Specifying windows for high-rise buildings

Main focus when specifying windows for high-rise buildings
There are two key factors that needs to be considered when specifying windows and doors on high-rise apartment blocks.

The first and most important is safety in operation and the second is weather performance.

Glazing Strategy
At the early stages of design, the decision on how windows are to be cleaned, maintained and re-glazed needs to be addressed. This decision really boils down to whether the proposed strategy is an external or an internal one.

If an external strategy is chosen, this means the use of special plant, such as roof-top mobile access equipment and/or abseilers for example.

If an internal strategy is chosen, then the design and choice of window is critical. There are various types of hinges/operation of windows on the market that allows cleaning the external pane of glass from the inside. These include – top-hung reversing, horizontal pivot, vertical pivot, side swing reversing and side guided, all of which open out. Then there are inward opening windows – side hung and tilt & turn.

Of all the above types of operation the safest by far, in our opinion, is with an inward opening window, such as the side hung or tilt and turn. The reason being is that any cleaning, maintenance or re-glazing is carried out safely within the apartment room.

Cleaning
With outward opening windows there can always be an element of having to lean out to operate the windows and if hinge mechanisms have not been regularly maintained they can become “sticky” and difficult to operate, especially if they are quite large. This has a risk, in that the occupant may have to reach out a long way to try to pull the window shut.

Other potential issues with outward opening windows on high-rise buildings is with the wind. When opening a window outward, particularly large side hung or side swing windows, the sash can be caught by a strong gust of wind, acting like a sail on a boat. The forces applied by such a gust could even lead to the sashes being ripped off the hinges.

The use of fixed lights on high-rise buildings will always cause an issue on an internal cleaning strategy, in that there will always be a need to lean out of an adjacent opening window to clean them. Therefore, these should be limited in size, so that the occupants do not have to lean very far to clean them.

Re-glazing
When it comes to re-glazing from inside, this can only be done if windows have internal beads or can be opened into the room and safely re-glazed from inside.

Please be aware, some internally beaded windows still require the glass to be moved outside the building, turning at an angle to bring it back in, which can be a risk, particularly on large panes.

Our Recommendations
At Idealcombi we always recommend the use of our Futura+i inward opening tilt and turn windows and matching fixed sashes. The tilt function allows you to vent the room while the turn function allows the window to be cleaned safely from inside the building, or if necessary be re-glazed safely. The fixed sashes are all capable of being safely re-glazed from the inside.

The key function on the tilt and turn handle means that children cannot open the window in turn function, if the key has been removed.

Balcony Doors
In respect to doors leading onto balconies on high-rise buildings there is also the appropriate operation to consider.

Outward opening doors will have the same potential issue as outward opening windows, when it comes to high winds, but to a higher degree as a door is bigger and heavier than a window, so the forces are much higher.

The safest door operation for high-rise is either sliding doors or inward opening doors.

At Idealcombi we have a wide choice of sliding doors and inward opening doors that can be considered.

Window Performance for High-Rise Buildings
Due to greater wind pressure on high-rise buildings it is essential that all doors and windows are tested to high weather performance. If possible, the wind loadings for the building should be ascertained so that the performance of the windows and doors can be checked through, against independent test certificates that they meet the requirements in respect to air, wind and water.

It is also essential that calculations are produced in respect to the installation, so that the correct fixings can be used.

At Idealcombi all our systems have been independently tested and meet a very high performance standard (Click image to see example). On all our large high-rise projects we will provide a full design drawings package with structural calculations for wind loading and installation (See below for example).

I hope the above has answered some or all of your questions.
If you have further questions, in regard to specifying windows for high-rise buildings, feel free to get in touch on JRH@idealcombi.com or request a meeting.

Thank you for reading.

James Hutchins
General Manager

High-rise buildings

The high-rise building is generally defined as one that is taller than the maximum height which people are willing to walk up; it thus requires mechanical vertical transportation. This includes a rather limited range of building uses, primarily residential apartments, hotels, and office buildings, though occasionally including retail and educational facilities. A type that has appeared recently is the mixed-use building, which contains varying amounts of residential, office, hotel, or commercial space. High-rise buildings are among the largest buildings built, and their unit costs are relatively high; their commercial and office functions require a high degree of flexibility.

