Thermal management

Most of the solar energy gained by buildings in summer occurs through unshaded or poorly shaded windows.

Where the fitting of external louvers is not possible, the installation of window blinds, either in an opaque or translucent material will reduce the amount of solar energy entering the classroom.

Blinds also provide a flexible, cost effective shade device which can be easily adjusted throughout the day to achieve the desired levels of light and shade.

Shade levels can be specified depending on activity requirement i.e. block out or filtered light.

What are the types of blinds suitable for schools?

Block out - opaque blinds

Blinds using opaque materials have greater capacity for preventing solar energy from entering the space than see through materials. Lighter colours and less open fabrics reflect more heat than darker, open weave fabrics. The following figures indicate the percentage of solar energy entering a room compared with an unshaded window taken as 100%):

• dark blinds allow 85% of the solar engery to enter a room
• medium blinds allow 65% of the sloar engery to enter a room
• white blinds allow 55% of the solar energy to enter a room

Filtered light - translucent fabrics

These blinds have the following characteristics (when fully closed):

• Blinds made of translucent fabrics maintain a filtered view to outside and maximise the use of natural light which reduces the need for artificial lighting during the day
• They also reduce glare and reflection levels providing uniform shading across a window while maintaining cross flow ventilation
• Provide protection against UV radiation

Heat loss through windows can be reduced by up to 70% by closing the blinds at the end of a winter day.

Most of the solar heat gained by classrooms in summer is through unshaded windows. This combined with certain types of construction materials used in walls to the north (and to a lesser extent east and west) can increase the internal temperature of rooms. One strategy to reduce the amount of solar heat gain to a room is to shade walls to the north and windows to the north, east and west of a building.

The design of school buildings over the decades has incorporated a range of shading options and designs. These include roof eaves, verandas and sun screens. Unfortunately there are some buildings that had no design features to minimise solar heat gain.

The most effective way to control solar heat gain is by the correct orientation of the buildings. This is obviously not possible for existing buildings. North facing windows with overhanging eaves will allow for partial sun shading in summer and maximum penetration of sunshine in winter. For two or more storeys the effect of eaves will be minimal over the entire facade.

Windows facing to the east and west will not be protected by even the widest eaves, and will need to be shaded from the sun by other means.

The aim of external louvres is to stop solar radiation ‘hitting the face’ of the windows and walls. Once this has occurred the solar heat will be transferred into the room. External louvers also maintain some views to the outdoors, permit an adequate level of natural light, maintain adequate ventilation and allow access to the window for maintenance.

Light coloured metal louvre awnings are one of the best solutions for sun protection with up to 90% of heat being reflected away from the windows and walls.

It is important to remember that if the windows face north then horizontal louvres provide optimum protection from the sun. For east and west facing windows vertical louvres provide the best protection from the sun.

Incorporating insulation into existing school buildings has many environmental and comfort benefits.

Even the best constructed school buildings can suffer from heat transfer, unless they are adequately insulated. In summer 42% of a building’s heat is gained through the ceiling, 24% through the walls and approximately 10% through the floor. In winter, heat is lost at a similar rate.

To compensate for the losses through poorly insulated buildings heating and cooling appliances need to be run at elevated power levels and for longer periods of time to be effective. This means the increased production of greenhouse gas emissions.

Insulation assists in keeping heat within a building in winter and slowing the flow of heat into the building during summer. Insulation is also excellent sound absorbers and can assist in reducing noise transmission through walls, ceilings and floors.

By using insulation rather than heaters and air-conditioners, you are not only reducing g greenhouse gas emissions, but also cut the cost of heating and cooling by over 40% with ceiling insulation having potential savings of 20-30% on energy bills alone.

During warmer periods of the year proper ventilation of the roof and learning spaces will assist in cooling the teaching and learning environment. The major advantage of roof level vents is the ability to make use of the natural draw created by rising hot air and the action of wind over a building.

While roof ventilation systems may be entirely passive or fan-assisted, rotary turbine roof ventilators are the most cost effective, energy efficient, effective solution to for create air flow and improve ventilation in schools. The spinning action of the rotary turbine, in conjunction with the buoyancy of hot air rising (stack effect), assists with the extraction of stale, warm air from either the ceiling space, or a room with a register (a grille) in the ceiling which also encourages fresh air to enter the space.

Night flushing (sometimes called purging) is a system to reduce the internal night time temperature of a room to that of, or near to, the ambient external air temperature. This is achieved by extracting hot internal air and replacing it with cooler external air.

Rooms will not feel as warm first thing in the morning and, with a lower starting temperature, rooms will take longer to heat up. Frequently this means the hotter part of the day will occur outside of school hours.

Only some existing building designs can be easily retro-fitted for night flushing. Where buildings have high level awning, louvre or hopper type windows located on external walls under the existing eaves, the windows can be programmed to open during the coolest part of the night in summer. In combination with the use of rotary roof ventilators cool night-time air will be drawn into the classrooms via the high level windows and hot air will be expelled via the roof ventilators.

Landscaping to provide shade and climate management is a simple, cost-effective approach to improving the energy efficiency of your school. Landscaping can reduce the heat build up in buildings, reduce carbon dioxide and help to control and minimise land degradation through the principles of ecological sustainable development.

Effective landscaping can improve the energy efficiency of school buildings and reduce greenhouse gas emissions by minimising the need for mechanical air cooling and heating.

Shading

Medium height cylindrical trees planted in a row will provide shade from the low angle sun on the eastern and western sides of a building. Taller deciduous trees on the northern side of a building will provide shade in summer and keep the building cool. When their leaves have fallen they will let the sunshine through to warm the building.

Windbreaks

Rows of suitable, evergreen trees can be located to screen school buildings from cold, winter winds and reduce the wind chill factor.

Schools should consult bushfire management plans and minimise any bushfire hazards. Noxious or irritant plants and plants that prone to drop limbs should also be avoided.