Adding continuous insulation for interior renovation?

[PatrickGSR94]

We have an existing building that we have to run through COMcheck for our local jurisdiction, which requires R13+R3.8 CI. The building is currently uninsulated framed walls, with sheathing and brick on the exterior. Since we're opening up the walls, and the walls currently have no insulation, there are no exceptions that apply, so we have to install insulation.

So the question is, can the continuous insulation go on the INTERIOR side of the framing, before gyp board? Because we're definitely not going to be removing all the brick veneer just to add a single layer of continuous insulation on this thing.

 

[steveray]

You typically just have to fill the cavity in a remodel, so R11 to 15 in a 2x4.....If it is a change of use or unconditioned to conditioned, that is another matter....

 

[PatrickGSR94]

You typically just have to fill the cavity in a remodel, so R11 to 15 in a 2x4.....If it is a change of use or unconditioned to conditioned, that is another matter....

apparently the only 2 exceptions in COMcheck are: 1) exterior wall framing exposed but insulation left intact, or 2) wall framing not exposed. In our case the exterior wall framing has been exposed and there is NO insulation. So it seems those 2 exceptions would not apply, so the CI is still required to meet COMcheck.

So then the question: can the continuous insulation be installed on the interior side of the exterior wall framing, instead of the exterior? Surely a code would not require an owner to remove existing brick veneer from their entire existing building. That would be a massively wasteful expense for what seems to be minimum benefit.

 

[classicT]

apparently the only 2 exceptions in COMcheck are: 1) exterior wall framing exposed but insulation left intact, or 2) wall framing not exposed. In our case the exterior wall framing has been exposed and there is NO insulation. So it seems those 2 exceptions would not apply, so the CI is still required to meet COMcheck.

So then the question: can the continuous insulation be installed on the interior side of the exterior wall framing, instead of the exterior? Surely a code would not require an owner to remove existing brick veneer from their entire existing building. That would be a massively wasteful expense for what seems to be minimum benefit.

In my experience, COMcheck has not typically been required for existing buildings.

That said, do you have the latest version of COMcheck? Are you selecting that this is an addition/alteration when setting up the calculation?

 

[PatrickGSR94]

Okay we got it figured out, using the U-value method. R-20 in the cavity framed wall results in the same U value as the R-13 + 3.8 Ci. So we can do 3 inches of closed-cell spray foam insulation in the stud cavity and get it into compliance.

Yes this jurisidiction requires COMcheck even on alterations.

 

[steveray]

Okay we got it figured out, using the U-value method. R-20 in the cavity framed wall results in the same U value as the R-13 + 3.8 Ci. So we can do 3 inches of closed-cell spray foam insulation in the stud cavity and get it into compliance.

Yes this jurisidiction requires COMcheck even on alterations.

Do they use the IEBC or anything for existing buildings? Or for that matter the IECC?

For example.....

Exception: The following alterations need not comply
with the requirements for new construction, provided that
the energy use of the building is not increased:
1. Storm windows installed over existing
fenestration.
2. Surface-applied window film installed on existing
single-pane fenestration assemblies reducing solar
heat gain, provided that the code does not require
the glazing or fenestration to be replaced.
3. Existing ceiling, wall or floor cavities exposed
during construction, provided that these cavities
are filled with insulation.

 

[wwhitney]

3. Existing ceiling, wall or floor cavities exposed
during construction, provided that these cavities
are filled with insulation.

Does that mean "filled with insulation" at the time of exposure, or "filled with insulation" before closing them up? Because the OP said there's no existing insulation.

Cheers, Wayne

 

[classicT]

Does that mean "filled with insulation" at the time of exposure, or "filled with insulation" before closing them up? Because the OP said there's no existing insulation.

Cheers, Wayne

In the full context of the section, it means that you are not required to insulate to the current code requirements where you will fill the existing wall cavity completely with insulation. Basically, insulate to the maximum extent possible without reframing the wall.

2021 IECC R503.1.1 Building Envelope​

Building envelope assemblies that are part of the alteration shall comply with Section R402.1.2 or R402.1.3, Sections R402.2.1 through R402.2.12, R402.3.1, R402.3.2, R402.4.3 and R402.4.5.

Exception: The following alterations shall not be required to comply with the requirements for new construction provided that the energy use of the building is not increased:

1. Storm windows installed over existing fenestration.
2. Existing ceiling, wall or floor cavities exposed during construction provided that these cavities are filled with insulation.
3. Construction where the existing roof, wall or floor cavity is not exposed.
4. Roof recover.
5. Roofs without insulation in the cavity and where the sheathing or insulation is exposed during reroofing shall be insulated either above or below the sheathing.
6. Surface-applied window film installed on existing single pane fenestration assemblies to reduce solar heat gain provided that the code does not require the glazing or fenestration assembly to be replaced.

 

[steveray]

Basically, insulate to the maximum extent possible without reframing the wall.

I do not agree with that....That would require foam....fill the cavity means just that...Fill the cavity with some insulation...

 

[classicT]

I do not agree with that....That would require foam....fill the cavity means just that...Fill the cavity with some insulation...

You don't agree with your interpretation of what I said. You presumed I meant with the highest R-value insulation possible. That was not my intent - besides, foam would not be the best insulation by R-value. Could use aerogel, right?

But yes, the intent of the code is to fill the cavity with conventional insulation (fiberglass batt).

 

[steveray]

I was going to make a joke about whatever they insulate the space shuttle with instead of foam, but....Agreed...

 

[tmurray]

We are talking about the highest insulation possible, but what about the other direction. Technically, air has an insulation value, so there is no such thing as an uninsulated cavity. So, they could "leave the insulation intact" by not insulating the space. Certainly not keeping with the spirit of the code, but technically correct.

And as we all know, being technically correct is the best kind of correct.