About Us

Since 1983, Holden Mechanical Contractor’s has provided motivated, skilled, mechanics to today’s most advanced industries, for the design, engineering, fabrication, installation, repair, retrofits, and preventative maintenance of mechanical systems. Our business is centered on our ability to work with our clients in order to determine the most efficient solution for their needs, and then to realize that solution safely and efficiently. Our services revolve around design and consulting, turnkey project management, fabrication and manufacturing, installations, and service support. We maintain an office in Worcester, Massachusetts, equipped with a white room, and general manufacturing facility.

Holden Mechanical utilizes experience and technology to go beyond today’s industrial requirements to provide safe, quality, and cost efficient solutions. Our second workforce services most industrial and commercial mechanical needs. Today we offer plumbing, HVAC, and mechanical piping services so complete and divers, that they range from the very basic to the most sophisticated and complex systems. By utilizing Holden Mechanical our customers increase their profitability and minimize risks, this fact is the basis for our many long‐standing relationships with our customers.

Our many years of experience, attention to safety, and unrelenting quality control have been our building blocks for success in the industry. Maintaining focus on customers satisfaction and our ability to provide value‐added service from inception to completion creates a strong working relationship with our customers. Our dedication to safety and job related training eliminates risk and translates into efficiency for our customers. Our personnel are trained in critical safety areas, and provide manufacturer approved training for as many applications as possible. This commitment assures minimization of waste, and conservation of time. Perhaps the greatest convenience that we offer our customers, is the service of our field supervisors. Our field supervisors coordinate customer satisfaction and project completion, they possess the ability to quickly and efficiently perform through scope and design changes, as well as submit quotations and consulting, while at the job site.

Holden Mechanical customers come from the aerospace, chemical process, food and beverage, manufacturing, educational schools and institutions, healthcare, semiconductor, laboratory/research, pharmaceutical and biotech arena.



Hot Water or Steam Boilers, Heat Exchanges, Hydro-air Comfort Systems, Hot Air Furnaces, Rooftop Equipment, Energy Retrofit/Replacement Planning and Implementation, Gas or Hydronic Piping Installation, Geothermal Heat


Duct System Design, Custom Fabrication and Installation, Industrial Ventilation, Central Fan Filtration Systems, Fume Hoods and Dust Collectors, Laboratory Exhaust, Welded Flues and Breeching, Air Balancing for Comfort

Air Conditioning

Variable Refrigerant Flow Split Systems, Chilled Water Systems, Geothermal Water Source Heat Pumps, Data Centers and Computer Server Rooms, Economizer Systems, Humidity Control


Heat Reclaim Strategies and Installation, Walk-in Coolers and Freezers, Ultra-low Temperature Environments, Machinery Cooling, Refrigerated Warehouses, Ice Bank Process Cooling


Our team designs with you in mind. Clients and project are unique, so we approach each one differently. We pride ourselves on innovative thinking for all of our designs and refrain from letting common industry practice prevent us from making use of new and affordable technologies.


When the time comes for renovation or new construction, clients may need assistance to make the appropriate choices. Thielsch Engineering has extensive experience in condition assessments of building sites and electrical systems to assist with proper site selection. Our goal is to help client find a good location for their facility.


Holden Mechanical provides installation and 24/7 maintenances services. When we say customer service, we mean it. We know that your Mechanical needs are critical and essential to your business, so we make it our business to go out to your facility, day or night, and get your equipment up and running.

Additional Services

Process Piping
Sprinkler Design and Installation
Containment Piping (Site assesments, plastic and metals, fitting minimization)
High Purity Delivery Systems (High Purity/Ultra high purity "gas and chemical", Exotic metals, rare thermoplastics)
High Purity Orbital Welding
Valve Box Design and Manufacturing (custom designs, analytical testing "HP, UHP, or standard", Modular)

Our Commitment

Diversity, Inclusion, Equity

At Thielsch they are more than just words – it is what drives us to create a workplace reflective of the communities we serve.  It is how we develop our teams, cultivate our leaders and engage with our diverse communities.  At Thielsch, everyone is encouraged to bring their full, authentic selves to work.

In the Workplace

Through our commitment of advancing diversity, equity, and inclusion at Thielsch, we are focusing our efforts on the attraction and retention of individuals who have historically been marginalized. In 2021, our CEO and President, Vin Graziano, along with the board of directors put out a further commitment to diversity, equity, inclusion by hiring our first Head of Diversity & Inclusion. This role focuses on ensuring that our workplace acts as a responsible partner both internally and externally by ensuring our workplace, language, and services is reflective of our vibrant community.

Supplier Diversity

At Thielsch Engineering, Inc. (TEI), we are proud champions of diversity, equity, and inclusion for our employees, customers, and our community. Our supplier diversity program demonstrates our ongoing commitment to our vendors, contractors, and suppliers by ensuring that Minority-owned, Women-owned, LGBTQ-owned, and Veteran-Owned enterprises have an opportunity to work with us in meaningful ways.

We hold in high regard being good stewards of the dollars our customers and partners spend with us and are working to ensure those dollars are supporting businesses and individuals who have been historically marginalized, underrepresented, or have experienced barriers in accessing opportunities.

Through this ongoing effort and commitment, we aim to make continuous improvements to our supplier diversity program and ask that you partner with us to ensure we are supporting your business in the best manner possible.


Our business model is one of reciprocity where profit adds value to all stakeholders: our employees, customers, the environment, and society. Sustainability is imperative for long-term operational success, and it is incumbent upon businesses to venture beyond legal obligations; to be stewards of the Earth and equity through measurable and actionable changes in our operations. Thielsch Engineering, Inc. (TEI) is solemnly committed to environmental, social, and corporate governance and further integrating sustainable business strategies into every level of operation.

Non-Financial Accounting

The challenges posed by climate change demand more aggressive actions from individuals, businesses, and organizations alike. We acknowledge that the depleted conditions of our climate, oceans, forests, and other ecological systems on Earth have negatively affected and even displaced the most vulnerable human populations among us. In 2021, our CEO and President, Vin Graziano, along with the board of directors demonstrated their commitment by hiring a full-time Sustainability Analyst to conduct non-financial accounting of our energy source and consumption, greenhouse gas emissions, water use, and waste generation. Thielsch takes the position that human activity has caused climate change and that “waste” should be viewed as a resource that can be managed within a circular economy.

Integrated Customer Solutions

Thielsch offers a broad portfolio of engineering, energy, field, and laboratory services to reduce operating costs and increase profitability by extending the operating life of capital equipment, improving reliability and safety, and conserving energy. Our engineering expertise, national recognition, and lasting commitment to sustainability distinguish us as exceptionally equipped to mitigate negative environmental impacts and reduce costs for our customers.

Sustainability at Thielsch is a dynamic venture, continuously improving as new technologies are developed, science teaches us more, and diverse perspectives are brought into the fold so that we can provide solutions to the greatest engineering challenges we face.

Contact Us

Corporate Office

Holden Mechanical Contractors
255 Brooks St. Worcester, MA 01606