Siding is a critical part of a home, and many factors go into the installation process. One aspect many forget is siding insulation. Do you need insulation under your siding? If you do, what’s the right choice for your home or business?

If you’re interested in learning more about insulation under siding, you’ve come to the right place. Read on to learn more about insulation, when you don’t need it, and the types available to you. The more prepared you are, the better your siding experience will be.

Do I Need Insulation Under My Siding?

It may seem like a pain to get insulation installed under your siding. If you have the walls, why add another layer? Aren’t the walls enough?

There are a few reasons for the insulation under siding. Here are the prominent three:

  • It increases energy efficiency
  • It provides excellent insulation
  • It makes the walls thicker

You can save money, benefit the world, and make your house solid with insulation.

Of course, you don’t need insulation if you don’t want it. However, avoiding the addition can make your home less efficient.

There is one reason why you would not need insulation under your siding.

When Do You NOT Need an Insulation Under Your Siding

Some types of vinyl siding come with insulation already installed. If this is the case with your siding, it would be a waste of money to install additional layers. It’s already part of the structure, and you don’t need to add more.

Check to see what type of siding you have on your home. If it already comes with built-in insulation, you don’t need to worry about spending additional funds on insulation under your siding. It’s already energy efficient and ready to go.

Types Of Insulation to Put Under Siding

If you want to put insulation under your siding, it’s critical to choose the right one. There are many varieties on the market. It can feel impossible to select the ideal option. Luckily, we have some recommendations for you.

Here are four types of insulation for siding:

  • Rigid-foam insulation board
  • Blow-in insulation
  • Fiberglass batting
  • Foil-backed insulation

These will serve you well.

Let’s talk more about each of these insulation options. You can use the information to determine which choice is ideal for your home.

Rigid-Foam Insulation Board 

This item is a stiff foam board. It has various materials that work well to keep the heat inside a home. It works well under multiple sidings, providing a powerful backdrop between R-1 and R-15. You can typically find these boards for about $10 per 10 square feet.


  • Generally high R-value
  • Moisture control
  • Excellent prevention against thermal bridging
  • Preventative against air leaks 


  • Can be expensive to install
  • Structurally weak
  • Requires a professional to install
  • Sensitive to any UV light exposure

Blow-In Insulation

This type of insulation is unique because it goes into the area between the siding and inside walls. It can easily reach cracks and crevices that more solid forms of insulation cannot. You can typically find blow-in insulation for about $0.44 – $1.50 per square foot of foam.


  • Fills gaps effectively 
  • Can go around wall studs
  • Many varieties are flame resistant


  • The process can be messy
  • Possibility for sag in high places
  • Causes issues when wet 

Fiberglass Batting

Fiberglass batting is a soft and flexible option that goes up before the interior walls rise. It works well with many types of sidings, including vinyl siding. Fiberglass batting typically costs $3.40 – $4.00 per ten-square-foot area.


  • Simple installation
  • Resistant to moisture
  • Renewable, can be recycled


  • Bad installation means poor efficiency
  • Hogs energy
  • Doesn’t work as well as other insulations

Foil-Backed Insulation

Foil-backed insulation is a type of insulation that works well in warm climates. The foil back reduces the heat that hits and stays in your home. It works well with wood and sidings that conduct heat. Foil-backed insulation typically costs $0.10 – $0.90 a square.


  • Effective in hotter climates
  • Lightweight and easy to handle
  • Works as a vapor barrier
  • Does not degrade over time


  • Pricier than other options
  • Must be combined with other choices in cold environments
  • Needs to be clean to work 

Do You Need Insulation If You Have an Insulated Siding?

If you have vinyl siding with insulation already inside, you don’t need to invest in additional insulation. It will cost more money, and you don’t need it unless the location you call home is below zero for most of the year. Insulated vinyl siding will do well on its own.

If you have insulated siding and notice high energy bills, you may need to add more insulation. Keep track of your costs to determine if additional insulation is necessary for your area.

What Kind of Insulation Should I Use Under Vinyl Siding?

The best type of insulation under vinyl siding seems to be foam board. With this item, you can experience an easy installation process and satisfactory insulation results once it is in place. Many foam boards are much more cost-effective than other insulation varieties on the market.

Most people use foam boards with vinyl siding. It fastens in place without much work. However, if you use it and decide you don’t like it, you can always take advantage of a different form of insulation.

Can You Install Vinyl Siding Over Rigid Insulation?

Yes, you can install vinyl siding over rigid insulation if the nails can go through the foam and attach to a firm base. If there is nothing for the metal to latch to, it won’t stay in place.

Install the vinyl siding by placing it directly over the foam board. You can then use nails to put everything in the right spot, checking to ensure the nails have taken root in a firm nail bed. It’s an excellent option, whether you’re creating a new building or attempting to turn an old one into something different. 


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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