Existing Building Furring Walls

[fungineer]

For a project in WI (Uses the IECC 2015 with some modifications), we often work on uninsulated masonry buildings. Within these buildings there may be areas where an existing office was located that have some furring. In a project where the interior is gutted for a new user, the exterior face will be left with say 20% furring wall, and 80% exposed cmu.

Based upon C503.1, exception 3 by the purest application of the code I have (2) options:

1. If the furring is left in place (with gypsum/etc.) nothing is needed to be done on either the furring wall or non furring wall protion.
2. If the cavities for the furring are exposed, they must be filled.

Now's the real question:
If the full space were to be a shop, and the furring was demolished, confirm which options are allowed (not which are good practice):

• Improve the existing wall over the full length to meet current code.
• Improve the existing wall only over the length of the previous furring to meet code.
• Provide new furring with cavities, which, once filled would be equivalent to filling the cavities of the previous furring, over that length only (as a minimum). (This would seem to meet the intent but I'm not sure how that's actually handled).
  • As stupid as it is to have 400 feet of wall with only 80 feet of it insulated and furred out, that technically seems to be what the code would required (albiet not a good design).
• Leave the entire wall exposed and do nothing -
  • By the letter of the code I don't believe this is allowed. However, project happen all the time where an existing building shell is grayboxed for a new tenant or owner. The new tenant has no idea where the previous furring did or did not exist, so its often treated by some as if it was never there.

 

[steveray]

Was the furring intended to be part of the thermal envelope? Or just a nailer? Methinks the latter....This one gets really picky, just helped a buddy with it this week and came out to not required....In his instance...

 

[fungineer]

Though it varies from project to project, more often then not it was to be a nailer to attached gypsum to. That said, if the furring was filled with insulation, it's hard to say it wasn't for both. Usually if I have the original plans it's just marked "Gypsum finish over stud furring as required", fill cavities with insulation.

 

[Sifu]

Unless there is a change from unconditioned to conditioned I would say only the alterations need to comply. If you expose a cavity and it isn't filled, then fill it, if it is you can leave it alone. If you aren't adding any cavities, then you aren't required to do anything. As silly as it may seem, the small portion of insulated wall is viewed as a baby step in the hope that any future alterations will steadily increase the energy efficiency. If, however, the building was previously unconditioned, and you are adding any then you must comply with the code.

 

[steveray]

Is the furring capable of forming g an envelope or does it stop at the floors leaving a gap? Or stop above the ceiling? If so, I say no...