The ''impluvium'' (pl. ''impluvia'') is a water-catchment pool system meant to capture rain-water flowing from the ''compluvium'', or slanted roof. Often placed "inside", instead of "outside", a building, it is a notable feature in many architectural traditions.

Greco-Roman impluvium

In Greco-Roman architectural studies, the ''impluvium'' refers to the sunken part of the atrium in a Greek or Roman house (''

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''), designed to carry away the rainwater falling from the ''compluvium'' of the roof. It is usually made of marble and placed about 30 cm below the floor of the atrium, and emptied into a subfloor cistern.

Construction and use

Inspection (without excavation) of ''impluvia'' in Paestum, Pompeii and Rome indicated that the pavement surface in the ''impluvia'' was porous, or that the non-porous stone tiles were separated by gaps significant enough to allow a substantial quantity of water caught in the basin of the ''impluvium'' to filter through the cracks and, beyond, through layers of gravel and sand into a holding chamber below ground. A circular stone opening protected with a puteal allows easy access by bucket and rope to this private, filtered and naturally cooled water supply. Similar water supplies were found elsewhere in the public spaces of the city, with their stone puteals showing the wear patterns of much use. In wet seasons, excess water that could not pass through the filter would overflow the basin and exit the building, and any sediment or debris remaining in the surface basin could be swept away. In hot weather, water could be drawn from the cistern chamber (or fetched by slaves from supplies outside the ''domus'') and cast into the shallow pool to evaporate and provide a cooling effect to the entire atrium: as the water evaporated, air drawn in through the ''compluvium'' was cooled and moved throughout the house to cool the surrounding living spaces, a form of

passive cooling Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from ...

. The combination of ''compluvium'' and ''impluvium'' formed an ingenious, effective and attractive manner of collecting, filtering and cooling rainwater.

West and Central African impluvium

Denyer, ''African Traditional Architecture'', defined an ''impluvial style'' of architecture in West Africa, wherein "four buildings usually faced one another across courtyard". Buildings of the "style" (really, a "

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

-based" type), did not necessarily feature an ''impluvium'' to capture rain. Further complicating matters, some texts have conflated Denyer's ''impluvial style'' with ''impluvium'' itself, and thereby take ''impluvium'' to refer not to the use of mechanisms to capture water, but instead to court yard-centered house plans.

Examples

''Impluvia'' have been observed in many West/Central-African architectural traditions, including those of the Igbo,

Yoruba The Yoruba people (, , ) are a West African ethnic group that mainly inhabit parts of Nigeria, Benin, and Togo. The areas of these countries primarily inhabited by Yoruba are often collectively referred to as Yorubaland. The Yoruba consti ...

Edo Edo ( ja, , , "bay-entrance" or "estuary"), also romanized as Jedo, Yedo or Yeddo, is the former name of Tokyo. Edo, formerly a ''jōkamachi'' (castle town) centered on Edo Castle located in Musashi Province, became the ''de facto'' capital of ...

, Jola and

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. These ranged in complexity: Yoruba ''impluvia'', referred to as ''akodi'', sometimes only amounted to pots placed at the corners of vast rectilinear courtyards, while some in Ketu, Benin Republic, were drained into underground tanks. Commoners in the Benin kingdom usually had houses with multiple ''impluvia'' in their one or two court spaces, sometimes drained out of the house by pipes. As Nevadomsky et al. note, these ''impluvia'' were meant to remove rain water so that the open roof could be used as a light source and source of fresh air. While many previous examples have been rectilinear, the ''impluvia'' of Senegal could also be designed around round floor plans; this has become the basis for the 'Case à Impluvium" in Ziguinchor, Senegal, a centre of the arts run by the ''Alliance Franco-Sénégalaise''.

Origins

19th and 20th century European travelers were often surprised to find parallels to classical culture in those architectural traditions that had clear ones: "In the Bamum area there is an interesting type of hut. In referring to it Ankermann says: "The men's houses (Herrenhäuser) in Bamum, in contrast to those of the women, show a most complicated structure. I was very much astonished when I entered for the first time to find myself in an actual Roman atrium with an impluvium in the middle, with the roof sloping towards the middle, and supported by columns". This resulted in a number of theories attempting to tie West and Central African ''impluvium'' to Greco-Roman, Egyptian, and Portuguese influences. While Kalaous rejects the possibility of Portuguese influence, he writes that "The Old Mediterranean influence seems to be more plausible but did not necessarily come via Egypt... Of course, this does not prove that there were contacts between the Etruscans and the peoples of what is now Southern Nigeria, but the existence of impluvium there (and elsewhere in West Africa) is certainly not easy to explain in terms of a quite independent origin." Denyer, on the other hand, notes that "No really large settlement could have taken place in this area outhern Nigeriabefore a means of collecting water had been found", to save for the dry season and to manage erosion. Most bluntly, Nevadomsky et al. write that "One need not postulate an external source for what was in all probability an independent evolution of space and form. The impluvium house could easily have arisen in a climate of hot sunshine and heavy seasonal rainfall."

References