vinyl siding project

Old 03-07-19, 04:18 PM
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vinyl siding project

I was hoping to get some opinions on a little siding project on my home I am getting ready to hire out.

Where: Oklahoma
House Type: brick home with steps in the roof sided with old hardboard.
Project: replace all of the "wood" siding with vinyl. About 61 square feet.
these areas all have livable space on the other side of the wall (it is a loft area in the home).

the contractor wants to use 1/4" fan fold insulation (below is a link) directly over OSB, and no house wrap.

Is there a need for house wrap in this climate?
Is 1/4" fan fold insulation enough insulation?

It is the first (1/4") in the following brochure:

Thanks for your time!

Last edited by PJmax; 03-07-19 at 04:38 PM. Reason: rewrote link
Old 03-07-19, 08:08 PM
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61 sq ft, huh? So a 6.1 ft x 10ft area? Guess I haven't seen steps in a roof, so not sure what you are trying to describe. Are you talking about dormers?

2 things. First, according to the brochure, their 1/4" fanfold is not specifically listed as a WRB... but the 3/8" and 1/2" are. The seams would all have to be taped, and from my experience the tape does not stick for long. Any leaks will leave the OSB unprotected. I would not recommend having fanfold as your only WRB.

Secondly, fanfold's main purpose is not for its R-value. Fanfold it typically used over the top of existing clapboard siding to give you a flat surface to nail the vinyl siding to. It also isn't air tight... so if wind can blow behind it, that kind of negates part of it's "advertised" r-value. You would never use fanfold if you want more R-value. For that, you would use 4x8 sheets of rigid foam.

A WRB is required by all building codes, so you need something. If you aren't concerned about r-value, forget the fanfold and use housewrap as the main WRB to protect the sheathing. If you want better insulation, forget the fanfold and use thicker foam. If you want a cushion behind the siding, put up EPS foam sheets over your WRB. But IMO fanfold would make a poor WRB... and that "assumes" they follow the instructions to tape seams, and that they use the right kind of tape, and that the tape will stick for more than a few minutes/days/weeks/years.
Old 03-08-19, 10:06 AM
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thanks for the reply, sorry I wasn't very clear on the areas to be sided. Yes, one area is a dormer, the other 2 areas are where the roof steps up. There is an elevation change in the roof plane, creating a sidewall, a picture would help, but point is, it needs siding.
Since they are small areas, one piece of fanfold will cover each spot eliminating seams. Unless, the folds themselves are considered seams?
Thank you

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