Rim Joist Insulation Faced or Unfaced – Complete Discussion

Almost every home in the U.S. has a crawl space (hollow area under the house vented to the outside). A crawl space offers some potential benefits and provides some problems. A disadvantage is that it leaves the home open to humidity, which can lead to molds and wood damage.

One of the solutions to this problem is rim joist insulation. But here’s a catch, rim joist insulation can be faced or unfaced.

Which is better, rim joist insulation, faced or unfaced?

Usually, rim joist insulation is unfaced. Rim joist insulation is very often done between the space of two rooms of similar temperatures. So, there is a meager chance of developing moisture. That’s why unfaced insulation gets more preference. However, the insulation type may shift according to situation needs.

This may not be sufficient for you. We’ve written a complete piece on it. So, set aside some time, and let’s dive into the specifics.

Best Type of Insulation

There are so many types of insulations

  • rolls and batts
  • rigid planks
  • blown-in insulation 
  • reflective insulation 
  • soundproofing acoustic insulation, and more

When there are many options, it becomes harder to know if you are making the right choice. There is no exception in the case of insulation projects.

But there’s one more concern. You can classify all these types of insulation into “faced” and “unfaced.” That is when everyone becomes confused as to whether the insulation must be faced or unfaced.

Faced Insulation

Faced insulation includes a material sheet attached to one side. Kraft paper, foil, plastic, or vinyl can all be used. The most popular, however, is kraft paper facing. But for commercial and industrial buildings, vinyl is the right one.

The advantage of faced insulation is that it creates a vapor barrier that helps excess moisture from damaging the wood. Another advantage is that the flanges offered by this insulation enable it to staple with joists or studs. 

Faced insulation costs a bit more than the unfaced one as it includes extra materials. But in the long run, faced insulation protects against disastrous moisture effects.

Remember that the faced side of your insulation should be laid down against the closest surface of your living space.

Unfaced Insulation

This insulation doesn’t include an attached moisture barrier. However, if you need a vapor barrier sometimes, you can add one. For that, you will have to use plastic sheeting.

Unfaced insulation is usually used while insulating over existing insulation. Otherwise, you might face unwanted situations.

Faced or Unfaced Insulation?

Using faced or unfaced insulation is not about which one is better or convenient. It is more like which one is needed according to the situation such as kerdi board vs cement board. Facing is just adding a vapor barrier, so it is used where it is required.

Homes with crawl space are more sensitive to cold and moisture than concrete foundation ones. So, things like mold and rot are more likely to appear in crawl spaces.

Moisture or vapor barrier is created by the insulation facing. As a result, employing facing insulation appears to be a better option.

However, make sure that only one layer of faced insulation is applied. If you need to add multiple layers of insulation, use unfaced ones for the rest. 

Also, the faced insulation should not lie against the second unfaced insulation layer. Otherwise, there will be moisture traps, and you might face many problems.

Insulating Rim Joists

Rim joists are mainly responsible for most of the cold air flow through your house. Insulation of the joists can work well in reducing this.

Usually, sealing the rim joist is done to prevent the cold air from flowing through. But after that, insulating the rim joist is also essential.

Now, as the insulation is done between two rooms of similar temperatures, unfaced insulation is the best solution.

But remember that insulation methods may vary from expandable foam to pieces of rigid foam and so on. Only the final touch will be done by unfaced insulation. 

So, we hope that answers rim joist insulation faced or unfaced.

How to Insulate Rim Joists

Sealing and insulating rim joists can be done in a matter of hours. For this, you will need some tools. These are box cutter, caulk gun, circular saw, step ladder, tape measure, etc. You will also require acrylic caulk and expanding foam. 

If you don’t know any reliable sources for these tools, here we’ve created a customized toolset to ease your pain-

We hope this listing will help you greatly while buying the products.

However, cut the rigid foam insulations into strips to insulate the rim joists. Then caulk around each section of foam. After that, use a box cutter and cut the insulation to length. 

This work will require patience, so don’t be in a rush. If you concentrate enough, you will finish the work within two to three hours.

So, these are the things to keep in mind while insulating rim joists.


Are rim joists necessary?

A rim joist is required when framing a house or a deck. They finish off the open ends of your floor framing and create the edge of your floor frame.

What is the purpose of a rim joist?

A rim joist is attached perpendicular to the joists and provides additional stability for the edges of the joist while topping off the end of the floor or platform system while framing a deck or floor system.

Should you insulate rim joists?

Rim joists are above grade. So, it makes sense to insulate the joists to the same level as above-grade walls. 

How do you cover rim joist insulation?

Spray foam is considered the best to seal the rim joist area. It is generally installed by a professional insulation contractor. The spray foam easily fills in and packs all the cracks and openings in the rim or band joist areas.

Why is my rim joist wet?

Moisture and mold in the rim joist can cause the rim joist to get wet.


Faced and unfaced insulations have different roles to play, and both of them are useful depending on the requirements. Both have their unique characteristics.

We tried to give you a detailed explanation on rim joist insulation faced or unfaced. We hope you will be able to better understand rim joist insulation faced or unfaced.