Fifty-some years after it was introduced, vinyl siding
accounts for about one-third of all sales of residential
siding, outpacing every other exterior cladding. The
product’s minimal maintenance requirements and durability
are certainly attractive to homeowners, but its popularity is
probably best understood in terms of price. Hands down,
standard-grade vinyl siding has the lowest installed cost per
square — about 28 percent lower than that of either fiber
cement or wood.
The flip side of costing less, however, is the accompanying
stigma of being, well, cheap. Some consider the material
insubstantial and flimsy-looking. And while that perception can
partly be blamed on poor installation practices, it’s
also true that there have been problems with the product itself
— namely a tendency to yellow, fade, and chalk over time.
To their credit, vinyl-siding manufacturers have spent the last
decade addressing these issues, and as a result there are now a
good number of high-quality, high-performing siding lines on
the market, with far more color and style options than ever
before. Moreover, major manufacturers are arguing that vinyl
siding is a green building material — perhaps even the
greenest of all siding options.
All of which raises a couple of questions: First, is vinyl
siding a convincing substitute for the more traditional and
costlier siding materials it mimics? And second, does it have a
place in sustainable — or green — projects?
Composition
PVC (polyvinyl chloride) resin, the main component in vinyl
siding, is derived from two basic ingredients — calcium
chloride (salt) and ethylene (natural gas) — combined in
a polymerization reaction. PVC contains smaller amounts of
other ingredients as well, such as calcium carbonate (used as a
dimensional stabilizer) — but it does not contain
phthalates (a plasticizer) or lead, as many people believe (see
“Is Vinyl Siding Green?,” below).
All vinyl siding consists of two layers — a relatively
thick substrate and a far thinner capstock, typically .005 mils
to .008 mils thick — heat-fused together. They’re
produced by forcing the PVC resin — in powdered form
— through extruders. Final siding thickness ranges from
.040 mils in the entry-level product up to .050 mils in premium
lines. Generally, the thicker the product, the more rigid and
stable it is and the higher its impact resistance. Most
professional installers won’t recommend anything below a
.042 product.
The capstock contains various ingredients that the substrate
does not, including titanium dioxide — a UV inhibitor
used in many weatherable products — and pigments to
produce the surface color. Vinyl waste produced during the
manufacturing process is routinely ground to powder and
returned to the substrate mix. In the least expensive lines
— the thinnest, .040 mil entry-level products —
carbon black pigment may be used to produce a uniformly colored
substrate called grayback. Costlier grades avoid using grayback
because it shows through scratches in the capstock. A better
way to achieve color consistency — and the approach taken
by almost all premium siding lines — is for the substrate
to be pigmented to match the capstock.
Polypropylene. In recent years, cedar-shake,
decorative-shingle, and even stone profiles have joined the
plastic-siding stable (see Figure 1). Unlike
plank-style siding, these profiles are made not from PVC but
from much thicker, solid-color, injection-molded polypropylene.
Polypropylene — a thermoplastic polymer — is
durable, impact-resistant, and versatile. Identified as a #5 in
plastic recycling programs (PVC is a #3), it is commonly used
to make bottle caps and large molded parts for automobiles. As
with PVC, post-consumer polypropylene is not widely
recycled.
Figure 1. With injection-molded polypropylene —
which takes on just about any shape — manufacturers can
reproduce stone and wood siding textures more convincingly than
ever before. Crane’s Bellastone (left) has real stone
grit embedded in its surface. Cedar-shingle profiles are
popular in the Northeast in full-coverage applications
(middle), while decorative shingles can be found anywhere
(right).
Color
Until relatively recently, homeowners who wanted barn red,
forest green, ocean blue, or any other dark-hued siding
weren’t looking at vinyl. Problems with unacceptable
color fading dictated a limited palette of whites and pale
tints. But manufacturers discovered that using various acrylic
formulations in the capstock — rather than PVC —
made it possible to offer a much broader spectrum
(Figure 2). Today, almost any color goes, even
custom shades. For instance, Ply Gem sells more than 700 hues,
with custom color matching available for a $75 swatch charge.
Darker colors do come at a premium, though: They cost about 30
percent more than conventional, pale-hued PVC capstocks.
Figure 2. Acrylic capstocks resist the fading
problems long associated with vinyl siding, allowing darker
colors to be produced. Hundreds of shades are now available,
including Royal Building Product’s Rustic Red (left) and
Country Green (right).
Virtual preview. Several manufacturers offer online
color-visualization programs, which allow homeowners to model
various trim and siding color combinations on different styles
of homes. This is a useful, even critical tool when choosing
vinyl siding, especially considering the product’s
durability and the likelihood of living with the final
selection for 30 years or more.
