A FRESH LOOK AT NATURAL VENTILATION IN AUSTRALIA

Photo credit: Valley Drive, G.James Windows and Doors, AGWA Design Award Winner 2019

A FRESH LOOK AT NATURAL VENTILATION IN AUSTRALIA

Australia’s most livable and desirable homes all have something in common. It’s that special x-factor you can’t see, touch, or buy. It’s the flow of outside air into and through the home that gives you a calm, fresh feeling — natural ventilation.

Natural Ventilation is an important topic, but it can often be misunderstood. ‘In this day and age, we are all generally aware of the importance of removing aerosols from indoor spaces as a means of reducing the spread of airborne viruses and most of us are aware of the benefits that natural ventilation provides whether that is reducing sick days in the workplace or improved academic performance in the classroom', according to David Auret from EBSA.

Many studies have shown that the benefits of natural ventilation go beyond just making you feel good. In fact, good air quality and flow have many more benefits, including improved health for occupants, reduced likelihood of mould developing, and energy savings all year round.

‘But all of that can be achieved very easily by simply incorporating manually operable windows into any building. In fact, that is essentially what is done to achieve compliance with the NCC Regulations, where AS 1668 requires 5% of the floor area of a habitable room to be provided as natural ventilation. That is where natural ventilation is often misunderstood, compliance versus function’ continues David.

The most effective products for natural ventilation are well-designed and wellplaced windows and doors. So, whether it’s for a new build or a renovation, planning for natural ventilation goes a long way towards achieving that special x-factor feeling that buyers and residents look for.

NATURAL V MECHANICAL VENTILATION

The Australian Government’s website for sustainable home design (www.yourhome. gov.au) defines ventilation as ‘the intentional introduction of outdoor air into a building to maintain good air quality. Ventilation methods can be natural (eg, windows and doors) or mechanical (eg, fans and air conditioning)’. 1

David Auret says, ‘natural ventilation is not just about the windows however, it is the seamless integration of all the parts to work in harmony’. He continues, ‘window automation has gone digital, and this technology is revolutionising the industry’.

Older homes with poor sealing would naturally let fresh air in and allow vapourladen air to diffuse through the structure. This was not ideal on cold winter nights or hot summer days, but it did contribute to natural ventilation and prevented condensation from occurring.

Photo Credit AWS

Photo credit: EBSA

In contrast, contemporary buildings and homes are increasingly designed to be airtight, as a way of blocking out noise, pollution, and extreme temperatures. However, unless someone is opening their windows every day, natural air will not flow into the building, making the inside and outside environments very different, resulting in high moisture levels and low quality, stagnant air.

‘Most countries around the globe are looking to reduce their carbon footprint, and not relying on HVAC is the smartest solution for homes and workplaces’, explains Ivan Kinsela from Kintrol Window and Door Automation. ‘Over $US18 billion was invested in automatic windows and doors last year alone, which indicates a positive shift toward natural ventilation.’

Ivan suggests that to progress the movement toward natural ventilation, industry should consider the following:

• Replace older windows with modern and easier to operate windows.

• Increase the sizes of windows, skylights, roof windows, and curtain walls to let more light in and encourage airflow.

HOW NATURAL VENTILATION CAN REDUCE COSTS

According to Architecture and Design 2 heating and cooling account for up to 50% of energy used in Australian homes, and so the appetite for natural ventilation as a cheaper and more environmentally friendly alternative to mechanical ventilation systems is growing.

Natural ventilation uses natural forces to enable a building to breathe by varying the openings (windows, doors, louvres and skylights) when the weather conditions allow. Fortunately, Australia’s warm summers and mild winters provide the ideal conditions for natural ventilation in buildings.

David Auret from EBSA, points out that ‘inviting nature in through open windows is fantastic, when conditions are suitable for natural ventilation, but at other times it is important to ensure that mechanically conditioned air is not lost through poor performing windows, or that outside air is not penetrating the building increasing the cost of conditioning the space. The long-term costs of inefficient windows will continue to be felt as energy prices continue to rise, and our advice is to select the best thermally performing windows available within your budget and to pay attention to air leakage’.

