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Community and Q&A

Insulating a home with plaster walls

RSHO | Posted in General Questions on

I purchased an older home. There is no insulation in the walls. Exterior walls are 1 inch thick wood with vinyl siding over it. Interior walls are 1 inch thick boards with a plaster lathe strip over studs then plaster lathe and plaster installed as it should be. First floor has 10 foot ceilings, second floor has 8 & 9 foot ceilings. Gutting out interior is to time consuming to insulate. I am considering blown in insulation and using Perlite that I can do myself. Would Perlite be a reasonable insulation choice. Any information would be appreciated.

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "I am considering blown-in insulation."

    A. Good.

    Q. "I am considering using Perlite that I can do myself. Would Perlite be a reasonable insulation choice?"

    A. No. Perlite doesn't slow down air flow, so it's a poor choice. The standard approach is to install cellulose.

    I strongly suggest that you hire an experienced insulation contractor to install dense-packed cellulose in your empty stud bays. If you want to do the work yourself, you can -- but there is a learning curve associated with this work. You can be tripped up by blocking in the stud bays, or unusual wiring. You need to understand where to drill your holes, and how to aim the hose.

    Ideally, you need a powerful insulation blower to dense-pack your walls. If you do the work yourself, you won't have that equipment -- you'll be using a rented insulation blower (or a machine that is lent out for free by Home Depot or Lowe's). This equipment can work when used to insulate empty stud bays -- but you really need to know what you are doing to get one of these underpowered machines to provide a reasonable density.

    For more information on this topic, see How to Install Cellulose Insulation.

  2. srenia | | #2

    I have client that wants to gut good plaster walls to get better insulation. Been a struggle to convince them not to do this. The cost alone is way too high since a third party is going to do it. So ultimately they'll head my advice.

    Martin's advise is right on. I would add that the cellouse installers use a FLIR/infared camera. Even the best cellouse installer will miss a spot because of unusual placement of a stud in the wall. The infared camera should catch those spots.

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