Community Energy Efficiency Program (CEEP)

The Community Energy Efficiency Program (CEEP) is an initiative of the Australian Government that provided $106 million to 160 local governments and non-profit community groups between 2012 and 2014. The CEEP provided co-funding to implement projects that deliver a range of energy efficiency measures in council and community owned buildings, facilities and sites; particularly where this would benefit low socio-economic and other disadvantaged communities or support energy efficiency in regional and rural councils. As a successful recipient of CEEP funding, the Townsville City Council is undertaking upgrades including improvements to heating, ventilation and air conditioning systems, indoor lighting upgrades, hot water upgrade, outdoor lighting and water chiller installation across a number of sites.

The project also involves a community behaviour change component of which this report provides guidance on use of policy and incentives by governments in Australia and internationally to encourage or require white roofs in order to reduce heat entering buildings and the associated energy costs and greenhouse gas emissions. The project includes the implementation of the Community Based Social Marketing (CBSM) methodology developed by Doug McKenzie-Mohr, complimented by applying ‘Thematic Interpretation and Communication’ advised by Professor Sam Ham, University of Idaho. The CEEP will build on from the findings of the ‘Townsville, Queensland's Solar City’ program, and in particular the ‘Townsville Residential Energy Demand’ (TRED) project.  

There are a number of reasons why the TCC CEEP project has selected the behaviour, that of ‘Having the roof painted white’, namely:

• It is a well-recognised way to reduce energy demand in the home,
• The activities associated with the behaviour are not technically onerous,
• The opportunity to build on previous research and community engagement findings, previous industry relationships developed in CitySolar program, and previous piloting of tools and strategies at the behaviour level.
• The opportunity to continue the momentum in the community on the behaviour.

A Brief Summary of the Value of White Roofs

With its high incidence of solar radiation and high year-round temperatures Townsville is the ideal location for white roofs as the benefits increase at temperatures above 24°C. There are a range of potential benefits of white roofs, including:

Reduced temperature inside buildings

A trial undertaken in Townsville between 2011-2013 found that following the application of a white roof, residents experienced noticeable reductions in temperature in their homes, with the maximum roof cavity temperature reducing by between 9.5 and 17˚C and the maximum internal temperature reducing by 1.2 to 2.5%.[1]

Reduced energy consumption for cooling

The trial undertaken in Townsville between 2011-2013 also found that following the application of a white roof, residents experienced noticeable reductions in electricity demand related to cooling. The majority of dwellings experienced sizable reductions in electricity consumption in the range of 20-60%,[2] with an average energy saving over the 14 homes of just over 30%.[3] These findings are similar to a 1993 trial in Florida, USA, having slightly higher rainfall and similar temperature profiles to Townsville. The trial found that summer cooling energy use in nine homes was reduced by between 11 - 43 percent after resurfacing roofs with a white coating. Average reduction was 19 percent.[4]

Improved performance of photovoltaic panels

Photovoltaic panels are typically designed to operate most efficiently at 25°C. However a dark roof can reach temperatures approximately 60°C, and the efficiency of solar panels can decrease by as much as 0.4-0.5% for every 1°C above 25°C.[5] Hence compared to a white roof that is typically at ambient temperature, a dark roof at 60°C will reduce the efficiency of a solar panel in the order of 15%.

Reducing greenhouse gas emissions from fossil energy

Painting roofs (along with other dark-coloured surfaces such as roads and pavements) white has the potential to provide substantial climate change mitigation. Studies estimate that converting 100m² of dark roof to white can offset the emission of 10 tons of CO₂ equivalent over the lifetime of the roof.[6]

Enhancing the performance of insulation

According to the ANSI/ASHRAE Standard 90.2-2004, the resistance of ceiling insulation can be increased by up as much as 50% when solar reflectance and thermal emittance values of roof coatings are at least 0.65 and 0.75 respectively.^[7] Additionally, high temperature conditions can accelerate the decline in the resistance of certain types of insulation.^[8] This is particularly relevant considering the roof cavity temperature in homes in Townsville can reach temperatures in the range of 40-50°C.[9]

Performance of electrical wiring

The performance of electrical wiring is affected by temperature, as electrical conductivity varies inversely with temperature. This means that wiring in hotter roof spaces uses more electricity to deliver the required electricity to an appliance. In practice, a temperature increase of 1°C can increase the resistance of the metal in the wire by just under 0.4 percent.^[10] Studies in Townsville show that white roofs can reduce the roof cavity temperature in the order 9.5-17°C, which corresponds to a reduction in energy demand of 3.8-6.8%.[11]

Impact on ducted air-conditioning

As cool roofs reduce the roof space temperatures, that can be as much as 40-50°C during summer in Townsville, they may provide additional energy savings by reducing heat transfer to air-conditioning units and ductwork (that are typically poorly thermally insulated).^[12] In effect, before the home is cooled the resident is paying for the air-conditioner to overcome the heat created in the roof space and then the heat entering the home from the roof.

Impact on Roof longevity and Cyclone Strength

White roofs are subject to less diurnal thermal expansion and contraction, due to their lower surface temperatures, and may consequently have a longer service life.^[13] Higher temperatures in the roof space may also affect wooden structural members by drying them out and reducing structural strength, an important aspect in cyclone prone areas such as Townsville. Given timber in Townsville will have a high moisture content due to the high ambient humidity (in the order of 15-20%) the impact of temperatures in the order of 40-50ºC can be a reduction in bending strength of 15-25%.[14]

Reducing Urban Heat Island

The Urban Heat Island effect can cause daytime average air temperatures in cities to be 2-5ºC higher than surrounding rural areas.[15] In cities, white roofs may decrease the surrounding summertime air temperature by 1-2ºC.[16] Research is showing that the lower surface temperatures of cool roofs may reduce a building’s contribution to the urban heat island effect, potentially also diminishing smog formation.[17] An investigation into the 1995 heat wave in Chicago found that having a black roof was a major risk factor in mortality for people living on the top floor of a building.[18]