# Insulated or Non-Insulated Vinyl Siding?



## dv817 (Jul 18, 2011)

My home was built in the 80"s, I have brick on the first floor, and I am planning to installing siding on the second floor. Does anyone know if it is wiser to install a premium vinyl siding that comes with the insulation, or install a premium non-insulated vinyl siding combined with a higher R-value rigid foam insulation? Most of the insulated vinyl sidings I've seen have R-values of 5 or less. I realize I can achieve two to three time that R-value with the rigid foam insulation, but I'm not sure which option is the more expensive or efficient. 

I would appreciate any feed back you my offer.

Cheers


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## jklingel (Dec 21, 2008)

I'm not a pro, but how the hey is insulation in siding worth jack stink when siding is not air tight? insulated siding makes as much sense as breasts on a bull, unless i'm missing something (besides a few screws). btw, if you put foam on the outside, make sure you have enough to keep the sheathing underneath it warm (to avoid condensation). generally, that means 2" of foam over 2x4s, 3" over 2x6s.


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## parts (May 6, 2009)

The main advantage of the foam on the back of the panels is that it makes them nice and firm with no play like there is in regular vinyl. The for the insulation value of it is negligible. One disadvantage is it does not pop off easy with a zip tool if you need to do anything behind it or replace a piece


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## AGWhitehouse (Jul 1, 2011)

I wouldn't recommend the insulated siding because of air movement like jklingel said.

If you are going to put rigid insulation on the exterior envelope you will need to pay attention to it's vapor permeability. Most structure were built with a vapor barrier on the interior side. If you put enough foam on the exterior side that a vapor barrier (< 1 perm) is made you will trap moisture within the wall and create an opportunity for mold growth.


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## dv817 (Jul 18, 2011)

*Installing Radiant Barriers under Vinyl Siding*

If one installs foil radiant barrier under non-insulated vinyl siding, obviously it will reduce radiant heat, but will it cause a vapor barrier that could trap moisture in the walls and create an opportunity for mold growth?


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## AGWhitehouse (Jul 1, 2011)

dv817 said:


> If one installs foil radiant barrier under non-insulated vinyl siding, obviously it will reduce radiant heat, but will it cause a vapor barrier that could trap moisture in the walls and create an opportunity for mold growth?


If the barrier has a low perm rating then yes. <1 perms is considered a vapor barrier by the IBC. If the foil faced barrier is permeable (i.e. has perforations), then it will reflect the heat and allow for vapor transmissions.


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## dv817 (Jul 18, 2011)

AGWhitehouse,

I had a feeling that would be the case. I just did some research online after reading your valuable comments, and I did not previously know that foil radiant barrier comes in perforated and non-perforated. Additionally, I also learned that the minimum rating for a perforated product should be 5 perms.

Thanks for you help!


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## Gary in WA (Mar 11, 2009)

Check to see if the foam is EPS, as it probably is (which you don’t want). Do your homework….. http://docs.google.com/viewer?a=v&q=cache:M8LGdKfi1yMJ:www.dow.com/PublishedLiterature/dh_013e/0901b8038013ede3.pdf%3Ffilepath%3Dstyrofoam/pdfs/noreg/179-06011.pdf%26fromPage%3DGetDoc+permeability+ratings+of+sidings&hl=en&gl=us&pid=bl&srcid=ADGEESj2HlSU9SGLtx6MUOmbi_mJRuEufjmOjvbs-LJtrZ50rKT1Yqwgm3jPzvQt5dNG3lofjVwH_jVsuwCMAKQzEBcCPOlz7kpvTnXH5mfDcTRkUcHaW2aZAWJrAiBYUoXbY44FW&sig=AHIEtbT1X6_1p3ibUPYAt5jlOsa_kZRRgw

Radiant barrier requirements, and “double vapor barriers” with XPS; http://docs.google.com/viewer?a=v&q...iZ9vwo&sig=AHIEtbRlhNBCWID8xGZ54EyM707m0gPdXQ

Gary


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## Gary in WA (Mar 11, 2009)

And the one I was thinking of but couldn't find until now: http://hubpages.com/hub/Does-Foam-Board-Insulation-Under-Siding-Help-Save-Energy

Gary


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> Check to see if the foam is EPS, as it probably is (which you don’t want). Do your homework…..


