AC myths 8: Insulation can be daft
Thursday 15 September 2011, 4.15pm HKT
(Continued from Part 7)
In this penultimate part of the series, the received wisdom about insulation might not be so wise for AC use.
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Insulate your premises when you install an AC.
This is only a half-myth, because it is a legitimate factor to consider in some regions. In places like Hong Kong, though, it’s pretty stupid to see this recommendation for residential premises.
Hong Kong is a concrete jungle. Wait, not in real terms. Urban land use here only figures 15% of the total land availability. But the concrete parts of the place are seriously concrete. Srsly.
Many cities around the world make some abject effort to plant trees and other shrubbery on the sidewalks and generally around town.
Hong Kong makes no such effort. Here, plants are considered a ‘visual impact’ on property prices (I kid you not!) or bad feng shui or “noise-causing” (Shome mishtake here—Editor).
But if and when our municipal authorities do plant, they’re doin’ it wrong.
Many times you will see government contractors plant new trees along sidewalks — a good thing — but then they go all barmy and proceed to concrete over the base, so that the tree suffocates to death nearly always within 2 or 3 years of planting. And then the government arborialists wonder why.
(I can’t believe I’ve actually lived the day to have to write that.)
But Hong Kong IS a concrete jungle, practically speaking. (Singapore, too, although they won’t admit it.) Concrete jungles retain a lot of heat.
When you’ve got something like cars, the underground train system, four million phonelines and 13 million mobile phones (for a population of 7½ million), 6,000 high-rises of 20-plus storeys, plus cable TV, Internet lines, etc, etc — that’s a lot of heat sources and a lot of heat retention. Living and working inside a concrete structure all the time, insulation is irrelevant here.
But insulation is highly relevant for some places — Australia, Canada, the UK and the USA being prominent examples.
In Australia, if there’s no roof insulation, the AC is working against the heat load on the roof, and that can be considerable. Bedrooms there tend to be downstairs and well-insulated from the floors above, and there is some insulation in the exterior walls.
For office buildings, Hong Kong forgoes much of the conventional Anglo-American-centric insulation wisdom and go straight into installing mirrored exterior glass panes to reflect away light and heat. We use specially formulated, man-made marble slabs for building exteriors and interiors. Porcelain tilework is nearly everywhere inside. We don’t have earthquakes, tornadoes or even tsunamis like some places do, so we can afford to use those building thingies.
We use 3M Panaflex Awning and Sign Facing 945 GPS material (a kind of flexible plastic tarpaulin) for hoardings and backlit signages — much more versatile than the woodboards, Sheetrock gypsum panels or Perspex sheeting often used in the West.
Shameless self-plug: The Naked Listener has the distinction of introducing Panaflex to Hong Kong in the 1980s. Got no money out of it, though.
For residential buildings, we’re starting to use more reflective paint on rooftops and exterior walls than previously to reduce heat transfer. This is a costlier version of what Hong Kong did in the 1950s: whitewashing the outer walls.
FACT: Any normal white or light-coloured exterior wall paint will reflect light and heat off of a building structure.
Short of installing mirrors on the outside — not a bad idea, actually.
Protip: Whitewash your building’s exterior once a year. Every little bit helps, and white has the best heat/light reflectability than any other colour.
Think about why power stations and nuclear reactors are always painted white. Think why space rockets and spacesuits are in white. Think why there are no black or dark-coloured palaces.
Protip: Whatever you do, don’t paint your exteriors in dark pink (a.k.a. terracotta, burnt ochre, cemetery rose), brown or green — they’re the pits for heat/light reflection, they absorb heat and infrared radiation second only to all black, and they just look plain shite.
Which is why office buildings around the world almost never use those colours (except bloody Hong Kong and China).
Protip: When you use the AC, curtain off any incoming direct sunlight, which heats up the place. Even better, get those one-way mirror films and use them on window panes for general heat/light reflection.
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Low-cost and no-cost energy-saving protips for the home and office.
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© The Naked Listener’s Weblog, 2011.
Images: Shrubbery and house via CurbedWire ♦ Hong Kong concrete jungle via TrekEarth ♦ Golden mirror window panes by Only2perCent via WallpaperWeb ♦ Green-white building in Hong Kong via Airconco ♦ Luke Skywalker Building via Wikipedia.