Basement Wall Insulation: How to Do it, Benefits and Options

Written By Adam Paul - Waterproofing Expert

Basement wall insulation is the process of adding materials to the interior or exterior walls of a basement to enhance thermal efficiency, moisture control, and comfort. It helps to reduce heat loss, prevent condensation, and improve a home's overall energy efficiency. When you install basement wall insulation, you should follow these six steps.

When you insulate basement walls you can use spray foam, fiberglass, rigid foam board, mineral wood, and cellulose insulation. You should insulate concrete basement walls, block basement walls, framed basement walls, foundation basement walls, and interior partition basement walls. Basement wall insulation increases energy efficiency, improves thermal comfort, increases moisture control, and soundproofing, increases home value, protects the foundation, and increases the sustainability and versatile use of basement space. 

Suppose the basement wall is not insulated properly. In that case, it may cause many structural problems and health problems to occupants due to increased dampness and mold, and mildew growth in the basement.

How to Insulate Basement Walls in 7 Steps?

Follow these 7 steps to insulate the basement wall

1. Check the moisture level in the basement and waterproof the walls if needed
2. Clean and prepare basement wall surface
3. Install a vapor barrier or insulation board on the basement walls
4. Measure and cut insulation panels or batts
5. Attach the insulation to basement wall studs or directly to the walls
6. Seal gaps in the wall with spray foam or caulk
7. Tape and finish the drywall joints on the basement wall and apply finishing touches

1. Check the moisture level in the basement and waterproof the walls if needed

First, check the basement wall for any sign of moisture or dampness on the walls. You can use a moisture meter and if the reading is below the 15% you can insulate the basement walls safely. If you see any kind of spot dampness, paint peeling, or a musty smell, you should waterproof the basement wall to prevent trapping moisture behind the insulation.

When answering the question What you should know about basement waterproofing?, you should know, which waterproofing membranes you can use and how to do it. You can waterproof the basement by using a liquid membrane or sheet membrane. Cementitious waterproofing is the best option for basement wall waterproofing. If the basement wall has wider cracks and leaks you should apply PU crack injection methods to seal the cracks and joints in the basement walls. After preventing water and moisture problems in the basement wall you should clean and prepare the surface for insulating.

2. Clean and prepare the basement wall surface

Before installing insulation you should clean the basement walls to create a smooth, debris-free surface for insulation. You can a use stiff-bristle brush or a wire brush to scrub away dirt, dust, and any loose or flaking paint. For stubborn spots in the basement wall, you can use a masonry cleaner and mild detergent can help lift grime effectively.

After the basement wall is cleaned you should inspect the walls for cracks or holes. You should fill any gaps with hydraulic cement or masonry filler to prevent air leaks. Smooth out the patches, ensuring an even surface across the entire basement wall. Then let the walls dry completely before moving forward to avoid trapping any moisture under the insulation.

3. Install a vapor barrier or insulation board on the basement walls

After completing the drying process of the basement wall you should install a vapor barrier to add an extra layer of protection. Use a 6-mil polyethylene plastic sheet as the vapor barrier, cut to fit each wall section. Then secure it with construction-grade adhesive or staples to the studs. It should be used to cover every part of the wall.

If you need higher thermal insulation, you can use insulations with higher R-values, such as rigid foam insulation boards such as XPS or EPS. 

4. Measure and cut insulation panels or batts 

After the vapor barrier or insulation board is placed on the basement walls, you should measure each section of your wall where you’ll install insulation. Record the height and width carefully. Then use these measurements to mark your insulation panels or batts precisely before cutting them.

For rigid foam panels, use a straightedge and utility knife to score and snap each piece to size. For fiberglass or mineral wool batts, use a utility knife or insulation saw for a clean cut. You should cut the batts slightly wider than the wall cavity (about ½ inch) to ensure a snug fit.

5. Attach the insulation to basement wall studs or directly to the walls

Attach your insulation panels or batts to the basement wall structure. For framed basement walls, fit fiberglass or mineral wool batts snugly between the studs; staple the flanges to the sides of the studs to keep them in place.

If you’re using rigid foam insulation panels on the basement walls you should apply construction adhesives directly to the back of each panel in vertical lines or a grid pattern. Then press firmly onto the wall. For extra security, add masonry fasteners or insulation anchors at each corner and along the basement wall edges. 

6. Seal gaps in the wall with spray foam or caulk

After installing the basement insulation you should inspect all edges, corners, and seams for gaps. You can use spray foam insulation to seal larger gaps when it expands to fill spaces effectively. For smaller gaps in the basement wall insulation (¼ inch or less), you can use high-quality, paintable caulks.

