The short answer to that question is NO. You don't have to remove the existing insulation before adding more. However, removing the insulation allows us to perform a much better job of air sealing leakage points in the attic as they become easier to see and seal. If you have signs of rodents in the attic you definitely need to remove the old insulation as it will contain rodent fecal and urine tracings. These can become airborne and create unhealthy situations in the home.
Foam board insulation is typically installed using long screws with wide washers. The screws are typically an inch or so longer than the thickness of the foam board to allow it to securely attach to the framing behind it. Once all of the foam boards are in place, then one part spray foam is used to air seal any gaps between foam boards.
The procedure for removing attic insulation varies depending upon the type of insulation that is existing.
Fiberglass Batts are removed by literally walking/crawling around in the attic with 50 gallon trash bags. The fiberglass batts are picked up off of the attic floor, folded up, and stuffed into trash bags. Then these bags are carried out of the home, thrown into a truck, and eventually taken to the dump to be disposed of.
Blown (fiberglass, cellulose, or other) insulation is vacuumed out of the attic with a large gas powered vacuum machine. A crew of 2-3 people is typically what is sent to perform vacuuming existing insulation from an attic. One or two people go into the attic with a long flexible hose that sucks the insulation through it. The hose is connected to a "drop box" which allows large or heavy items to fall into the box instead of going through the vacuum which could damage it. Then, one person sits in the truck and makes sure the old insulation goes into large cylindrical bags that are 5 ft. long and 4 ft. ion diameter. The bags are eventually taken to the dump and disposed of properly.
That's a trick question! It depends upon the type of insulation being installed, the brand, and the application for what it's being used. Cellulose insulation can vary in R value depending upon how tightly its packed. Fiberglass can vary depending upon where and how its installed. However, for the most part, here are a list of average R values per inch of depth: Fiberglass batts= R3.2/inch Blown Fiberglass=R2.6/inch Blown Cellulose=R3.6/inch Dense Packed Cellulose=R3.0/inch Open Cell Spray Foam=R3.5/inch Closed Cell Spray Foam=R6.5/inch Expanded Polystyrene Foam Board=R3.6/inch Extruded Polystyrene Foam Board=R5.0/inch SilverGlo Foam Board=R5.0/inch Polyisocyanurate Foam Board=R6.0/inch
Cellulose insulation is made of recycled newspaper. The recycled newspaper is shredded and treated with chemicals that help to make it fire resistant, and to repel insects and rodents too.
The answer to this depends upon the type of spray foam you are asking about. There are two types of spray urethane foam insulation to consider. Each are used in different conditions and to solve different issues in a home. The first is closed cell with an R value of approximately 6.5 per inch of thickness depending upon brand and application. The second is open cell with an R value of approximately 3.5 per inch of thickness depending upon brand and application.
There is a LOT more than you would think that goes into your pricing that we need to see to provide even an estimated cost to you. What is the existing insulation made of? How deep is it? Do we need to remove it, or can it stay? How do we access the attic? Do you need longer soffit baffles? Are there fire hazards we need to worry about? Are there metal or brick chimney's? Do bathroom exhaust fans go through the roof or gable end of the attic? Any exposed electrical wiring? All of these questions (and more) need to be verified by our building science experts during the evaluation. The evaluations are typically free, so why not?