6 ways to increase your roof’s cooling power


THE GARDEN roof of Filipina and German environmental advocate couple Agnes Calda and Christoph Ranzinger’s farm house in a town in Cavite, which was inspired by the public buildings in their home city in Munich where most government structures are made of green roof. Built from locally sourced materials in 2006, the Ranzingers’ house is surrounded by coconut trees, coffee plants, fruit trees and organic vegetables. They named their small farm Sintang Lupa, or Love of Earth, and turned their dream of building the first green roof in the Philippines into reality. Photo by ROMEO GACAD/AFP

The roof above our heads can do more than just shield our households from the scorching rays of the summer sun. In fact, architects stress that the roof’s heat-deflecting capabilities can be enhanced by these six easy-to-do steps:

1 Use a roof sprinkler. Install a simple sprinkler system on your roof using some of the used water stored in a tank or containers. Water is an effective way to cool down the roof, particularly during the hottest time of the day, and even at night. This sprinkler system can also primarily be set to water plants in the pots mounted in the roof.

2 Drying zone. Convert the roof area into a laundry drying zone. You can place clotheslines across the roof and hang your wet laundry there during the day—preferably late morning to late afternoon. Ideally, the wet laundry should be unwrung, so the water dripping from the laundry can also keep your roof wet (and cool).

3 Trellis power. Architect Boy Morcilla suggested to Inquirer Property that a decorative wooden or cement board trellis built over your roof could deflect sunlight, and at the same time allow air to flow freely on the roof. If you decide to do so, plan the orientation of the trellis members so that they can offer the maximum shade during the time they are most needed.

4 Nature on the roof. The trees and shrubs around your house add to that “green” factor, absorbing that heat-retaining greenhouse gas carbon dioxide, and giving off refreshing oxygen during the day. Yes, plants are cool, literally.

5 Proper materials for the roofing. If you’re one of the few who are about to buy a new home, how do you make sure that it is already naturally cool from the top? Make sure that the builder used the proper materials for the roofing. Galvanized aluminum is better than galvanized iron for deflecting heat. Gypsum boards can also do the trick.

6 A roof garden. Landscape architect Paulo Alcazaren can’t emphasize enough the importance of a roof garden. He shared a simple rule for greening a city congested with buildings: What you lose on the ground you replace with greenery on top.

Alcazaren explained that 1,000 square meters would be a fairly ideal area to maintain a roof garden. He added that a roof garden requires the proper selection of plants and maintenance of drainage and water supply.

He described most buildings’ roofs as predominantly empty spaces, with only the air-conditioning system, cooling towers of chillers, water tanks and remnants of unused construction materials occupying rooftops.

Putting together a green roof, however, is not just about dumping soil and sticking in plants left and right. A green roof must also achieve a balance of architecture, and at the same time strike a harmony with the greater surroundings. In this regard, the building owner would need a structural engineer and a professional landscape architect to design the whole space.

Once you plan to “green” your roof, do it correctly. Turning roofs into gardens has one immediate benefit: an estimated three- to five-degree reduction in temperature on the floors beneath.

A word of caution, though: As Philippine Association of Landscape Architects president Dickie Altavas revealed, a green roof executed incorrectly could be more of a problem than a solution.

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  • Paliwaweng

    you can see almost all houses built nowadays had disregarded the basic concept of the primary concern of what a house should be; that is a place where you can feel utmost comfort.
    Thus, a concept or design to begin with should focus on how to make a house with natural ventilation.
    There are plenty of choices to begin with like rooftop vents where it will enable a natural flow of air within the house interior and provide a continuous air circulation.

  • Barak_O

    back to basics
    use nipa or cogon for roof

  • dikoy321

    Voice from Germany:

    A friend of mine built his home in Cebu, perfect TEMP inside, all year long !

    Save money

    Use 30 cm thick hollow-blocks as outside walls !

    Heat stays outside and cool air stays inside the house, no need for A/C units that are HOLES in your pockets as well as holes on the wall where a thief could sneak-in !

    The way Filipinos build homes, copied after US standards (bungalows), concrete or hollow blocks and GI sheets for roof, are OUT-OF-PLACE in such a HOT CLIMATE like Tropical Philippines !

    Learn from the Germans – build with Local materials (thatched roof from Anahaw or Palm leaves and then Bamboos for posts).

    Bamboos grow fast, harvestable in 3-5 yrs !

    Trees need much much longer, even mahogany needs at least 15 yrs !

    Plant bamboos and Palm trees for construction needs !

    Plant trees for long-term needs and ecology !

    Find more REASONS to plant than CUT trees !
    Forward Philippines !!!

    • tanginanio

      nature friendly suggestions but here in the philippines we have strong typhoons. i dont think bamboo and palm leaves can withstand the stronger typhoons we have here.

  • WeAry_Bat

    ” What you lose on the ground you replace with greenery on top.”

    Or on the side, or on along the fire escape ladder well…Buildings are land multipliers but they did not put the balancing equation to heat which are plants.

    So these architects, designers and what, they thought of increasing human space and mechanical air conditioning as replacement. Where do they put the air conditioners? Not at the roof, sometimes on the ground floor.

    Every spot where there was a building, there was heat and humidity. Placed together row after row, block after block, city after city in Manila with the result of a heat island.

    A heat island more than three times of what nature can provide to balance the heat. So even at 1am, I discover the bathroom still has heat and humidity. Heat has now a much longer overtime than office workers.

    But (developer name aside) I saw a new type of residential building with several stories of ‘holes’ for ventilation and alternate floors for commune and cooling, which is a good idea as going through the aisle, I could feel the wind blowing. Less electrical cost, I guess.

  • Jake Lopez

    You guys forgot to mention that if you paint your roof white, it will reflect 17% of the light and heat. A lot of people paint their roofs with fancy colors, white is still the best reflective color.

    • A. H. Forrester

      Painting the roof white is always good in hot climates, but the greater the distance the G.I. sheet or metal roofing surface to the ceiling of the room below is the key here. Cross venting to allow the hot air in the attic space to escape is another major consideration. In the States and in Military housing like at Clark Field before the perfectly good houses were all, are and i mean ‘ALL’ looted down to the last nail by those overseeing the handover back in 1992, had insulated ceilings lined with spun pink and yellow rockwool fiberglass insulation, double skinned metal roofs in very light colors, and properly vented attic spaces. This kind of forethought, design , and common sense design is worth the effort and produces comfortable living space.

      • stromboli67

        Good suggestions. I’d add one more – have wide overhangs to keep as much of the exterior wall surfaces under shade, & awnings over windows would help too. If you are a bit adventurous you may consider vertical landscaping applied on exterior walls, an upcoming trend.

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