Insulated Vinyl Siding vs Non-insulated Vinyl Siding

Hi Carl,

Thanks for the knowledge on byoh. My question concerns vinyl siding.

My house has a stucco front and three sides of inexpensive vinyl siding over black paper.

The vinyl siding is only 10 years old but has no insulation between it and the OSB (Oriented strand board, also known as wafer board)

Will I gain much by redoing the siding and adding XPS (XPS = Extruded Polystyrene foam) or siding that already has built-in insulation?

If so, does it also need a vapor barrier (i.e. Tyvek)?

I had two CertainTeed recommended contractors give me conflicting advice:

The first said to go with Tyvek and the insulated siding, while the second recommended Tyvek, XPS and uninsulated vinyl siding.

The second recommendation has me concerned about trapping moisture.

Of course, I do not want to make the expenditure if the project won't yield the
desired result.

Thanks in advance.
Laurence C.


Hi Laurence,

I assume that the gain you are looking for or the desired result is saving money through energy savings.


Images and Insulated Vinyl Video courtesy of The Michigan Bureau of Construction Codes.
Insulated Vinyl Video

If the vinyl siding on your house is in good shape (no dents, tears, or fading), I seriously doubt that you’ll gain much by spending the money to replace it, certainly not by adding the small amount of exterior insulation that using insulated vinyl siding or XPS and non-insulated vinyl siding will give you.

Talk with your local utility company that provides your energy for heating. They should be able to calculate the “heat loss/gain” differential between insulated vinyl siding and the non-insulated vinyl you currently have now. The same analysis for your second contractor’s method can be calculated and compared too.

In the pecking order of heat loss/gain, the walls are number 3.
Exterior doors and windows are number 2.
Ceilings are number 1.
So, if the energy savings doesn’t pay for the siding replacement in ten years, I say forget it.

On my web page Insulated Vinyl Siding with Videos you can find the advantages of insulated vinyl siding. They are:
  • Better insulation.
  • Improved appearance and durability.
  • Easy installation
The good news is that although the solid core siding systems ($181/sf) cost 30 percent more than conventional vinyl siding ($141/sf), that's about the same as vinyl siding over 3/4 foam sheathing (R-4) ($189/sf)! (Source: NAHB Research Center)

Tyvek with the second contractor’s method is, in my opinion overkill, as the XPS alone should be sufficient.

But Tyvek breathes, so if you use it along with XPS it shouldn’t create any moisture problems.

For an excellent source on understanding the need for controlling moisture read:
Understanding Vapor Barriers from building science.com

Good luck,
Carl Heldmann, byoh.com