Cross-section of a building exterior with fiberglass insulation sandwiched between concrete blocks and brick, with a hard hat resting on the ledge at right

Block walls have their advantages. They resist extreme weather conditions, such as floods, strong winds, and high temperatures. 

Block wall insulation is a little complex but not impossible, especially for existing walls. Here we’ll discuss the benefits of block wall insulation and why you should do it. 

So, let’s get into it!

Why Should You Consider Block Wall Insulation?

You should consider block insulation because it reduces heat loss, especially on cold nights and during winter. It also helps with mold reduction and noise control, blocks pest and dust intrusion, and controls air exchange.

However, despite all their benefits, blocks have poor insulation capabilities, which is a disadvantage, especially during winter.

Now let’s take a closer look at these distinct advantages.

1.) Air Leak Prevention

A common misconception among people moving from colder states to warmer areas, like Florida, is that there is no need for block wall insulation because of the mild climate. Houses in Florida are mainly built using concrete blocks because they can withstand hurricanes and strong winds.

Concrete blocks retain heat but are also porous, meaning there is a lot of heat transfer, both inside the house and outside. 

Block wall insulation, such as foam injection, fixes the problems arising from the porous nature of blocks. When you prevent air transfer, your home will be warmer on cold nights, and you don’t have to worry about overworking your air conditioning system.

An installer injecting RetroFoam in the wall cavity of a home from holes in the exterior siding
Courtesy of Cincinnati Retrofoam

2.) Energy Bill Savings

After Hurricane Andrew hit Florida in 1992, Miami-Dade County developed strict building codes, requiring houses to be built using blocks, concrete, and stucco. 

Today, households in the county spend an average of $220 per month ($2,640 per year) on electricity bills. This figure is 24% higher than the annual national average of $ 2,135. 

One way to save on energy bills is by using block wall insulation. Depending on whether you air-seal all the block walls or only in some rooms, you may save 15-50% of your monthly energy bills. 

If the wall doesn’t suffer any cavity damage, block wall insulation can last for 80-100 years. When you do the math, that’s quite a bit saved in energy bills over the years. 

If you live in Florida and are keen on balancing costs, efficiency, and safety, check out our article on alternative construction options.

3.) Humidity Control

Blocks have very tiny pores which retain moisture. Air movement from outside into the house, and vice versa, doesn’t help matters because it results in water vapor diffusion. The humidity builds up in the block walls, affecting the air quality in your home.

A row of concrete blocks standing vertically in a line

Over time, mold may also grow within the walls, which spells doom, not just for your walls but your health.

Block wall insulation ensures condensation doesn’t occur within the walls, especially when warm air comes into contact with the cold blocks. In addition, it seals all the pores, so the moisture is not trapped in the walls. 

This feature allows your air conditioner to control humidity levels, as it is supposed to do. Any excess moisture in the air undergoes purification and gets released through the vents, not the walls. 

For more on how to control the humidity in your home, even as you work on insulating block walls, check out our article on the best home humidifiers.

4.) Improved Heating and Cooling System Efficiency

Air exchange is not just harmful to your block walls but also to your air conditioning system. Fortunately, you need not worry about air transfer when heating or cooling your home. Additionally, you don’t need to adjust your thermostat because the set temperature is not as effective as expected. 

5.) Preventing Wall Damage

Have you noticed mildew spores on walls close to water sources, such as the bathroom and kitchen? These spores ruin the aesthetic appeal of your home, and because they stand out, one can easily confuse them for dirt. 

A homeowner helding his head looks in disbelief at mold growth in the corner of the wall under his bathroom cabinet

You cannot keep painting your walls to fix mildew spores without addressing the root cause: moisture within the block wall. It would help if you insulated your block wall, as doing so prevents the growth of mildew spores. Only then will you successfully deal with the unattractive spots on your wall.  

