Month: August 2013
Another option for permanent buildings is the self-contained roof top units or RTUs. Systems designed to utilize either split or RTUs will require some equipment placement on site. In the case of a split system, charge lined (suction and return) carrying Freon must be routed between the condenser and fan-coil unit. In the case of RTUs, the units must be placed upon the roof curb, typically by crane, then flashed out.
Common to virtually all HVAC systems in multi-unit complexes is the need to cross mate lines with supply and return ducts. Normally good design has these crossovers relegated to single diffusers and registers allowing the use of flexible duct. Depending upon the sophistication of the mechanical system and the end user, a test and balance of the system may be required. T&B’s can be very expensive depending upon system complexity and whether a certified report is required. The purpose of a T&B is to verify unit performance and tune the duct work to provide the desired air volumes to the areas designated on the mechanical plans.
Roller sets allow the building to remain on the ground. The module is placed on roller dollies that sit atop an aluminum track. Tracks are normally 10-feet long and the module is moved laterally with the use of a cable hoist or come-along. Because of the track length limited movement can be achieved before the track needs to be repositioned. This requires jacking up the building off the dollies, moving the track, repositioning the dollies, then dropping the building back down to start the process over again. Ideally rollers are limited to the final (less than 20-feet) lateral movement required for module placement.
Crane sets are an easier way to place modules upon a site. The module is lifted off the ground, swung into place, then lowered. This ease, however, comes at a price. Moreover, the hourly price of crane rental increases depending on crane size. In addition, there are delivery, set-up, teardown, and return costs to contend with.
Production at the site is greatly enhanced with the use of a crane that offsets some of the labor cost. Where a crew might set 3-4 modules per day with rollers, a crane will allow that same crew, if well organized, to double or even triple it’s daily output. Some sites, due to access or foundations, will mandate the use of a crane. Cranes must always be used for multi-story structures. A crane crew normally consists of an operator, a rigger and sometimes an oiler. Typically the crane rental is inclusive of crew cost.
To assure the module’s load is balanced during the lift, a spreader bar is utilized. The spreader bar spreads the lift point from a single point at the hook to the building’s quarter or third points. Placing a sling on a lifting eye at that point allows the module to be lifted with only a vertical lifting element. Lateral loading during a lift can cause structural damage to the building as well as shifting of the load which could lead to a dangerous situation.
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The first modular building similar to those we see today was constructed in the late 1700s. As the English began to colonize Australia, they realized the need for housing and fast. A London carpenter, H. Manning, started to construct homes in his shop that were built in components, and shipped to the new land. Once the building arrived it could be assembled in a matter of days by the British Emigrants.
In 1854, during the Crimean War, (fought between the Russian Empire and the alliance of the French and British Empires) Florence Nightingale, who was stationed at the British Army Hospital in Scaturi, sent a plea to the government in hopes of finding relief to overcrowding and poor conditions. A British civil engineer by the name of Isambard Kingdom Brunel answered the call and started to design and build a pre-fabricated hospital that could be shipped to Crimea from England. Five months later the hospital was erected in the area of Renkioi and would eventually serve 1,300 patients. In addition to the hospital treating wounded soldiers, it also offered the “modern” conveniences of ventilation, a flushing toilet and even rudimentary temperature controls.
The next major advancement in modular construction was in 1910 when Sears & Roebuck started to sell prefabricated buildings out of the now famous catalogue. Through 1940 over 500,000 buildings were shipped to their destinations by railcar. Although simpler than today’s modular buildings, many are still in use today throughout various areas of the U.S. The largest collection of the Sears & Roebuck buildings can be seen in Elgin, IL, where 200 of the original prefabricated homes still stand.
Times have changed and so has the modular building industry. Modular construction has expanded and can be used to produce a variety of applications, providing anything from temporary offices and single classrooms to entire education campuses and high-rise buildings. An example of modern modular construction is the Woverhampton Development, a massive student residence project being currently constructed in Manchester, England. The 805 module structure will rise 24 stories, making it the U.K’s tallest modular building. Although modular construction has evolved over time, it has consistently been a reliable and effective construction method.
Myth 1: Modular buildings are not good for the environment.
Modular walls are fabricated away from the construction site in a specialized factory by trained professionals. Because these walls are made off site, there are far less wasted materials, and the materials used are far more “green” than traditional methods.
Myth 2: Modular buildings can only be used as temporary structures.
Many have seen modular buildings used as temporary structures for schools that need to quickly add some extra classrooms. Although modular construction can be used for this purpose, modular construction can actually do much more. Modular buildings have track records of being used for decades, with durability that is as good as structures built by traditional methods.
Myth 3: Modular buildings lack an aesthetic appeal.
Another common misconception is that modular buildings are lacking a certain creativity and architectural beauty. With modular construction the sky is the limit! There are a vast amount of customizable options that are often easier to design than traditional construction. Modular construction offers a host of accessories such as doors, lighting, windows, and fixtures.
Myth 4: Modular buildings are built poorly.
Since modular buildings are fabricated off site, they are built with exceptional quality. Modular walls are built within a controlled environment by factory trained professionals. These walls are built to be durable, as they need to be transported to the job site. As previously mentioned, modular walls have a reliable track record of lasting decades.
Myth 5: Modular construction takes too long.
Quite contrarily, modular construction is actually built and assembled quite quickly! Modular projects are often completed 20% – 40% faster than traditional construction. Design and engineering time is also significantly decreased, and installation quickly and efficiently accomplished.