[Greenbuilding] innovative solution sought

[conservation architect]

The challenge of the eave detail can certainly defeat the feasibility of what I suggested.  However, a vapor permeable foam over the roof structure would create an exceptionally air tight house if the continuity with the wall can be achieved.  Even though inside air is not vented, vapor can pass though EPS foam and is carried away by air that never was inside the thermal envelope.  

Eli 
www.lightfootdesignbuild.wordpress.com


From: Sacie Lambertson 
Sent: Saturday, September 10, 2016 2:13 PM
To: Green Building 
Subject: Re: [Greenbuilding] innovative solution sought

In response to my query looking for innovative inexpensive ways to extend old 2x4 rafters to allow for about 8" of dense pack cellulose, I've received a number of responses.

Included is the suggestion we rebuild the roof by placing more insulation on top and make it vented.  Am afraid this is a non starter because we don't want to have to rebuild the existing soffits AND vented roofs are not a good idea in an otherwise tightly built house.  Also rec. the suggestion we sister/scab wider wood onto the 2x4s, which is exactly what I want to avoid.

OTOH scabbing cheap plywood onto the rafters is a good idea.  We wouldn't have to do this for every rafter nor for the full length.  Maybe we could install cables across the scabbing to hold the netting in place after it the dense pack cellulose has been blown in.

Welcome further comments/ideas.

Sacie

On Fri, Sep 9, 2016 at 11:32 AM, Nick Pyner <npyner at ihug.com.au> wrote:

  Cheap plywood shot to the side of the rafters? 



  On 10/09/2016 12:59 AM, Sacie Lambertson wrote:

    All, We have an old house in which we want a well insulated unvented attic.  We are replacing the existing roof (with metal) and installing a minimal layer of XPS on top of the sheathing. We plan to use closed cell spray underneath followed by dense pack cellulose between the rafters.  The problem is the rafters, which are only 2x4s in this old house.  I am looking for a creative least expensive way to provide more rafter depth for the insulation. 

    (We do not want to build up the insulation on the top of the roof  sheathing because doing so requires the added cost of completely rebuilding the existing soffits, which are in good condition).  

    Will appreciate all your useful suggestions.

    Sacie

     

_______________________________________________
Greenbuilding mailing list
to Send a Message to the list, use the email address
Greenbuilding at bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org


  _______________________________________________
  Greenbuilding mailing list
  to Send a Message to the list, use the email address
  Greenbuilding at bioenergylists.org

  to UNSUBSCRIBE or Change your List Settings use the web page
  http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org




--------------------------------------------------------------------------------
_______________________________________________
Greenbuilding mailing list
to Send a Message to the list, use the email address
Greenbuilding at bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20160913/f8998dc4/attachment.html>