Foundations

The foundations of high-rise buildings support very heavy loads, but the systems developed for low-rise buildings are used, though enlarged in scale. These include concrete caisson columns bearing on rock or building on exposed rock itself. Bearing piles and floating foundations are also used.

Structural systems

Wind loads

The structural systems of tall buildings must carry vertical gravity loads, but lateral loads, such as those due to wind and earthquakes, are also a major consideration. Maximum 100-year-interval wind forces differ considerably with location; in the interiors of continents they are typically about 100 kilograms per square metre (20 pounds per square foot) at ground level. In coastal areas, where cyclonic storms such as hurricanes and typhoons occur, maximum forces are higher, ranging upward from about 250 kilograms per square metre (50 pounds per square foot). Wind forces also increase with building height to a constant or gradient value as the effect of ground friction diminishes. The maximum design wind forces in tall buildings are about 840 kilograms per square metre (170 pounds per square foot) in typhoon areas.

The effect of wind forces on tall buildings is twofold. A tall building may be thought of as a cantilever beam with its fixed end at the ground; the pressure of the wind on the building causes it to bend with the maximum deflection at the top. In addition, the flow of wind past the building produces vortices near the corners on the leeward side; these vortices are unstable and every minute or so they break away downwind, alternating from one side to another. The change of pressure as a vortex breaks away imparts a sway, or periodic motion, to the building perpendicular to the direction of the wind. Thus, under wind forces there are several performance criteria that a high-rise structure must meet. The first is stability—the building must not topple over; second, the deflection, or sidesway at the top, must not exceed a maximum value (usually taken as 1 /₅₀₀ of the height) to avoid damage to brittle building elements such as partitions; and, third, the swaying motion due to vortex shedding must not be readily perceptible to the building occupants in the form of acceleration, usually stated as a fraction of gravity, or g. The threshold of perception of lateral motion varies considerably with individuals; a small proportion of the population can sense 0.003 g or 0.004 g. The recommendation for motion perception is to limit acceleration to 0.010 g for wind forces that would recur in 10-year intervals. The fourth criterion involves the natural period of the building structure. This is the vibration period at which the swaying cantilever motions of the building naturally reinforce and enhance each other and could become large enough to damage the building or even cause it to collapse. The natural period of the building should be less than one minute, which is the period of vibration due to the shedding of wind vortexes.

Earthquake loads

Earthquake or seismic forces, unlike wind forces, are generally confined to relatively small areas, primarily along the edges of the slowly moving continental plates that form the Earth’s crust. When abrupt movements of the edges of these plates occur, the energy released propagates waves through the crust; this wave motion of the Earth is imparted to buildings resting on it. Timber frame buildings are light and flexible and are usually little damaged by earthquakes; masonry buildings are heavy and brittle and are susceptible to severe damage. Continuous frames of steel or reinforced concrete fall between these extremes in their seismic response, and they can be designed to survive with relatively little damage.

In two major earthquakes involving large numbers of high-rise buildings, in Los Angeles in 1971 and Mexico City in 1985, lateral accelerations due to ground motions in a number of tall buildings were measured with accelerometers and were found to be of the order of 0.100 to 0.200 g. In Los Angeles, where the period of the seismic waves was less than one second, most steel-frame high rises performed well with relatively little damage; continuous concrete frames also generally performed well, but there was considerable cracking of concrete, which was later repaired by the injection of epoxy adhesive. In Mexico City, however, the period of the seismic waves was quite long, on the order of a few seconds. This approached the natural frequency of many tall structures, inducing large sidesway motions that led to their collapse. Based on this experience, determination of the seismic performance criteria of buildings involves the lateral resistance of forces of 0.100 to 0.200 g and consideration of the natural period of the building in relation to the period of seismic waves that can be expected in the locality. Another important factor is the ductility of the structure, the flexibility that allows it to move and absorb the energy of the seismic forces without serious damage. The design of buildings for seismic forces remains a complex subject, however, and there are many other important criteria involved.

