How To Insulate A Basement: Your Step-By-Step Master Guide

How To Install Prodex Insulation in a Basement

Did you know that 10-30% of your home’s heat can be lost through the basement?

An uninsulated basement can become a breeding ground for moisture, which can lead to problems like mold and mildew. According to the US Environmental Protection Agency, the humidity indoors should not be above 60%, with 30% to 50% marking the ideal range.

Basement insulation prevents heat loss

Along with mold, basement moisture can cause odor and become a nesting ground for an army of unpleasant invaders like rodents and bugs. It can also serve as a risk to the overall building structure.

Basement insulation provides numerous benefits. Here, we’ll share everything you need to know about how to insulate a basement, including the process for inside vs. outside, and our recommendation for the best type of insulation for your basement.

Considering basement insulation? Check our product list!

How To Insulate A Basement: The Moisture Test

Before you begin the process of installing insulation, the first step is to determine whether moisture is present in your basement. To do so, you can conduct this very simple test:

  • Take a piece of plastic wrap sized 10″ x 10″
  • Tape it on the wall where you may have potential moisture problems such as wet spots, stains or peeling layers
  • Make sure you seal the edges of the plastic wrap
  • Let it sit for several days
  • Check the result:
    • If the plastic is wet on the internal side (the side facing the wall) you likely have a leak
    • If the plastic is wet on the side facing the room, you have condensation issues

The same test can be done on basement floors by holding a plastic sheet in place using sand bags or another heavy object.

If the sheet is wet on top, it's an indication of high moisture levels inside. If the underside of the sheet is wet, it indicates moisture entering the basement from the ground and possible radon emissions.

Insulating A Basement From The Inside vs. Insulating A Basement From The Outside

Installing insulation on the outside of your basement can optimize weather protection.

On the other hand, inside insulation typically involves more economical and practical considerations, such as appearance, reduced heating costs and more.

Of course, using both is also an option, but let's compare the advantages and disadvantages of inside and outside basement insulation.

Insulating A Basement From The Inside

To insulate your basement from the inside, you can use rigid insulation boards, drywall, polyurethane spray foam, foam board, fiberglass or Prodex.

Some of these options can also be combined to increase efficiency.


  • Can be performed during any season and in separate stages
  • Insulating an entire wall is easy, cheap and leads to high insulation performance
  • Can be done on your own without the need of professionals
  • Does not disturb the rest of the home in any way
Inside basement insulation


  • Causes of moisture need to be identified and resolved before applying basement insulation, otherwise the newly insulated areas might rot
  • Problems might remain hidden and develop further, if insulation is installed without assessing basement moisture
  • Plumbing, electrical panels, stairs and partitions may obstruct work and make the process more difficult and expensive

Insulating A Basement From The Outside

Outside basement insulation can be achieved with polyurethane boards, rigid mineral wool boards or high-density polystyrene.

The process of outside insulation can require digging around the foundation and adding flashing materials to serve as waterproof barriers, to ensure that water will not find access behind the insulation.


  • It is easy to apply insulation on outside walls
  • Structural and moisture problems (cracks, eroded mortar) can be easily detected and eliminated
  • Foundation repairing, waterproofing and drainage system installment can be done at the same time
  • The process does not disturb residents of the home
Outside basement insulation


  • Machine digging depends on access
  • Excavation is not recommended in winter and spring due to low temperatures and high water levels
  • Soil storing can pose an issue
  • Bushes, fences and on-removable steps can complicate the process
  • Some foundation types like brick and rubber may be supported by the soil and removal may lead to risks for the building
  • Underground services (electricity, gas, sewage) may be interrupted during digging

Basement Insulation Equipment Checklist

One of the fastest and easiest ways to insulate your basement is to use a reflective insulation like Prodex. The technical process is simple and the list of equipment needed is short.

All you need is reflective and double-sided tape, glue (ideally super metal sealant), a screw gun and a utility knife.

Use the reflective tape to seal insulation seams and to create vapor barrier. Reflective tape is resistant to sunlight and cold, durable over time and easy to apply.

Apply double sided tape wherever you need to keep insulation in place or to seal seams.

Use super metal sealant instead of nails or staples for various surfaces like pained metal, galvalume, wood, concrete, fiberglass and fiber-reinforced plastic.

All you need is 60 minutes for the super metal sealant to dry without holes. No holes equals a better R-value!

