You never want to use faced fiber glass when you are adding another layer to existing attic insulation. What you should use in this situation is unfaced fiber glass that does not have any vapor retarder. When you learn how to lay attic insulation, you’ll realize that the insulation facing acts like a vapor retarder and will help to lower the level of moisture that enters through a wall or any other surface. If you added a second vapor retarder over layers of faced insulation, any amount of moisture, no matter how small, that gets through the first layer will actually condense onto the second. Some damage to ceilings or walls will occur because of this condensation and the areas will be stained. If the condensation continues for a long period of time, then there may even be structural damage.

Any decent guide that tells you how to lay attic insulation should always cover the subject of radiant barriers. There are three main types of radiant barriers. Single layer film material, bubble film or multilayer, and then single films that are put directly on the underside of the sheathings on the roof, are the three most common types. However, you must know that radiant barriers are not actually insulation. In fact, they do not even have an r-value. The fact is that you can find radiant barrier products which actually use the concept of trapped air and that enables them to have an r-value, even though it will be very small.

Another interesting fact when learning how to lay attic insulation, is the difference between summer r-value and winter r-value. Summer r-value is actually the insulation rating when examining the heat flow in a downward direction. Winter r-value is when you examine the heat flowing upwards. Even though radiant barriers are sometimes used, it is almost always more cost effective and overall effective to simply use quality insulation products. Also, in truth, the actual heat flow which is resisted by radiant barriers is usually much less than what the manufacturers claim. Learning how to lay attic insulation is a skill that anyone can pick up as long as they learn the right methods that are safe and effective.

Read More:

1. Attic Radiant Barrier – Cut Heating and Cooling Bills