Greencap Eco-News  |  Issue 12 |  October 2022

Sustainably Staying Cool This Summer

As part of Greencap's commitment to all things sustainable, we are pleased to send this regular communication where Greencap's own Eco-Sustainability Committee team members provide interesting facts, quick eco-tips, and recent environmental news.

This issue includes information on the impact of climate change and Urban Heat Island (UHI) effects on an increasingly urbanised population, together with a comprehensive list of simple actions we can take at home to sustainably stay cool this summer.

While another record breaking Australian summer might feel a long way away for those currently being impacted by flooding and wet weather associated with a third year of La Niña, our changing climate means that over the coming decades, we can expect:

• Extreme rainfall events and cyclones are likely to become more intense
• Potential severe thunderstorm days are expected to increase
• Higher sea levels will increase flooding in coastal cities and towns
• Hotter and drier conditions will lead to more droughts and bushfires
• Heatwaves will become hotter and longer

Source: https://www.climatecouncil.org.au/resources/how-will-climate-change-affect-australia/

What is compounding the impact of these increased extreme heat events is the fact that more and more Australians are choosing to live in cities, with over 86% of total population ‘urbanised’ as of 2021.

Urban Heat Island (UHI) effects caused by high thermal mass building materials (which absorb and retain heat), lower levels of vegetation, and human activities such as use of air conditioners, can raise average urban temperatures by as much as 3°C compared to those of natural environments. Urban heat can also be increased by human activities that generate heat, such as transport, industry, and electricity usage.

Urban heat and UHI effects are in turn increasing the heat-related impacts of climate change in urban areas, increasing temperatures and severity of extreme hot weather events.

"Strategies to help urban areas reduce the impacts of urban heat include reducing greenhouse gas emissions, increasing vegetation and green spaces, providing shade structures and water misting, using reflective building materials, and incorporating sustainable and water-sensitive design practices into urban planning and new developments.

- Source: https://www.climatechange.environment.nsw.gov.au/urban-heat

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So being smart with your cooling choices this summer is a great way to reduce your carbon footprint.

As our cooling demands increase moving forward, keeping homes comfortable in an energy-efficient, sustainable way is a major challenge. Passive design approaches and increasingly stringent building requirements* tackle this for new homes and renovations via efficient thermal envelopes, passive cooling and ventilation, technological innovation, careful placement of thermal mass, façades and shading, and air tightness. National Construction Code mandates do not address the existing housing stock however, where opportunities to enhance thermal performance are more limited, and can be costly or disruptive to implement.

Regardless of the age or type of your home, there are many simple actions you can take that will have a significant impact on thermal comfort and energy costs.

* National Construction Code 7-star Nationwide House Energy Rating Scheme (NatHERS) ratings become mandatory for new homes and renovations across Australia as of 1 May 2023.

Shade, Shade, Shade!

Heat gain from solar radiation drastically affects local internal thermal comfort, and preventing this heat gain via shading is highly effective.

External shade can be created by:

• Installing external louvres, awnings, pergolas or shutters to shade glazing
• Planting vegetation up or next to walls, and directly outside east and west facing glazing

Shading external walls prevents radiant solar heat gain of exposed thermal mass (which then takes a long time to cool down). Planting vegetation outside windows creates natural shade and shields low angle sun. Finally, mature trees (if you are lucky enough to have any) can provide roof shade.

If you cannot create external shade, then maintain internal shade by drawing curtains or blinds on east and west facing windows during the day to combat low angle sunshine.

Air Tightness and Ventilation

Air Tightness

A lot of older Australian homes are very leaky! Making your home airtight is an easy and low-cost way to improve the building’s thermal performance, by preventing hot air entering in summer (and conversely stopping it escaping in winter). Draught excluders; sealing gaps in floorboards, external doors, chimneys, window frames, and ceiling/wall penetrations; and checking insulation around perimeter of ceilings and around recessed lights can all help to stop that hot air getting in (or out). 

Ventilation

While air tightness is important for thermal efficiency, it needs to be paired with ventilation, which helps remove indoor pollutants, moisture (which can cause mould), and odours. 

Does opening windows help cool my home?

It depends! In drier conditions, and where the ambient night-time temperature is lower than the internal temperature of your home, opening windows at night allows hot air to escape and let cooler, fresher air in. In humid conditions, opening windows on a warm summers night will allow dry, cooled internal air to escape and let warmer, wetter air in (creating challenges with condensation and mould).

Roof Ventilation

When poorly ventilated, roof void temperatures can get up to 50 – 60°C in hot weather. This creates a temperature gradient between the cooled, internal spaces of your home and the roof void, causing heat transfer into the home through the ceiling, even where these are insulated. Any cooling systems then need to work harder to maintain comfortable indoor temperatures. Unventilated roof voids can also exacerbate mould problems in humid environments. Mechanical ventilation of a roof space (e.g. by installing solar ventilators) can reduce temperatures by displacing hot air with cooler incoming air.

You can also place a bowl of ice cubes in the path of your fan to cool the air, or hang up wet towels in the opened windows airflow for an evaporative cooling effect.

‘Cool’ roofs, or those with light coloured roofing materials or solar thermal reflective coatings, can help reflect solar radiation and prevent your home heating up in the first place, and combat UHI effects at the same time.

Mechanical cooling tips:

• Ensure ceiling fans are set counterclockwise and on a high-speed setting in summer to push air downwards to create a cooling effect.
• Place pedestal fans in the centre of ‘use areas’ of each room to maximise local cooling 
• When you do use air conditioning, set it at the highest temperature you are comfortable with (aim for between 24- 26 °C). A good rule of thumb is not more than 7°C below the external temperature. Every additional 1°C of cooling increases energy consumption by around 10%.
• If you have zoned, ducted or multiple split systems, keep internal doors closed so you only cool occupied spaces, limiting the volume of air the system needs to handle at a time.

​Further reading:

• Your Home - Australia's Guide to Environmentally Sustainable Homes
• Australian Passive House Association

• Source 100% renewable electricity by 2030 in Australia
• Halve the carbon footprint of their designs and advice by 2030
• Delivering Net-Zero emissions across its global value chain by 2040
• Reduce absolute Scope 1 and 2 market-based GHG emissions by 60% by 2030 (from a 2020 base year)
• Reduce absolute scope 3 GHG emissions by 30% over the same timeframe

Learn more: https://www.wsp.com/en-AU/news/2022/wsp-to-halve-the-carbon-emissions