Certified color standards. With colors being
developed so rapidly, many shades haven’t yet stood the
test of time against fading. In 2006, the Vinyl Siding
Institute (VSI) expanded its certification program for vinyl
siding to include color retention; currently about 350 shades
are listed. Colors continue to be added as they successfully
complete the two-year outdoor accelerated testing, which uses
the ASTM color retention standard for plastic siding. Certified
colors are identified by specific package labeling and can also
be reviewed online at vinylsiding.org.
As a relatively new exterior cladding, polypropylene siding
has not yet achieved PVC siding’s certified-product
status. According to VSI technical director Dave Johnston, a
certification program for the polypropylene product is in the
works. “Plans call for holding off on applying the
color-retention certification until the basic product
certification is in place,” he says. “ASTM D6864
[the standard for color retention] includes
‘plastic’ siding within its scope, but we want to
study its applicability to polypropylene before going
further.”
Lower luster. For many homeowners, one of vinyl
siding’s less desirable characteristics is its telltale
plastic shine. But over the past decade or so, manufacturers
have modified the capstock formulations in their product lines
to minimize the objectionable sheen. “We’ve been
able to dial down the gloss a little bit more than in the past,
to give it a more fresh-painted look,” says Ply Gem
marketing VP Jerry Blais.
Embossing — an attempt to break up the sheen with a
wood-grain effect — has also improved. Baltimore
specialty remodeling contractor Bert Labhar insists that
Crane’s “triple-6 and double-7 inch profiles really
and truly look like cedar.” And indeed, with imprints
taken from actual cedar boards, many of these textures are
quite convincing. However, since it effectively thins the
material, embossing can degrade the impact resistance of the
siding, so it’s best to choose a thicker (read costlier)
product if the homeowner wants a wood-grain look.
Insulated Siding
Contoured EPS foam backers for vinyl siding were first
introduced about 10 years ago, pioneered by Vipco (now called
Crane) in cooperation with Progressive Foam Technologies
(800/860-3626,
fullback.com). With a
flat back and a profiled face designed to fit snugly behind the
vinyl profile, foam backer lends the siding a firmer feel.
“One of the things people tend not to like about vinyl
siding is that it doesn’t feel very rigid,” notes
Ply Gem’s Blais. “Foam gives it what we call
knockability — you can touch it and it feels firm and
substantial. It helps a lot.”
Most manufacturers have started offering a premium, composite
siding product — a distinct category identified as
insulated siding — with foam integrally bonded to the
vinyl (Figure 3). Progressive also offers a
field-applied “drop-in” product it calls the
Fullback Thermal Support System. With nearly 800 distinct
profiles available, it can be fit behind every lap siding
profile on the market — and it qualifies for the current
25C tax credit of up to $1,500. In either approach, contoured
insulation adds an estimated 30 percent to the cost of a
typical siding job.
Figure 3. In addition to adding R-value, solid EPS
foam backing gives vinyl siding a feeling of solidity.
Integral, composite products like the Alside samples shown here
offer one-step installation; another option is to use
“drop-in” foam backer, which is available for
nearly every siding product on the market.
Insulated siding products offer a couple of advantages over
standard hollow-back panels, namely easier handling and faster
installation — primarily because they eliminate the need
for a foam underlayment. Also, laminating foam to vinyl
profiles allows manufacturers to produce vinyl profiles with
larger, flatter faces — 6 to 9 inches wide — that
would otherwise lack sufficient rigidity (Figure
4).
Figure 4. The foam backer on Royal’s reinforced
siding (left) is heavily contoured to optimize ventilation.
Crane’s insulated siding (right) has a ribbed profile
that directs moisture to engineered venting slots .
Impact resistance. Errant baseballs and stones thrown
by lawn mowers can result in cracked or punctured siding.
(It’s a good idea to order a little extra siding and
store it for incidental repairs, since matching siding may be
difficult to find later on.) Foam backer helps in this regard,
too, because it improves impact resistance. Testing shows that,
when insulated, a previously hollow-back product’s impact
rating jumps from 60 to 90 psi to 160 to 340 psi.
R-value. Originally, insulated siding R-values were
determined using the ASTM “guarded hot box” test,
an apparatus used to measure the thermal conductivity of
full-size materials or assemblies. But testing a multitude of
panel profiles was expensive and time-consuming, so
manufacturers now rely on a computer simulation of the hot-box
method to rate new profiles. While the resulting R-values are
fairly reliable, VSI is currently spearheading an effort to
develop an ASTM standard specification for all products
designated “insulated vinyl siding.” The objective
is to establish a verifiable minimum baseline R-value
(tentatively R-2) and thereby gain building-code recognition
for insulated siding as a distinct insulating product.
As to how the varying thickness of a contoured profile may
affect R-value, Tim Holt, Progressive’s director of
product development and innovation, says, “If you average
the foam between the thickest and the thinnest parts and get
7/8 inch, the R-value of the foam will be consistent with
7/8-inch-thick foam.” EPS foam has an R-value of 5 per
inch.
