Bioclimatic design: the decisions made before the façade is drawn

The sustainability conversation on the coast usually arrives late and from the wrong side: solar panels on a house designed to need them. The correct order is the reverse — first reduce demand, then cover what remains.

Bioclimatic design is exactly that: using the form of the building to do the work a machine would otherwise do. In the humid tropics of Banderas Bay, this is what gets decided before the first façade is drawn.

1. Read the lot before the program

Before deciding how many bedrooms, four pieces of information define the project:

• Solar path: where the morning sun enters and — more importantly — where the afternoon sun hits.
• Prevailing breeze: on this bay it generally comes from the sea toward land during the day. It is a free, directional resource.
• Runoff: where water travels in heavy rain. Building across the natural path of water is paid for every summer.
• Existing vegetation: a mature tree gives shade no overhang matches and takes decades to replace.

2. Orient for the west, not for the view

Here is the central tension of any coastal project: the best view and the worst sun tend to be on the same side. On a west-facing coast, sunset over the water is the sales argument and also the façade that heats up most.

It is not resolved by giving up the view. It is resolved by interposing layers: deep overhang, habitable terrace, movable screen, vegetation. The view stays; direct radiation never reaches the glass.

3. Shade before insulation

In cold climates the strategy is to insulate. In the humid tropics the priority is that radiation never touches the surface. High-performance glass helps, but it costs more and delivers less than a properly sized overhang.

Order of effectiveness, highest to lowest:

1. Fixed exterior shade: overhangs, porticos, roofs.
2. Movable exterior shade: louvers, shutters, brise-soleil.
3. Vegetation: trees to the west, vines over a pergola.
4. Solar control glass.
5. Interior curtains — which by then only block light: the heat is already in.

4. Cross ventilation: two openings, not one

Humidity is fought with air movement. Cross ventilation requires two openings on opposite or adjacent façades, not one large window. A room with a single window, however enormous, does not ventilate: it exchanges air by diffusion, which is glacially slow.

Three devices that work on this coast:

• High exhaust openings: hot air accumulates at the top and needs a way out. It is the principle of the palapa.
• Double height with a roof vent: a thermal chimney that pulls cool air from below.
• Interior courtyard: generates pressure and temperature differences that move air even when there is no wind outside.

5. Thermal mass, with caveats

Thermal mass — thick walls that absorb heat by day and release it at night — works beautifully where nights cool down. On the coastal strip, in high summer, the night does not always cool: humidity holds the temperature.

Which is why on the coast a light, heavily ventilated envelope often outperforms a massive wall, while up in the sierra — El Tuito, for instance, where Guacamayas Estates operates — thermal mass makes complete sense again. There is no single rule for the whole region.

6. Rain as part of the design

The rainy season on this coast is short and intense. What has to be settled on the drawing:

• Slopes and drains sized for heavy rain, not average rain.
• Overhangs that throw water away from the base of the wall.
• Waterproofing with maintenance access: if you cannot reach it, it will not be maintained.
• Harvesting, if the project contemplates it: a large roof collects a far from trivial volume in a few months.

7. Materials that survive salt

Within a kilometer of the sea, salt is an active agent. What gets expensive when chosen badly: hardware and window systems in the wrong steel, ordinary exterior light fixtures, untreated fasteners, air conditioning without coil protection. A coastal project that does not specify corrosion resistance grades is not finished.

8. What you can demand without being an architect

If you are evaluating a preconstruction purchase, these are questions anyone can ask and that say a great deal:

1. How deep is the overhang on the west façade?
2. Does this unit have cross ventilation, or only one façade?
3. Which way does the terrace face at five in the afternoon?
4. What can be built on the lot across the way?
5. What is the real electricity consumption of an equivalent unit already delivered?

The last one is the most uncomfortable and the most useful. A development that solved the climate in the design can answer it without flinching.

The material side of all this — palapa, parota, chukum, stone — is in the companion piece on contemporary tropical architecture. And if you are looking for who can execute it, the builders directory and the architecture and design directory group those working in the region.