# Is it worth it to DIY spray foam insulate?



## Alan (Apr 12, 2006)

I only have a 2x4 exterior wall. That is not going to change.


That said, the only readily available 2x4 insulation around here is R-13. I'm a little disappointed at that, since i'd rather put the most dense insulation made in there.


I realize that the cost is going to be much greater for a spray foam kit, but at this point, i'm only insulating a small section of the wall about 8 feet long. By the time I am done with the kitchen project i'll have about 18 feet insulated.

With no real timeline in mind as far as when I will get to insulating the rest of the exterior walls, is it worth it to spend the extra money on a diy spray foam kit? Should I just go with what fiberglass I can get locally and call it good? Are there any other decent options that i'm overlooking?


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## rpmnow (Apr 2, 2013)

*Retrofit insulation*

I've been tormenting over how to insulate my late 1950s house walls as well. 

Regarding your comment about wanting dense insulation, dense, or mass normally translate to heat conduction rather than insulation value, but what you may mean is something more solid / monolithic that loose fill insulation.

Unfortunately fiberglass bat insulation is what would even give you the R13. Loose fill is less insulation value, like only around 7. Many of us don't want to tear our interior drywall out to intall fiberglass bat, and I'm not sure I want to mess with loose fill for only R7 or so. 

The potential problems with foam, on the other hand, include the hazard of gas pressure popping your drywall at the seams and out-gassing formaldehyde fumes making you sick for some period of time afterwards. 

The only other option readily available at the big box building supply store is blown-in cellulose (paper), which I'm afraid will settle over time and become dense (more heat conducting) at the bottom of the wall, and void at the top.

Having said all that (probably not much help), if anyone out there has a really good solution to retrofit insulation I'm definitely interested as well.


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## Nailbags (Feb 1, 2012)

Alan said:


> I only have a 2x4 exterior wall. That is not going to change.
> 
> 
> That said, the only readily available 2x4 insulation around here is R-13. I'm a little disappointed at that, since i'd rather put the most dense insulation made in there.
> ...


Check in to doing a BIB system to have a certified BIBS installer do it for a 2x4 wall it will give you a R 16 rating. and you will have a better return on your investment with in the first two years. then heaven only knows. with just foam.


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## Windows on Wash (Aug 30, 2011)

Alan said:


> I only have a 2x4 exterior wall. That is not going to change.
> 
> 
> That said, the only readily available 2x4 insulation around here is R-13. I'm a little disappointed at that, since i'd rather put the most dense insulation made in there.
> ...


If you stay with batts, use something like Roxul. Much denser than FG and doesn't have the convective loss potential.

If you want foam, put in rigid board that it cut and cobbled to the space. That will give you the higher R-Value per inch if you use something like Polyiso but you need to be aware of the net vapor permeance via this approach whether it is Polyiso or XPS.


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## HomeSealed (Jan 3, 2008)

You do not want to blow loose fill cellulose (or anything else for that matter) into a wall cavity. The proper method is dense packing, and there are some fg products that can be dense packed now as well. The typically fg batting is another cost effective solution. The Bib system is nice, but not really diy.
Spray foam is great, but very costly when you look at the cost to added benefit ratio.


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## asinsulation (Apr 11, 2011)

The major problem in seeing what kind of insulation will benefit you the most is just comparison of r-values. It is not just that easy.  With your spray foam, you are getting your vapor barrier, your airsealing, and your insulation in one application. Depending on how valuable your time is, and if your idea is comfort, it may be best for you. If it's a project you can spend a little more time on, and your priority is return on your investment, a basic airseal and densepack/batt may be your answer.

Keep in mind as well, doing a GREAT job on 18 foot of wall is not going to make a drastic difference either way. So unless you intend on addressing other aspects of the home as well with a spray foam application, you may want to use a more conventional method.


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## Windows on Wash (Aug 30, 2011)

asinsulation said:


> The major problem in seeing what kind of insulation will benefit you the most is just comparison of r-values. It is not just that easy. With your spray foam, you are getting your vapor barrier, your airsealing, and your insulation in one application. Depending on how valuable your time is, and if your idea is comfort, it may be best for you. If it's a project you can spend a little more time on, and your priority is return on your investment, a basic airseal and densepack/batt may be your answer.
> 
> Keep in mind as well, doing a GREAT job on 18 foot of wall is not going to make a drastic difference either way. So unless you intend on addressing other aspects of the home as well with a spray foam application, you may want to use a more conventional method.


