How To Install Fanfold Insulation- Stuff That Makes Sense!

FanFold insulation is one of the major underlying instruments for home insulation. Many of you are well aware of this fact.

What many of you don’t know is how to get started with the installation process. Well, that’s not entirely your fault. More than 80% of the people would try and seek some sort of professional help before starting.

We’re sure the DIY enthusiast among you is feeling a bit agitated by now. You don’t need to be!

Because throughout the course of today’s content, we will try and explain how to install fanfold insulation stuff that makes sense. We will provide enough information for you to conduct your own research and do a thorough job. 

Let’s start with the very basics.

How does insulation really work?

The principle of insulation is very easy to understand. The goal of roof insulation (which is the most common) is to trap the heat inside the home during the chilly winter days.

Air is a very bad conductor. And the insulation process takes advantage of this.

When roof insulation is in place, it works like a barrier that doesn’t let any heat past it. As air is a bad conductor, the possibility of heat leaking out is low. And as there is insulation in place, the conduction process has limitations as well.

Add these two things together, and you have an insulation system that works!

FanFold Insulation: The quality and use case

The FanFold underlayment insulating material is a product of Plasti-Fab. It’s essentially an underlayment.

The purpose of the underlayment is to protect the inside of a structure by not letting dirt and debris get in. It’s like putting on a protective seal before putting on the vinyl siding (which is the main purpose of FanFold underlayment 90% of the time).

It’s got an Expanded Polystyrene insulation core with sleek lamination on both sides. The sides have grid lines, which come in handy during installation.

It comes in ½-inch and 3/8-inch thickness. The typical area coverage is 4×24-feet, where a 192-square feet coverage is rated.

Among some of its core features and benefits, the following standout:

  • The flatness of the design overall is very uniform.
  • It doesn’t slide off the surface, which is nice.
  • The ease of use is on point.
  • It’s one of the more lightweight options out there.

Applications of FanFold Insulation

We will now try and break down the applications of FanFold insulation.

As a roof underlayment

It’s got multiple advantages to offer as roof underlayment. Apart from the quick and easy installation, the membrane itself offers a lot of unique features.

For instance, the EPS insulation acts as a solid shield for roofs. Also, the laminated sides hold any damaging effects from the sun.

Protective boarding and Re-siding

The protective properties of FanFold metal exterior insulation are very solid compared to some of the more extravagant options out there. Although it’s not the best by any means, it still does a good job of holding against water leakage and more.

Also, if you need any shielding from the outside debris, then the FanFold underlayment can take care of that as well.

Another application of the FanFold is its ability to hold on to the aesthetics of the house wrap. Once you have it on, there’s very little chance of damage and leaking, which is a very good thing.

Let’s say you want to sell your house and move to another location. In that case, all you have to do is change the wood siding and put new ones over the FanFold. That’s all you need to do. 

How to install FanFold insulation: The correct way to do it

It’s time for us to show you how you can install FanFold all by yourself.

But before that, let’s take a look at vinyl siding.

Insulated Vinyl Siding

You get two advantages with insulated vinyl siding. One, you get an increase in the overall efficiency, which is basically a healthy jump in the R-value. Two, this type of insulation also wraps around the insulated siding, which is crucial for keeping the beauty of the home intact.

Whenever you’re dealing with vinyl siding, you will find FanFold to be close by. The reason is simple-professionals like to use this underlayment with existing vinyl siding for the best possible results.

So, how do you install FanFold?

Step one: Don’t start work on a windy morning

It is possible to lose composure if you don’t have the proper weather. So, we would ask you to start working on a day with no wind.

Step two: Line up and staple

All you have to do now is take a sheet from the stack and start from the top. Try to be as gentle as you possibly can.

As you lay it down, staple it to hold it in place.

Step three: Continue with step two until you reach the end of the roof

Keep unfolding sheets and stapling them to the base. Do this till you get to the very edge.

Step four: Cut, Angle, Place, Staple, and Repeat

Keep applying the sheets to the desired locations. Cut out the excess as you move on to the doors and windows.

Try to cut the sheets to proper angles wherever needed. Also, apply to the gable ends if the attic isn’t heated. This will ensure that there are no leaks.

And that’s basically all there is to understand.


  • Should you tape fanfold insulation?

Yes, you should carefully tape the seams of the fan-fold to be an effective weather-resistive barrier. After taping the seams, they become unable to provide a pathway to pass water through the structure under the foam.

The best tape you can have is the contractor’s tape from 3M, as long as it is not a foil-faced foam.

  • Does fanfold have an R-value?

Fanfold has an R-value of 2.27 @25F. The quality of the InsulFoam brand insulation is the same as the core of R-Tech. In addition, it has amazing water-resistant properties, compressive strength, and amazing dimensional stability. 

  • Does Fanfold work as a moisture barrier?

Yes, after installing the exterior fan fold insulation between the siding and your home’s exterior wall, it will work as a moisture barrier. It is a foam-type of insulation.

Fanfold offers energy efficiency and protection of your house wrap from moisture. It also creates a thermal insulation layer.

  • What is InsulFoam used for?

You will notice the usage of versatile rigid foam insulation board in retrofit and new roofing, drainage boards, house wrap, radiant heated board, perimeter insulation, crawl space, under a slab, below grade, weatherproofing protection barrier, continuous insulation sheathing, insulating sheathing, wood siding underlayment sheathing, interior and cavity walls, and exterior.

  • Does foam board insulation need a vapor barrier?

No, a vapor barrier is not necessary for foam fiberglass insulation. Some of the foam insulation types, such as foam board insulation and closed-cell spray foam, the insulation itself put an end to the movement of most water vapor.

Final Thoughts

We know it’s been a bit exhausting for many of you. Also, the steps on how to install fanfold insulation stuff that makes sense seem almost too easy.

First of all, if you’ve taken in all the information, then you’re pretty much ready to do your own research. Second, the steps need mastery, which will come to you naturally after a while.

We think we should stop it here for today.

Stay with us to find out more about the matter. Cheers!