Corporate Officers

David Dugger SKMES President

David Dugger

President & CEO – Knoxville

David Dugger started his mechanical construction career in 1971 as a sheet metal and piping apprentice while studying mechanical engineering at the University of Tennessee. He has held many management positions during his career as well as project management and estimating. David has been involved with a variety of projects in terms of both in size and complexity ranging from healthcare, manufacturing facilities, institutional, commercial office and mix-use buildings. He holds licenses in over twelve states and has extensive experience in the design/build areas of mechanical construction. David is a strong supporter of the mechanical industry, previously serving as national and state president and board member in Tennessee and other national and local committees.

Brenda Duff SKMES Treasurer

Mark Lucas


Mark entered the Mechanical industry in 1988 as a service technician with Fred Hayes Mechanical Contractors.  Soon after the company joined the Comfort Systems USA family, Mark was promoted to Service Manager in early 1998 and later that year became Vice President of Operations, overseeing all field operations for the company.  In 2001, Mark was again promoted to President of Comfort Systems USA (Bristol), Inc.  Mark’s extensive background and knowledge of service operations enabled him to lead the company to be recognized seven times as a Comfort Systems USA company of the year.  Mark is active in community organizations, serving as Chairman of the Board for the Bristol Chamber of Commerce in 2007 and leading the United Way Fundraising Campaign in 2017.  Upon the merger of CSUSA-Bristol with sister company ShoffnerKalthoff MES, Inc. in 2019, Mark took on the role of Senior Vice President for the Southwest Virginia and Northeast Tennessee operations, overseeing Bristol, Roanoke and Johnson City locations.

Gary Coulter SKMES Senior Vice President

Gary Coulter

Senior Vice President

Gary Coulter has more than 35 years of experience in plumbing and piping work. He entered the field in 1974 and worked on projects ranging from schools and hospitals to industrial jobs. Gary started working for ShoffnerKalthoff in 1984. He became Senior Vice President of SKMES in 2014. Gary has been involved with numerous projects involving pre-construction services, design/build, plan and spec and negotiated work.

Brenda Duff SKMES Treasurer

Will Nulton

Senior Vice President

William Nulton started his career in the mechanical contracting field 1994, after graduating from Tennessee Technological University with a Mechanical Engineering Degree.  Through his career, William has held various roles within the industry giving him a unique and diverse perspective of the mechanical construction industry.  His experience spans across many types of facilities including: institutional, heavy industrial, light manufacturing, healthcare, higher education, K-12 schools, and process refrigeration.  William holds contracting licenses in multiple states and disciplines.  He joined Comfort Systems USA in 2007 and assumed the role of Sr. Vice President for the ShoffnerKalthoff team in 2018.   


Todd Wolf SKMES Chief Financial Officer

R. Todd Wolf

Chief Financial Officer

Todd Wolf earned an accounting degree from the University of Tennessee and is a Certified Public Accountant. His career spans the restaurant industry as well as construction. In 2006, Todd was offered the position of Chief Financial Officer of ShoffnerKalthoff. He currently oversees accounting, insurance, human relations and information technology for ShoffnerKalthoff. Todd is an active member of the Rotary Club of West Knoxville.

Kevin Keck SKMES Vice President of Construction

Kevin Keck

Vice President of Construction

Kevin Keck has more than 20 years of experience in the Mechanical Industry. He started working for ShoffnerKalthoff Mechanical in 1992 in the HVAC and Plumbing field. He worked as a sheet metal field foreman for more than 11 years and became a Project Manager and Estimator in 2005 and was promoted to Vice President of Construction in 2014.

Bill Campbell SKMES Vice President Electrical Division

Bill Campbell

Vice President of the Electrical Division

Bill Campbell has more than 30 years of experience in all facets of electrical construction, in both fieldwork and management. He graduated from the University of Maryland in Business Administration. He started working at SKMES in 2006 as Director of Operations and was promoted to Vice President of the Electrical Division in 2014. Bill has managed electrical projects up to 25 million dollars in size. His project experience includes healthcare, institutional facilities, industrial, high voltage, commercial and specialty projects.


Brenda Duff SKMES Treasurer

Brenda Duff


Brenda Duff has more than 20 years of experience in the construction industry and over 30 years in the field of Accounting. Before joining ShoffnerKalthoff as Controller in 2012, she worked for another electrical contractor in Knoxville. She was promoted to Treasurer in 2014. Brenda splits her time volunteering for church and community organizations.

Brenda Duff SKMES Treasurer



Tammy earned her Business Management – Accounting degree from Emory & Henry College in 1995.  Later that year, she began her career in the Mechanical Accounting industry at Fred Hayes Mechanical Contractors.  When the company joined the Comfort Systems USA family in 1997, Tammy was promoted to Controller for Comfort Systems USA (Bristol), Inc.  Upon the merger of CSUSA-Bristol with sister company ShoffnerKalthoff MES, Inc. in 2019, Tammy assumed the role of Controller – Service, overseeing financial operations within the Service divisions of the company. 

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