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Leave the roof insulation alone!

BayPointArchitect

BayPointArchitect

Sawhorse
Joined
Oct 19, 2009
Messages
525
Location
Lincoln
Given:

Roofing contractor wants me to say that if the existing rubber roof membrane is either replaced or if the building owner is asking for a second layer of rubber roof membrane, then the continuous insulation above roof deck needs to be removed and replaced - unless it meets the current R-30 requirement (Zone 5A). That seems zealous to me.

2018 IECC Section C503 Alterations
Exception: The following alterations need not comply with the requirements for new construction, provided that the energy use of the building is not increased:
#5. Roof recover.

Definition of roof recover:
The process of installing an additional roof covering over an existing roof covering without removing the existing roof covering.

I keep telling people that unless the existing roof insulation is damaged, then you can leave the existing R-20 in place and then lay down another layer of EPDM or TPO. Anyone else out there have a different opinion? Or maybe I am wrong again.

As always, thanks in advance.

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner
 
The roofer is right...And get the engineering analysis that the increased snow retention won't compromise the structure...On a replacement, not on a roof you can go over...

C503.2.1 Roof replacement. Roof replacements shall
comply with Section C402.1.3, C402.1.4, C402.1.5 or
C407 where the existing roof assembly is part of the
building thermal envelope and contains insulation
entirely above the roof deck. In no case shall the R-value
of the roof insulation be reduced or the U-factor of the
roof assembly be increased as part of the roof
replacement.

C402.1.3 Insulation component R-value-based
method. Building thermal envelope opaque assemblies
shall comply with the requirements of Sections C402.2
and C402.4 based on the climate zone specified in Chapter
3. For opaque portions of the building thermal
envelope intended to comply on an insulation component
 
Steve you cited roof replacement … BPA is talking about recovering.

BPA ... the section you quoted gives an exemption for “without removing the existing roof covering.“. I would say that means the old membrane has to remain in place for the exception to apply.
 
Yes....yes I did...

[BS] ROOF RECOVER. The process of installing an additional
roof covering over a prepared existing roof covering
without removing the existing roof covering.

[BS] ROOF REPLACEMENT. The process of removing
the existing roof covering, repairing any damaged substrate
and installing a new roof covering.

Baypoints first sentence had both in it, if you removing the roof membrane, you upgrade the insulation...Very few roof coverings allow another layer......
 
BayPointArchitect said:
Given:

Roofing contractor wants me to say that if the existing rubber roof membrane is either replaced or if the building owner is asking for a second layer of rubber roof membrane, then the continuous insulation above roof deck needs to be removed and replaced - unless it meets the current R-30 requirement (Zone 5A). That seems zealous to me.

2018 IECC Section C503 Alterations
Exception: The following alterations need not comply with the requirements for new construction, provided that the energy use of the building is not increased:
#5. Roof recover.

Definition of roof recover:
The process of installing an additional roof covering over an existing roof covering without removing the existing roof covering.

I keep telling people that unless the existing roof insulation is damaged, then you can leave the existing R-20 in place and then lay down another layer of EPDM or TPO. Anyone else out there have a different opinion? Or maybe I am wrong again.

As always, thanks in advance.

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner
Click to expand...
You said: "the building owner is asking for a second layer of rubber roof membrane, then the continuous insulation above roof deck needs to be removed and replaced "

Why would you remove and replace perfectly good insulation?
If you did want to increase R factor then why not just mechanically fasten an additional layer with or without base sheet ( as per manufacturer's warranty, ) and then the additional membrane?

what am I missing?
 
Genduct said:
You said: "the building owner is asking for a second layer of rubber roof membrane, then the continuous insulation above roof deck needs to be removed and replaced "

Why would you remove and replace perfectly good insulation?
If you did want to increase R factor then why not just mechanically fasten an additional layer with or without base sheet ( as per manufacturer's warranty, ) and then the additional membrane?

what am I missing?
Click to expand...
If I were doing something to meet minimum code and not spend more money than necessary, I would want to leave the existing insulation alone and make sure that I had a water-tight rubber roof membrane. Around here, it is good business practice to give attention to a rubber roof every 10 to 15 years. But since we anticipate that the insulation requirements will continue to increase from R-20 to R-30 to R-35 with each code adoption, it seems egregious to require an upgrade to a layer of insulation that was perfectly acceptable according to the previous code edition.
 
steveray said:
Welcome to the IECC....it gets sooo much worse...
Click to expand...
Seems like with Mechanical equipment, we should defer to what the Manufacturer feels is needed to Warrant the Job,

So, if they allow extra insulation And perhaps a mechanically fastened separation sheet, We should not get into the middle of that situation

God Knows that the Building Science Aspect has more than one approach and many differences of opinion. But that goes beyond the Code MINIMUM or Does it?
 
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