Reflective Foil Insulationin Tropical Climates

Prepared By

Silver Batts Insulation Systems

In Association with

Sanrok Enterprises

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Problem

IT’S HOT!ButPeople in the tropics have a laid-back outdoorsy life-style– they don’t like being cooped up in an air-conditioned house.

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Solution

Reflective Insulation

can provide significant comfort improvements

Without Air Conditioning

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Thermal Management- Europe/US

Structure: Sealed envelope.

Access: Air-lock doors.

Analysis: Heating and cooling numbers, based on

internal/external air temperature difference.

“Mechanicals”: Heating/AC,bulk insulation.

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Thermal Management – Tropical

Structure: Partial envelope; high-set floors;high roofs; broad eaves orbalconies; well ventilated.

Access: Door or open doorway; louvre windows permanently open.

Analysis: Total heat load = air temperature + radiation.

Cooling devices: Ceiling fans, evaporative coolers.

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Thermal ManagementTraditional Tropical Architecture Design principles: Roof ventilation dissipates solar heat gain. Raised floors assist downward heat loss. Light timber construction cools rapidly at night. Cross-ventilation adds to thermal comfort.

A modern improvement: SILVER BATTS reflective insulation eliminates

heat gain through roof without storing heat at night.

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Insulation Engineered for Warm Climates

WaveCore Silver Battsare designed for sub-tropical and tropical climates

Equivalent to fibrous insulation between joists.Winter: up to R6.7 Summer: up to R1.7

Maximum resistance against heat coming in.

Minimum resistance against night-time shedding of heat.

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Why doesn’t fibrous insulation work in warm climates?

Fibrous insulation captures air pockets;preventing convection. very effective at keeping heat in; Butless effective at keeping heat out. Heat flow down is mostly radiation, which shines through fibrous insulation at high temperatures.

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In Warm ClimatesRadiant Heat Matters!

Stephan-Boltzmann Law of radiation: w/m2 = e c t4

where e = emissivity c = 5.67 ∙ 10 - 8

t = temperature (Kelvin)Net radiant heat transfer from a fibre-cement roof at 80 degrees Celsius to a 40 degree ceiling is 300 watts per square metre.

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Thermal ManagementSubtropical Insulation

Professor Richard Aynsley says -“use reflective insulation with

lower resistance against heat flow up, to facilitate shedding heat at night”.

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Measuring Temperature in Warm Climates

Operative temperature = weighted average of air and mean radiant temperature.

For air velocity < 0.2 m/s, use the simple average of air and mean radiant temperature.

Mean radiant temperature = the weighted average of all surrounding surface temperatures.

(Note: relative humidity is ignored throughout this discussion.)

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Operative Temperature – Equation

to ≈ (hrtr + hcta)/(hr + hc)Where

to = operative temperature hr = coefficient of radiant heat transferhc = coefficient of convective heat

transferta = air temperaturetr = mean radiant temperature

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Measuring Operative Temperature

A thermometer enclosed in a black copper globe 150mm diameter measures radiant and conductive heat load, reasonably closely approximating Operative Temperature.

Globe Temperature ≈

Operative Temperature

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A Rule of Thumb

Empirical work by Aynsley et al* indicates that typically -

1o increase in ceiling temperature ≈ 0.2o increase in operative temperature.* Aynsley R., Melbourne W. and Vickery B. (1977), Architectural Aerodynamics, Applied Science, London, p182.

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Operative Temperature in an Open Shed

On a hot sunny day in summer * –Air temperature 42o Wind speed <2 m/sSolar irradiation 1,000 w/m2

Roof temperature 90o

Operative temperature 51.4o

* Typical conditions for semi-arid subtropical climate; internal air temperature assumed equal to external.

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Reflective Foil In an Open Shed

For bright aluminium, e (emittance) = 0.03

radiation = e c t 4 ≈ 0 w/m2

Mean radiant heat 42o

Operative Temperature 42o

Foil under the roof eliminates radiant heat,reduces Operative Temperature by almost 10o.

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Operative Temperature in a Hot House

On a warm sunny day in summer * –Air temperature 32o Wind speed <2 m/sSolar irradiation 1,000 w/m2

Ceiling temperature 60o

Operative temperature 37.6o

Eliminating radiant heat in ceiling can cut operative temperature by 5.6o

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Foil in a Sealed Buildings orwith Ceiling Fans

In sealed building, heat transfer by conductionmust be addressed.

Multi-Layer Silver Batts provide a cost- effective space-saving solution.

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Single-Layer Reflective Foil Laminate

In an open shed, where the air temperature is the same as outside, foil reduces radiant heat, stops condensation.

(Fibrous insulation over the foil adds no benefit.)

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Multi-Layer Silver Batts in Residential Ceilings (1)

Multi-Layer Silver Batts: a highly effective insulation for tropical and sub-tropical climates.

Pictured: High-Top WaveCore Silver Batts.

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Multi-Layer Silver Batts in Residential Ceilings

Installation over ceiling joists eliminates heat bridge.

High-Top WaveCore Silver Batts Equivalent* R value:

Heat flow down: R 6.7 Heat flow up: R 1.7 * R value of bulk insulation between joists required to achieve equal overall resistance.

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Multi-Layer Silver Batts under Steel Roof

Multi-Layer Silver Batts are the most effective of insulation against heat flow down in enclosed buildings.

Pictured: Sydney warehouse with WaveCore Silver BattsR2.8 summer

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Multi-Layer Silver Batts under Concrete

Multi-Layer Silver Batts are the most effective of insulation against heat flow down in enclosed buildings.

Pictured: Sydney office block with Triple Layer Silver Batts.R2.4+ summer

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Multi-Layer Silver Batts in Portable Buildings

Multi-Layer Silver Batts are the preferred solution where superior summer performance is required.

Pictured: Melbourne portable classroom with WaveCore Silver Batts.R3.9 summer

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About Silver Batts Insulation Systems

• Established 1999.

• Division of Amalgamated Metal Industries P/L.

• Patents in Australia, NZ, US, Japan, China.

• Systems for residential, office, and industrial.

• Markets in Australia, Japan, India, NZ.

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Valued Clients - Australia

Australian client base includes most major commercial builders:• Multiplex,• Australand,• Baulderstone, • Meriton.

Pictured: King Street Warf development, Sydney; fitted with Triple Layer Silver Batts.

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Export Clients - Japan

Pictured: Certificate of “Superior Insulation” from Japanese Ministry of Construction.

In Japan,Silver Batts are marketed in partnership with Matsumoto Kenko. Clients include Mitsui and Panasonic.

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Silver Batts vs Fibreglass;Features

Issue Silver Batts Fibreglass

Condensation Non-absorbent; moisture resistant

Absorbs water; can lead to damage to structure.

Ease of installation Fix to structure

Support needed in steel sheds.

Seasonality Best in summer

Best in winter.

Summer Heat retention

Allows rapid night cooling

Retains heat well at night

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Silver Batts reflective foil insulation;A solution for HOT climates

Silver Batts provide a

One-Way Heat Valve prevent heat gain during the day; but allow rapid cooling at night.