Licensed/Insured Commercial Plumbing, Heating, Ventilation & Air Conditioning Contractors in Massachusetts Also Providing Full Service Electrical Contracting Services For Small, Medium and Large Businesses in Massachusetts. Gervais Mechanical is one of the most trusted commercial/industrial mechanical contractors in Massachusetts providing the cheapest, most affordable plumbing, heating and air conditioning products coupled with state-of-the-art installation/repair services. Gervais Mechanical offers the finest commercial HVAC system installation/repair and HVAC system maintenance programs for large scale buildings including rooftop HVAC system installation, repair and replacement services.