RTU Repair & Diagnostics
Fast, accurate diagnostics and repairs for all major commercial rooftop unit brands. Our certified technicians restore system performance quickly, minimizing downtime for your Long Island facility.
Long Island's commercial buildings demand dependable rooftop unit performance year-round—from humid summers to harsh winters. Denair HVAC delivers expert RTU service, repair, preventive maintenance, and emergency response backed by 19+ years of experience, manufacturer-certified technicians, and a commitment to minimizing your downtime and operational disruptions.
Comprehensive RTU solutions for Long Island commercial facilities—from routine maintenance to full system installation and emergency repairs.
Fast, accurate diagnostics and repairs for all major commercial rooftop unit brands. Our certified technicians restore system performance quickly, minimizing downtime for your Long Island facility.
Proactive maintenance plans that extend rooftop unit lifespan, reduce energy costs, and prevent costly breakdowns. Free preventive maintenance included for up to 18 months on all new RTU installations.
Turnkey commercial rooftop unit installation with full project management, value engineering, and end-to-end coordination—saving clients up to 35% on HVAC budgets.
Round-the-clock emergency RTU service with same-day response—usually within 4 hours. Technicians arrive fully equipped to handle urgent repairs on all major rooftop unit brands.
Modernize aging rooftop HVAC equipment with targeted retrofits and expert system tuning to optimize performance, energy efficiency, and compliance—without full system replacement.
Smart controls and automation solutions integrated with your rooftop units to significantly reduce energy costs and environmental impact across your commercial property.
Our certified technician visits your Long Island facility to conduct a thorough inspection of your rooftop unit, evaluating system condition, performance history, and any immediate concerns to develop an accurate scope of work.
See how Denair HVAC has kept commercial facilities running efficiently across Long Island and the greater New York area.
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"
"Crew was respectful, fast, and left our place spotless. Five stars."
"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"
"Impeccable install. You can tell they're pros the moment they walk in."
"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."
"Denair is the most dependable HVAC service company in New York!"
"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."
"excellent work and quality"
"Denair is professional and courteous."
"I know DENAIR for years dealing with their commercial insurance matters. I know they provide best in class services and have recommended them to a couple of major construction industry players. I can definitely say – the bigger the project the bigger my commission is"
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"
"Crew was respectful, fast, and left our place spotless. Five stars."
"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"
"Impeccable install. You can tell they're pros the moment they walk in."
"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."
"Denair is the most dependable HVAC service company in New York!"
"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."
"excellent work and quality"
"Denair is professional and courteous."
"I know DENAIR for years dealing with their commercial insurance matters. I know they provide best in class services and have recommended them to a couple of major construction industry players. I can definitely say – the bigger the project the bigger my commission is"
"I didn't even know about their referral program sending DENAIR to one of my commercial tenants. It was a nice surprise to get paid for referral. Based on the tenant's feedback, the job was well-done. Now it's no brainer to recommend DENAIR to all my tenants"
"I was able to upgrade my cooling towers through the help of Denair and I did love their Service rendered, Wonderful Experience."
"I am very pleased with the service and professionalism we receive from all the techs and staff at Denair."
"Great company, our office was getting hotter by the minute. Denair had a tech on site with in the hour and the ac working perfect in two hours"
"Crew was respectful, fast, and left our place spotless. Five stars."
"They have the best Engineering Service I have ever seen; they are always available on request and perform the maintenance in the most efficient way. Great Service."
"Really great to work with, awesome staff, happy to work with them anytime again in the future! Highly recommend."
"Dennis was always available when I called on him. Never was any additional work generated on any quote/contract awarded. Reliable, expert and a pleasure to work with. A real value!"
"Impeccable install. You can tell they're pros the moment they walk in."
"What a great service. I randomly called to get multiple system inspected in my building. They came on time, done a great job and provided a detailed report. I love their transparency."
"Denair is the most dependable HVAC service company in New York!"
"I recently used Denair for some repairs to my small two-story office building, and I have to say they are the most honest, hard-working and value focused HVAC provider I have ever experienced! Not only was the price competitive, but more importantly they helped reduce my energy costs from an..."
