[Greenbuilding] Cob as an alternative to spray foam sealant?

[RE-USE Consulting]

Hey all - 



It's good to hear that someone is looking for an alternative to spray foam.  I specialize in building deconstruction and the buildings we have disassembled with spray foam have been 'fun'.  The foam is oversprayed all over the place, it breaks off in many little lightweight pieces making it a nightmare to clean up, it contaminates recyclable wood, and it lowers or eliminates the resale value of whatever it is applied to.  



Keep in mind that whatever green points you are earning take a hit when the structure you build has to be demolished in the future.  Wool and clay sound great from my perspective at the far end of the project.  My $0.02. 



Dave Bennink 

RE-USE Consulting 

360-201-6977 

USA: www.reuseconsulting.com 

Canada: www.building-deconstruction.net 

National Building Deconstructor of the Year - 2009 




----- Original Message ----- 
From: "natural building" <naturalbuilding at shaw.ca> 
To: "Green Building" <greenbuilding at lists.bioenergylists.org> 
Sent: Friday, January 28, 2011 1:04:11 PM 
Subject: Re: [Greenbuilding] Cob as an alternative to spray foam sealant? 

Frank, shrinkage depends on a number of factors and can range from between 5% all the way up to 50% for certain types of clay. Furthermore, the amount of moisture in the mix will affect the degree of shrinkage. That being said, as a 'rule-of-thumb' you can expect about 10% shrinkage in the clay content of your mix. If the clay is mixed with cellulose matter such as wood chips or straw, these will swell and shrink independently depending on the moisture in the mix. 


My suggestion would be to try using two or three coats / applications with each successive layer filling the cracks and shrinkage that occurs in the previous. 


Regards 








Steve 


www.naturalbuildingsite.net 
naturalbuilding at shaw.ca 


On 28-Jan-11, at 9:16 AM, Frank Cetera wrote: 


I'd like to know the same thing Steve (using a clay slip mixture, what's the perlite for?).  Even if no one has ever attempted it, is there anyone that can provide any professional opinion on the matter? 

Steve Satow, would it be a big deal if the cob shrank when it dried when filling in shell air gaps?  If you dabbed the cob across any gaps and left extra on the sides to shrink some?  How much does cob typically shrink? 

"Ever since then, 
I've had the idea kicking around in my head to try a clay slip/perlite 
mixture sprayed into wall cavities like gunnite or shotcrete, anyone 
know if this has ever been attempted? 

I know it wouldn't be nearly as airtight or as insulating as spray 
foam, but it would be better than nothing and still completely 
biodegradable. :)" 

  
~Frank 
www.alchemicalnursery.org 

Message: 5 
Date: Wed, 26 Jan 2011 13:53:51 -0800 
From: natural building < naturalbuilding at shaw.ca > 
To: Green Building < greenbuilding at lists.bioenergylists.org > 
Cc: Greenbuilding at bioenergylists.org 
Subject: Re: [Greenbuilding] Cob as an alternative to spray foam 
       sealant? 
Message-ID: < 6EF75DF2-312E-47C8-9390-B75AEE63557E at shaw.ca > 
Content-Type: text/plain; charset="us-ascii"; Format="flowed"; 
       DelSp="yes" 

Sheep's wool was traditionally used for caulking log homes. 
You can still buy it ( http://www.goodshepherdwool.com ) treated with 
Borax to make it more resistant to decay and fire (like blown 
cellulose insulation) and it might work better in cracks because it 
will swell, whereas cob is going to shrink as it dries. 

Regards, 
Steve Satow 

www.naturalbuildingsite.net 
naturalbuilding at shaw.ca 

On 26-Jan-11, at 1:40 PM, Frank Cetera wrote: 

> Is is doable to take wads of cob and seal up the cracks and air 
> seeps that are throughout the shell of the house? 

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Message: 6 
Date: Wed, 26 Jan 2011 14:15:22 -0800 
From: Steve < steve at greengeek.ca > 
To: Green Building < greenbuilding at lists.bioenergylists.org > 
Subject: Re: [Greenbuilding] Cob as an alternative to spray foam 
       sealant? 
Message-ID: 
       <AANLkTikHJ7gdqfLeXNr= KNOF4SjreNFa+ZA_VXmUZUzm at mail.gmail.com > 
Content-Type: text/plain; charset=ISO-8859-1 

A couple of years ago I was talking with a relative about ways to 
build structures with modern techniques and traditional (natural) 
materials, and the subject of spray foam came up. Ever since then, 
I've had the idea kicking around in my head to try a clay slip/perlite 
mixture sprayed into wall cavities like gunnite or shotcrete, anyone 
know if this has ever been attempted? 

I know it wouldn't be nearly as airtight or as insulating as spray 
foam, but it would be better than nothing and still completely 
biodegradable. :) 

-Steve 
-- 
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