Vapor Barrier vs Underlayment

When it comes to making your dream house, often vapor barriers and underlayments sound closer than your fingers. Aren’t they the same, you ask? Well, technically no. 

Though both of them work as moisture restrictions, they are completely different materials. Underlayment may be a flat piece of cork, foam, and so on. Whereas, vapor barriers are a piece of plastic or foil sheet, which stops the diffusion of moisture. 

Between vapor barrier vs. underlayment, there are a lot more differences than that meets the eye. 

A vapor barrier is so thin, it hardly does anything else other than moisture control. On the other hand, an underlayment reduces noise, mold, and mildew, and also acts as a compression layer. 

Vapor Barrier vs Underlayment

Is underlayment the same as a vapor barrier?

Underlayment isn’t the same as a vapor barrier. Though both of them can restrict the flow of moisture, a vapor barrier is just a thin piece of modified plastic or foil. Whereas, underlayment are thick cork-like material that restricts moisture, sound vibration, and also compression resistance. You will get better moisture protection from underlayment than a vapor barrier. 

Vapor Barrier Vs. Underlayment: Comparison chart

In a hurry? Why don’t you go through the quick comparison chart? It will take you a few seconds to know the ins and outs of vapor barrier vs. underlayment.

Features Vapor barrier Underlayment 
Thickness0.152399 mm to 0.508 mm6.35 mm- 12.7 mm
MaterialPlastic or foil sheetPlywood, cement fiberboard or cement board
Moisture controlYesYes
Sound control NoYes
Compression qualityNoYes
Used inInterior and exterior wallsEverywhere including ceiling, wall, floor, etc.
PriceLess than 0.5 dollars per Sq. foot$3.58 – $5.60 per square foot
Used forMoisture control onlySound impending, compression protection, moisture, and so on.

Vapor Barrier: What is it?

A vapor barrier is just a thin piece of modified plastic, which can decrease the condensation of water vapors in interior walls. It is a lifesaver for areas where the inside of the home is warmer than the exterior. Let’s see some of the benefits of the vapor barrier: 

Moisture control

For vapor barriers, the prime goal is to restrict moisture buildup in walls. When the air outside your home is colder than the inside, water drops can form in between the wall layers. Not good, is it? Vapor barriers can reduce it and save your walls from early damage. 

Mold and mildew prevention

Molds and mildew need water to burst out. Moisture inside the dark wall layers is a perfect breeding ground for them. A vapor barrier acts as a protective layer for walls, so no molds can mature inside them. You won’t need to remodel anytime soon. 

Reduction of musty odor

Sometimes, your house may smell bad due to the stagnant moisture inside the walls. Wall moisture and bacteria buildup are the main culprits here. A vapor barrier will eliminate any moisture buildup to up to ⅓ quarter. Bacteria can’t survive in such a harsh environment, making your home smell more natural. 

Increase energy efficiency

In cold climates, your AC needs to work 24/7, just to keep the house warm. Then again, moist walls will disperse the heat from the inside faster to the outside cold. Turns out, there is a solution for that. Using a vapor barrier will help decrease moisture, and efficiently store the heat energy. 


  • Reduces the risk of condensation and moisture damage
  • Acts as a barrier to mold, mildew, and bacteria
  • Helps to keep homes warm in colder climates
  • Reduces energy consumption


  • It may not be necessary for all climates

Underlayment: What is it?

Underlayment is a thick piece of protective layer that adds an extra layer of protection to surfaces. You can expect an underlayment to act as a compression layer, moisture barrier, noise reducer, and so on. If you want your beloved home to stay rigid for years to come, there is no alternative to underlayments. Let’s see some features of underlayments: 

Dampening of noise

Underlayments are quite thick. It adds an extra layer of sound protection from your neighbors, street traffic, and so on. Additionally, underlayments can improve in-room or in-car sound quality, making your home more peaceful. 

Moisture protection

If you live near the coast or in areas where humidity is higher, your walls may sweat. Turns out, a simple underlayment will help protect your walls or flooring from unwanted moisture. Now, you don’t have to worry about the moisture that migrates from the home and into wooden floors.

Compression resistance

Sometimes a single hard blow can damage your wooden walls or floors. But hey, just use an underlayment of crying out loud. Having a porous nature, underlayments can consume most of the impact from hits, blows, or sudden foot traffic. 

Temperature regulation

Underlayments are great at regulating the home’s internal temperature. During the winter, underlayments prevent heat from escaping to the wild. Similarly, during summer days, the outside heat can’t warm up your home that easily. 


  • Protects from impact and blows
  • Reduces noise and unwanted sound
  • Improve home sound clarity
  • Prevents heat from entering and escaping
  • Better moisture control


  • Its kinda expensive 

Vapor Barrier vs Underlayment: Who will win?

Well, if there was a head-to-head comparison between a vapor barrier and underlayment, the underlayment would churn out better for homes. Vapor barriers are just a thin piece of plastic, whereas underlayment are an extra layer of protection for walls, floors, etc. Here are some reasons why underlayment are better than vapor barriers: 

Better moisture control (Underlayment win)

This shouldn’t come as a surprise that thicker materials will prevent more moisture. Underlayments have a thick foam-like construction, whereas vapor barriers are just thin plastic. It’s not even thicker than your regular plastic bag. So, if you need to choose, pick an underlayment. Adding both of them together will give your home better long term results. 

Sound reduction (Underlayment win)

Underlayments act as a sound-reducing barrier for homes where external sounds are common. Vapor barriers don’t have this feature and will never have it. So, if you live near public roads, or your neighbors make too much noise, an underlayment is a way to go.

Impact resistance (Underlayment win)

The impact from blows, sudden hits, or regular foot traffic makes surfaces lose their durability faster. This is where underlayments come into play. Due to its porous nature, underlayments can take years of usage without too much deformation. Underlayments will protect your home floors, walls, ceilings, and so on. 

Temperature control (Underlayment win)

Here underlayments take the lead with their foam-like construction. In summers, heat can’t accumulate in homes, making them cooler. Then again, in winters, your home will stay warmer than the other side’s environment. Condensing water won’t be an issue for underlayments as well. A thin piece of vapor barrier will hardly do anything other than restrict a few quarters of moisture.

Ease of installation (It’s a draw)

Both the vapor barrier and underlayment are easy to install. All you need is some steady hands, glue, and pins. There are DIY options as well. It’s your call on which one to choose. 

Costing (Vapor barrier wins)

Underlayments cost significantly more than vapor barriers. You can expect vapor barriers to cost about 0.5 dollars per sq. feet. On the other hand, underlayments will pitch a price about 10 times that of vapor barriers. However, with all those useful features of underlayments, it’s hard to complain. 

What underlayment to use for a moisture barrier?

You try any regular class 1 underlayment as a moisture barrier. However, with better quality and price, you will get better long-term results. You can try out the ECF underlayment, which has a 6-mil moisture barrier layer for maximum vapor control. 

If you have concrete, wooden, or marble subfloors, an ECF underlayment will work wonders. Especially for moisture-prone subfloors, get an ECF underlayment or an underlayment version with an inbuilt moisture barrier. 

End Note

Well, folks, this is all for today. Hope now you know the differences between a vapor barrier and underlayment. Both of them have their uses. If you live near the coastal areas, chances are you will need a vapor barrier more than anything else. 

Then again, during cold winters, condensed water may accumulate inside the walls, making both underlayment and vapor barrier an absolute necessity. 

If you need compression control, temperature regulation, and reduced outside noise, underlayments are the way to go.

So, bye for now. Have a good day.

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