Why no on EPS? It is a very breathable foam product that is great for adding some R-value without creating a double vapor retarder system. XPS is a wonderful product, but can only be applied in a thin layer for retrofit due to its lower permeability rating and chance of creating a double retarder.


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## Gary in WA (Mar 11, 2009)

Read the links on post #8..........

Gary


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> Read the links on post #8..........
> 
> Gary


Ok...that was a pros/cons comparison of EPS backed vinyl siding and XPS sheathing. What of EPS sheathing vs. XPS sheathing? That's my question...


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## Gary in WA (Mar 11, 2009)

ESP has it's place if you don't mind less R-value for the thickness, or adding a housewrap. Long as you never have a water leak from siding, windows or roof. From page 14: “However, the EPS wall appears to have stable moisture
cycling behavior, and is even drier than the original wall
during the wintertime peaks. Although these simulations
might point to EPS as a promising option for exterior insulation
retrofits, there are some drawbacks to this material,
including lower R-value per inch, lower compressive strength,
poorer workability (edge cutting), and difficulty in detailing
the material as a water control layer/drainage plane.” 
http://www.buildingscience.com/docu...ential-exterior-wall-superinsulation-retrofit

It’s the water………. http://docs.google.com/viewer?a=v&q...iZ9vwo&sig=AHIEtbRlhNBCWID8xGZ54EyM707m0gPdXQ


Gary


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## Tom Struble (Dec 29, 2008)

eps is the correct type of foam when used on an attached vinyl panel

and you really need to understand how air ''sticks'' to a surface to understand 
that even though it may not be air tight it can still be an effective way to add extra insulation to your home


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## Gary in WA (Mar 11, 2009)

“The impact of forced convection
upon thermal performance”, page 4,
mentions wind-washing “short-circuiting” insulating sheathings. With all the joints and trim connections with vinyl siding, I doubt you would get benefit of the air-space (R-1) and possibly not even the outside air film R-value of 0.17 of insulated siding, since it’s just hanging there, tacked at the top. http://www.aecb.net/PDFs/Impact_of_thermal_bypass.pdf

R-value of air-spaces, bottom of graph: http://www.coloradoenergy.org/procorner/stuff/r-values.htm

I’d rather use a rigid sheathing with a housewrap or paper, knowing you’d get the listed R-values, staying drier as vinyl siding leaks water: http://sidingmaster.com/documents/NewReportaboutsidingtrappingmoisture.pdf



Why would you want an air space between the insulation and the sheathing to negate any R-value, possibly raising the dew-point of the wall at the inside sheathing: http://www.greenbuildingadvisor.com/blogs/dept/musings/are-dew-point-calculations-really-necessary

The foam has to be next to the sheathing, without an air space, to be effective; http://www.greenbuildingadvisor.com...lating-minimum-thickness-rigid-foam-sheathing

Gary


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## Tom Struble (Dec 29, 2008)

the insulation thats attached to the siding is ''not just tacked'' as you say,it is firmly held in place between the panel lock

and the installation detail is all the foam is butted,there are no big gaps between the foam


and Gary please when you reply to me don't give me all those links,it's kind of annoying


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## Gary in WA (Mar 11, 2009)

Sorry about that. No more links for you. Ventilating air pockets, water channels, fire-retardant and bug resistant insulation, now if it was fire retardant and non-fading vinyl that still looks good after 10 years, it would be a quality product. (My opinion). With no air movement and an insulating air film, one would still need a foam board for the required exterior insulation to make-up the low R-value of vinyl in most of the U.S. and Canada, if interested in dew points. 

OP, have you decided which way to go yet?

Gary


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## Tom Struble (Dec 29, 2008)

thankyou:wink:

i'm not trying to be an advocate for insulated vinyl siding,but installed right it will do as advertized


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