Insulate Under Vinyl Siding?

Do You Need to Insulate Under Vinyl Siding or Should you Install Insulated Vinyl Siding?


Re-siding your home? You may have considered vinyl siding, but have you considered using insulated vinyl siding or insulated foam sheeting underneath a standard vinyl siding? Fact is, standard vinyl siding is engineered to be more of a cladding than an insulating barrier. That said, it has a lot of advantages over other siding materials, including that it’s low maintenance, which is especially appealing to a busy homeowner or one who doesn’t have a budget for repainting or staining wood siding. The downside to vinyl is that it doesn’t have the same thermal properties that wood or other most other materials might. There are two ways to go when insulating: add insulated sheathing beneath the siding job or purchase and install insulated siding. There are numerous options for vinyl siding profiles, but many reasons you might want to upgrade to insulated siding.

Some vinyl profiles lose their shape with age and heat, which can lead to waves in the siding and other imperfections. Insulated siding fills the voids in the profile, offering a stiffer, more uniform appearance. Non-insulated vinyl siding will structurally benefit from insulated backers as they level out imperfections and add support to the panels.

The obvious reason to use insulation is that it reduces heat loss and lowers your heating bills. Much of the heat lost in a home is due to gaps between the studs and pink fiberglass insulation. Many older homes have no insulation, which means even greater heat loss. Rigid, foam-backed siding reduces thermal bridging which can add R2-R2.7 value to your home’s insulation rating, depending on the brand you buy (source: Some insulated siding can even qualify your home for an energy star rating. Insulated vinyl siding adds about 11% more airtightness to your home, which could save you 1-11% in utility bills.

Insulated vinyl siding can increase the ROI on your home because it’s low maintenance, doesn’t require painting or caulking, and increases the energy efficiency of your home. It has a longer life expectancy than products like fiber cement siding (or poorly-maintained wood, which will degrade rapidly without frequent repainting/finishing). Vinyl siding will not incur water damage, and it helps your home breathe because it doesn’t trap it.

If you are trying to decide between using foam sheeting (plus WRB wrapping) or insulated vinyl siding, be sure to discuss the R values with your contractor. Some will use R-1 rated foam, which doesn’t add a lot of insulation to your home (although it will provide structural support to your siding and a moisture barrier when properly wrapped). The higher-R-rated sheets cost considerably more. Make sure you know what the contractor is putting on your home and what your added R value will be. *Note that you can opt for both insulated siding AND foam sheeting, and some codes may even require you to use the sheeting as it provides a water barrier, which prevents rotting and mildew. Be sure that your contractor knows about codes in your area when applying foam and WRB. Most new homes are now built using the sheeting and WRB..

Another benefit of insulation is that it reduces noise. If you live near a highway or on a busy road, this would be a desirable addition to your home project. Insulated siding is more expensive than standard but, in most cases, it does hold it’s shape better than other profiles and that might justify the higher cost. Be sure when you're making upgrade decisions to get real samples from your contractor and check out our other article on vinyl vs. wood siding.

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