Classification of structural systems

The types of structures used for high-rise buildings must meet the lateral load performance criteria outlined above, and they must be reasonably efficient in the use of material and of reasonable cost. The most efficient high-rise structure would meet the lateral load criteria using no more material than would be required for carrying the building gravity load alone; in other words, it would have no premium for height. This economic criterion of “no premium for height” has led to a classification of high-rise structures, each of which has only a small premium for a particular range of height (Figure 2).

High-rise structures begin at the lowest range with the rigid frame in both steel and concrete. Some or all of the joints between the beams and columns are rigidly joined together by welding the steel or pouring the concrete in situ, and lateral resistance is provided by the rigid joints; this system can rise about 90 metres (300 feet) with little premium. The next type is the rigid frame with a vertical shear truss in steel or a shear wall in concrete to provide greater lateral rigidity; it has a range of 38 to 150 metres (125 to 500 feet). The framed tube structure in both steel and concrete brings more gravity load and more structural material to closely spaced columns at the building’s perimeter, again increasing lateral rigidity; this type is reasonably efficient from 38 to 300 metres (125 to 1,000 feet) in height. The trussed tube with interior columns, which can also be executed in both steel and concrete, introduces diagonal bracing on all sides of the building’s perimeter. The bracing also carries gravity loads and further raises the lateral rigidity, making this a low-premium structure for the region of 240 to 360 metres (800 to 1,200 feet). The bundled tube, which consists of a number of framed tubes joined together for even greater lateral rigidity, begins to be practical at about 75 metres (250 feet). It was the form of the steel structure used for the Sears (now Willis) Tower in Chicago. Beyond this height there is another system that appears to have a low premium: the superframe. In this structure much of the building’s gravity load, and therefore its material, is brought to a diagonally braced superframe tube at the perimeter by interior transfer trusses of various configurations. No true superframes have yet been built.

How dangerous is high rise window cleaning?

Published by Kiril Topalov on September 17, 2019

It’s always a pleasant experience to look at properly cleaned windows. Regular window cleaning is important for both home and business buildings. Having uncleaned windows spoils the whole look of our property. Cleaning the windows of a high-rise building is definitely a dangerous business.

For this reason most owners of modern high-rise buildings and glass-fronted offices use the services of window cleaning companies as they save considerable amount of time and effort. That is why being a window washer is a responsible job.

Although it may not seem a really a hazardous one, high-rise window cleaning is a job that hides some risk as it involves scaling a building that sometimes reaches more than 15 meters. The job of window cleaning requires a specific set of skills and training in order to be performed properly.

Cleaning high-rise windows is something like rock climbing. It demands mobility and following work safety measures. As some buildings tower at impressive heights, the use of secure professional harness and climbing equipment is obligatory.

You provide many office workers in high or mid-rise buildings with great views. Window washers are responsible for cleaning the dirty glass windows of homes, offices, stores, and high-rise buildings.

But window cleaning of high rise buildings is on the list of most dangerous jobs in the world. Working as a window washer definitely brings a certain amount of danger. And for this reason window cleaners should follow strictly the necessary safety measures during their work.

This type of job is definitely not for everyone as it requires you to be industry-trained and have zero fear of heights. Being a high-rise window cleaning definitely requires bravery. The job of a window cleaner is a challenging one and it requires from the worker to be physically capable and have some preparation in advance.

We should make sure that we are equipped with the needed cleaning tools to complete the cleaning task in a correct and safe way. High-rise widow cleaning is a risky job and it should be done with the right equipment tools.

As is the case with every job being a window cleaner has its advantages and disadvantages. The level of danger this job brings really depends on our work experience, a level of protection and safety gear condition and also the window cleaner’s individual manner of work.

Pros and cons of being a window cleaner

Great views

This advantage depends on the building’s location of course, but in general window cleaners see more often beautiful air views than office workers.

High demand for workers

High-rise window cleaner is truly an in-demand job. Owners of high rise buildings are always searching for good window cleaners and especially such with longstanding experience. So if you are planning to get a career in high-rise window cleaning, you won’t wait too long to be called back after the interview.

It’s important to mention that each state and city have its own regulations when it comes to high-rise window cleaning safety and these safety measures vary. Sometimes future window washers are required to have passed some safety courses in order to get the job’s position.

Freedom

Professional window cleaners spend a considerable part of their time outside. Being suspended high in the air offers beautiful scenes. This type of job provides a sense of peace, solitude and independence unlike office desk jobs for example.

