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Not sure if this the right category, but I'm remodeling my master bedroom and have insulation questions.

First some background. Older home, 1930 build, meaning-no insulation in the exterior walls. Bedrooms on second story with vinyl siding exterior and plaster/lath interior walls.

The masterbed room is cold in winter and drafty in some spots, so while I am repainting walls, fixing cracks I am considering blowing in insulation to increase the room's comfort. I am thinking of blowing from the inside. I am prepared to do some work on the walls, so the holes don't bother me. However, I don't want to replace all the plaster/lath with drywall.

My questions about blowing insulation revolve around moisture buildup. From what I can tell, there is no moisture barrier under the siding, and obviously by keeping the interior walls, I won't be able to put a moisture barrier under the interior surface.

If I were to blow in cellulose insulation, will that create condensation or moisture issues within the wall? And if so, is there a potential for mold in the cellulose insulation? Is there another insulation material that I should consider?
With my limited knowlege of this type of housing construction, I know that the airflow does a good job of keeping things dry within the walls, but not a good job of keeping the cold air out! And, I don't want to create more problems by adding insulation.

Sorry for the long post. Any advice greatly appreciated. I am considering kicking this part of the project off in a week or so. I may have a contractor handle the insulation, but since it is not a large room I am considering making it a DIY. Just want to be informed either way I go.
 

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This is one of those times to call in an insulation contractor----They will likely suggest a low expanding foam----That is a product not available to us lowly DIY types---

The foam will flow past most obstructions -and provide the vapor barrier you need--

Others here might know of a DIY wall fill--so just wait--we will see.--Mike--
 

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Moisture Barrier Myth

The idea that you must put a vapor barrier or retarder in every wall has long been discredited. As far back as the late 1970s published studies involving hundreds of homes clearly showed that retrofitting uninsulated homes without vapor barriers with insulation resulted in no moisture problems. Today building science recognizes that in most climate zones a warm-in-winter vapor retarder is more likely to cause problems than to prevent them. If you have water incursion from the exterior, insulation in the cavities may retard the drying process. As you noted, the air that's blowing through the cavities now probably keeps them fairly dry, even if some water is seeping in. The research I mentioned suggests that this is not an endemic problem.
 

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In older homes, the multiple layers of paint are adequate enough to serve as a vapor barrier. The purpose is to prevent warm humid interior air from condensing inside the wall.
 
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