Are Cinder Block Walls Energy Efficient? [Do They Need To Be Insulated?]

Cinder blocks are cost-effective and solid concrete ideal for houses and other construction projects. But can they sustain the efficiency of your home during summer and winter or do they need to be insulated? We made thorough research to answer questions you may have!

Porous by nature, cinder blocks have little thermal resistance. They can let air through, so they need insulation to raise their R-value.

The next factor you may have in mind is the best insulation option for cinder block walls. Read on as we will discuss that aspect and other important considerations in depth.

What are Cinder Blocks Made of?

Cinder blocks are made of Portland cement and coal ash. The mixture is pressed into casts before it is heated to dry or air-dried.

These blocks usually have hollow cores in the center, thus, are weak and lightweight. For that reason, they are commonly used in construction projects that don’t have to bear too much weight.

How Long Do Cinder Block Walls Last?

If they are quality built and have been coated with a waterproof membrane, cinder block walls can last between 50 to 100 years. A waterproof coating is required for them to withstand external elements for long-term, since they are lightweight and low-density. Typically, cinder blocks’ lifespan is shorter than concrete blocks’.

What is the R-value of Cinder Block Walls?

This mainly depends on the density of the material. But an 8-inch thick cinder block wall can have an R-1 to R-2 value without any type of insulation. The blocks allow heat to transfer easily through the wall.

How Much Do Cinder Blocks Cost?

The cost of a cinder block ranges from $1 and $3. Building an 8 x 15 wall can cost you up to $1,440 in total including the labor. Calculate the surface area first to determine the total number and cost of cinder blocks you’ll need.

Types of Cinder Blocks

Cinder blocks have 32 different shapes and dimensions under distinct categories. That includes: 

• Pier blocks: These come in different sizes and can either be a solid or hollow pier with a smooth finish. 
• Stretcher blocks are used to combine another stretcher block, hence they have half-hollowed ends and smooth sides. They either have solid or hollow cores. 
• Sash blocks are utilized for window openings in block walls. They can be solid, hollow, single, or double.  
• Hollow return corner blocks make it easier to connect two walls with a brick weave on the edge. A 45° angle makes a more solid wall construction. 

Ways to Insulate Cinder Block walls

The insulation approach can change, depending on whether the top wall is covered or exposed. That said, here are some of the best insulation methods for cinder block walls: 

Spray Foam Insulation

This is the popular option for insulating concrete houses. The material expands after being sprayed, sealing gaps, holes, and cracks on the walls, thus preventing any air movement. Depending on the type, it can have up to R-7 thermal resistance, and with proper maintenance, it can last for more than 80 years!

Concern about the appearance of the walls after spray foaming? You may need to enclose the insulation within the drywall. But if not, it might not be necessary. The price is probably the only drawback of spray foam, which ranges from $0.44 to $1.50 per board foot.

Cavity Wall Insulation Beads

This is recommended for cinder or concrete block walls with the top exposed. The polystyrene mixture in the form of a bead is injected into the wall with a bonding agent to fill the wall cavity and eliminate any cold spots.

It can significantly reduce your energy consumption in no time! The downside is the beads will flow out when you have to cut through the walls.

Foam Insulation Board

Polystyrene foam board, also known as foam board, is one of the most convenient insulation methods. Homeowners can install it behind the blocks without hassle as it is lightweight and mess-free.

It is usually installed with an adhesive designed for polystyrene. Dry the wall and fill any cracks or gaps first. Apply the adhesive on the wall exterior with a utility knife, then place it on the block wall. Ensure that it’s properly sealed to prevent air leaks.

However, the foam insulation board method is prone to mold infestation- it can absorb condensation within the wall.

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Perlite Loose-fill Masonry Insulation

This inert volcanic rock expands through the use of special heat, then is treated with repellent material. The process creates numerous tiny cells which account for its thermal and fire resistance.

It’s like pouring a sand-like mixture into the wall cavity. But just like the cavity insulation beads, the sand-like materials will come pouring out when you cut through the wall.

Injection Foam Insulation

Injection foam insulation fills any crevices and stops all air movement in between walls, making it one of the best insulation options. You need to drill a hole in the middle of the wall, then pump the mixture into the cavity.

It offers up to R-5 per inch, making your home more energy-efficient! However, it costs more than the other type of insulation. The thing is it lasts for up to 20 years.

If you already have existing cinder block walls, your choices might depend on your situation or be limited. So it is important to talk to your contractors before you begin the insulation process. 

Pros and Cons of Cinder Blocks

If you are considering cinder blocks for your home construction, Here are some pros and cons to take into account:

Pros

Affordable: Cinder blocks' price depends on the shape and dimension but they are usually cheaper than other types of blocks.

Easy to use: Cinder blocks are designed with concave edges, so they connect easily with another hollow block. You can stack them as desired without hassle.

Durable: Unlike woods that can rot and deteriorate easily, cinder blocks last for decades, so you don’t have to worry about them collapsing. But to ensure that they last longer, apply a waterproof coating.

Available: You can find cinder blocks wherever you are in the world without having to go for miles. They are available in many local stores.

Cons

Prone to buckling and bowing: Several joints in between the blocks make cinder blocks prone to shifting. The repair can be expensive, depending on the extent of the damage. For that reason, they are best used for non-load bearing walls.

Prone to water leaks: The joints in between each block can also let water in, which can saturate the core of the blocks and lead to dampness in the basement and other areas of the house.

Can Cinder Blocks Crumble?

Cinder blocks that have been exposed to flooding and water leaks without proper treatment, will eventually break off and collapse. Water can cause the structure of the cinder blocks to break away.

Ways to Maintain Cinder Blocks

External elements such as weather, water, and impact can cause cracks and shrinkage, but there are ways to protect your cinder block walls including:

• Application of water repellents to prevent water penetration
• Reapplication of waterproof coatings to protect the structural integrity
• Periodic maintenance to remove dirt and stains
• Control joints to relieve concrete stress

Conclusion 

Cinder block walls are durable and cost-effective, but they have low thermal resistance which can make your home uncomfortable during summer and winter. Fortunately, there are many ways to insulate them. However, the insulation method depends on the age and construction of the structure. Don’t hesitate to talk to your local contractor if necessary.