Ferrous Metal Rooftop Elements and Upkeep – PART V

In the past several weeks, on our blog, we have been looking at specific facets of challenges and upkeep requirements of non-roof items on rooftops, in a series on flat roof problems associated with ferrous metal non-roof components.  These are elements that are not actually part of the roof itself. The roof itself will include elements such as the field membrane and the elements of terminations and even elements of flanges or prefabricated rubber type materials to fit around penetrations. These items are actually different and separate from the rooftop itself yet they are installed on top of the rooftop and often have elements of mounting or connection which go through the roof itself. 

Today, we will talk about electrical cabling and related support  systems, and in the next article we will discuss the implications of ferrous metals and penetrations through roofs for low volt cabling connections and mounting of photovoltaic solar panels on rooftops and some of the potential problems associated with those elements on roofs and methods of preventing leakage and required upkeep.

The outline of this series of articles follows:

    • Common types of non-roof components found or flat roofs
      • Access Systems 
      • Historic Brick chimneys
      • Air Exhaust systems
      • HVAC systems
      • Electrical power distribution
      • Low Volt and communication wiring and satellite / antennas
      • PV Panels and mounting structures
      • Guardrails and fall protection systems
  • Roofing problems caused by oxidation of ferrous metals
    • Delamination 
    • Staining and bondability
    • Structural component failure
    • Leakage through metals
  • Methods of Repair and sustainability 
    • Standard Coatings
    • Substrate preparation
    • Advanced re-coatings
    • Special roofing provisions

Electrical power distribution

First, it’s important, just to start, to understand why electricity is needed on a rooftop. Most roofs don’t actually require any electrical power at all. In fact, electrical power on a roof is really only required when there is mechanical or other types of equipment on the roof which needs electrical power resources.  HVAC Systems such as rooftop heating, ventilation, and air conditioning (HVAC) units typically need electricity to operate the fans, compressors, and controls. While, HVAC equipment is the quintessential example of things that require electricity on a roof, there are other systems that need power as well, they are just uncommon.  

The picture below shows an example of a set of small condenser units installed on a rooftop without ductwork, essentially this equipment is just used for cooling refrigerant and then sending it back to Independent Air Handlers within the building.

condenser units on roof
Each of the condenser units shown in the picture above require an independent circuitry of power from within the building. pitch packets have been installed to seal the roof at the individual penetration, but the sealant at these pitch pockets is now defunct after having not been resealed for many years.

Some other types of equipment that also need electrical power on roofs follow as well.   Some of these types of systems are never found on simple historic row home flat roofs such as those in Capitol Hill and Dupont circle or Georgetown areas. Some of these types of systems only occur on commercial or large industrial flat rooftops.  A list of some of these items follows:

  1. Exhaust Fans: Commercial and industrial buildings may have rooftop exhaust fans that help with ventilation and air quality. These fans are powered by electricity.  In Capitol Hill for example there are tons of restaurants jammed into the small historic buildings and the same on H St NE.  The roofs of these buildings are packed with commercial kitchen exhaust fans and associated motors.
  2. Elevator Machinery: In some buildings, particularly high-rises, the machinery and controls for elevators are located on the roof. These systems require electrical power.  There are less historic high-rises in DC than modern, but both types need elevators and that elevator equipment needs power brought up to the rooftop.
  3. Lighting: Rooftop lighting is used for safety, security, and signage. It is directly powered by electricity.  Lighting on rooftops would be very uncommon in historic rowhomes in Washington, DC, but in recent years many building owners have added decks to their rooftops.
  4. Communication Equipment: Antennas, satellite dishes, and communication equipment often need electrical power for operation.  In most cases though, specifically with rowhomes the power requirements will be low voltage only which is often provided through communication wiring.
  5. Solar Panels: While solar panels generate electricity, they require electrical components for inverter systems, monitoring, and distribution to the building.  In our next article we will talk a lot more about PV solar panels and associated mounting systems.
  6. Water Heaters: Electric water heaters can be found on the roof of some commercial buildings to supply hot water.  These systems are often installed in closets and even on exterior walls of rowhomes, it’s extremely rare to find this type of equipment on rowhome roofs.  
  7. Fire Suppression Systems: Fire suppression systems, such as water pumps, may be located on the roof and require electrical power for activation.  This type of installation would be very rare in residential row homes, but it’s actually common in large commercial buildings especially where there are pumps and risers to run throughout the building,
  8. Roof Deicing Systems: In cold climates, roof deicing systems that prevent ice buildup often use electrical heating elements.
  9. Lightning Protection Systems: These systems use grounded conductors to protect buildings from lightning strikes. They may have electrical components.
  10. Signage and Billboards: Rooftop signs and billboards use electricity for illumination and any moving parts.
  11. Security Cameras: Surveillance cameras and security equipment located on the roof may require electrical power for operation.
  12. Access Control Systems: Card readers, keyless entry systems, and electronic access control devices use electricity.

A close up picture of the messy hodge podge of piping and wiring through a pitch pocket is shown below.  

pitch pockets
Pitch pockets are superior methods of sealing flat roof penetrations; however, in this case the problems of sealing are related to later modifications and changes in the original pitch pocket which has destroyed the original sealant.

Another picture below shows a related but different issue.  This is a Romex NM wire.  Wires of this type are not allowed, by the NEC and ICC building codes, to be installed exposed on a rooftop without a UV protecting cover. 

wires on roof
Wires of this type deteriorate and essentially rot in an accelerated manner when directly exposed to UV rays from the sun.

Smart and proactive replacement, construction, upkeep and maintenance of low slope roof and mansard roof systems requires an enthusiastic interest and understanding of historical methodologies, 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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