True...it is easier and you need to determine what you time is worth.

Problem is that most of the small kits have terrible yield and are tough to work with and easy to make a mess of.

I would also add that while the air barrier part of spray foam is invaluable in my opinion, they may not be getting the vapor retarder level that they actually need (staying true to code) with open cell foam in some applications.

I personally think that vapor retarder levels need to be looked at and re-evaluated, but OC spf isn't a vapor barrier.


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## Burnt (Apr 1, 2013)

Windows on Wash said:


> Problem is that most of the small kits have terrible yield and are tough to work with and easy to make a mess of.


Not sure about the yield but they are not tough to work with at all. I used last year to insulate and seal all my joist sills in the basement and it worked like a charm.


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## Windows on Wash (Aug 30, 2011)

Burnt said:


> Not sure about the yield but they are not tough to work with at all. I used last year to insulate and seal all my joist sills in the basement and it worked like a charm.


They are okay to work with but your representative experience (i.e. 1 time) is probably not a fair assessment.

I have worked with dozens and we have had kits for work and we have had bad hose sections that burst or nozzles that did not portion out product properly. Not all the time but more than once. Have a hose burst on a homeowner that is not ready for it and you have an epic mess. :laughing:

As compared to a professional rig...they are much more difficult and the yield is considerable less. Remember how much product was still in the cans when you were done? That money..


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## Alan (Apr 12, 2006)

asinsulation said:


> If it's a project you can spend a little more time on, and your priority is return on your investment, a basic airseal and densepack/batt may be your answer.


In this case, i'm in no big rush, so maybe this is what I should stick with. The spray foam seems messy anyway...

What should I look for? The only thing I can find local is owens corning r-13.


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## Nailbags (Feb 1, 2012)

There far better brands out there for Fiberglass batts. you want to use a HD high density batt, it will if put in place correctly will yeild you a R 15 that is the best you can hope for with fiberglass. even with the Blown in blanket for 2x4 walls.
and cellulose will give you a R-12 with a dense pack. here is the link. http://www.energy.wsu.edu/Documents/BFG%20Supplement%20C-Jan2011.pdf
and for a vapor retarder you have to use something that has a perm 1 or less.
here is the link to that as well. http://www.energy.wsu.edu/Documents/BFG%20Supplement%20E-Jan2011.pdf
hope that informs you to what you need.


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## fetzer85 (Dec 4, 2009)

I think WoW hit the nail on the head recommending rigid foam board. Won't be a huge pain since you only have a small wall to do. Is it an old house? ie, does it have true 2x4's or modern undersized? If true you might be able to fit 2 layers of 2" board for an r value around 20. Even if it's modern 2x4's you'll still have no problem hitting an airtight r15.


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## mikegp (Jul 17, 2011)

Roxul now has R-15 batts that fit 2x4 walls. Are those available in your area? They are very easy to install. Cutting rigid foam to fit the cavities could be annoying.


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## Alan (Apr 12, 2006)

My wife was out of town last week, and she picked me up a package of the roxul r-15. Very nice stuff, I am impressed. Thanks to all for suggestions.



Next thing I need to do is put up some kind of vapor barrier over it, yes? What's the right kind of stuff to use?


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## Windows on Wash (Aug 30, 2011)

Alan said:


> My wife was out of town last week, and she picked me up a package of the roxul r-15. Very nice stuff, I am impressed. Thanks to all for suggestions.
> 
> 
> 
> Next thing I need to do is put up some kind of vapor barrier over it, yes? What's the right kind of stuff to use?


What is the exterior wall made of and like?

http://www.buildingscience.com/docu...heet-310-vapor-control-layer-recommendations/

Climate Zone 4c

Probably likely that you don't really need one if you seal up the exterior sheathing and take the ADA (Airtight Drywall Approach) on the interior.

If you have something where you be concerned about a vapor push from the exterior, might make sense to have some rigid foam at the outside wall to help mitigate that push. That being said, this can create other condensation potential if not done properly.

Gary is the psychrometric chart chart wiz.


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## Alan (Apr 12, 2006)

Windows on Wash said:


> What is the exterior wall made of and like?
> 
> http://www.buildingscience.com/docu...heet-310-vapor-control-layer-recommendations/
> 
> ...


The exterior there is plywood sheathing, and tar paper (siding coming soon). We don't really get that cold here, but we do get some wind, especially against that wall.


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## Windows on Wash (Aug 30, 2011)

Put rigid foam under the new siding and you will really improve the efficiency of that wall assembly.


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