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Should I Add Insulation In Older Home Exterior Walls

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Cody asks:

I have an inquiry regarding dense-pack cellulose for exterior sidewalls of an older home that I’m hoping to get some insight on.

I live in upstate New York (Zone 6) in a home built in 1958. The home has no insulation in any of the exterior sidewalls. The only retrofit option I’m aware of in this instance without tearing down all of the drywall in the entire house is to dense-pack cellulose through small holes drilled in the sheathing. I obtained quotes for this work from a few reputable local insulation contractors, all of whom suggested they regularly do this type of application and have no concerns with it.

In doing a lot of independent internet research on the practice of dense-packing exterior sidewalls with cellulose, however, there seem to be varying opinions as to whether or not it’s a good idea. Some say it’s a time proven practice that’s been done successfully for decades without issues. Others, however, insist it’s a surefire way to ‘destroy’ or ‘kill’ an older home. Those of the latter opinion seem to focus on the fact that old homes of the vintage of mine (again, built in 1958) were purposely built without insulation in the exterior sidewalls in order to allow the house to ‘breathe’ and air itself out, if you will. They argue that by packing the exterior sidewalls full of cellulose you cut off the ability of the house to ‘breathe’, setting the stage for moisture, mold, rot, etc. A certain population of folks out there suggest literally not insulating the walls of older homes like mine. Period.

My intent in getting the walls of my home insulated is both to generally increase comfort in the winter months (i.e. cut down on drafts) and hopefully lower my heating bills a bit. If this comes with the risk of potential mold and rot issues down the road, however, I’m questioning whether or not it’s a wise move to get this work done.

Curious to know your thoughts on the matter. Is there any merit in the argument that dense-packing exterior sidewalls will inevitably result in moldy, rotten studs, and destroy your home?

Thanks for your time!


cellulose insulation wall retrofit installation

Cellulose insulation is blown into walls of older homes.

CIMA encourages adding/updating insulation in older homes when done by an insulation contractor experienced in the proper procedures. Dense packing an older home such as yours is an excellent idea. And cellulose insulation is the perfect product for the job. See more on our website Retrofit page. The benefits include lower energy bills, more comfort and less exterior noise. Those that have a counter opinion do have a valid point and it does need to be addressed. While the idea of a house breathing is somewhat absurd, a more accurate statement is that the indoor environment must be controlled for pollutants, indoor air quality (IAQ) and moisture. Once insulation is improved, the home will not have the “leaks” or actual infiltration or exfiltration of air it once had. That means the water vapor (relative humidity) can rise. This is what can cause the mold and health issues some warn about. It is just as important that exhaust fans be properly installed and used as part of the home retrofit. Review this aspect with contractors as you continue to evaluate options for updating the insulation in exterior walls of your home.


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