Using urea extended phenolic binders with a resin to urea solids ratio below 60/40 can significantly reduce production costs in the manufacture of fiberglass products without adversely affecting product performance or producing formaldehyde or ammonia emissions at unacceptable levels. The phenolic binders are produced by reacting urea with phenolic resins that are prepared in a reaction in which the formaldehyde and phenol are initially present in mole ratios of greater than 3.75:1. In preparing the phenol/formaldehyde based binder, the molar ratio of free formaldehyde to urea must be carefully controlled in order to minimize emissions of ammonia and formaldehyde. Typically this molar ratio is kept between 0.8 and 1.0, therefore, higher free formaldehyde resins may be reacted with a higher percentage of urea to maintain the target formaldehyde to urea molar ratio. No ammonia is needed in the making the phenolic binder.
