Where to start – Rooftop equipment plants unveiled for urban environments
Commercial flat rooftops, also more accurately referred to as low slope roofs, are often used as functional areas for mounting and installing equipment. The type of rooftop equipment installed on rooftops can range from HVAC units, condensers, cooling towers, modulated chillers, generators, exhaust fans, et cetera. These systems are call rooftop equipment plants.
Learn more about ducted air systems on rooftops at a more specific article on the IDS Encyclopedia at the following link:
In the 3 pictures below you can see examples where rooftops have been used for installation of a variety of equipment.
Installation of rooftop equipment of this type introduces a set of challenges.
1. ACCESS. Simply, if equipment is installed on the roof, that equipment must be serviced and maintained on a routine basis. This means that service workers must access the rooftop more frequently than they would for typical roof maintenance. In such cases, a designated access portal or stairway doghouse must be built into the building framework.
2. ADDITIONAL PENETRATIONS. Most flat or low slow roofs require some penetrations through the roof membrane for things like plumbing vents and exhaust vents. However, in the case of a rooftop filled with additional equipment, there are many additional penetrations through the roof membrane. Rooftop penetrations require significant additional roof membrane detailing and flashing. Examplesnof additional detailing may be in the form of roof boots, goosenecks, pitch pockets, and more. This additional detailing requires additional cost, planning, and coordination to build the roof system and requires additional ongoing maintenance.
3. CONDENSATION AND DISCHARGE. Rooftop HVAC condenser units create a discharge known as condensate. Condensate is air vapor in a liquid form and this generally somewhat dirty water must be conveyed or carried through piping or the condensate water must sheet flow to an appropriate drain. Condensate drains in themselves can be an additional system. Additional systems add complexity to building construction and maintenance and where there is additional complexity generally there’s more coordination and upkeep required. In the case of condensate drains that sheet flow on the membrane itself, this type of installation creates additional water directly on the membrane of the roof which can add a level of complication and wear.
4. RAIN WATER DIVERSION. Low slope rooftops are engineered so that water can drain and flow in a controlled manner. Where HVAC equipment is installed on a rooftop, if the installation is not coordinated to account for the intended flow of rainwater, equipment can be a common impediment and cause the build-up or ponding of water.
5. VIBRATION DAMAGE. Mechanical equipment and fans have motors that run and therefore have a significant amount of near constant vibration. This type of vibration accelerates wear on bearing points, stands, penetration points, and attachment points. Vibration isolation systems are normally incorporated into the design and installation of equipment; nonetheless, membrane and roof systems have additional and accelerated wear due to equipment vibration.
6. FOOT TRAFFIC. Since rooftop equipment requires near constant monitoring, adjustment and maintenance, rooftops with equipment have a significantly higher amount of foot traffic. That additional foot traffic also will wear out roof membranes at an accelerated rate. Sacrifical foot traffic mats can be installed on rooftops, and they can help but foot traffic is still required outside of desinated foot paths. Also, sacrifical wear layers are known to trap grit and moisture between themselves and the actual roof membrane. Grit can cause excessive wear and damage to the roof membrane and trapped moisture can lead to organic growth on the roof membrane and also accelerated deterioration of the roof membrane.
Even considering all these other challenges introduced by installation of rooftop equipment, top equipment, it can still be considered a net positive configuration. In other words in many cases it’s still better to install equipment on the roof then trying to use valuable square footage on the inside of the building or on the site. Some sites are restricted or very limited and don’t have space for the equipment background level. As well, some buildings have very high values for interior space and it may be better to use the rooftop instead of sacrificing useful and otherwise highly desireable interior space.
