Fire resistance

Loose-fill fiber glass is naturally fire resistant.

Installation standards and practices

Fiberglass loose-fill insulation typically is installed in attics and walls with blowing machines, but most attics can be poured in place if necessary. Although installation methods may vary slightly depending on the material, the machine used, or the actual job-site conditions, the NAIMA standard guidelines will provide a general framework to better understand installation procedures.15

In order to estimate the amount of loose-fill fiberglass insulation to be installed, the area to be insulated is measured first. This should be the net area only, since the area occupied by framing members should be deducted from the total wall or attic space. From these calculations, the required number of bags or pounds of insulation is determined from the bag label chart for the desired R-value. (ASTM C764 requires that each bag of fiberglass loose-fill insulation be labeled with technical information, including the maximum net coverage per bag of the particular insulation for all commonly specified R-values.) Any deviation from the quantity specified will affect the desired R-value. This holds true in both open – and closed-blow installations.

According to NAIMA, thickness must not be used as the sole fac­tor in determining the R-value of loose-fill insulation. When blown – in insulation is installed properly (at the recommended weight per square foot or bags per 1000 ft2), it may have an “installed thick­ness which is greater than the stated minimum thickness.” This is sometimes described as overblow in order to compensate for any potential insulation settlement. If the correct number of bags are installed and the thickness exceeds the minimum thickness, the labeled R-value will be achieved or exceeded.16

If these products were installed at the minimum thickness, the overblow would produce a coverage per bag that would exceed the maximum net coverage shown on the bag label, but the weight per square foot would be less and the R-value would be lower than the intended R-value. In any event, if the thickness installed using the correct number of bags is less than the stated minimum, then addi­tional material must be added to bring the installed thickness up to the required minimum thickness.16

If an existing installed insulation amount needs to be verified, NAIMA provides a few recommendations. These involve taking measurements of the insulation thickness, removing and weighing a known area of insulation, and calculating the weight per square foot of the insulation. The measured weight per square foot and the installed thickness are then compared with the value shown on the manufacturer’s label. Meeting or exceeding the labeled values ensures that the proper R-value has been achieved.16

Installers are required to provide a data sheet verifying the amount and achieved R-value installed. This is known as the United States Federal Trade Commission’s Labeling and Advertising of Home Insulation Rule, and it mandates that the con­sumer is to receive a signed and dated contract or receipt for the insulation thickness installed. The receipt for loose-fill insulation must show the type of insulation, the coverage area, the thickness, the R-value, and the number of bags installed. The installer also must provide a manufacturer’s fact sheet. The fact sheet for loose – fill insulation must contain, in addition to the manufacturer’s name, address, and type of insulation, a chart containing the R-val – ue and coverage information. Installers must have this information and must show it to customers before they agree to buy the insula­tion. Similarly, a seller of new homes must put the following infor­mation in every sales contract: the type, thickness, and R-value of the insulation that will be installed in each part of the house.16

General work practices applicable to all work involving synthet­ic vitreous fibers (SVF) such as fiberglass (rock wool and slag wool) have been established by OSHA. Excerpts of the guidelines are as follows17: