A two-level full factorial experimental design with three variables, formaldehyde-to-phenol (F/P) molar ratios, hydroxy-to-phenol (OH/P) wt%, and reaction temperature was implemented to determine the effect of the variables on the properties of phenol-formaldehyde (PF) resol resins for insulation foam. Ten resins were prepared with F/P molar ratios between 1.5 and 2.5, OH/P wt% between 0.5 and 1.5 and reaction temperature between 80 and 90 ℃. The effect of three independent variables on the resin properties was analyzed by using three-way ANOVA of SPSS. All three production variables had a significant effect on resin properties. The F/P molar ratio and OH/P wt% were found to have the most frequent effect on resin properties. F/P molar ratio and OH/P wt% had an increasing effect, while reaction temperature showed a decreasing effect on free formaldehyde. The present study confirms that experimental design is a very valuable and capable tool for evaluating multiple variables in resin production.