open cell vs wet blown cellulose? | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

open cell vs wet blown cellulose? Post New Topic | Post Reply

Author	Comments
andy buff Posted: Sep 17, 2011 09:42 AM	open cell vs wet blown cellulose? i have a house on lake ontario we are ready to insulate whats going to be better long term wet blow cellulose or spray foam...it's all about the buget.so will open cell perform as well as wet cellulose. my concern is wet applied paper, vapor difusser film then dry wall wont the moiture be trapped? and for open cell which will be the more price competitive..is it better to paint the foam or paint the drywall with vapor primer or is two coats primer two coat paint enough...thanks skinny
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Sep 17, 2011 06:16 PM	I would recommend open cell foam over wet blown cellulose any day! A builder and I were just talking about that today and I asked him how long he waited to allow the cellulose to dry before sheetrocking. I would say at least 2 weeks with it being drier inside the house -that means a dehumidifier running almost continuously. He stated the contractor (who I know personally) stated, "waiting a day should do it!" I know from experience that it isn't dry after a day or even a week -especially in humid summer days. Now that the temp is decreasing, I would say you're much safer at about a week to 2 weeks minimum but not less than that! OC spray foam is the most cost effective choice! Where along lake ontarion are you building, because I understand that most of the shoreline is all zone 5-6 and only requires a class III vapor retarder which our foam meets even at 3" thick. So, no additional vapor retarder is required - no paint on foam or drywall! Even though you are painting the wall with 1 coat of primer and two coats of latex, this is also a vapor retarder. So, you can drop me a line and I can try to help you -jim@coler.com
mason Posted: Sep 17, 2011 08:29 PM	To add to Jim's comments, the sprayfoam acts better as an air barrier which reduces the potential for moisture transfer into the building as well as providing better energy performance. Open cell foams have varying perm ratings depending on the formula, so pay attention to the suppliers data sheet on how much to use to act as a vapor retarder.
Dennis Davidson Posted: Sep 19, 2011 06:11 PM	If the spray cellulose takes two weeks to dry then they did it wrong or used the wrong product! Just like foam, there are different types of cellulose designed for different applications and cellulose should not be lumped into a single category. That would be like saying open cell and closed cell foams are the same thing. When spraying a stud cavity with cellulose, very little water should be used because the dry material has the glue in it and is activated when sprayed with a mist of water during the application. A typical 2X4 stud wall fill with cellulose should dry out in about two days or less. We could debate the pros and cons of open cell vs cellulose forever and each has it place but I have been installing both spray foam and spray cellulose for over 30 years. The one substantial difference between them is that the spray cellulose is fire resistant and is, in some cases, used over spray foam as a fire resistant barrier.
andy buff Posted: Sep 19, 2011 09:53 PM	macs whats an average-ballpark sqft price for damp cellulose 2x6 walls what would the r-value be...thanks for the info
JohnPeters Posted: Sep 20, 2011 06:29 AM	Jim, Climate zones 5 and 6 only call out for a class III vapor retarder? I thought for sure they were calling out for class II. Did something change over the last couple of years? Regardless, I am with you - no need for additional vapor resistance with OC in our climate zones.
mason Posted: Sep 20, 2011 02:47 PM	John did catch that about the vapor retarder. The IRC section on exterior walls allows a class III vapor retarder in zones 1-4 but marine 4-8 requires class II vapor retarder. Section R 601.3 Vapor retarders: "Class I or II vapor retarders are required on the interior side of frame walls in Zones 5.6.7.8 and Marine 4"
Dennis Davidson Posted: Sep 20, 2011 08:50 PM	Skinny, I don't know what the market is like in your area for residential spray cellulose work so it wouldn't be very professional to talk pricing for there. However, in my area the price of spray cellulose for stud walls is about the same price, sometimes less, as open cell foam. 5 1/2" of cellulose in a 2X6 stud wall will give you an R-20.9 which equals R-3.8 per inch thickness
andy buff Posted: Sep 20, 2011 10:44 PM	Macs thanks for the low down where are you located.is it the glue thats expensive or do people use Perrier water to spritz the paper? i never would of guessed that it would cost the same as foam..anyway thanks for your imput

Author

Comments

andy buff

Posted: Sep 17, 2011 09:42 AM

open cell vs wet blown cellulose?

i have a house on lake ontario we are ready to insulate whats going to be better long term wet blow cellulose or spray foam...it's all about the buget.so will open cell perform as well as wet cellulose. my concern is wet applied paper, vapor difusser film then dry wall wont the moiture be trapped? and for open cell which will be the more price competitive..is it better to paint the foam or paint the drywall with vapor primer or is two coats primer two coat paint enough...thanks skinny

jimcoler

I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs.

