There is nothing new or innovative about orienting buildings so they benefit from seasonal variations in the sun’s path and wind patterns, but getting it right can deliver many advantages for a home and its occupants.
Passive heating and cooling measures can play an important role in improving the energy efficiency of a home by reducing or even eliminating the need for auxiliary heating and cooling.
The YourHome guide, a manual to environmentally sustainable homes delivered by the Australian Government, notes that because of a warming climate, the focus on passive solar cooling as opposed to heating has grown more pertinent.
One passive cooling design technique commonly used in private, public and commercial applications to maintain a comfortable indoor climate is night purging – the removal of heat from a building by bringing in cool night air without the use of active HVAC cooling and ventilation. Typically, this is done by leaving windows and openings closed in the day, and opening them up at night to flush warm air out of the building.
Night purging, or flushing, is particularly great for the summers, when daytime temperatures are so hot that bringing unconditioned air into the building will not cool it down. It works via stack ventilation (the idea that hot air rises and cold air sinks due to their pressure differences) and wind ventilation (the pull of air into and through building), so night air and breezes cool the thermal mass of a building.
However, the success of night purging is dependent on a number of conditions, such as ensuring the interiors of a building have large areas of exposed internal thermal mass (coolth is stored in thermal mass), and the right climate with temperature fluctuations between day and night.
Here are five ventilation products available in Australia that let the cool night air in:
ecopower ventilators by CSR Edmonds
Claiming to be the world’s firsttrue hybrid ventilator that works in all conditions, even when there is no wind, ecopower combines German electronic commutating (EC) motor technology with Edmonds’ Hurricane ventilator design.
The motor is mounted in a direct drive configuration, with the bearing system of the motor becoming the bearing for the turbine. This means that the ventilator can be driven by just wind, or by both wind and electric power simultaneously.
The lack of fan and motor assembly also leads to an increased flow rate of approximately 40 per cent in wind driven mode.
The commercial product can be controlled by digital measures such as temperature, time, wind speed, humidity, or gas concentration, and generates low noise levels. Each ventilator weighs less than 19kg and uses single phase power so no significant electrical rework or power supply is necessary.
Nature’s Fan Pearl Double Glazed Vertical Window by Jewel Windows
Nature’s Fan Pearl is a vertically operating window that allows cool air to naturally enter a home below, and warm air to escape from above. Two panes of glass slide past each other simultaneously and easily, providing uninterrupted views.
Images: Jewel Windows
The vertical window is thermally enhanced by a sash ‘T’ section provided in its rigid PVC, which acts to reduce the transfer of external heat in summer and maintain warmth in winter. The Pearl windows are also said to be superior to awnings or traditional sliding windows in promoting natural air circulation of breezes – temperature monitored tests have shown a room is, on average, five degrees lower when the Pearl window is fully extended.
Whilst some night purging window systems have security issues, this product is marketed as an anti-intruder barrier. The ‘T’ section of Pearl conceals the pair of Kevlar cords, preventing them from being cut from outside the window as it hides the stainless steel pulleys from view.
Healthy Home Ventilation System from HRV
The HRV ventilation system harnesses fresh night time air, which is filtered through an electrostatically charged deep-pleat filter and subsequently circulated throughout the home with windows either closed or opened. This air, free from allergens, pollen, dust, vehicle pollution and toxic gases, creates a cooler indoor environment and reduces the air conditioning load required for the next day.
The system can also be used for passive heating. SolaMate panels, which sit on roofs facing the sun, absorb light and energy to warm the air entering the home. An accompanying smart controller works out when to turn it on and off automatically, allowing occupants to enjoy responsive heating and cooling benefits.
Healthy Home Ventilation is approved by the National Asthma Council’s Sensitive Choice Programme.
Altair Powerlouvre™ Windows and Powerlouvre Apptivate® Control Unit by Breezway
Manually opening windows every night can be a tiring task, but this Breezway innovation is a sure way to stem arguments about who’s on ‘window duty’. The Altair Powerlouvre Windows are designed to electronically manage cross ventilation and natural airflow, and when fully open allow up to 90 per cent natural ventilation without the need for artificial cooling systems.
Images are copyright of the Breezway Group of Companies
Available in heights up to 2.7 metres, they can be incorporated in various applications, such as out of reach locations or as floor-to-ceiling feature windows. The complementing Powerlouvre Apptivate Control Unit and App allow the windows to be controlled by a touch sensitive wall plate, or remotely by compatible smartphones and tablets.
Automatic operation in response to an in-built temperature sensor or specific times means that the windows can open at night for night purging, and close when a comfortable indoor temperature is reached. They can be opened or closed fully, or set at a precise intermediate position.
Smartbreeze by Smart Roof Australia
This ventilation system, designed for Australian conditions, harnesses solar heated air to heat homes on a cold day, and assist with cooling by redirecting radiant hot air from roofs, which can build up on a warm day and increase the heat load in the home.
‘Purging’ occurs both during the day and night. In the day, a 30w solar panel is employed to power fans to move the hot air from the roof space, replacing it with cooler ambient air from the outside.
At night, the smartbreeze damper opens, allowing cooler air to be filtered and blown into the home when the air is cooler outside than it is inside. A continual movement of hot air from inside the home to the roof before being purged creates a thermal chimney effect, providing 24/7 natural ventilation on hot days.
Smartbreeze is developed to suit metal and tile roofs on either new or existing buildings, and suitable for pitched or flat roofs. It can also be linked to existing heating and cooling systems with an interface to provide green energy as a priority.
Images: Smartbreeze and TESC