If you need extra moisture protection to the basement wall you should cover the insulated wall with moisture resistant drywall such as green board or purple board. You should position the drywall panels over the basement insulation and secure them to the wall studs or directly to the foam board with drywall screws, spaced about 12–16 inches apart.

7. Tape and finish the drywall joints on the basement wall and apply finishing touches

After installing basement wall insulation you should apply drywall tape over the seams where two panels meet and Then use “mud” to cover the tape. Then apply it using a drywall knife to blend into the basement drywall surface. Then use a grit sandpaper for smooth finish the basement wall. After this process, you can apply primers and desired paints on the basement walls.

What are the 5 types of Basement Insulation? 

These are the most used 5 types of basement insulations

1. Spray foam insulation
2. Fiberglass insulation 
3. Rigid foram board insulation
4. Mineral wool insulation
5. Cellulose insulation

1. Spray foam insulation: Spray foam insulation consists of isocyanate and polyol resin. When these components mix together they expand upon application to fill the gaps and cracks in the basement walls. These foams provide excellent thermal resistance to basement walls. Foam insulation is air-sealed, has a high R-value, is moisture resistant, soundproof, and long-lasting. Foam seal is highly recommended for the basement walls which are irregularly shaped areas, hard-to-reach spaces, and around plumbing and electrical penetrations in basement walls.
2. Fiberglass batt insulation: Fiberglass batt insulation consists of glass fibers. These are typically available in pre-cut panels that fit between wall studs in the basement wall. Fiberglass batt insulation is cost-effective, non-combustible, easy to install, has good thermal performance, and eco eco-friendly. Fiberglass batt insulation is good for the framed basement walls where the insulation can fit snugly between studs.
3. Rigid Foam board insulation: Rigid foam board insulation is a large, solid panel that is made from polystyrene, polyisocyanurate, or polyurethane. Rigid foam boards have higher R-value, are moisture resistant, lightweight, and easy to handle, and have durable basement wall insulations. These are effective for both interior and exterior basement walls. 
4. Mineral wool insulation: Mineral wool insulation is made from natural or recycled materials: basalt rock or slag. Mineral wool is available as batts or loose-fill form. Mineral wool insulation is fire resistant, soundproof, water resistant, sustainable, and consists of thermal performance. These are suitable for basement walls, where higher fire resistance and soundproofing are needed.
5. Cellulose insulation: Cellulose insulation consists primarily of recycled paper products treated for fire resistance and pest control. Cellulose insulations are eco-friendly, highly thermal resistant, effective air barrier, soundproof, and highly moisture resistant. Hence this material can be used for basement walls and ceilings.

What 5 Types of Basement Walls Should Insulate?

You should insulate the following 6 types of basement walls.

1. Concrete basement walls: Concrete basement walls should be insulated to improve thermal performance and reduce energy costs. 
2. Block basement walls: Block basement walls should be insulated to enhance energy efficiency, and minimize moisture issues: Framed basement walls should be insulated to reduce the potential for condensation and moisture issues while improving overall energy efficiency.
3. Framed basement walls: Framed basement walls should be insulated to maintain comfortable temperatures and prevent heat losses in the basement.
4. Foundation basement walls: Foundation basement walls should insulated to reduce the potential for condensation and moisture issues while improving overall energy efficiency. 
5. Interior partition basement walls: The interior portion of basement walls should be insulated to soundproof and increase the thermal comfort in the basement.

What are the Benefits of Basement Wall Insulation?

The benefits of basement wall insulation can increase energy efficiency, improve thermal comfort, increase moisture control, and soundproofing, increase home value, protect the foundation, and increase the sustainability and versatile use of basement space. 

What if the Basement walls are Not Insulated?

If the basement walls are not insulated properly it may cause several problems which cause to negative impacts to the structure as well as occupants. 

When basement walls are not properly insulated, that becomes a major source of energy loss in the house. Because houses consume additional power to control the temperature and humidity in the basement which causes to increase in energy bills. 

Without adequate basement wall insulation, cold air seeps into the basement during winter, creating drafts that spread to the upper floors. This impacts to heating systems work harder. In summer, heat transfer from the surrounding soil raises basement temperatures. This affects to cooling system efficiency.

As well as lack of basement wall insulation causes mold growth and dampness. It causes weak structural elements and degrades air quality. Also, mold and mildew growth caused to negative impact to occupant health and led to expensive repairs in the basement.

Read more: How to Remove Basement Mold In 5 Ways?

Why you Should Insulate the Basement Ceiling?

The basement ceiling should be insulated to improve the thermal stability in the basement. Basement ceiling insulation should be done if the basement is unfinished or unheated, reduce the noise between floors, and protect the pipes and ducts in the basement ceiling. Basement ceiling insulation can help to regulate the temperature in the basement. It helps to prevent heat loss and protect pipes from freezing.