I've expanded my knowledge into t

Posted: Sep 17, 2011 06:16 PM

I would recommend open cell foam over wet blown cellulose any day! A builder and I were just talking about that today and I asked him how long he waited to allow the cellulose to dry before sheetrocking. I would say at least 2 weeks with it being drier inside the house -that means a dehumidifier running almost continuously. He stated the contractor (who I know personally) stated, "waiting a day should do it!" I know from experience that it isn't dry after a day or even a week -especially in humid summer days. Now that the temp is decreasing, I would say you're much safer at about a week to 2 weeks minimum but not less than that!

OC spray foam is the most cost effective choice! Where along lake ontarion are you building, because I understand that most of the shoreline is all zone 5-6 and only requires a class III vapor retarder which our foam meets even at 3" thick. So, no additional vapor retarder is required - no paint on foam or drywall! Even though you are painting the wall with 1 coat of primer and two coats of latex, this is also a vapor retarder.

So, you can drop me a line and I can try to help you -jim@coler.com

mason

Posted: Sep 17, 2011 08:29 PM

To add to Jim's comments, the sprayfoam acts better as an air barrier which reduces the potential for moisture transfer into the building as well as providing better energy performance.

Open cell foams have varying perm ratings depending on the formula, so pay attention to the suppliers data sheet on how much to use to act as a vapor retarder.

Dennis Davidson

Posted: Sep 19, 2011 06:11 PM

If the spray cellulose takes two weeks to dry then they did it wrong or used the wrong product! Just like foam, there are different types of cellulose designed for different applications and cellulose should not be lumped into a single category. That would be like saying open cell and closed cell foams are the same thing. When spraying a stud cavity with cellulose, very little water should be used because the dry material has the glue in it and is activated when sprayed with a mist of water during the application. A typical 2X4 stud wall fill with cellulose should dry out in about two days or less.
We could debate the pros and cons of open cell vs cellulose forever and each has it place but I have been installing both spray foam and spray cellulose for over 30 years. The one substantial difference between them is that the spray cellulose is fire resistant and is, in some cases, used over spray foam as a fire resistant barrier.

andy buff

Posted: Sep 19, 2011 09:53 PM

macs whats an average-ballpark sqft price for damp cellulose 2x6 walls what would the r-value be...thanks for the info

JohnPeters

Posted: Sep 20, 2011 06:29 AM

Jim,

Climate zones 5 and 6 only call out for a class III vapor retarder? I thought for sure they were calling out for class II. Did something change over the last couple of years?

Regardless, I am with you - no need for additional vapor resistance with OC in our climate zones.

mason

Posted: Sep 20, 2011 02:47 PM

John did catch that about the vapor retarder. The IRC section on exterior walls allows a class III vapor retarder in zones 1-4 but marine 4-8 requires class II vapor retarder.

Section R 601.3 Vapor retarders:

"Class I or II vapor retarders are required on the interior side of frame walls in Zones 5.6.7.8 and Marine 4"

Dennis Davidson

Posted: Sep 20, 2011 08:50 PM

Skinny, I don't know what the market is like in your area for residential spray cellulose work so it wouldn't be very professional to talk pricing for there. However, in my area the price of spray cellulose for stud walls is about the same price, sometimes less, as open cell foam.
5 1/2" of cellulose in a 2X6 stud wall will give you an R-20.9 which equals R-3.8 per inch thickness

andy buff

Posted: Sep 20, 2011 10:44 PM

Macs thanks for the low down where are you located.is it the glue thats expensive or do people use Perrier water to spritz the paper? i never would of guessed that it would cost the same as foam..anyway thanks for your imput

You need to login to reply to this topic. Please click here to login.