Insulating Existing Walls: What You Need to Know Before Starting

Have you discovered that your home has poor energy efficiency ratings? Is your energy bill through the roof?

If you’ve got old and drafty house walls, insulating them could help you make your home more energy efficient and get your energy bills under control.

But what type of insulation should you use? Should you hire a professional to insulate existing walls?

See below for everything you need to know about insulating existing walls.

Why is Insulation Important?

Insulation is crucial for maintaining a comfortable indoor environment and maximizing energy efficiency. Inadequately insulated walls can lead to heat loss during the winter and heat gain during the summer. This causes your heating and cooling systems to work harder and consume more energy.

By properly insulating your home, you create a barrier that slows down the transfer of heat. It can help maintain a consistent temperature inside your home and reduce the load on your HVAC system.

Determine the Existing Insulation

Before embarking on an insulation project, it’s crucial to assess the current insulation in your walls. Older homes may have little to no insulation, while newer ones may already have some insulation in place. Identifying the type and condition of the existing insulation will help you determine the best course of action.

To inspect the existing insulation, you can either hire a professional energy auditor or perform a visual inspection yourself. Energy auditors are trained to assess insulation and identify any areas of concern. If you decide to do it yourself, look for signs of insulation, such as:

  • Fiberglass batts
  • Cellulose
  • Foam

You might need to remove a small section of the wallboard to get a clear view. Note any areas that lack insulation or have damaged insulation.

Insulation Options for Existing Walls

When it comes to insulating existing walls, there are several options available to homeowners. The choice of insulation material depends on factors such as:

  • Budget
  • Climate
  • Available wall space
  • Personal preferences

Fiberglass Insulation

Fiberglass batts or rolls are one of the most popular insulation choices for existing walls. They consist of small glass fibers that trap air, reducing heat transfer.

Fiberglass insulation is affordable, readily available, and relatively easy to install. It can be fitted between wall studs or blown into wall cavities.

Cellulose Insulation

Made from recycled paper products, cellulose spray insulation is an eco-friendly option. It is dense and provides excellent soundproofing.

Cellulose insulation can be blown into existing walls, filling cavities and gaps effectively. This makes it ideal for retrofitting and improving the insulation performance of older homes.

Spray Foam Insulation

Spray foam insulation is a versatile option that expands upon application, filling gaps and creating an airtight seal. It has excellent insulating properties and can provide superior energy efficiency.

Spray foam insulation is often used in hard-to-reach areas and provides an effective barrier against air infiltration. Professional installation is typically recommended for spray foam insulation.

Rigid Foam Insulation

Rigid foam insulation boards are a popular choice for insulating existing walls. They have high insulating values and can be used in combination with other insulation types.

Rigid foam is moisture-resistant and provides excellent thermal performance. These boards are usually cut to fit the wall cavity and can be installed between studs or on the interior or exterior of walls.

Natural Insulation Materials

For those looking for environmentally friendly options, natural insulation materials like:

  • Sheep’s wool
  • Cotton
  • Cork

These insulating materials offer good insulation properties and are renewable and biodegradable.

Evaluate Wall Cavities

Before installing insulation, it’s important to assess the condition of your wall cavities. Wall cavities are the empty spaces between the interior and exterior walls. Depending on the construction of your home, the wall cavities can vary in size and accessibility.

If your wall cavities are already filled with insulation, it might be necessary to remove or add to it. In some cases, the existing insulation may be damaged or insufficient. If the cavities are empty, you can proceed with insulation installation.

However, it’s crucial to note that certain types of wall construction, such as solid masonry walls, may not have accessible cavities. In such cases, alternative insulation methods, such as insulating from the exterior or using interior insulation panels, may be required.

Challenges to Consider

Before starting an insulation project, it’s important to be aware of potential challenges that may arise. These challenges can vary depending on the construction of your home and the condition of the existing walls. Here are a few common challenges to consider:


Insulating existing walls can be more challenging than insulating new construction since the wall cavities are already enclosed. Accessing the wall cavities may require removing exterior siding or interior wall coverings, which can add complexity to the project.

Moisture Issues

Moisture can be a concern when insulating existing walls. If moisture is present within the walls, it can become trapped and lead to mold or rot. It’s crucial to address any existing moisture issues before installing insulation to ensure the long-term integrity of your walls.

Electrical and Plumbing Considerations

Existing walls may contain electrical wiring, plumbing pipes, or other utilities. Care must be taken to avoid damaging or interfering with these systems during the insulation process. Consulting with a professional or electrician may be necessary in certain cases.

Hire Professionals or DIY

When it comes to insulating existing walls, you have two options: hiring professionals or doing it yourself (DIY).

Hiring professionals is a good idea if you’re not experienced in home improvement projects or if you want to ensure the insulation is installed correctly. Professionals have the right tools and know-how to do the job properly.

However, if you have some DIY skills and feel confident, you can try doing it yourself with certain insulation materials like fiberglass batts. Just make sure to research and follow instructions carefully to achieve good results.

A Guide To Insulating Existing Walls

Insulating existing walls can be a cost-effective way to reduce your energy costs. Be sure to do your research, check available regulations, and seek professional advice before you start. Start by taking a few small steps to insulate your existing walls and make the most of your energy savings today!

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