How To Update Insulation In Walls Of Old Homes

Homeowners Often Forget Walls When Updating Insulation.

Updating the insulation in older homes is critical to making living spaces more comfortable and monthly energy bills more manageable. Unfortunately, most homeowners only think as far as the attic forgetting to consider insulating exterior walls when considering an upgrade.

Depending on the size of the home, their can be as much or more surface area in the exterior walls than the attic. If the wall cavities are not properly insulated (or perhaps not insulated at all which can be the case in very old homes,) the benefit of adding insulation to the attic will be minimized. While more complicated and expensive, it is possible to insulate existing walls. Here’s how the process works.

First, the wall insulation must be evaluated. A home energy audit completed by a qualified Building Performance Institute (BPI) energy auditor provides a complete evaluation of the home. The auditor usually conducts a variety of tests including a blower door test and a thermographic scan. The latter is critical to assessing the insulation in the walls. It utilizes an infrared camera to compare the temperature differences of exterior walls, which will help reveal insulation levels in wall cavities. If the report determines deficiencies, adding insulation to the wall cavities should be considered.

Next, finding an insulation contractor who understands how to update insulation in the walls of a home is essential. A professional insulation contractor can evaluate the exterior walls of the home to determine feasibility of adding insulation. Typically, homes with removable siding are the best candidates for adding insulation to the walls. If it is not practical to go through the exterior side, it is possible to go through the interior side of walls. Although this can create more disruption to homeowners, the process is similar.

Once it is determined that insulation can be added to the walls, here is how the process usually works and which products are most suitable for the job.

  • Where there is removable siding, sections are carefully removed on the exterior walls where the audit identified deficiencies.
  • Small holes are drilled into the substrate of the wall, taking care to avoid interior wiring and plumbing chases. (Or, if going from inside the home, holes are drilled through the drywall.)
  • A dense pack insulation material is blow into the wall cavities through the holes to fill the space. This requires specialized equipment and properly trained installers knowledgeable in the procedure.
  • Once the wall insulation is installed, the holes are patched and sealed and the siding is reattached as needed.

Choosing the correct insulation product is important. As noted, it requires a material that can be dense packed via a tube through the holes in the wall. Options are fairly limited to cellulose insulation and foam insulation. In most instances, cellulose insulation is the best product for the job. Here’s why:

  • It is less costly in most cases. Foam is more expensive and a low-rise product must be used in very slow increments increasing the time required.
  • It is less time consuming. As noted, foam must be installed at very slow intervals. Cellulose can be continuously applied. So the project takes much less time using cellulose insulation.
  • Fewer holes are required in the walls. Typically, slightly larger holes are needed for cellulose while more smaller holes are used for foam.
  • Cellulose insulation can be used where there is existing fiberglass insulation in the walls. Foam cannot.
  • Cellulose insulation provides more sound control than foam typically reducing the amount of outside noise in the home.
  • Cellulose insulation includes a fire retardant and is an approved fire block component in walls. Using the product will add to the fire protection in the home. Foam is a petroleum-based product and inherently flammable.

Yes, compared to the cost of updating insulation in an attic it is more expensive per square foot to retrofit insulation in walls. But adding attic insulation over rooms where there is insufficient insulation in the walls will only achieve half of the energy efficiency needed. Learn more about retrofitting walls with cellulose insulation and get referrals for qualified contractors from cellulose insulation manufacturers.

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