Replacing batt insulation between rafters.

[BayPointArchitect]

Given:
2018 IECC and project is located in climate zone 5A.
Minor remodel to an existing three story apartment building. It is non-substantial because the cost of the remodel ($20,000) is less than 50% of the overall value of the apartment building. And the energy use of the building is not being increased.
Plans were thoroughly review and approved during the permit application process.
The building inspector sees that the building owner is removing the old R13 batt insulation and replacing it with new R13 batt insulation.

Question:
Section C503 states that existing ceiling cavity need not comply with the requirements of new construction provided that these cavities are filled with insulation. Is it acceptable for the new insulation to be equal to the existing insulation but less than the prescribed value of R38?

As always, thanks in advance.

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

 

[Keystone]

I’d ask what level of renovation.

If the insulation is being replaced and the space permits additional depth, I’d also be inclined to state yes it shall comply.

 

[Mr. Inspector]

Question:
Section C503 states that existing ceiling cavity need not comply with the requirements of new construction provided that these cavities are filled with insulation. Is it acceptable for the new insulation to be equal to the existing insulation but less than the prescribed value of R38?

NO

 

[ICE]

No

 

[Genduct]

You removed and replaced but couldn't ADD to the existing? SO you don't have the additional cavity depth?

 

[Paul Sweet]

If it is a flat roof there needs to be a 2" air space above the insulation.

 

[steveray]

Roof/ceiling gets tough as there is typically room to add, were the cavities exposed?

Exception: The following alterations need not comply
with the requirements for new construction, provided 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 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.
4. Construction where the existing roof, wall or floor
cavity is not exposed.


If they were not exposed AND the energy is not increased, no upgrade required....

 

[e hilton]

Most of the cost is the labor, which they are already spending. Should have been a very minor upcharge to increase the insulation.

Looking at home depot, r13 is $0.44/sf and r38 is $1.59. You’re saying they couldn’t afford $1/sf more?

 

[steveray]

Most of the cost is the labor, which they are already spending. Should have been a very minor upcharge to increase the insulation.

Looking at home depot, r13 is $0.44/sf and r38 is $1.59. You’re saying they couldn’t afford $1/sf more?

I'd say a 200% increase is a lot more....

 

[redeyedfly]

I'd say a 200% increase is a lot more....

261%!!

 

[steveray]

I hate math...especially when I am not getting paid for it....

 

[bill1952]

.

I'd say a 200% increase is a lot more....

And 5% of the total project cost. Seems significant.

 

[ICE]

I'd say a 200% increase is a lot more....

You have to pay to play.

 

[e hilton]

I'd say a 200% increase is a lot more....

Maybe, in that context. But we don’t know the total sf involved, or the project budget.

 

[bill1952]

Maybe, in that context. But we don’t know the total sf involved, or the project budget.

the project budget was in the first post - $20,000

 

[e hilton]

the project budget was in the first post - $20,000

That was 4 days ago.
Why was the old insulation removed? Why not add another layer of r13?

 

[bill1952]

That was 4 days ago.
Why was the old insulation removed? Why not add another layer of r13?

I don't know there is room for another batt and that doesn't answer the question of prescribed R38.

 

[e hilton]

and that doesn't answer the question of prescribed R38.

No, but 2 layers of r13 would be easier to approve than one layer, if it’s not going to be r38.

 

[bill1952]

No, but 2 layers of r13 would be easier to approve than one layer, if it’s not going to be r38.

if they fit

 

[e hilton]

if they fit

Given what we know … it probably does. We don’t know if the roof rafters are bound on the bottom by sheetrock and on the top by roof sheathing. So i’m assuming there is some amount of attic space.

 

[ICE]

Cathedral batt insulation gets it up to R30.

 

[Paul Sweet]

"Cathedral batt insulation gets it up to R30."

But you need 2 x 12 joists or rafters (and probably add baffles) to get the necessary air space if there is no attic space.

 

[bill1952]

Seems like we need joist size and if flat roof on them or attic space.

 

[ICE]

Seems like we need joist size and if flat roof on them or attic space.

Well here's the thing about that....if there is no room for anything other than R13, I'd say that the discussion was over before it got started.