Is the rigid foam board under vinyl siding really insulating your home?

By Kim Cox:

Before I answer this question, let me give you a little background on vinyl siding installation in our area.

As you know, here in Maryland, temperatures can fluctuate a lot, no matter what season it is.

And vinyl, by virtue of its composition… expands and contracts with changing temperature. That’s what vinyl does. So if it’s not installed correctly to allow for expansion and contraction, it warps, twists, and maybe even breaks.

If it’s attached to the home incorrectly, without proper backing, it will appear all wavy… looking more like a curvy mountain road than a straight wall. It ain’t pretty.

So there are some guidelines that professional vinyl siding contractors follow to make it look great, and prevent your brand new siding from getting damaged from the elements.

First…You must correctly nail the siding to the house (a little loose), so the siding can move a little when it’s supposed to. (no worries… your siding will stay attached)

Another biggie is to use the right backing material behind the siding.

The correct method uses rigid foam board to lend support to the vinyl siding and keep everything nice and straight. Because think about it, if you’re covering old clapboards or shingles with new siding… It sure isn’t flat, is it?

CertainTeed vinyl siding makes this house look great!

CertainTeed vinyl siding with the correct rigid foam board backer makes this house look great!

But herein lies the problem... If they use a backer board at all, contractors will often call it, and sell it, as insulation board. This is misnomer, and some will even claim it helps with overall energy efficiency.

You see… In reality, rigid foam board (which sometimes comes in fanfold) usually only has an insulating factor of R-1, and DOES NOT add any appreciable insulation effect to your home.

And even though some manufacturers call it rigid foam insulation (for the purpose of vinyl siding), it  basically has the same insulating value as a piece of plywood.

All it does is give you a flat, smooth surface to properly nail your vinyl siding onto. That’s it!

So if you’re comparing proposals to install new vinyl siding on your home, please be aware of this important fact.

An honest, professional vinyl siding contractor will tell you exactly what you’re getting.

There are “insulated” rigid foam products  that will increase the insulation factor, but you’ll pay much more for R-5 to R-7.

I just want you to know the difference so you can compare apples to apples when getting quotes for vinyl siding.

Whether your home is in Frederick, or Silver Spring, over to Columbia, Maryland, or any community in between, we can help!

To get your free, no-obligation vinyl siding quote, or
to ask a question, call Kim at 301-368-3551

On Top Home Improvements, Inc.
10818 Avonlea Ridge Place
Damascus, MD 20872
Tel: 301-368-3551
Click to E-mail

Posted in Siding

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