Ground Loop Heating and Air Conditioning

Our roots go back to Dublin Sheet Metal, founded by our grandfather, Alfred Cullum, after he learned aircraft sheet-metal work in the Air Force. Today, we are a third-generation, family-owned HVAC team based in Darlington, Maryland. For more than 40 years, we have designed and installed residential and light commercial HVAC systems, growing into a geothermal-focused team that has completed thousands of installations throughout Maryland and surrounding areas.

Residential and light commercial geothermal heating and cooling is what we do every day. Our IGSHPA-certified installers design and install geothermal systems, lay ground loops, connect equipment, and answer questions at the job site. Our service technicians work on hundreds of geothermal systems each week, giving them extensive day-to-day experience with geothermal maintenance, diagnostics, and repairs. We service all brands, including WaterFurnace, ClimateMaster, Enertec, HydroDelta, Bosch, and many others. We can also install, repair, and maintain other HVAC equipment, including heat pumps, boilers, air conditioners, gas and oil furnaces, and mini-splits.

Honesty, thoughtful design, and quality workmanship guide our entire team. We provide accurate, all-inclusive pricing before repair work begins, so our customers understand the cost and can make an informed decision. For larger projects, we coordinate with general contractors, project managers, architects, designers, site managers, and other subcontractors to help the installation proceed smoothly and with as little disruption as possible. We serve customers throughout Maryland, including Baltimore and Harford, Anne Arundel, Howard, Baltimore, Cecil, Carroll, Montgomery, Prince George’s, Kent, and Queen Anne’s counties, with emergency service available 24 hours a day, 365 days a year. Whether we are installing a new geothermal system or maintaining existing equipment, we remain available to answer questions and help make homes and buildings more comfortable and energy-efficient.