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Subsidence Towers

Principles of Performance

Towers to-date

Subsidence towers which have been developed by Emilis Prelgauskas architect include those:

  • integral to the building envelope of the Davelea House at Kuitpo
  • elements in the roof form of the Monarto Zoo visitors' centre
    building by Phillips Pilkington architects
  • addition to office of Human Kinetics at 57a Price Ave, Mitcham
    renovation of a heritage 1880's former community church building shell
  • addition to the southern cooling pergola of this architect's home office at Monarto
  • tower to the Library building, Playford Primary School
    building by Jackman Gooden architects
  • tower as part of southern cooling pergola to Knight house at Humbug Scrub

Principles of Performance

The performance of these installations varies markedly, which is a reminder that passive systems rely on their integration into the project as a whole for their achieved outcomes.

Satisfactory operation occurs in the Davelea, Human Kinetics and Monarto house towers, where the layout features good relationship between tower position and open plan interior, good water delivery, and occupants inducted to operate the passive system.

Unsatisfactory outcomes can be tracked to where -

  • intermittent occupants are looking for conventional solutions rather than hands on interaction with passive systems
  • individual installation issues.
These included water delivery problems at Monarto Zoo, exhaust air path issues in the Playford building, and the positioning of the tower in relation to the Knight house, a conventional brick house with perimeter verandah.

As well, a number of design studies have been prepared for:

  • the first study preceding the constructions above
    addition to existing A.P.Lands housing
  • commercial property studies -
    • tower head to the former Halifax Street Centre for Urban Ecology office
      on the rear parapet wall
    • part of a 16 floor retrofit of 96 King William St.,
      Adelaide to student apartments
      project by Diekman + Gnezda architects.

  • other residential studies -
    • the Hollands residence at Torrens Park with a tower head set
      inside the dutch gable roof space
    • the Crottogini cottage at Bowden with a tower head in the
      valley between roofs
    • addition to southern cooling pergola of the Gillis house at Loftia Park

As this architectural practice is based in an arid area, cooling of buildings
for comfort is a high priority.

Conventional solutions assume a building developed to average standards, with mechanical systems added to change air temperatures back to the comfort range. Such systems include reverse cycle air conditioners, geo-thermal systems, and evaporative cooling.
The first two systems use electricity in their action to absorb heat from the air and pump it away. In the case of the air conditioner, the heat ejection is often into air substantially warmer than the interior space. As well, the compressor may be in direct sun or an area of trapped warm air. In such environments, these systems struggle to function.
All these systems utilise electricity at a rate out of step with the generation capability of small renewable energy systems. Evaporative systems generate cooling by increasing the latent heat capacity of the indoor air by adding moisture; an acceptable strategy in dry warm climate areas.

This architectural practice focusses on reducing dependance on any mechanical system to achieve comfort in buildings. This is done by incorporating appropriate orientation, openings, thermal mass and insulation in the building, and designing a building layout to the climate responsive principles described on other pages.

Where continuous periods of hot weather are prevalent, these principles can usefully be enhanced with environmental systems which to some degree replicate cooling of conventional systems. Subsidence tower is such a technology.

  • The principle is to humidify the air volume at the top of a shaft. The increased mass of that air is greater than ambient, and the air volume descends into the building through its own mass; drawing after it new air at the top of the shaft to in its turn be humidified.

  • Early examples of such evaporative air conditioning was used centuries ago in the Middle East, with porous ceramic pots leaking moisture into the air at the top of a shaft or ceiling space.

  • Today the benefits of this system include the low water and energy requirements; about 30% and 15% respectively compared to comparable evaporative airconditioners. The subsidence tower avoids all energy use except the pump to supply water to the tower head drip system.

  • Testing of such systems commenced in Arizona in the late 1980's, and modelling was published by Prof. Baruch Givoni of UCLA in 1995. (refer to the book 'Passive and Low Energy Cooling of Buildings')
  • Locally , the first proposal was by Paul F. Downton for subsidence towers as part of the Halifax EcoCity Project in 1992. These towers (7 in total at 1000m3 volume each servicing the 300 apartment project) were modelled on the UCLA basis as validation in 1995.

  • This architectural practice first modelled subsidence tower action for the A.P. Lands study above (a 1994 study for a project in the north west of South Australia. This was for a detached dwelling at Umuwa in the Anangu Pitjantjatjara Lands for ATSIC and the SA Housing Trust - Aboriginal Housing Unit; with a 35m3 tower). The tower was designed to testing of various commercial filter media at the architect's Monarto property to establish water flow rates and evaporation/cooling effects. The proposal was subsequently modelled on the UCLA basis.

The other studies and practical subsidence tower applications above have subsequently followed.

The Davelea tower has been reported in the international CADDET energy efficiency reporting site.

Subsidence tower action is dependant on concurrent air outflow from the building. In the US, a separate thermal chimney was built-in; in local proposals the venting action of the thermal temperature imbalance across the sunside/shadeside of the building itself is used.
(see Cross Ventilation page).

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