Rooftop Mechanical Equipment Requirements – Part II

Everything you need to know about rooftop mechanical equipment requirements

In the last article on our company’s blog and website, we posted a discussion related to the challenges of proper installation of HVAC systems on a rooftop and through a low slope roof membrane. These complications involve both properly Sealing exterior duct work to keep the elements out of the ductwork which leads to the building interior.

The building code, section M1411.8  requires that it supports refrigerant piping. Refrigerant piping and tubing shall be securely fastened to a permanent support within 6 feet (1829 mm) of the condensing unit.  This type of rule is rarely followed at typical urban rowhome rooftop HVAC equipment, most commonly, refrigerant piping or tubing is installed unsupported for the length of the installation.  It is not correct, but is unfortunately commonplace.  

The picture below shows a typical, albeit incorrect, installation of refrigerant piping.  Our company applied the UV resistant membrane, concentrically, on the refrigerant linesets.  This covering both resists UV which can otherwise rapidly eat through the insulation covering normally found at the low pressure line and kep water out of the interstitial space between the tubing and the insulation.  From that internal space water can run down the angled pipework right into the building, especially if the pitch pocket is not properly sealed to the piping.

improper installation of refrigerant piping on rooftop

Section 306 – Access and Service Space.  In particular, Section 306.5 – Equipment and Appliances on Roofs or Elevated Structures, requires that where personnel have to climb higher than 16 feet above grade to access equipment there shall be a permanent means to access the equipment.  This section also includes a requirement for a level walking/working surface for roofs having a slope greater than 4 units vertical in 12 units horizontal (33-percent slope).  Additionally the access shall not require climbing over any obstructions greater than 30 inches in height and the use of a portable ladder for the access is prohibited.  The requirements for access are similar to the requirements found in OSHA 1910 Subpart D – Walking and Working Surfaces.

rooftop mechanical equipment requirements by law

The infrastructure for seismic and wind load resistance is rarely provided in mounting and securement of rooftop equipment at Washington, DC rowhomes, but the building codes include numerous requirements for such amendments.  Out company works in a separate area of construction, but we believe these provisions are largely skipped or omitted by HVAC contractors in an effort to cut costs.  We do not condone and omissions of code requirements but we see that the industry is hellbent on saving costs and doing everything cheaper and cheaper at the expense of quality. 

proper mechanical equipment installation guide rooftop 

So far, we have talked about several different types of requirements, but altogether there’s several types of work categories of requirements before the installation and proper mounting of mechanical equipment.   Some of those categories follow:

  1. Weathertightness of the equipment 
  2. Seismic restraint
  3. Wind resistance support
  4. Pipe and cable support
  5. Vibration isolation 
  6. Access requirements
  7. Penetration sleeving and sealing

How to Maintain A Flat Roof System

Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science.   Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building. 

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the roof and related systems of your building in Washington DC, contact us or fill out the webform below and drop us a line.  We will be in touch if we can help.

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