Air conditioning
Supporting rooftop AC
Sam Birch, technical manager at Big Foot Systems, talks safety, longevity, suitability, flexibility and ease of installation – all factors for consideration when retrofitting or upgrading AC on flat roofs
ontractors are increasingly being asked to upgrade air conditioning (AC) to meet higher cooling demands. But on busy rooftops the challenge is how to ensure the AC is supported safely and effectively. The following are a number of tips to help
C Roof strength and load management
With lighter roof construction becoming more commonplace, it’s essential to know how much weight a roof can take when retrofitting or upgrading AC on flat roofs. Safety is a vital consideration and the roof must be robust enough to support the load. Load management through the existing structure is a key consideration to ensure an installation is safe and secure. Understanding the existing roof build-up is vital here, such as roofing materials, the compressive strength of any insulation and the locality and size of the existing framework, columns, beams or trusses. Companies, such as Big Foot, calculate permissible loads to ensure correct load management and dispersal.
Roof membrane
Single ply membrane for flat roofs is gaining in popularity due to its ability to meet increasingly strict energy requirements driven by Part L of the Building Regulations. However, single ply membrane is fragile and sensitive to footfall, making it very easy to crack or puncture the roof when installing plant, threatening the many benefits of the membrane and causing costly problems. This creates a challenge for HVAC contractors when installing plant on a single ply membrane roof. Traditional penetrative support systems on flat roofs can compromise roof integrity causing thermal bridging, possible leaks, or potentially affecting roof warranty requirements. One solution is to use non- penetrative, repeatable support structures which are adjustable to the demands of each project without damaging delicate single ply membranes.
Flexibility and adaptability
In the past, when installing HVAC plant on flat roofs on new buildings, contractors often craned in steel RSJs or cast traditional concrete plinths as supports for mounting plant on roofs. However, once installed these supports provide little or no flexibility should the specification of the plant change or
require re-siting at a later date. Fortunately, non-penetrative, repeatable support structures overcome these installation headaches, allowing HVAC contractors to easily install AC which fits around busy rooftops. These structures are configurable in that they can be adjusted according to the demands of each individual project. In fact, the latest non-penetrative solutions are ideal since they are easy to retrofit and extend in the future, helping to accommodate future requirements. Offering a quick and simple solution to AC installation on flat roofs, these non-penetrative solutions, such as Big Foot System’s Standard Frame, are incredibly adaptable, allowing installers to configure the frame to meet a building’s needs. These versatile, modular frameworks feature adjustable leg assemblies that allow multiple height options (ideal for projects which have planning height restrictions or where the frame needs to go over pipes or existing upstands etc) and offer a choice of lengths to give the flexibility to create the frame configuration to suit each install.
Stability and safety
Equipment specific support solutions are crucial to ensure equipment is stable and secure. With the potentially high wind speeds found on rooftops it is essential that AC units are supported securely to avoid tipping over with potentially dangerous consequences. Wind resistance can be a concern when supporting tall and relatively light AC equipment on flat roofs, but this can be dealt with by selecting the appropriate non-penetrative frame. Units can be positioned back-to-back to reduce impact area and wider frames can be used to generate greater stability to resist tipping. Back-to-back systems supported on a Big Foot Standard Frame have the ability to withstand wind speeds up to and in excess of 100mph, giving contractors the peace of mind that the AC equipment will stay securely installed, reducing health and safety risks.
Longevity
Traditional AC support methods, such as cut down struts, do not offer a robust support solution on flat roofs so cannot guarantee longevity when it comes to supporting an AC unit. This is a concern since if they fail, an expensive cooling unit could be damaged. By selecting non-penetrative supports manufactured from galvanised steel, consultants can be assured that the support system will do its job for years to come. The ability of these non-penetrative support systems to be reconfigured and re-used when requirements change adds to their longevity.
Quick install
Non-penetrative support systems are quick and easy to install, ensuring project cost and time clarity, negating the need for time consuming and costly penetrations through the roof in the form of poured or pre-cast concrete plinths, steels or fabrications. Supports such as Big Foot’s Standard Frame are suitable for many applications including mini splits, VRF/VRV condensers and small AHUs and afford further installation flexibility thanks to their adjustable leg assemblies, allowing uneven surfaces to be easily tackled and making positioning the frame easy.
December 2019
www.heatingandventilating.net
www.heatingandventilating.net
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