See below for ideas on how to repair the damage on your walls:

Type Of Wall DamageApplicationMaterial
Concrete block insulationUnfinished walls Foundation walls New construction Major renovationFoam board Foam beads
Foam Board/ Rigid BoardFoundation walls Unfinished walls Floors CeilingsPolystyrene Polyutherane Phenolic Polyisocyanurate
Insulating Concrete Forms (ICFs)Unfinished walls Foundation wallsFoam Boards Foam Blocks
Loose Fill and Blown-inOpen wall cavities Enclosed walls. Cellulose Rock or slag mineral wall
Spray foam and foamed-in-placeOpen new wall cavities Unfinished floors Enclosed existing wallsPhenolic Polyurethane Cementitious Polyisocyanurate
Structural Insulated Panels (SIPs)Unfinished walls, floors, and ceilingsStraw core insulation Foam board or liquid board core

6.) Stale and Earthy Odor Removal

When block walls collect moisture, mold grows, leaving your home with a stale, earthy smell. No matter how much you clean, aerate, or diffuse your home with pleasant scents, the mold smell lingers. 

This odor can cause significant discomfort, whether you are at home with your family or are hosting family and friends. Unfortunately, the only defense against mold smell from block walls is insulating them. 

7.) Keeping Insects From Your Home

As mentioned above, block walls are porous. Thus, besides moisture, insects may also penetrate the blocks, finding their way into your house. Fortunately, some foam insulators contain insecticides which help to keep insects away. 

8.) Increased R-Value

Walls are made from materials and layers influencing the wall’s R-value (resistance to heat flow). Different materials offer different heat resistance levels, so the material you use for block wall insulation affects the R-value of the wall. 

Hence, when choosing the type of wall insulation to use, you need to consider your state’s recommended R-value. The higher the R-value, the more capable the material will provide insulation. 

9.) Increased Home Value

Block wall insulation can increase your property’s value by 2-6%. Buyers are always looking for the one thing that makes a property stand out, and insulated walls will do just that. 

You will have greater bargaining power if you have insulated walls. Then, not only are you more likely to sell your property, but you’ll also do it at a better price. 

10.) A More Comfortable Home

Block wall insulation goes a long way in making your home more comfortable. You don’t have to worry about the house being too hot or too cold or choosing between discomfort and saving energy bills. By insulating your block walls, you get both. 

11.) Protecting Your Investment

When you compare the cost of concrete blocks to other building materials, such as drywall and wood frames, blocks cost much more. Ultimately, block walls impact the value of the property. 

Moisture damage will not only leave you with lots of maintenance costs for your block walls, but you will also see the value of your property diminish. Block wall insulation is the best way to stop hemorrhaging money through maintenance and protect your investment. 

Tips on How To Choose Block Wall Insulation

The type of block insulation that’s best for you depends on factors like cost, where you need the insulation, and the status of the building (new or existing wall). 

Waterproof coating applied to a section of a basement wall.

Since there are several types of block wall insulation on the market, here are helpful tips on choosing the most suitable one:

  • Find out the R-value you seek from the wall insulation – the R-value will be influenced by the size of the blocks and the level of insulation offered by the different block insulation options. For example, an 8-inch (20.32cm) block wall contains a thermal resistance value of R-1.9 to R-2.5. 
  • Is the wall open at the top or not? – for example, Polystyrene bead cavity wall insulation is excellent for block walls that are open at the top. These beads are usually added during construction. The downside is if you need to break down the wall for any reason, the beads will pour out.
  • Are you insulating walls under construction or existing walls? – block wall insulation is best done when the house is under construction. You will have more insulation options than when fixing an existing wall. For example, when insulating an existing wall, you may be forced to use spray foam or injection foam, even if it doesn’t fit your budget. 
  • Consider the cost – spray foam and injection foam tend to be more expensive because they offer continuous insulation. These foams seal air flow completely. On the other hand, the cheaper alternatives are polystyrene beads, foam boards, and mineral wool. 
  • Is it a DIY project, or are you hiring professionals? – although it is always best to use a professional when insulating your wall, some insulation, like the blanket and reflective system, can be part of your DIY wall insulation project. However, liquid foam insulation is more complex and needs someone with expertise and experience handling this type of block wall insulation. 

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