The Physics of Freezing

The Physics of Freezing at the Iranian Yakhchal

The Iranian Yakhchal (meaning ice pit in Persian) is a type of ancient structure and system used to produce, harvest and store ice in winter for cooling uses later in the year. The Max Fordham R+I Group has undertaken a range of building physics analyses to investigate and infer how the Yakhchals functioned. The analysis techniques developed have potential wider uses in the design of contemporary low energy architecture.

We used numerical modelling methods to simulate the various heat transfers that control the ice making and ice storage processes. This allowed us to make estimates of the amount of ice that could be made and the amount of ice that could be retained (not melt) over the course of a year. The study provided insight into the performance of very high thermal mass structures that is relevant for both the historical analysis of Yakhchals and for the design of modern buildings.

The study of Yakhchals is not new. In fact it has been somewhat of a favourite for architects, engineers, physicists, historians and archaeologists for many years. For a general overview including transcripts of eye witness accounts from the 1600s see the paper by Hosseini & Namazian. For comprehensive details of all known (129) remaining Iranian Yakhchals see Jorgensons’ book, Ice Houses of Iran: How, Where, Why.

Although widely studied, the type and extent of Yakhchal analysis we have carried out has not been done before and so we are pleased to be able to add something of value to the Yakhchal literature.

Our study of Yakhchals was carried out in conjunction with Oliver Wilton at the UCL Bartlett School of Architecture as part of a series of joint studies on the theme of Interseasonal Architecture; that is, architecture that harvests and/or stores an environmental resource in one season for use in another.

A more detailed and technical description of our work on the analysis of Yakhchals can be found in our peer reviewed paper New insight on passive ice making and seasonal storage of the Iranian Yakhchal and their potential for contemporary applications", which is available to download at the end of this page. The work was included in the Passive and Low Energy Architecture conference 2017.

  • The Yakhchal
  • The Yazd Climate
  • Ice Production
  • Ice Storage and the Function of a Dome
  • Further Reading