Tag Archives: heat exchange ventilation

Split Systems

Now, when energy is either scarce or expensive, it’s worth remembering that air conditioning accounts for one fifth of all electricity used by buildings. It’s also worth remembering that air conditioning really only means heating air or cooling air because, if you want your air filtered, purified, humidified or dehumidified, then what you need is an AHU – an air handling unit. Air conditioners come in all shapes and sizes but the first experience of domestic air conditioning for many people last century was an evaporative air cooler.

It was possible to build them into a hole in a wall but it was also was common to see them fitted into part of a window opening. Evaporative air coolers still exist and, for example, you can still see them in many places such as the poorer or more traditional areas of Dubai.

In apartments more upmarket they’ll be concealed in louvred enclosures on the underside of the balcony above. This enclosures are sometimes part of the external design but never so much as to be a distinct design element. In this next image, they’re the wood-coloured enclosures along the the balcony ceilings.

You’re also likely to see evaporative air coolers in places such as the tropics or the Middle East where heating isn’t typically requied. Or in cities such as New York where cooling is occasionally required even if heating is traditionally provided separately. Even so, split system air conditioning is still the preferred choice for summer-only use in places such as central Russia (upper left), Damascus (upper right) and Moscow (lower).

Split system reverse cycle air conditioners are also the preferred choice in the temperate climates that requires only moderate and occasional heating and cooling. Passive heating and cooling and for lowering the energy requirements of buildings are all good things and, if these measures are implemented along with a sensible degree of usage restraint, then split system air conditioners aren’t such a bad option.

The first mini-split systems were sold in 1954–1968 by Mitsubishi Electric and Toshiba in Japan, where its development was motivated by the small size of homes. Multi-zone ductless systems were invented by Daikin in 1973, and variable refrigerant flow systems (which can be thought of as larger multi-split systems) were also invented by Daikin in 1982. Both were first sold in Japan. Variable refrigerant flow systems when compared with central plant cooling from an air handler, eliminate the need for large cool air ducts, air handlers, and chillers; instead cool refrigerant is transported through much smaller pipes to the indoor units in the spaces to be conditioned, thus allowing for less space above dropped ceilings and a lower structural impact, while also allowing for more individual and independent temperature control of spaces, and the outdoor and indoor units can be spread across the building.

  • Split-system reverse-cycle air conditioners don’t occupy window space.
  • They’re relatively inexpensive to purchase.
  • They’re simple to install and can be retroactively fitted.
  • They can provide heating as well as cooling.

Split system air conditioners aren’t as energy-efficient as chilled and ducted systems, but their low overheads make them ideal for reducing the initial cost of new builds, and for existing owners wanting a temperature-controlled environment at low cost. In this next photograph, the building on the left is a hotel that’s been retrofitted with ducted air conditioning. The identical building on the right is an office building that relies upon split systems. Its exterior isn’t as pretty but this building is more likely to have the original interiors still intact. Both buildings most likely had window mounted evaporative air coolers until the 1980s.

  • The outdoor and inner units can be spread across the building.

Hmm. The condensers of split system air conditioning systems are installed on the outside of buildings and are generally regarded as either ugly or a necessary evil because they’re additions to existing structures and (thus) outside any aesthetic “wholeness”. Buildings aren’t generally designed with the locations of split system condensers in mind. Apartment balconies are the most unobtrusive and convenient place to put the condenser but there is the obvious disadvantage of them taking up balcony space. Another is that condenser noise is easily transmitted through the balcony doors. There’s not much that can be done about that other than to install them above or outside the balcony. This is fine if there is one but, if not, the most likely location is on the wall next to or below a window, as in the example above.

These next two examples have the condensers placed in surrounds of a material vaguely the same colour as the masonry. These enclosures seem to be a readily accepted compromise – the status quo – the state-of-the art, as it were. The surrounds don’t make the condensers invisible but are regarded as an improvement aesthetically. Condensers are still installed where it is easiest. The surrounds are sometimes given a degree of design input but they invariably remain afterthoughts separate from the building’s design. This is understandable because the charm of split system air conditioners is that they can be installed without any thought before construction or after.

The building is 1924 Normandie Apartments [or the Wukang Building] by Shanghai architect Lazlo Hudec.

These next three examples don’t disguise the condensers but instead draw attention to them by geometrically linking their positions to the facade design. It’s a different way of architecturalizing them. For me the third example is the most successful but ornament these condensers are not.

The next level of bringing condensers into the design of the building involves creating places for them that aren’t balconies but purpose-built shelves. The shelves in this next example could still be read as balconies and, as above, the controlling geometry is an architectural one.

It’s the same with this next example but the condenser surrounds are no longer balconies. It reminds me of that old adage “If you can’t avoid something then make a feature out of it!” That stock photography exists for these geometrically controlled condensers suggests they’re not as inconspicuous as their designers imagine.

Many Chinese multi-storey residential buildings have condenser shelves but, as the spurious condensers in these next photographs show, there’s no obligation to use them.

More recent apartment buildings are more likely to have partially screened shallow shelves. These screens can’t fully screen the condensers for that would reduce their efficiency. Instead, token screens indicate the condensers aren’t meant to be seen. In a way I get it.

Some apartment buildings have their condenser shelves recessed and this seems like a good compromise if you have a floor plate with deep-set rooms requiring windows.

In this next example, condensers of the same size and type are distributed across a facade of a different colour. It looks like there are rules for the installation height and position on the outside of a balcony. This method attempts to regulate all the visual attributes (Colour, Pattern, Shape, Position, Alignment and Size) of the compressors while accepting an uneven distribution across the facade. It’s not bad. The irregularity becomes an incidental feature.

This next example (from Hong Kong) is also a good compromise. The condensers are exposed in an orderly array on what’s obviously the rear of the building. There’s a controlling geometry but not an architectural one. They’re in full view yet where they are tells you they’re not intended to be looked at. Arrangements such as this are only possible if there’s a sole management entity. I imagine this building is a hotel.

Some buildings luck out with deep window reveals or, in the case of this next building, a cornice! The condensers have been randomly bought and installed in the easiest possible location – although it’s fortunate that the 1st (2nd) floor is double-height. The success of this method lies in the primary aesthetic function of the reveal/cornice not being to disguise the condensers. The condensers are given a physical place but denied a conceptual one as far as the aesthetics of the facade are concerned. Unlike the example above, the condenser shelf doesn’t look like a condenser shelf. Despite having a secondary practical function, the architectural device stays firmly architectural and overridingly aesthetic. This is probably as good as it gets and moreover, as good as it needs to be.

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