The effect of vibrations due to manufacturing and transport on the thickness, density, and calculated thermal resistance (R-value) of loose-fill rock wool insulation installed in two manufactured home units has been determined. Thickness and density measurements on blown attic insulation were made after installation, at the end of the manufacturing process, and after the units were towed 426.5 km (265 miles). These measurements were used to calculate R-values for the attic insulation. The end sections of the two units showed an overall insulation thickness decrease of about 16% and an average R-value change from 5.50 to 5.08 K · m²/W (31.2 to 28.8 ft² · h · °F/Btu). An estimated R-value greater than 5.29 K · m²/W (30 ft² · h · °F/Btu) resulted from averaging the end and middle sections of the two units. The effect of reduced thickness along the edges of the attic space was not included in the estimate.