Our Business

Our technicians take pride in their work and make sure it is done right the first time. We know the harmful effects of dirty air in the home and work diligently to make your house clean and energy efficient.


As a member of the local Plumbing, Heating and Air Conditioning Guild, our team receives regular factory training to update their skills. We can always recommend the latest technology for your installations and will troubleshoot your problems in no time.

Our Team

Michael Grissom

Phone: 240 674-3100

Email: mike@cornerstone-hvac.com


Born in Frederick, Michael Grissom always had the itch to take things apart to see what went on inside and put them back together and make them work again, or atleast try. He ruined a few of his parents appliances during this phase of his life, almost taken out by a vacuum cleaners DC voltage motor, he learned about electricity and got his mind going. Mike ended up finding his niche in the Heating and Air Conditioning program at the local High School Votech program. From humble beginnings as a shop runner, he worked for an HVAC Company out of Rockville fresh out of Trade school but soon got tired of the long drive and averaging 6 hours out of an 8 hour day stuck in traffic he came back to Frederick and Started with Souther States Petroleum division (Oil Burner Heating) which would begin a 36 year Carrer of Oil Burner Service. After Southern States He moved over to Ewing Oil working out of the Frederick Branch servicing almost every oil appliance in Frederick County it seemed. He Then had a short stint working with a Frederick HVAC Comany in Frederick, He moved on to Mick's Heating and Air in Thurmont, Maryland until August of 2005 when he finally decided enough is enough working for another Company. Mike Took his Masters test, Got his insurance and on August 5, 2005 Cornerstone Heating & Air Conditioning, Inc. began running Calls as an Official Business in Frederick County, Maryland. So far, he has managed to keep the business going even during the horrible 2016 when we saw a lot of small businesses go under, We were extremely fortunate to have the customers that we do have and managed to grow the business into what it is today. Mike has a Great troubleshooting abillity that other companies can't match and when it comes to Oil Heating, other companies contact him on a regular basis in the winter months to help out their techs with oil burner work. Mike is second to none in the area of Boilers and Hot Air Furnaces, Heat pumps and A/C. He was a Student at Frederick County Votech Heating & Air Conditioning Program for 3 years and attended Lincolin Tech Technical School After leaving High School. He is not perfect, but you will not find a more determined individual when it comes to your HVAC needs.

Dave Puddy, Ductman. Dave has a long history of doing duct work. He started out with the big Companies like General Heating and worked his way up the Duct man Ladder. He became Key part of the Cornerstone Team in May of 2009, Dave can basically make anything out of sheetmetal and is very proud of the finished product he produces. Even though most of his work get sealed up behind walls and in chases, he always makes sure to take the time to ensure all joints are properly sealed and wrapped with the proper insulation when needed. He is not the fastest guy in the world, but nothing that is rushed ever lasts and I have never had to go back due to any duct issue. He has a Keen eye when it comes to installing the duct as well. Anyone can slap duct together and hang it, but few can do it the correct way, with pride. He always wants to be onsite during start up as he insists on checking the airflow for himself. His skills have helped Cornerstone gain the reputation of outstanding Quality production of Custom Duct work and metal related Products. On May 11, 2019 Dave has Been Employed By Cornerstone for 10 years now.

Anthony (Tony) Peter, Install start up and Service Technician

Tony is a young man still learning the trade. He was my helper and also Dave's helper as well at one Time of Day when we worked at another Company 14 years ago. He has been to different schools and been trained by me and David as well, although he still has a ways to go, he will soon a full time employee to help me take Cornerstone to that next level. He has very good customer relations skills and is easy to talk with.

Call Us Today!

Cornerstone Heating & Air Conditioning, Inc.

101 Radio Ln 101

Thurmont, MD 21788


Phone: 240 674-3100

Email: mike@cornerstone-hvac.com


Cornerstone Heating & Air Conditioning, Inc., Residential Air Conditioning Contractors, Thurmont, MD

Special Offers

Upgrade to a new energy efficient air conditioning unit and receive a 1 year Labor warranty on any installation performed by Cornerstone Heating & Air Conditioning, Inc.

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