Research published in Architecture and Design 3 reveals that buildings using natural ventilation can expect a reduction in capital costs of 10-15%, compared to air-conditioned equivalents, as well as achieving significant reductions in operating costs with reports finding naturally ventilated offices have 25- 33% lower annual energy costs.

Even when the outdoor temperature is the same as the indoor temperature, some ventilation is still required, as building occupants and devices within a building generate heat, which must be dispersed through ventilation.

Steve Harrison, General Manager Breezway Australia and New Zealand explains that ‘when cooling is required for occupants’ thermal comfort, and the outdoor air temperature is lower than the indoor air temperature, outdoor fresh air can be used to achieve indoor cooling. Increased ventilation equals decreased energy costs’.

Air Leakage impacts the operating costs of a building in terms of heating and cooling and while windows provide natural ventilation, David Auret from EBSA reminds us ‘they should also be fully compliant with the NCC, which means air leakage must be measured in both directions, air infiltrating into the building and conditioned air escaping from the building. This is extremely important and is often overlooked by designers. They should ensure compliant products are selected for air-conditioned spaces, which may be different to those available for use in non-air-conditioned spaces’.

For businesses and schools, natural ventilation can help reduce costs associated with sick days and loss of productivity. An international review of green schools found a 41.5% improvement in the health of students and teachers (such as reduced incidence of asthma, flu, respiratory problems, and headaches), up to 15% improvement in student learning and productivity, and up to 25% improvement on test scores from good lighting and ventilation. 4

A 2005 study of 10-year-old school children further showed that increasing ventilation rates could improve the children’s performance in tasks representing eight different aspects of schoolwork, from reading to mathematics. 5 This reinforces that the benefits of natural ventilation go beyond just energy saving.

CONSIDERING VENTILATION POST COVID-19

Safe Work Australia reported that COVID-19 could be transmitted in poorly ventilated indoor settings. It further noted that good ventilation was important in minimising the build-up and stagnation of infectious aerosols indoors, including those containing the COVID-19 virus. 6

Until now ventilation has not been a primary focus for building design. ‘Air conditioning (AC) tends to be the go-to solution to keep classrooms, offices, public buildings and aged care settings cool’, explains Leigh Rust, Director from Safetyline Jalousie. ‘Most nursing homes use reverse-cycle split-system air conditioners or warm air heating systems, but most of these units do not introduce fresh air into the spaces they serve. And without natural ventilation, building occupants are exposed to many health risks.’

‘Take a full classroom for example. The levels of C0 2 can rise to four times the optimal amount (from 1000 ppm to 4000 ppm). When this occurs, students can suffer from a lack of oxygen, leaving them unable to concentrate. Students can also suffer from headaches, nausea, and constantly feel tired and sleepy from lower oxygen levels.’

When staff or students don’t have time to open and close windows each day or the weather is not ideal, schools and businesses simply cannot achieve sufficient natural ventilation. This problem inspired Safetyline Jalousie to collaborate with Blue Squared Window Automation to find a solution: a complete turnkey natural ventilation, temperature and humidity, informing occupants and operating a room's louvre windows to open to provide fresh air and flush out polluted air before it reaches hazardous levels.

Photo credit: Jarrod Bryant Photography

'The SmartAir automation allows the louvres to respond to the conditions of the environment, without the need for human intervention. Essentially enabling a building to breathe for itself', explains Leigh.

David Auret, from EBSA, says there has been a fundamental shift in building, particularly, in the commercial space because of COVID-19, with natural ventilation now being a driving force behind design. He continues ‘when it comes to building spaces that can help reduce the transmission of respiratory viruses, designing a building that thinks and breathes for itself is among the most effective post-COVID solutions’.

