WeatherMasters is no longer affiliated with the Dr. Energy Saver franchise, but they do a great job producing educational videos on many things related to Home Energy Efficiency!
Some times it is necessary to remove the existing insulation when:
Rodents, birds and animals find attics a great place to nest and when present, their droppings can pass on a number of parasites and diseases, and these can be very serious for the occupants of a home.
It is important to isolate the attic to protect the homes air supply from any air-borne contamination before disturbing or removing the insulation, then sterilize the attic with an antimicrobial disinfectant before reinstalling new insulation.
With an attic is full of insulation, it can be very difficult to locate all the cracks crevices and small openings that are responsible for energy loss, bad air infiltration and heat convection. The largest amount of heat loss occurs as warm air rises and escapes from the attic.
Removing old insulation allows for the best air-sealing results and have better home efficiency before upgrading to a better insulation product. Air-sealing helps prevent air infiltration into the home thus improving indoor air quality.
Vermiculite is a mineral mined from the earth, composed of shiny flakes that look like mica. When this mineral is put in an oven, it expands like popcorn. Expanded vermiculite is lightweight, fire-resistant, and odorless; since it has an R-value of about R-2 per inch, it was used for decades as an insulation material.
The problem with this wonderful material besides it's low R-value per inch is vermiculite contains friable asbestos. When inhaled, vermiculite dust can cause cancer.
There are also other insulation products that can compromise your health. Insulation installed before the 1970's such as fiberglass and urea-foam insulation is found to emit formaldehyde which can cause adverse eyes, nose respiratory issues.