Use your utility knife to cut insulation pieces and use the screw gun to fasten the insulation in designated spaces and ensure continuous layers that will not allow condensation.

How To Insulate A Basement: The Process

Basement insulation can be applied in several different ways depending on the type of insulation you use and the areas you decide to cover.

Learning how to insulate basement walls, along with the ceiling and floor if desired, can help improve the temperature and moisture parameters in the basement, along with the upper floors of your home.

We highly recommend choosing Prodex for your basement insulation due to the easy and fast installment process and its ability to block condensation and moisture.

The step-to-step processes below covers various installment situations using Prodex.

Applying Insulation On Concrete Walls

Recommended Prodex type: 48 Inch, Fast Action, 10M, 72 Inch, White or Rustic

  • Use double-sided tape and super metal sealant to fix Prodex to the wall. Run the insulation horizontally along the wall.
  • Bind seams with reflective tape.
  • If you want to avoid seam tape, use Prodex options like 10M or Prodex Fast Action that have an adhesive line on one side of the roll.
  • Staple, screw or use super metal sealant to place the insulation underside of the studs.
  • Push the insulation inside the cavity to ensure a two-inch air-gap.
  • Attach drywall.
Wall basement insulation with Prodex

Applying One Layer To Stud Plus Drywall

Recommended Prodex type: 48 Inch, Fast Action, 10M or 72 Inch

  • Staple, screw or glue Prodex insulation to the underside of the studs.
  • Push the insulation into the cavity to create a two-inch air-gap. It serves as an additional insulation layer and improves the overall insulation performance.
  • Attach drywall.
One layer of Prodex to stud plus drywall

Applying One Layer Between Studs

Recommended Prodex type: 24 Inch or 16 Inch

  • Depending on your stud spacing, staple one layer of Prodex insulation between the studs.
One-layer Prodex between studs

Applying One Layer Attached to Stud

Recommended Prodex type: 48 Inch, Fast Action, 10M, 72 Inch, White or Rustic

  • Staple insulation to the underside of the purlins.
One-layer Prodex attached to a stud

Applying Two Layers Over/Under Stud

Recommended Prodex type: 48 Inch, Fast Action, 72 Inch, White or Rustic

  • Use super metal sealant to attach insulation to the wall before installing the studs.
  • Push insulation in to ensure 2+ inches of air-gap which will improve insulation performance.
  • Bind seams with reflective tape.
  • Use Prodex Fast Action with an adhesive line, if you do not want to tape the seams.
  • Roll insulation perpendicular to and over studs.
  • Use super metal sealant or your screw gun to attach larger insulation rolls to the underside of the studs. Gluing the insulation can help improve the appearance.
  • Tape the seams with reflective tape or use Prodex Fast Action to avoid seam taping.
Two-layer Prodex over/under stud

Applying Two Layers, One Between And One Attached To Studs

Recommended Prodex type: 48 Inch, Fast Action, 72 Inch, White, Rustic, 24 Inch or 16 Inch

  • Depending on stud spacing, use one layer of Prodex 24 Inch or 16 Inch between studs.
  • Staple, screw or glue larger rolls to the underside of the studs.
  • Glue to improve the appearance.
Two-layer Prodex, one between and one attached to a stud
Need help installing your basement insulation? Contact us!

What Is The Best Insulation For A Basement?

In our 18 years of expertise, we have worked with various insulation options and we can confidently say we recommend Prodex as a high-quality basement insulation.

It is a product with innovative technical characteristics and it can solve the most common basement problems.


  • Stops condensation
  • Prevents heat transfer in and out
  • Acts as a vapor barrier
  • Stops air transfer
  • Prevents rodents, bugs and birds
  • Prevents mold and mildew
  • Installs easily

There are more than 15 types of Prodex available at Insulation4Less.

The types of insulation most appropriate for a basement include Prodex 48 Inch, Fast Action, 10M, 72 Inch, White Prodex Total and Prodex Rustic.

Made of reflective reinforced foil on each side and a closed-cell polyethylene foam center, Prodex as zero flame spread, improved tearing resistance and an R-value between 15.3 and 22.

Each type has additional characteristics that can further enhance their use, such as an adhesive line (Prodex Fast Action) or attractive decorative features, either with white facing (White Prodex Total) or imitating wood effect (Rustic).

Not sure what type of insulation to use? Contact us!
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