Photo credit: Safetyline Jalousie

THE NATIONAL CONSTRUCTION CODE AND VENTILATION

The National Construction Code 2019 (NCC) stipulates in clause 3.8.5.2:

‘Ventilation must be provided to a habitable room, sanitary compartment, bathroom, shower room, laundry and any other room occupied by a person for any purpose by any of the following means:

(a) Openings, windows, doors or other devices which can be opened—

(i) with a ventilating area not less than 5% of the floor area of the room required to be ventilated; …’

While the NCC should be considered the minimum design standard, many designers and architects are understanding that increasing the ventilation requirements beyond the NCC’s minimum threshold of 5%, not only makes sense, but also improves the comfort and amenity for building occupants, reduces energy consumption, particularly in warmer climates, and reduces air-borne pathogens and toxins, creating healthier and more livable spaces for people to inhabit.

DIFFERENT WINDOW AND COMPONENT TYPES THAT ASSIST NATURAL VENTILATION

‘The fact that air rises as it heats has been used for centuries as a way to draw fresh, cooler air into a building. This is one of the prime reasons that double height voids and windows positioned close to the ceiling are common features of naturally comfortable homes’, explains Steve Harrison, General Manager Breezway Australia and New Zealand.

Cross, or wind-driven ventilation

Wind hits the side of the home it creates positive pressure on one side and negative pressure on other. Then when windows are open, the difference in pressure forces air through the building and creates natural cross-ventilation.

‘Louvre style windows (90% ventilation openings) work most effectively to achieve cross-ventilation, closely followed by sliding windows (40% ventilation openings)’ explains Steve.

Stack or buoyancy-driven ventilation

Temperature differences between inside and outside air creates movement, which forces air to enter and exit the building via low and high vents or openings. Steve says, ‘automatic high louvre, high awning, and louvre window styles work best when trying to achieve stack ventilation min a home or building’.

Quiet window actuators

So why should a homeowner or developer consider installing window automation and what is often overlooked? David Auret, from EBSA, explains, ‘First, window automation technology has advanced considerably in the past decade and digital actuators are now leading the way. These actuators communicate directly with the window controllers to provide live feedback, including window position, fault reporting and other events. Digital systems allow for any single window to be controlled independently of the others and make interfacing with CO 2 and temperature sensors a breeze. What's more the cost of field cabling and the size of the control systems is nearly halved, making installation that much more affordable.'

Photo credit: EBSA

‘Digital automation systems go a long way to future-proofing any building, in so much as you can reconfigure the internal space without having to re-cable any part of the project. The technology is so advanced that remote access via secure cloud-based servers is possible, allowing technicians to program the controllers and actuators without stepping foot onsite, fantastic for buildings in remote locations. It is even possible to configure digital systems so that the service technicians are notified of a system fault, often before the occupants are even aware.’

While the industry standard products operate at 65 dB, specialist contractors have actuators that operate at less than 35 dB which is whisper volume. ‘Each 10 dB increased is a perceived doubling in volume, so 35-45 is a double, 45-55 is a double and 55-65 is a double — so triple the noise of specialist solutions. Using noisy actuators can lead to upset residential users. In schools, for example, the noise can lead to the disruption to classes, so much so that the systems are sometimes disabled,’ according to David.

Photo credit: Breezway

Photo credit: Breezway

David points out that some louvre actuators operating at up to 1800 N force, meaning 180 kg of closing force acting against a child’s hand caught in a closing window. He continues, ‘so, where windows are within reach of the public, actuators with integrated anti-pinch functions should be used. These systems will detect a child’s hand and will reverse direction to prevent crushing. Where windows are within reach of the public and anti-pinch is not provided, then for liability reasons, automatic systems integrated to sensors and or remote (unsupervised) operation are not recommended’.

