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Insulating Wall Cavities With Cellulose Best For Older Homes

cellulose insulation wall retrofit installation

Cellulose insulation is blown into walls of older homes.

The best way to achieve the highest level of energy savings in older homes is to fully insulate the total building envelope.  While most homeowners often add or upgrade attics many fail to consider insulating the exterior walls.  This leads to continued inefficiency, greater energy consumption, higher utility bills and impacts on the environment.

The Situation

The majority of houses in the U.S. are old according to statistics from the federal government and studies like this one by the online journal  Older homes are suspect in the global warming/climate change crisis due to the fact most are under insulated.  This results in higher energy consumption and increased release of CO2.  According to some estimates, houses account for as much as 21 percent of U.S. CO2 emissions.

The Hidden Insulation Problem In Older Homes

To be effective, the entire building envelope should be insulated.  It would be unthinkable (and likely a local building code violation) to construct a new home without properly insulating the attic and exterior walls.  In most cases, the biggest problem with insulation in older homes is hidden from view – in the exterior walls.  It is sometimes said that the focus on insulation retrofit is attics, because heat rises, so most heat is lost through the attic. That is incorrect. Hot air rises, but thermal (heat) energy flows uniformly in every direction. The emphasis is on attic insulation because it is an easy job. A visual check of an attic is usually simple. Adding or upgrading insulation in attics can and often is done by homeowners as a DIY project.  But insulating walls requires more forensic investigation, a professional insulation contractor and greater investment.  Homeowners who ignore exterior walls fail to achieve the highest possible savings and protection of the environment.

The Misunderstanding

Retrofitting exterior walls in older homes is more expensive than doing so in the attic.  However, homeowners are often misled with incorrect information that expensive and disruptive interior demolition is required.  The fact is exterior walls in many older homes can be insulated from the outside without any impact on interior living spaces.  Homes with wood or other siding materials are great candidates but even those with brick or other hard exteriors can be insulated from the outside.  This does require a professional insulation contractor, and it will be more expensive than insulating an attic, but the cost can be well worth the benefits.

The Process

Homeowners considering any insulation retrofit project should follow this process to ensure the best possible results:

1.  Get An Energy Audit

The first step is to get a comprehensive energy audit.  When done by a professional energy auditor this will identify air leaks and insulation deficiencies.  Typically an energy audit will include a “blower door” test to show air leaks and infrared camera analysis to identify where insulation is missing or lacking.  Some local utilities provide free energy audits or can recommend approved professional energy auditors.  Either way, this is an important step in obtaining the highest energy efficiency possible for an older home.

2.  Seal The Deal

Results from an energy audit will usually show air leaks that need to be sealed.  Some leaks may require the assistance of a professional.  But caulk is inexpensive and a great DIY task that many homeowners can handle.  Eliminating gaps around doors, windows and attic spaces where air can get in or out of a house is critical to improving energy efficiency.  Don’t skip this important step in sealing the deal when improving energy efficiency for an older home.

3.  Retrofitting Exterior Wall Insulation

When it comes to retrofitting exterior walls in existing homes without interior demolition the options are more limited than with attics. Insulation material has to be dense packed in a process where the insulation is blown in through holes drilled in the exterior wall. See this step-by-step overview of the process.  Such work should only be done by an insulation contractor experienced in this highly specialized process. These contractors will have the knowledge and proper equipment specifically designed for retrofitting exterior walls. Homeowners should follow best practices for hiring a contractor when selecting a company to retrofit their home (or for any other insulation work.)

4.  Selecting The Best Product For The Job

Cellulose insulation is ideal for retrofitting exterior walls in older homes.  It is the original “blow-in” insulation product that is specifically designed for dense pack installations.  Cellulose can easily be installed in exterior walls from the outside.  The dense cellulose fibers fill the the cavity and flow around many of the partial obstructions like wiring to fully insulate the wall space.  It also offers other important ancillary benefits that simply cannot be achieved in the same combination with other products:

  • Cellulose is made from recycled waste paper.  It is up to 85% recycled material much of it post-consumer waste.  This magnifies the environmental benefit well beyond just that of insulating a home.
  • The balance of the product is in safe fire retardant chemicals that are Class A fire rated to reduce flame spread and smoke development.
  • Cellulose insulation is an excellent sound control material that helps to limit exterior noise intrusions. Retrofitting exterior walls can reduce noise for a better living environment.
  • Older homes may not have an air/vapor barrier which is necessary when using many insulation products. Cellulose insulation typically does not require an air/vapor barrier in most climate situations.

5.  Finding The Right Contractor

The Cellulose Insulation Manufacturers Association (CIMA) has producer members that can help recommend insulation contractors experienced with their products and with installing insulation in exterior walls. Use the Contractor Referral Service on CIMA’s website to contact producers servicing your state for recommendations.

6.  Lower The Cost With Tax Credits & Incentives

There may also be ways to recoup some of the cost associated with an insulation retrofit. Many states and local utility companies offer rebates and incentives for home energy efficiency improvements and adding insulation typically qualifies.  Check the Department of Energy DSIRE website for ideas or contact your utility company.

Bottom Line

If a home is more than a few years old chances are it is under insulated costing the home owner money and needlessly adding combustion products to the atmosphere. Act now to retrofit and enjoy lower utility bills, improved living conditions and help lower the impact of CO2 on the environment.

2014-07-29 13:37:52
John Rising says:

Interesting article, but the link to the photos on how to is dead!

2014-08-01 08:48:27
CIMA Admin says:

We originally did not include a link to the content related to that photo in the story but have updated it now with one. Thanks for the feedback.

2015-10-16 05:44:24
danielvhenny says:

Nice article .Thanks for submitting

2015-10-21 03:15:44
danielvhenny says:

Nice article and information about cellulose insulation.

2015-10-26 05:23:41
danielvhenny says:

Really cellulose provides a good insulation in wall cavity.

2015-11-12 04:59:29
danielvhenny says:

Great idea and insulation techniques for older homes.Thanks for sharing.