Skip to main content
Home Improvement

Return to Question

Post Reopened by FreeMan, Rohit Gupta, ThreePhaseEel
deleted 385 characters in body
Added to review
Source Link
David Levner
David Levner
  • 225
  • 2
  • 5

I am asking this question because the addition to our house failed the first inspection because the inspector found some voids in the insulation. The company that provided the insulation (closed-cell foam) filled the voids and added more insulation in other places. However,Suppose there is no way to make all the foam exactly the same thickness.

In case the inspector wants to fail us on the re-inspection, I want to be able to give him a polite argument. I want to say that a small portion of a surface that has less than the required depth of foam doesn't matter if most of the surface has more than the required depth.

Here is a very simple question that, if I am correct, will give me the confidence I need to have a discussion with the inspector:

Suppose I have a wall and half of whichits area has R-value 10, and the other half has R-value 20, is. Is the total R-value of the wall 15? I think so but this is pretty new to me. Please tell me whether or not it is valid to average theIn other words, can R-values (weightedbe averaged weighted by area)?

Please justify your answer with math. R-value is defined as follows on page 454 of the 2020 Residential Code of NY State.

R-VALUE (THERMAL RESISTANCE). The inverse of the time rate of heat flow through a body from one of its bounding surfaces to the other surface for a unit temperature difference between the two surfaces, under steady state conditions, per unit area (h • ft2 • °F/Btu) [(m2 • K)/W].

I am asking this question because the addition to our house failed the first inspection because the inspector found some voids in the insulation. The company that provided the insulation (closed-cell foam) filled the voids and added more insulation in other places. However, there is no way to make all the foam exactly the same thickness.

In case the inspector wants to fail us on the re-inspection, I want to be able to give him a polite argument. I want to say that a small portion of a surface that has less than the required depth of foam doesn't matter if most of the surface has more than the required depth.

Here is a very simple question that, if I am correct, will give me the confidence I need to have a discussion with the inspector:

Suppose I have a wall half of which has R-value 10 and the other half R-value 20, is the total R-value of the wall 15? I think so but this is pretty new to me. Please tell me whether or not it is valid to average the R-values (weighted by area).

Suppose there is a wall and half of its area has R-value 10, and the other half has R-value 20. Is the total R-value of the wall 15? In other words, can R-values be averaged weighted by area?

Please justify your answer with math. R-value is defined as follows on page 454 of the 2020 Residential Code of NY State.

R-VALUE (THERMAL RESISTANCE). The inverse of the time rate of heat flow through a body from one of its bounding surfaces to the other surface for a unit temperature difference between the two surfaces, under steady state conditions, per unit area (h • ft2 • °F/Btu) [(m2 • K)/W].

Post Closed as "Opinion-based" by isherwood, FreeMan, Fredric Shope
Source Link
David Levner
David Levner
  • 225
  • 2
  • 5

Can R values be averaged?

I am asking this question because the addition to our house failed the first inspection because the inspector found some voids in the insulation. The company that provided the insulation (closed-cell foam) filled the voids and added more insulation in other places. However, there is no way to make all the foam exactly the same thickness.

In case the inspector wants to fail us on the re-inspection, I want to be able to give him a polite argument. I want to say that a small portion of a surface that has less than the required depth of foam doesn't matter if most of the surface has more than the required depth.

Here is a very simple question that, if I am correct, will give me the confidence I need to have a discussion with the inspector:

Suppose I have a wall half of which has R-value 10 and the other half R-value 20, is the total R-value of the wall 15? I think so but this is pretty new to me. Please tell me whether or not it is valid to average the R-values (weighted by area).