Photo credit: Kintrol

Photo Credit AWS

HOW A HOME’S ORIENTATION ASSISTS NATURAL VENTILATION

The orientation of a home can also greatly impact its ability to use natural ventilation. Samantha Anderson from AWS explains that ‘it’s rare to get the ideal house block orientation, so you need to be flexible with orientation and your house plan. Consider the use of each room in the home and how orientation might assist natural ventilation. As an example, bedrooms might be nice and warm on a winter’s day, but without the right windows they could be freezing by night! Consider low e glass with a thermally broken frame or an embedded frame, and the rooms would be at a much better temperature to sleep all year round’. Please see diagrams below as an illustration 7

Apart from the stated health benefits, let's consider something more fundamental like the ability of natural ventilation to cool us on a hot day. David Auret explains, ‘have you noticed that even on a 30-degree summer's day, a breeze will have a cooling effect? That is the often-overlooked benefit of natural ventilation, the fact that the air movement over our body works to cool us’.

‘But, when designing a building, the trick is not simply to put in more operable windows, but rather to ensure the placement and sizing is optimised to your particular location to maximise the cooling effect from airflow within the space. A very good example of this was the Parramatta City Council and Library building, which utilises thermal chimneys to draw air through automated double-glazed louvres, the louvres act as a damper of sorts ensuring that air velocity can be controlled by opening or closing individual louvre banks’ added David.

VENTILATION CONCEPTS MOST PEOPLE DON’T THINK ABOUT WHEN DESIGNING A HOME

Australia’s leading natural ventilation suppliers Leigh, Samantha, Ivan and Steve agree that ventilation and proper design are critical concepts that can help homeowners achieve low energy consumption and greater occupant comfort. Here are their tips when designing a home:

1. Design for cross-flow and passive ventilation. High level free air windows are highly effective in promoting natural cross-flow ventilation to improve thermal comfort levels and minimise the need for air conditioning. Passive ventilation can help to achieve the best comfort and energy year-round, without the need to be constantly opening and closing windows or letting pollution and bugs in.

2. Common places for air leakage include windows that have not been installed correctly or systems that do not seal properly when closed. Ensuring windows are adequately sealed will keep air from forcing its way in or out and allow a much tighter control of indoor air quality and avoid heating and cooling costs from ‘going out the window’.

Photo credit: EBSA

3. Consider an always-open solution. For spaces that do not have occupants in them every day (eg, holiday homes) consider an automated or ‘always open’ solution to ventilate your home. Automated windows are well-suited to stack ventilation out of reach, ideal for shared spaces where the building management system determines whether the windows should be open or closed, and where occupants are hesitant to open or close the windows (such as schools).

4. Think long-term. It can be really tempting to opt for cheaper windows and doors, but the long-term value delivered in choosing quality, high performance products will far outweigh any cost savings that might be achieved during the initial build phase. Most people happily pay extra for insulation in their walls and ceilings but think single 4 mm glazing for their windows and doors will be enough – it won’t be! Invest a little extra and select a more energy efficient frame with high performance glazing, to achieve greater comfort and lower energy consumption.

Photo credit: EBSA

5. Consider designing architectural ‘fins’ around windows. In rooms where it is not possible to place windows in opposite or adjacent walls for cross-ventilation, you can place projecting fins on the windward side to create positive and negative pressure to draw breezes through the room, as shown in the following diagram from Your Home. 8

1 https://www.yourhome.gov.au/passive-design/ ventilation-airtightness.

2 https://www.architectureanddesign.com.au/suppliers/ arens-international/new-white-paper-explores-theuse-of-natural-ventil#

3 https://www.architectureanddesign.com.au/suppliers/ arens-international/new-white-paper-explores-theuse-of-natural-ventil#

4 http://www.gbca.org.au/resources/greening-yourschool/why-green-our-schools/a-healthy-andproductive-placeto-learn/2152.htm

5 P Wargocki, DP Wyon, B Matysiak and S Irgens, 2005. The effects of classroom air temperature and outdoor air supply rate on the performance of schoolwork by children. Proceedings of Indoor Air 2005. Beijing, China: Tsinghua University Press.

6 https://www.safework.nsw.gov.au/hazards-a-z/ ventilation-at-work

7 https://www.yourhome.gov.au/passive-design/ orientation

8 https://www.yourhome.gov.au/passive-design/ passive-cooling

Photo credit: Breezway