Passive cooling means without using electricity; passive cooling is the cheapest way of cooling a home in both money, and environmental terms.
Sleeping outdoors in the tropics is comfortable, we aim to make homes as comfortable inside, as the tropical nights are outside. Instead of Africans living outside until the house cools, locals can go inside passively cooled homes before the mosquitoes start to bite.
What everyone in the tropics wants is a comfortable, cool, fresh, breezy home, that stops thieves, mosquitoes and animals from entering. Our goal here is to explain how to build a passive cooled home that stays at between 70 and 85 degrees, where maybe you need a light sheet to cover you at night, but never the need for fans or air conditioning that are expensive, unhealthy, and damaging to the environment.
Passive means natural, no mechanical cooling of home, the home is a cool home because the design utilizes science at optimal levels for human comfort.
Where is the coolest place to sleep in Tropics?
On the ground, under a tree. Yet, we can be robbed easily, animals can attack, and everyone is watching, there is no privacy. So we moved into homes to escape mosquitoes, animals, thieves, and to have privacy, we want to find a way to live naturally, but still have the benefits of a home.
Two Options in the battle to stay cool in the tropical climates:
1. Solar radiation wins, and heats the home, and you become uncomfortable.
2. The ground temperature wins, and we keep the temperature of home at ground temperature levels, or just a little above.
What is the ground temperature of your tropical home at 1 meter depth?
Goal: To cool all parts of the home (thermal mass) to the same temperature inside the home, as outside at 2-5 AM. Then we insulate, add radiant barriers, and shade the home fighting of entry of the heat of day. We are not cooling the home, we are retaining the temperature of the cool night air, and ground temperature for the whole day.
List of Passive Cooling Concepts
AIR MOVEMENT - Can feel 2-5 degrees cooler.
@ Windows on opposite walls for cross flow ventilation.
@ Keep centers of room open, free from obstructions, so air can circulate.
@ Do not block stairwells, hot air needs to rise.
@ Transoms above doors
@ Air rises, so create chimney effects, air buoyancy is the term to learn.
@ Fresh air feels cooler, moving air, when the temperature is the same inside, as outside, but no movement of air, it would be effectively cooler outside.
@ Know the circulation of your home, make a map on how you want the air to flow. Cool air enters, and hot air leaves.
@ Vent the attics (Solar chimneys.)
@ Sleep on mattress on floor, it is the coolest place of home.
@ Mathematically, a person needs to know how long to cool the cement, wall, wood, the house.
@ Overhangs over window need to be very long to stop any sun from landing on side walls of the home.
@ Sleep on water beds, touching the floor.
@ Insulation on outside, with radiant barrier
@ Paint outside white, to reflect heat. (Better yet, the roof is radiant barrier.)
@ Light colored roofs, we do not want roofs to absorb radiation.
@ At top of room is screens that allow the hot area to depart.
@ venting bricks installed at top of rooms, correct size if the person wanted to install a fan.
@ lowered ceilings installed
@ fan holes installed at top of rooms
@ Curtains are too block sunlight.
@ Rods need to be 12 inches after edge.
@ They block cool air from coming in
@ Think about curtains outside, in the weather.
@ They need to 100 percent block sun.
@ Screen doors and window screens. (This may be wrong, we may want insulated doors.)
@ Put broom in front of crack at bottom of door.
@ Hang clothing on door to increase insulation.
@ Allowing cool air to escape, or hot air to enter.
HOW TO LIVE IN THE HOUSE?
Put all closets, clothing and good against hot walls to serve as insulation.
@ Keep cooking outside, and far away from home.
@ Water, moisture, and humidity need separated from sleeping. Although it seems convenient to have the toilet and shower close, we need separated.
@ We wish maximum air movement in, and out of the house at night, to equalize the temperature, whereby both inside and outside are the same.
@ Concrete areas around the house need tree shade, or even watered to keep cooler.
@ Paint inside, and outside white to reflect radiation, and not absorb.
@ Shade concrete areas around the home, so they heat does not pass to the home by conduction.
@ Create evaporation outside the home, this absorbs heat.
@ Plant shrubs up against the house to climb the wall and insulate against sun.
@ Do not cut trees down to use as firewood, the shade of trees is the most important factor in cooling a home.
@ The direct sunlight should never touch an exterior wall, cover with awnings, curtains, canopies, trees, bushes, etc.
@ Water down walls from exterior during the day with hose, the water will absorb the heat of the thermal mass of the walls.
@ Fans blowing air into the home, works better than trying to blow the hot are out of the home.
@ Curtains installed to hang 12 inches from window, still provide privacy, but allow cool air to enter.
@ Curtain props, the make the bottoms of curtains hang out.
@ Plant trees around house, and in front of windows, doors, and other places where direct sun can enter the house.
@ We want the cools walls from night to stay cool all day long.
@ Stack, or make all closets, hanging on the hot walls to serve as extra insulation.
@ Hang draping curtains on walls about 8-10 inches from wall, to allow dead space between living quarters and room.
@ Double Roofs.
@ Want high SRI (Solar Reflectance Index)
Cover Roof with Radiant Barrier - Read: It's the roof Dummy
@ Above sheathing ventilation (ASV) - Space between roofing, and house. This means to allow an air space just below shingles that allows hot air to rise to roof vents and escape naturally.
@ Cover steel roofs with thatch.
THERMAL MASS (NUMBER 1 Priority)
@ Everything in your home collects either coolness or heat, we need to cool the house during the night.
@ Goal to bring inside temperature of house to same as outside within two hours of sunset.
SHOWERS AND TOILETS
@ Doors on shower area, and closed, pushing humidity outside the home.
@ Porch, Balconies, or other structures need to be used strategically to block the sun from every landing directly on a window.
@ High as possible vents, if possible make the whole top of wall a vent.
@ Low vents as possible, but make it so they close, and do not allow animals or rain to enter.
@ The more windows the better, then close, insulate during the day, but open at night.
@ Windows should allow air to enter from the complete window, sliding window that force the window to be half closed are to be avoided.
@ The sun should not ever be allowed to shine directly on a window from the outside, there should be awnings over windows.
WINDOWS - INTERIOR
@ Windows should not be on East or West walls, they should be on where there is the least amount of direct sunlights.
@ Insulated window shutters, to keep the cool in, and the heat out.
@ Sunlight should never be able to enter a window directly.
@ Awning on outside of windows.
@ Curtains that allow zero sunlight to enter.
WINDOWS - EXTERIOR
@ Put radiant barrier on glass
@ Put awning over windows, or curtains
@ Close shutter when direct sun is shining on the window.
@ Radiant barrier on windows will slow transfer.