Flexibility

This type of job offers flexibility and a person is able to run a business of their own besides working as a high-rise window cleaner. In this job sphere we cannot start our own business right away.

We may need to work as an apprentice first for some time period under another before starting to work for ourselves. We may also need to complete some safety courses for window washers that are required by our state.

Risk of falling or other injury

There is no doubt that the job of window cleaning brings many risks. Risk is an inevitable part of this job. This may sound surprising but deaths are rare in the high-rise window cleaning business. This is thanks to the fact that the workers are very serious about their personal safety and it’s on their top priorities list.

At the start of every work day window cleaners first make sure that all the climbing equipment and safety gear is checked and it’s not damaged. They inspect all the harnesses, cables and scaffolding to make sure they are in good working order. And properly installed safety equipment guarantees successful completion of the cleaning tasks, less cases of injuries and the result is more satisfied clients.

Accidents do happen but fortunately they don’t have a fatal end. Data from researches show that between 2010 and 2014, only one window cleaner of high-rise buildings was killed each year. In comparison to 1932 this is a great improvement and speaks a lot about the safety measures companies take. In 1932 one out of every 200 window cleaners in New York was killed each year on average.

Weather

Working outdoors has its plus and minus sides. The whims of the weather are an enemy to the window washers. Weather is something we cannot control and it can affect the duration and completion of a window cleaning project.

Cleaning the windows of a high-rise building during a windy weather may be a real challenge. Rains make the platforms slippery. Strong wind can not only slow down a cleaning project but it’s also bad for the stability of the scaffolding and the suspended platforms which increases the risk of incidents.

No phones and music rule

Window cleaning may seem easy at first sight but this type of work requires focus and distractions of different nature aren’t recommended for safety reasons. That is why window cleaners are not allowed to use smartphones or listen to music while working at the scaffolding.

This rule may vary from one cleaning to another and it depends on the size of the building the cleaners are working on. Holding a smartphone or wearing headphones while trying to clean a window at heights isn’t a very good idea. But window cleaners who work at smaller buildings can use phones or listen to music and radio podcasts.

Low-paid job

One of the disadvantages of this kind of job is that the salary isn’t high. In general window cleaners who fall in the apprentices category make 12$ to 16$ per hour. The daily wage of window cleaners can reach up to 35$. Some window cleaners with rich experience can make 50$to 100$ per hour.

On the other hand being an owner of window cleaning company is profitable. It’s said that owner of high rise cleaning companies make up to 125,000$ per year.

Male-dominated industry

Currently mostly men are working in the sphere of high-rise window cleaning services but this situation is gradually changing. The number of female window cleaners is increasing.

For high-rise building owners

Contracting a professional window cleaning company is undoubtedly the best way to achieve good appearance for our building no matter if it’s commercial or residential property.

Cleaning services of high quality aren’t very cheap but they are definitely worth their money. If you are an owner of a high-rise building make sure to make a research before choosing a cleaning company.

Our window cleaning service provider should have experience in the sphere of high rise window cleaning and also with positive company references. The use of specialized cleaning equipment, products and safety gear is a must.

Reasons why contacting an expert window cleaner is good for our business

Curb appeal is probably one of the top reasons why it’s good to get the windows of our high-rise building properly cleaned. Not only clean interior but also shiny windows always make a great impression on the customers. No matter how well-cleaned the building is on the inside, when the exterior is unkempt and especially the windows, this is a useless in trying to make a building look good. Regular window cleaning is essential if we care about our business and want to be successful.

Since window cleaning companies are required to provide their clients with perfectly cleaned windows, their workers should be experienced enough to be able to tackle all types of dirty windows. Renting an office space with windows that aren’t very well-cleaned may affect negatively our business.

A well-cleaned window offers a nice view. Imagine a high rise building with a large number of windows that should be cleaned. Well-cleaned windows add a curb appeal to a property we are trying to sell and also help us attract new clients by giving our business building an aesthetic look.

It doesn’t matter if we have a commercial or residential building, regular window cleaning is a key to making our property a beautiful and safe place for either working or living. It’s also a good way to catch the eye of new clients or make the property saleable.