Insulated Vinyl Siding: Is It Worth the Cost?

In This Guide

• Performance Studies
• Modest Increase in R-value
• Drying Capacity
• Considerably More Expensive
• Cost of Insulated Vinyl Siding
• Benefits

Insulated vinyl was first introduced to the market in 1997. It was an immediate hit, and has grown in popularity over the last 20 years. This type of siding is made of vinyl panels that have been laminated with foam-core backing.

The result is a reinforced panel of siding that looks straighter after it is installed. It is also more resistant to environmental hazards such as hail, ice and baseballs. The insulation bonded to the vinyl, or installed on the house beneath the siding, is commonly called expanded polystyrene (EPS).

As with other insulation, insulated panels are given an R-value which ranges from R2 to R5. Besides thermal protection for the underlying structure, insulated panels offer significant noise reduction. With these benefits, it’s no surprise that insulated siding has received more attention from homeowners and builders as the importance of energy efficiency has grown.

In this guide, we will answer the following questions that we are frequently asked:

• Will insulated planks make my house more airtight?
• Will the EPS serve as a thermal break for my house?
• How does EPS affect moisture on wood-framed houses?

Performance Studies

There have been two recent well-publicized studies of the movement of heat and moisture through buildings with insulated siding:

In 2010, ASHRAE published a paper regarding the moisture performance report on wood-framed structures with various cladding systems.

In 2013, Newport Ventures published a performance study on the energy savings of insulated siding.

One of the most glaring faults of insulated siding is that the EPS is not airtight. Siding is designed to interlock and provide enough space behind the strips to allow ventilation and moisture drainage. The insulated strips interfere with both of those functions.

Another obvious shortcoming is that the R value is only 2 to 2.7. This brings into question whether the increased cost of insulated siding is really worth the investment.

Modest Increase in R-value

This modest increase in R value might be helpful for houses with absolutely no insulation in the exterior walls may find minimal benefit. The studies mentioned above involved 5 different products installed in 5 single-family houses. The study spanned 5 cities and 3 climate zones.

They studied the following effects of installation of insulated siding, including:

• An improvement in the R-value of the outside walls
• Any decreases in thermal bridging
• Improvement in airtightness

The results of these studies proved that there was a moderate increase in R-value of R-2 to R-2.7. The use of thermal imaging assessed a slight reduction in thermal bridging. This is the loss of indoor temperatures to the outdoors and extreme outdoor temperatures affecting the temperature indoors.

Overall airtightness increased by 11%. The savings in utility bills delivered the more extreme results: In Indiana, homeowners saved about 1% on their utility bills, while in Colorado, they saved 11%.

The overall conclusion here is that insulated siding offers modest improvements when installed on existing homes.

Some industry experts are requesting that the Vinyl Siding Institute conduct similar experiments in both pressurized and depressurized conditions. Pressurizing involves pushing the siding out, away from the wall assembly.

The air tightness of the house could then be compared with depressurized conditions, in which air is pulled out of the void between the siding and the structure.

Drying Capacity

The NAHB Research Center conducted a study over a period of nearly 2 years. Their test field was in Maryland, which has a mixture of humidity. The goal of their tests was to compare the sheathing moisture in various structural claddings, including:

• Vinyl siding
• Brick
• Insulated siding
• Stucco

To conduct this study, the Center selected the month of August to do their experiments – a time of heat, varying humidity, and occasional severe rains. They injected water into the sheathing layer of various structures with the objective of simulating leaking that may happen with a storm that occurs over several days.

The results were encouraging to proponents of vinyl. Both conventional and insulated vinyl had the best drying capacity. The insulated version registered the lowest moisture content in normal conditions, and the conventional vinyl had the best results during the injection testing.

Experts think that the reason it dried out so much more quickly in ordinary circumstances is because of the warmth of the wall cavity behind the insulation.

Many who were involved in the study were surprised that the insulated siding dried quicker. Most had assumed that by filling much of the free-draining space behind the siding, the convective drying effect between the siding and the wall would be reduced. However, the results were the opposite, even with much of that space taken up with EPS.

It could be that the mild climate conditions affected some of the results. Some people want to see more experiments done with different of wall structures in harsher climates.

Considerably More Expensive

The benefits may be arguable, as far as R-values go. However, few will disagree that the insulation makes the vinyl planks more rigid and robust.

Regardless of the pros and cons of this product, the cost is often considered to be prohibitive. The siding material alone is roughly 50% more expensive, while the finishing pieces and trim is about 20% more expensive.

Cost of Insulated Vinyl Siding

The cost is heavily influenced by the brand, profile, style and color you select. It costs between $3 and $6 per square foot for materials and labor.

Benefits

• Improves the look and durability of traditional vinyl.
• Siding is more impact-resistant when strengthened with EPS.
• You don’t always have to get vinyl with EPS laminated onto it. You can find insulation foam, such as Thermowall, that can be used as underlayment.
• Some manufacturers offer insulated vinyl that provides some permeability for vapor. This allows the siding to “breathe.”
• Since these vinyl strips are somewhat reinforced with the EPS, they can sometimes be installed over existing siding.
• If you have irregularities in your exterior wall, the insulated planks can cover the problems, creating a solid look.
• Some manufacturers provide larger sections, which makes installation faster. It also reduces installation cost.
• There are specially manufactured sections that you can use on windows, door frames, and other corners.
• It has a noise-dampening effect for people in the house.
• This siding is more resilient to hail and other extremes of weather, as well as impact from other forces.
• It is easier to replace an insulated panel if it becomes damaged.
• The insulation reduces problems with seams and gaps, keeping the material from shrinking as badly.
• EPS does not absorb moisture.
• The product is about 40% longer, so there are fewer seams.
• You may be able to get energy tax credits for using this product.
• This insulated product is quicker to install than other drop-in foam products
• Some parts of the country report energy savings.

Conclusion

Considering that there are health concerns regarding the use of PVC in home construction, insulated siding, while growing in popularity, is still not the siding of choice of most contractors or homeowners.

In addition to the effects of PVC, EPS uses flame retardants, which also contain chemicals that most people would rather avoid in construction. In our opinion, there is not enough evidence that the benefits provided by this siding outweigh the potential problems.

Contractors often recommend a full energy retrofit, which would provide better airtightness and R value for the money.

What to Read Next

• Types of Vinyl Siding: 8 Styles to Choose From
• Best Vinyl Siding & Top Brands
• 8 Best Siding Options + Pros & Cons

Over to You

Have you had insulated siding installed? Have a quote for a project and not sure if it’s too high?

We would love to hear from you! Please leave a comment below on your experiences.