[email protected]> wrote in message
news:<[email protected]>...
>
> > "JackD" <[email protected]> wrote in message
news:[email protected]...
>
> >>You are increasing the thickness substantially and not
> >>compressing the batts to a level that the r value per
> >>inch is compromised. Insulation manufacturers make thinner
> >>higher R-value batts for cathedral ceilings by INCREASING
> >>the density of the insulation.
>
> > You are correct at least in part. It would be difficult to
> > make an absolute statement. There are a number of factors
> > to consider, and we just don't have enough information.
> > Frankly I doubt if there is going to be a serious increase
> > or decrease under the conditions noted
>
> What a bunch of pretentious crap on your part. JackD is 100%
> right, and you don't seem to have a clue because the R-value/inch
> improves even when the density is doubled, as it almost is with
> rigid ceiling tiles and was with rigid fiberglass insulation
> used in old mid-priced water heaters (cheapest heaters had low
> density soft fiberglass, premium-priced had polyurethane foam).
>
> 8" of regular fiberglass compressed between 2x6 studs will
> give about R-21, compared to R-19 for 6" regular fiberglass.