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Vinyl Siding

William Kibbel III, The Home Inspector

Our home has beveled wood siding on the 1850s section and on the mid 1900s addition. We are considering vinyl siding to reduce maintenance costs. I've done some research and found that insulation board can be installed behind the vinyl to reduce heating costs. Wouldn't these benefits outweigh the concern of it not being a "period material?"

To answer that question objectively, I'll need to suppress my own opinions about vinyl siding.

Well I tried and that's not going to happen. I don't like vinyl siding. I hate to see it on an old building. I don't even like it on new buildings. It's supposed to imitate wood, but I have never, ever said, "Wow, it looks so much like wood."


Although some manufacturers have recently developed a few profiles and textures that more closely replicate some old siding styles, the details of installation usually give it away.

  • Every panel of the average vinyl siding material imitates two panels of wood siding, creating double vertical seams.
  • "J-channel" trim is used at joints with other materials or surfaces and projections like window and door frames.
  • The original wide wood outside corner trim is replaced by a narrow, projecting corner post.
  • When the material contracts in cold weather, it exposes the un-faded color at the joints.
  • The extra siding layer now extends beyond window and door frames.
  • Original details, mouldings and trim are often altered or completely hacked-off to reduce the time, cost and skill needed to install vinyl siding.


The Vinyl Siding Institute's installation manual states, right at the beginning, "Vinyl siding has always been designed as an exterior cladding, not a weather resistant barrier." I interpreted this as meaning that vinyl siding leaks. The manual went on to state, "To achieve designed performance, vinyl siding must be installed over a weather resistant barrier". I guess I'm kind of old fashioned. I prefer exterior coverings that are designed and installed to keep the water out -- without relying on a concealed extra "skin."

Vinyl siding alone offers very little improvement to reducing heat loss. Adding rigid foam insulation board under the siding typically only provides an R-value of 4-7 per inch (in laboratory conditions), with some types of foam losing some of that value as they age. Unless you are adding several inches of rigid foam (creating cavernous window and door openings), the savings won't justify re-siding a home. It is well documented that the most cost-effective way to improve thermal performance is to add insulation to your attic, where up to 75% of your heat is lost. And seal those drafts.


The big claim for the advantage of installing vinyl is that it will last forever. I've seen wood siding documented to be over 350 years old. I've also seen 15-20 year old vinyl siding. The color is often severely faded. It's common to see ripples and bulges on large wall surfaces. It also can get brittle, being exposed to temperature extremes and UV, resulting in cracks, holes and damage from tree branches and the weed trimmer. After a severe weather event, like high winds, guess which exterior cladding is littered throughout the neighborhood. Here's a hint -- it's the stuff that can't be nailed tight to a house because it needs to be allowed to expand and contract. Have you ever seen individual panels that have been replaced? You can't miss them because they don't come close to matching the original, even if they're only a few years old.

So what do homeowners do when it looks awful? They paint it. It's not easy, the paint has to have the same rate of expansion and contraction as the vinyl. Paint it a darker color and it really heats up. Some manufacturers void the warranty if the siding has been painted. Deciding to paint, rather than replace the vinyl also initiates a cyclical maintenance project that was supposed to be avoided in the first place.

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