If a home is older than 25 years old and the attic insulation has never been updated, it would be a good idea to get a Home Energy Audit. If the insulation needs to be updated, it is possible to put new insulation over old insulation, unless it is wet. Any new roll or batt insulation installed over existing insulation in the attic needs to be without a vapor retarder. While insulation has a long lifespan, it does not last forever. If a home over 50 years old, you may find that replacing the insulation can save you a significant chunk of money on your heating and cooling bills. The modern standards for attic insulation in Maryland is R-38 which means you should see a minimum of 10-15 inches of blow-in insulation depending on the type of insulation used.
The first picture with the gray insulation is from a house built in 1950 and has boards placed over top of the insulation reducing its effectiveness. In addition to reducing the insulations effectiveness, you can see that the roof decking above the boards is showing signs of mildew and other microbial activity which will shorten the life of the building materials.
The second picture shows an improper installation of fiberglass installation in a crawlspace. It is important that the vapor barrier always face the “warm in winter” side of the house and the fiberglass bats face out. The main reason that insulation vapor barriers are installed in the warm on winter side of exterior walls is because the air, together with the water vapor it carries will pass through the wall and cool down which causes the relative humidity to rise.
The third picture shows a more modern application where the insulation was blown in and measured by the insulation installers. The homebuyers wanted to place boards over this insulation to use the attic for storage which is something I strongly advised against.
Old Line Home Inspections is certified to do a Home Energy Report with our home inspections which can be helpful for first time homebuyers or anybody buying an older home. For more details, please contact us at (410) 236-3027 or click here to schedule an appointment.