"excellent work and quality"
"Denair is professional and courteous."
"I know DENAIR for years dealing with their commercial insurance matters. I know they provide best in class services and have recommended them to a couple of major construction industry players. I can definitely say – the bigger the project the bigger my commission is"
Long Island businesses trust Denair HVAC for commercial rooftop unit service because of our unmatched technical depth, transparent pricing, and guaranteed results.
Technicians trained and certified by major RTU manufacturers, ensuring expert service on any brand across Long Island commercial properties.
24/7 emergency RTU service with arrival typically within 4 hours—because Long Island businesses can't afford extended downtime.
All unintended costs are covered at our expense. No surprise invoices—just transparent, value-engineered pricing that consistently beats the competition.
Founded in 2007 and recognized by Inc. 5000, Denair HVAC brings nearly two decades of commercial HVAC expertise to every Long Island project.
Dedicated specialists delivering expert commercial RTU service across Long Island.
Founder & CEO
Dennis founded Denair HVAC in March 2007 with one man and a beat-up used truck, driven by over 17 years of hands-on HVAC industry experience. Under his leadership, the company grew from a one-person operation to a recognized Inc. 5000 company generating over $2 million in annual revenue—serving major commercial clients across the New York Metro Area and Long Island. Dennis oversees the company's strategic vision, ensuring every rooftop unit project is delivered with the technical excellence, honest pricing, and commitment to client satisfaction that define the Denair standard.
Service Manager
Thomas leads Denair HVAC's service operations across Long Island and the greater New York Metro Area, ensuring fast response times, efficient technician scheduling, and consistent service quality on every commercial rooftop unit job. He manages the coordination between field technicians and client communication teams, keeping systems running reliably and reducing facility downtime. Thomas's operational rigor is a key reason Denair achieves same-day service response—typically within 4 hours—and maintains the high standards that commercial property managers depend on throughout Long Island's demanding climate conditions.
Application Engineer
Ramil designs and supports HVAC systems—including commercial rooftop units—tailored to each building's unique performance and energy efficiency needs. He oversees equipment selection, technical planning, and application support for Long Island commercial facilities, ensuring every RTU installation and upgrade delivers long-lasting reliability, measurable energy savings, and full code compliance. Ramil's engineering expertise is instrumental in Denair's value engineering process, consistently identifying opportunities to optimize system performance while reducing project costs for property managers and business owners across Long Island and the New York Metro Area.
Lead Estimator
Farrukh has been a cornerstone of Denair HVAC since 2010, bringing extensive expertise in bid proposal preparation, vendor coordination, and project cost analysis for commercial HVAC projects throughout Long Island and the New York Metro Area. As Lead Estimator, he is responsible for delivering accurate, comprehensive proposals that leverage Denair's value engineering approach—helping commercial clients save up to 35% on rooftop unit service and installation budgets. Farrukh's meticulous approach and deep knowledge of the Long Island commercial HVAC market ensure every client receives a competitive, transparent scope of work.
Commercial HVAC service call costs typically range from $150 to $500 depending on the complexity of the system, travel distance, and time of service. For rooftop units, diagnostic calls may run higher due to the equipment size and access requirements. Denair HVAC provides free estimates and transparent, fixed-price proposals so you always know the cost before any work begins.
Speak with a certified RTU specialist for a free consultation and honest answers.
Denair HVAC provides commercial rooftop unit service across Long Island and the greater New York Metro Area, including all five boroughs and surrounding counties.
11+ Regions
Service Area
24/7 Service
Emergency Availability
Within 4 Hours
Response Time
Contact us to confirm coverage and schedule your commercial RTU service today.
Recognized as one of America's fastest-growing companies
Full OSHA safety compliance on every rooftop job site
Licensed mechanical contractor serving New York commercial clients
Fill out the form below and a Denair HVAC specialist will respond promptly with a free estimate and tailored recommendations for your commercial rooftop unit needs.
For immediate assistance, feel free to give us a direct call at 718-791-5074 You can also send us a quick email at
For immediate assistance, feel free to give us a direct call at 718-791-5074 You can also send us a quick email at