Factsheet 1 - Thermal Comfort and Natural Ventilation

Overview

This factsheet focuses on indoor thermal comfort and natural ventilation inside a dwelling. Thermal comfort refers to the range and combination of environmental conditions including air temperature, humidity, air movement and radiation that most people find to be pleasant. Natural ventilation refers to indoor air‐movement that derives from natural sources such as outdoor breezes. Under present climatic conditions in subtropical environments, most people will be reasonably comfortable
through‐out the year simply by adjusting their level of clothing.

The concept of thermal comfort was initially coined by Professor P. Ole Fanger in 1970 [1], who, with his colleagues, performed groundbreaking research on the importance of indoor air quality, temperature and humidity for human health and the role of poor indoor air quality in causing illnesses such as asthma as well as symptoms associated with Sick Building Syndrome.

Liveability of dwellings can be improved by optimising thermal comfort, especially through maximising natural air‐flow. Dwellings can be oriented, designed and manipulated to improve thermal comfort. Maintaining a comfortable thermal environment can have environmental, economic and health benefits, including:

Health benefits due to improved air quality
Reduced reliance on mechanical heating and cooling and associated energy savings (for example, reduction in use of air‐conditioning means that energy bills are lower, and greenhouse gas emissions are reduced at the same time)

Research on thermal comfort has shown that occupants of naturally ventilated buildings are comfortable in temperatures that closely reflect the outdoor climate. [2]

A study in Sydney showed a reduction of energy use by 25 – 33% in naturally ventilated mixed mode buildings and high occupant comfort satisfaction scores. [3]

Research has shown that occupant control over an operable window is related to perceived well‐being. [4]

What our findings revealed

Residents’ Perceptions of Thermal Comfort
Preference for Natural Air‐flow
Balconies Enhancing Thermal Comfort

Residents’ perceptions of thermal comfort
Survey results from the QUT High‐Density Liveability Study indicated two thirds of respondents rated the average temperature of their living space as comfortable (neither too warm nor too cold) while 12% reported it was too warm and 1% reported it was too cold. Residents highlighted a range of different design features that impacted on their climatic experience within their dwellings. Features that contributed to thermal comfort include natural air‐flow and control over exposure to the sun’s heat and light; dwellings with balconies and other outdoor living areas; internal and external modifications (e.g. shades and blinds); and orientation of the dwelling to maximise breezes during summer months and to maximise access to the sun’s warmth, and daylight, in winter months.

Preference for natural airflow
Residents generally expressed a preference for natural air‐flow over air‐conditioning. The majority of residents (80%) had space cooling equipment in their dwelling while 53% had space heating equipment. However, survey results indicated when thinking about ‘climate control’ in summer, residents were more likely to open the windows and doors (83%) rather than turn on the airconditioning (63%). Qualitative interviews supported residents’ preference for natural air‐flow over air‐conditioning, as long as other negative impacts such as noise or air pollution were not introduced as an unwanted consequence:

We try and use the air conditioner as little as possible… if you open the windows you get a good breeze, it’s generally fine.

We’re lucky we’ve got flow through. We’re actually on both sides of the building. So you can open up one side and the other and get a breeze right through it, so in that respect it’s good. One that I’ve got that my in laws are living in, doesn’t have that facility and that can get a little bit stuffy. They rely more on the internal cooling rather than external breezes.

[I] open the back door and let the breeze go through. That’s just the simplest form of conserving energy. Most people would go and turn the air conditioner on. Well, yeah, there are times in the year where I have to do that but, you do simple things with what you’ve got to reduce the amount of energy you take to live there and you find that you can live more cheaply and very, very comfortably.

Interviews with residents suggest that a lack of natural air‐flow and cross‐ventilation is associated with an undesirable reliance on air‐conditioning.

Because we don’t get a breeze right through the apartment, we do use [the air conditioner].

All the (dwellings) in the centre of the building have a corridor so you don’t get the flow through of air, and therefore there is a reliance on air‐conditioners. These apartments are built so there is an airconditioner in the bedroom and in the living room in every apartment in the building.

Balconies enhancing thermal comfort
Balconies provide a good opportunity for natural air‐flow and improved thermal comfort. Balconies were considered to be important by 87% of survey respondents. Many of our interviewees expressed preference for spending time on their balcony and identified their balcony as a favourite design feature:

I: How’s the climate in summer and winter?
P: It’s really beautiful, because we get the afternoon sun and then there’s a little balcony out the back that gets the morning sun so it’s perfect.

P: It has been made significantly more liveable because they built that entire balcony in, glassed it in. It’s glassed on three sides. The sun comes in, heats that area and the warmth flows through into the main lounge area. I can usually get by in the wintertime just by putting a jumper and a pair of socks on.

Recommended Guidelines

As demonstrated above, in subtropical environments and beyond, building design that takes advantage of passive cooling and heating can reduce reliance upon artificial heating and cooling methods, improving the economic and ecological sustainability of dwellings while optimising thermal comfort for residents.

The following table presents practical suggestions for Residents, Building Managers, Designers and Developers with regards to maximising Thermal Comfort and Natural Ventilation.

Further Information

Queensland Development Code (QDC)
Mandatory standards in the Queensland Development Code are in addition to the Building Code of Australia. They refer primarily to buildings rather than lots.
http://www.dip.qld.gov.au/building/queensland‐development‐code.html

South East Queensland Regional Plan 2009 – 2031
The SEQ Regional Plan provides broader design principles for the subtropical climate of South‐east Queensland.
http://www.dip.qld.gov.au/seqregionalplan

Your Building
The Your Building web portal is an online Australian resource about sustainable commercial buildings. It provides information for investors, owners, and occupiers as well as developers, builders, designers, and facility managers.
http://www.yourbuilding.org/Search/Search.aspx?p=87&q=The+Second+Plank+
Building+a+Low+Carbon+Economy+with+Energy+Efficient+Buildings

Your Home Technical Manual and Website
A Federal government initiative, for use by tenants, home owners, builders, designers and developers, applying a series of checklists for what one wants to achieve, followed by implementation through a series of Fact sheets that are tailored for different climate zones.
http://www.yourhome.gov.au/

Hawaii Commercial Building Guidelines for Energy Efficiency
A comprehensive State government of Hawaii document, that provides an overview on natural ventilation and thermal comfort, design recommendations, application and relevance to existing code. While designed specifically for Hawaii, the climatic context has relevance to the coastal SEQ environment.
http://www.archenergy.com/library/general/chapter2_nat_vent_030604.pdf

Centre for Subtropical Design
www.subtropicaldesign.org.au

Think Brick Australia
www.designingforclimate.com.au

Cleaner Greener Buildings – Qld Government Legislation
New legislation in 2009 will prevent body corporates and developers from restricting sustainability features in their buildings such as light roof colours and window tinting.
http://www.climatechange.qld.gov.au/__data/assets/pdf_file/0003/25626/3_
P‐and ‐B_‐ _E1_web.pdf

References

Fanger, P.O., Thermal Comfort. 1970, New York: McGraw‐Hill.
Artkins, C. All in the Mind. Essential Matters 2007 [cited 2009; Available from: http://www.essentialmatters.com.au/resources/PropAust_Issue10_p68_69.pdf.
Rowe, D., Mixed Mode Climate Control. AIRAH, 1996. 50(12).
Bordass, B. The balance between central and local control systems. in Environmental Quality
90 Conference. 1990. Solihull, England.
Queensland Department of Local Government and Planning. Queensland Development Code. 30 April 2003. Available from: http://www.lgp.qld.gov.au/?id=247.