In existing homes, cellulose (here) or other loose-fill materials can be installed in building cavities through holes drilled (usually) on the exterior of the house. After the installation, the holes are plugged and finish materials replaced. | Photo courtesy of Cellulose Insulation Manufacturers Association. The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation — notably blankets and materials that can be poured in place. Other types require professional installation.