Found in 1871 by a group from Chicago, Illinois, Longmont took advantage of the building of the Colorado Central Railroad line and flourished as an agricultural community.  High technology saw the construction of a manufacturing and development campus, an air route traffic control center, and the arrival of commercial businesses.

Serving the beautiful Longmont, CO area with reliable HVAC services!

The downtown area has continued to experience a rejuvenation, and the community of Longmont now encompasses 22 square miles.  With more than 300 days of sunshine, there’s plenty of opportunity to appreciate the scenic views. Spend the day hiking Rabbit Mountain, visit the LongMont Museum & Cultural Center, tour the many brewing companies, check out the Sunflower Farm, or spend the day swimming, canoeing, paddle boarding, or enjoying 1,500 acres of parks.

For trustworthy heating & AC services, repairs & installations in Longmont, call Welzig Heating and Air today!

Welzig Heating and Air has provided skilled, affordable, and conscientious HVAC services in Longmont since 1994.  Family-owned, we take pride in quality. Handling both residential and commercial installation, retrofit, seasonal maintenance, and repair, we offer efficient and effective solutions to heating, cooling, air quality, and water heating challenges.  Contact us at (720) 336-3777 anytime, 24/7, and we’ll devote our considerable resources to ensure quick response and cost-effective results. We employ a team of highly trained, NATE-certified, factory authorized technicians who are dedicated to your satisfaction.

Here are some of the services that we provide throughout the Longmont, CO area:

AC Installation, Heating Repair & HVAC Installation

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HVAC Installation, Air Conditioning Repair & Heating Repair Boulder, CO, Longmont, CO & Louisville, CO

Heating Repair, HVAC Service & Air Conditioning Repair

Furnace MaintenanceAir Conditioning RepairHVAC Service

Satisfied Customers
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Dave Kaplan-Gomez and James Miltersen installed my new Tankless Water Heater. Both were polite and professional. Care was taken not to damage anything in my house which I really appreciated. I use Welzig for all my HVAC needs and highly recommend them.


Our 23-year-old A/C system ran out of “borrowed time” and became too difficult to continue maintaining. With great advice from Casey Welzig,, we replaced the old system with a Bryant Evolution A/C system. Max Loustaunau and Seth Bernhardt did an excellent job with removing the old system and installing the new one. Both of them are great to work with — very professional and very personable. We are really amazed at how much better the new system works!


Bob came out to look at our swamp cooler and was remarkably helpful and professional. Not only did he give me a knowledgeable diagnosis, but he also taught me a lot in the process. We’ll be calling him for all future needs with our cooling system.

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Longmont, CO