Wednesday, August 3, 2016

The Roman Domus as a Caribbean Urban Housing Solution

I've been on a bit of a kick right now learning about the Roman Domus; an ancient urban housing solution from about 2000 years ago. It all started with a simple question. Why do they have a pool of water (impluvium) in the center of the living room (atrium) like that?

Well, it turns out that the impluvium is a much more functional feature than I realized. It's actually a remarkable rainwater collection, storage and home cooling device all rolled into one. If you're looking for the best sustainability solutions, and I think we all should be, it makes a lot of sense to look to the past. To a time when fossil fuels were still locked in their original state and people had to make every day human life work without them. Once we've scoured the past for amazing resource saving ideas, then by all means fire up your gas oven or take a flight halfway around the world. Let's use our resources to their highest and best purpose. 

In this post I’ll address timeless issues, like rainwater collection, greywater systems, passive cooling, sustainable finance, and suggest some modern layout improvements to the domus for use in our lives today.

In short, ancient Romans collected rainwater from their roofs, filtered it through a sand filter and stored it in a subterranean cistern for later use in home cooling and cleaning. All for free. Let’s look at how we might reap some of the same benefits from clever design today. According to this handy Reddit thread:

Households usually collected their own rainwater from the roof to supplement aqueduct supply. The first rains would be allowed to run off the roof into a basin (impluvium) in the atrium of the house, and out through a drain into the street. Once the rain had washed the roof clean, the drain to the street was stopped-up, and another hole in the impluvium basin was opened to allow clean rainwater to fill the cistern. Usually the cistern mouth had a sediment trap on it as well, so that only clean rainwater would get into the holding tank.

Like so:

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. The circular stone opening (visible in the photograph, resembling a chimney pot) allows easy access by bucket and rope to this private, filtered and naturally cooled water supply. 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 can be drawn from the cistern chamber (or sourced from municipal supplies outside the domus) and cast into the shallow pool to evaporate and provide a cooling effect to the entire atrium. As the water evaporates, the surrounding air is cooled and becomes heavier and flows into the living spaces and is replaced by air drawn through the hole in the ceiling above (compluvium). The combination of the compluvium and impluvium formed an ingenious, effective and attractive manner of collecting, filtering and cooling rainwater and making it available for household use as well as providing cooling of the living spaces. (emphasis added)

In modern times, the manual labor used to draw water from the cistern would be replaced by pumps and the water itself could be sent to toilets and irrigation or could be treated and used to supplement or replace the city system (which is usually not 100% potable anyway).

Here are a couple more images of the atrium, compluvium and impluvium set up. The walls of the house are made of rubble mass wall masonry covered with painted plaster and sometimes stone or tile. The floor is also a stone or mosaic floor. The roof supported by wooden beams set into masonry pockets is slanted inward and features a ceramic tile roofing system with gutters and drain spouts from the four corners of the compluvium to direct rainwater into the center of the impluvium.

Since the atrium is exposed to seasonal weather changes, this system doesn’t make sense in temperate zone climates, but is ideally suited to tropical and sub-tropical zones. Looking at the typical climate in Pompeii where some of the best examples can be found I discovered that original Roman Mediterranean climate would have been slightly cooler, but not unlike the Deep South and Caribbean.

My wife is Dominican and we spend a fair amount of time in Santo Domingo, the oldest colonial city in the Americas. The Zona Colonial has a lot of really wonderful architecture,

and some of it even follows a loosely similar concept with interior courtyards and pools
Historic Landmark Hotel Doña Elvira
but the average house built over the last 50-70 years looks a lot like the examples below.

In most of the Caribbean it is quite common to live the entire year without air conditioning. Since it’s an island, the cost of electricity is high and once you become accustomed to the heat it’s bearable but not always comfortable. The rain is frequent, but usually pleasant and warm. Also water service is occasionally interrupted and the tap water is not always potable. It is wise to boil or filter city water before consumption. As local water systems age and the equipment to treat your own water drops in price, this may increasingly become the norm. In Santo Domingo burglary is (increasingly less of) an issue so most families put bars on their windows and balconies to keep out intruders.

Let’s take a look at the total floor plan for a typical domus.

You’ll notice the Roman domus has a few other advantages. The whole house is inwardly focused and places windows and potential 2nd floor balconies on the inside away from possible burglars. Also, because the streets would have been filled with people and animals, they were noisy and polluted. The Romans built their homes with street facing retail only reserving a single entrance door for themselves. These retail spaces helped to pay for the costs of the house and served the public interest. Today, it is easy to imagine creating a second floor above the retail spaces for live-work units that pay for the main house.

The central room (#5 tablinium) served as the meeting place for the house. It was the focal point and divided the public space in the atrium from the private space in the garden-court (#14 peristylium).

As a possible solution to urban housing in the Caribbean the Roman Domus would provide an excellent solution. In the Dominican Republic, they reserve their front yard primarily for the automobile anyway. It would be simple to re-purpose the two commercial spaces in the Roman design for a street facing garage that could eventually be converted to retail space in the event that the family needs the income or prefers to use taxis and transit. The need for security is similar to the Roman situation and providing bars on the roof over the compluvium and at the perimeter of the peristylium is an option.

Below, I’ve re-imagined the uses in a modern floor plan. Doing away with the traditional office-like tablinium and replacing that with an open kitchen. The meeting place of our modern lives. The kitchen I envision would have two mobile workstations on castors (shown in grey) that could be configured as service and prep islands or as casual dining and conversational surfaces. A second floor could be easily added for additional living space or to rent to the shopkeepers as supplementary income. The impluvium with cistern would remain and the collected rainwater could be used as grey-water to power toilets and irrigation or could be treated in a water treatment closet and used throughout the house. Adding electrical battery storage first and solar power cells second would enable the house to operate almost entirely off grid and would avoid any disruptions in service common on the islands. The garden could be edible or just a simple yet elegant backyard surrounded by covered walkway. As a typical fabric building, these homes meet most of the tests diagrammed in Steve Mouzon's exceptional work on the Smart Dwelling.

It is typical in the region to build the home structure with poured concrete columns/beams, the walls constructed of concrete block and plaster, and clay tile roofs. That is actually very similar to the traditional Roman construction and the added mass makes sense to help keep the house cool and durable. Even the heaviest rains can simply be wiped off the stone or ceramic flooring and masonry walls.
In a country with high energy costs and a favorable climate this system could make the interior of modern homes much more comfortable and solve several other major issues with typical Caribbean urban architecture.


Jules Pitt said...

Sadly I live in a colder climate, as I would love to live in a Domus.

Andres Duany showed some designs adapted from South American courtyard houses that remind me of your design a little bit. There were live/work, compound variations IIRC.

This is roughly the section of the presentation where he discusses it:

Anonymous said...

you will find courtyards in every mediterranean traditional architecture: Andalusian architecture, Maroccan architecture ...

Se also the japanese traditionnal townhouse, the Machiya:

Andrew Malone said...

Thanks Jules! That's great :-) It would probably be pretty easy to add rainwater collection to DPZ's configuration too.

Anon. That's remarkably similar. Cool. Nice find.

Andrew Malone said...

One more note. The Ohio Dept. of Health has an extremely detailed document on how to build and maintain a modern rainwater collection system for potable use. Posting the link here for posterity.

"Plans for Developing a Rainwater Cistern or Hauled Water Supply"