Quieter? Finally, various manufacturers’
product literature refers to insulated siding’s
“sound-deadening” qualities, but this is neither a
scientifically verified attribute nor a claim made by
Progressive Foam for the general product.
Performance
Vinyl siding requires less maintenance than any other siding
option. An occasional wash with soap and water is all it takes
to keep the product looking good for many years.
Exactly how long vinyl will last on the wall remains
anybody’s guess. The product came into widespread use
more than 30 years ago, and much of the siding from that time
is still up and going strong. Most manufacturers estimate
service life at around 30 years. Others consider 50 years a
reasonable expectation, while a 2007 NAHB study predicts
“lifetime” durability.
Standard (noninsulated) vinyl siding is also a first-rate
rain-screen cladding, because its hollow-back format allows for
air circulation and drainage. Unlike other siding products, it
requires no strapping or other means of providing an air space
between cladding and housewrap. At this point, it’s not
clear whether adding contoured backer compromises the
siding’s ventilating performance; no independent testing
has been done in this area. However, we do know that EPS has a
relatively good permeability rating of 5 per inch, and field
studies indicate that the many seams and venting slots in the
vinyl allow water vapor to dissipate. Furthermore, the
contoured foam backing appears to reduce the amount of
wind-driven rain that typically penetrates the hollow-back
product.
Wind resistance. High wind can be an issue for vinyl
siding; storm news commonly shows vinyl panels flapping in
hurricane winds and walls stripped bare. Yet all certified
siding products meet the ASTM standard for PVC siding, which
requires products to withstand pressure equivalent to 110-mph
winds. And for certain premium grades, the wind ratings go up
to 240 mph. Given these ratings — and the generous
warranties that back many grades — it seems more likely
that blow-offs are due to poor installation practices than to
product quality.
Stray rays. PVC is inherently a fire-resistant
material; it doesn’t readily support combustion —
which is not to say it never burns. It can definitely melt
— for instance, if an outdoor grill is operated too
nearby. Also, bizarrely enough, when it’s warm on one
side of window glazing and cold on the other, low-E panes can
become distorted and concentrate reflected sunlight in beams
that raise vinyl siding’s temperature to the melting
point. Siding installed opposite east- or west-facing windows
is most vulnerable. VSI and various window makers are allegedly
discussing this problem, but so far the only solution seems to
be to ask neighbors to shade the offending glazing, or to plant
vegetation to run interference.
Installation Upgrades
As with any exterior cladding, it pays to spend a little more
for good looks, especially in an upscale neighborhood.
Specialty remodeling contractor Bert Labhar, for one, believes
that contoured backing is “100 percent the way to
go.” Skip the backing, he says, and “the job
won’t look inferior the day it’s done — but
it will within a year or two. Siding expands and contracts, it
buckles and bows, seams start to show, you get bubbles and
indentations, and pre-existing wall lines telegraph through. It
just looks cheap.”
Lap reduction. The best way to reduce or even
eliminate repetitive patterns of double- or triple-course
lapped butts — a dead giveaway that the siding
isn’t wood — is to use longer siding lengths
(Figure 5). Panels of up to 16 feet 8 inches
are sold by all major siding manufacturers and, when compared
with standard 12-foot lengths, can reduce the occurrence of lap
joints by 40 percent. Single-course planks — with 5- and
7-inch profiles — are also available; with these the
random butt patterns seen in wood or fiber-cement siding can be
mimicked even more closely.
Figure 5. Continental Manufacturing’s
foam-backed Eliminator XL siding (left) comes in 29-foot
lengths to eliminate butt laps. It installs with screws through
integral ferrules in a sliding hem designed to minimize
buckling problems (right).
J-channel. Like wood siding, vinyl expands and
contracts with temperature fluctuations, but with proper
nailing, the elongated slots in the nail hem accommodate the
movement. At window, door, and corner terminations, the siding
must be cut short by 1/4 to 3/8 inch and the ends concealed in
J-channel trim.
On some homes, this can pose a problem: Outlining every
window, door, and corner board with channel just doesn’t
look right on a traditional facade. Some historic districts
prohibit J-channel trim altogether — which is no doubt
why, when you look at vinyl-siding product brochures,
it’s conspicuously absent from most of the images.
Figure 6. Cellular PVC trim with an integral edge
channel provides an attractive — albeit pricey —
alternative to the proprietary vinyl corner trims and window
lineals offered by most siding manufacturers. Kleer
Lumber’s Konceal (left) and CertainTeed’s
Restoration Millwork (middle) are sold in paintable white. The
Foundry’s IQm trim (right) has an acrylic capstock and
comes in some truly deep shades.
Probably the most common solution is to use trim coil and
integrate the channel when cladding over the existing trim.
Dedicated trim products — window lineals and corner-post
profiles — are also available with the channel built in,
for an uncluttered, “normal” appearance
(Figure 6). Strategic shimming behind standard
trim can also create the necessary recess.
Dave Holbrook is a JLC associate editor.