It is important to be able to get into the attic to perform periodic inspections. An opening into the attic should be large enough so that the average person can easily gain access with the aid of step ladder.


Adequate air movement through the attic is very important in keeping the home cool in summer. and warm in winter.  Venting is accomplished by a combination of soffit vents and roof vents. Roof venting is accomplished by round vents, ridge vents, gable vents, or power roof vents. The minimum recommendation for proper attic ventilation is one square foot of free air vent area for each 150 feet of attic space. Every venting device has a value of free air venting described for it so the calculations for proper venting can be made. In a practical sense, the attic should not be more than 15 degrees Fahrenheit warmer than the outside air. When the attic space is inspected, daylight should be seen at the eaves to indicate the soffit vents are open and not obstructed.


Providing a thick blanket of insulation is the best method of conserving heat in the home. Insulation may be made of cellulose, fiberglass, rock wool, or vermiculite and applied either in loose fill or in batts/blankets. Some rigid board insulation is available but is usually applied on the exterior side of the roof deck. Make sure that insulation does not block off any venting device.

Insulation and R-factor

Type R-factor per inch Min.

Fiberglass                   2.9 – 4.2

Cellulose                     3.5

Rockwool                    3.1

Vermiculite                 2

Foams                          4-10

R-38-R-60 is the recommended amlujnt of any type of insulation in the attic. R-13 is recommended in the walls.

Is vermiculite insulation a problem?
Prior to its close in 1990, much of the world’s supply of vermiculite came from a mine near Libby, Montana. This mine had a natural deposit of asbestos which resulted in the vermiculite being contaminated with asbestos. Attic insulation produced using vermiculite ore, particularly ore that originated from the Libby mine, may contain asbestos fibers. Today, vermiculite is mined at three US Facilities and in other countries which have low levels of contamination in the finished material.

How does asbestos cause health problems?
Asbestos can cause health problems when inhaled into the lungs. If products containing asbestos are disturbed, thin, lightweight asbestos fibers are released into the air. Persons breathing the air may breathe in asbestos fibers. Continued exposure increases the amount of fibers that remain in the lung. Fibers embedded in lung tissue over time may result in lung diseases such as asbestosis, lung cancer, or mesothelioma. Smoking increases your risk of developing illness from asbestos exposure.

What should I do if I have vermiculite attic insulation?
DO NOT DISTURB IT. Any disturbance has the potential to release asbestos fibers into the air. Limiting the number of trips you make to your attic and shortening the length of those trips can help limit your potential exposure. EPA and ATSDR strongly recommend that:

  • Vermiculite insulation be left undisturbed in your attic. Due to the uncertainties with existing testing techniques, it is best to assume that the material may contain asbestos.
  • You should not store boxes or other items in your attic if retrieving the material will disturb the insulation.
  • Children should not be allowed to play in an attic with open areas of vermiculite insulation.
  • If you plan to remodel or conduct renovations that would disturb the vermiculite, hire professionals trained and certified to handle asbestos to safely remove the material.
  • You should never attempt to remove the insulation yourself. Hire professionals trained and certified to safely remove the material.
  • Visit Vermiculite Insulation for more information

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