Today, most commercially available insulations are man-made. Most of today’s insulations can be used safely in a tightly constructed house where the insulation is well separated from the living space. Despite health concerns related to nearly all other building materials, insulation gets the most press coverage. This is largely due to the energy crisis of the 1970s in which urea-formaldehyde-foam insulation was responsible for elevated formaldehyde levels in some homes. As a result of health impacts, this product was banned and that type of insulation has disappeared from the market.
Sometimes the only way to insulate the walls of an existing house is to drill holes in the walls and blow insulation into the wall cavities. Existing attics can be insulated in a variety of ways, but blown-in insulations are often quicker and cheaper to install than batts. When carefully blown into sidewalls, insulation can help to tighten a house, thus minimizing infiltration while maximizing energy efficiency and comfort.
Chopped fiberglass is installed in a manner similar to that of cellulose. It is composed of small fibers of glass, but is loose in form so that it can be blown into wall cavities or attic spaces. Glass is inherently non-combustible and is not subject to being attacked by pests, so it does not need to be chemically treated like cellulose.
While there are risks to those who inhabit homes with fiberglass insulation, the most at risk are those who install, work near, or handle the insulation. Many homes with forced air heating systems have leaks. Leaky ducts can suck in fiberglass particles and spread them around the house. In addition, the resins that are used to bond the fiberglass can also emit small amounts of toxic fumes.
In most modern homes, however, the migration of fibers into the living space is negligible. In tightly constructed houses, insulation of all types is well separated from the occupants.
From a health standpoint, the various chemical additives can cause reactions in certain sensitive occupants. Symptoms vary greatly depending on the individual exposed. Because cellulose insulation is finely ground and powdery, it can filter through very small openings into the living space.
Cellulose insulation is often installed in existing wall cavities through small holes drilled in the exterior siding, which are plugged after the cavities are filled. Small gaps around electrical outlets can potentially be pathways for insulation to enter the living space of a house. In most cases, however, cellulose insulation is installed conscientiously and it remains inside building cavities, so it presents no health problems to the occupants. However, it is possible for amounts of the insulation to blow into the living space of an existing house during installation, meaning that installers must be careful to minimize such exposure, and then clean up thoroughly. New houses can also be insulated with cellulose, and if they are constructed tightly, the insulation will not be able to migrate into the living space.
The chemicals that spray polyurethane foam consists of create hazardous fumes during the application, which is why installers and nearby workers must wear personal protective equipment during the installation process. Once the foam has fully expanded and dried, however, it is inert.
However, it is important to remember that, if the chemicals are not properly mixed, they may not react fully and can remain toxic. In addition to the dangers associated with installation, the chemicals can potentially remain unreacted in the form of dust and shavings. This poses a risk when cutting or trimming the foam as it hardens, as well as when it is removed.
Energy conservation and insulation in particular, is often blamed for poor ventilation, indoor air pollution and, as a consequence, poor health. In this context, health issues are not directly due to the insulation, but are due to the failure to specify low-emissions furnishings and materials and to incorporate mechanical ventilation as part of the system.
Because there are no insulations available that are 100% safe, care should be taken to ensure that they are well separated from the living space. Tight construction techniques are the most effective means of separation to prevent both gases and particles from entering the home.