Do I need Attic and Roof Venting?
No. Attic and roof venting were developed because of the inferiority of fiberglass insulation. In our climate, in the winter, heat passes through fiberglass in attics with relative ease. Without ventilation this heat would just hang out in your attic causing two common problems. One, it will melt the snow on your roof, which in turn causes ice damming, which in turn causes ceilings to leak. Second, without a way to evacuate the heat from your attic, the warm air will rise and come in direct contact with the cold underside of your roof causing all the moisture in the air to condense into water. This typically results in mold and all sorts of other damage. Unfortunately, this ventilation is just a "band-aid" that creates a flue draft effect that pulls conditioned air from your living space more rapidly. Your house would actually be more energy efficient without the ventilation, but the lack of ventilation will cause the above-stated damage.
In the summer, ventilation is needed at certain times of the day when the attic is warmer than the exterior surface of the roof (typically the evening). With foam sprayed to the underside of the roofdeck, the attic will not reach temperatures that significantly harm roof shingles. Keep in mind that foam can be sprayed to an attic floor. This application still requires ventilation, but to protect the shingles on the roof, not the foam.
Why don't I have to ventilate with FoamLok?
Ventilation is only necessary because of the shortcomings of fiberglass and cellulose insulation. These are fibrous insulators whose physical design literally lets air go right through them. If you don't ventilate an attic that has fiberglass or cellulose insulation, heat will build up in the attic causing snowmelt (which leads to ice damming) and condensation (which leads to mold growth).
When applied to the underside of the roof, ventilation with FoamLok is completely useless. Because of foam insulation's air seal and efficiency, the dew point (the temperature at which water vapor condenses) on the surface of the foam will never be reached so long as the thickness of the foam is proper for your weather conditions.
Another reason ventilation has been used in attics is to keep the underside of the roof shingles cool so they won't curl due to heat stress. Research has shown that nearly 100% of the cause is the color of the shingle more than the cooling of the bottom side of the shingle. Also, with an underside of the roof application of FoamLok the underside of the roof sheathing is now insulated and is within a few degrees of the top of the roof. No material degradation of shingle life will occur with foam.