(This is the 2nd in a series of articles tackling how we might possibly deal with the indomitable heat in the Philippines. If you haven’t checked it out yet, visit War on Heat 1: The Cover Up. It might just save your life.)
Even if you were able to insulate your home 100%, it doesn’t mean it’ll be heat free. Try as hard as you might to keep it out, there will always be heat indoors. Your dog, the equipment you might have running, the sexual tension between you and the person beside you – all of these generate heat without having anything to do with the sun. At night the situation is even worse. As covered in part 1, your concrete hollow block walls re-radiate the heat into your space. Your enemy is already inside. You need a way to get that hot air out.
Designed to Breathe
While it might seem that the simplest solution is to open a window, its not as simple as asking the heat to climb out. Cooling a room doesn’t happen in a vacuum. The heat is in the air, and any air you take out has to be replaced by air from somewhere else. At the end of the day, you need three things to get heat out of a room:
- An opening for the egress for inside air
- An opening for the ingress for fresh air
- Force to circulate the air through your space
One Win scenario
If you’ve ever been stuck in a room with just one window, you’ll know that it’s next to useless in cooling the entire room. You pretty much have to put your face right to the opening to get any sort of fresh air. While generally there should still be an air exchange between the inside and the outside (physics wants pressure and temperature to equalize,) it happens very slowly. You could wait and stew in your discomfort for conditions to change. But given that your body is still generating heat, the change probably won’t get too far.
Add a fan and the room starts to feel better. The pressure from the fan is able to blow the saturated air around you off your skin and towards an exit. Given that your personal bubble is likely the hottest part of the room, any movement in the air around the you helps. The system isn’t as effective as it can be though. Step outside the throw of the fan and you’ll be slapped by the humidity. While there is some exchange between the colder outside air, having only one window means that whatever size opening you have has to function double duty as outlet AND inlet for air. As a result, very little air exchange with actually happens with respect to the whole room.
(in case your curious, run a fan without an exit and you’re essentially just circulating the same air. The movement might feel good to start, but in time, the heat you and the fan generate just makes the air stuffier.)
Inlet + circulation + outlet
By giving your space openings for the inflow and outflow of air, as well as a method for circulation, you create a space that breathes. The exit opening makes sure you’re able to eject the heat, the circulation makes sure your ventilate the entire space, while the entrance ensures you’re constantly supplied with fresh air. The openings work to 100% capacity instead of having to pull double duty.
Learning from the vernacular
Much of modern construction seems too stubborn to learn from what OG vernacular Philippine homes have always known – a house needs to breathe. The bahay kubo is the perfect example of this. Its sawali walls (panels woven out of splits of bamboo) allows for constant horizontal air circulation. While its nipa thatched roof allows hot air to exit from the top. The slatted floor, for its part, allows colder air from the silong below to replace what’s been ventilated out through the roof. Even the bahay na bato featured callados and ventinillas, allowing circulation of air between rooms, through to the exterior. What’s doubly impressive about these archetypes is that they’re designed to keep a space cool without the need for equipment.
Passive Cooling Design
Ideally, you’d have the system work passively and without any mechanical means. Given an entrance and an exit to your space, you’d want wind to come through and carry the heat away. Spaces should be designed with cross ventilation in mind. Openings should be on opposite walls, or at the very least, of a distance and orientation such that the path between the openings takes you through a long cut through the room. The longer the straight cut, the more air you’ll have exchanged at the end of the pass through.
You could also take advantage of heat’s natural tendency to rise (the stack effect.) This generally explains why lofts, mezzanines, and attics are often the hottest places in a house. You can take advantage of it though. Allow hot air to vent out through higher openings, while pulling fresher air in from lower.
To take advantage of passive cooling design you can utilize any combination of windows, clerestories, vents, chimneys, slits, slots, and slats of various sizes and orientations to try to coax the air through your space. Every project is different, and solutions will be just as unique. You just have to remember – good design has to breathe.
Should conditions not be ideal, and natural passive systems be inadequate, you can always resort to man made systems of cooling. But we’ll get to that in the 3rd part of this series: War on Heat 3. Mechanical Means
Have your own thoughts on possible ways to keep the heat of your home?
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