What considerations should be made on windows and doors in Canberra?

Climate Zone for Canberra

Canberra is considered to be a heating climate and we are in Zone 7, this means that we want to get the maximum sun that we can into our homes in winter and the least in summer.  Because Canberra gets so cold, we tend to run the heater while we are in the home.  Once we get the beautiful sun into our homes, we want to keep it there.  There are a several ways that you can do this:

• Replace your windows and doors with double glazed unit
• Install heavy drapes and pelmets (not much view after
• Install a second window next to the other one
• Install a piece of Perspex over the frame to create a cavity

If you are replacing your windows and doors then you want to make sure that you are getting the best bang for your dollar.  You will want a low uValue (insulation factor) – the lower the better.  The uValue measures how easily a window conducts heat, how much heat loss you will have and how well the window or door is insulated.  The measure should be overall window and frame and includes seals and spacers.

These are the common uValues for the main window choices:

Standard single glazed aluminium 4mm – 5.9

Standard double glazed aluminium 3mm/12mm air/3mm – 3.5

Thermally broken double glazed aluminium  - 2.5

Timber double glazed 4mm/16air/4mm – 2.4

uPVC double glazed 4mm/16 air/4mmea – 1.8

It is interesting to note that the uValue has the potential to improve up to approximately 0.3 stars for each unit reduction in uValue.  Each star corresponds to reduction in heating and cooling requirements by approximately 20% to 30%.  You will save approximately 10.000 to 15.000 MJ of energy per star which will save your heating bills of about $300 a year (source:  wers.net).

The frame plays a large role in getting the uValues right.   

Aluminium leaks heat and cold while timber needs to be maintained each year so that it stays in good condition.  uPVC is an insulated frame that doesn’t leak heat or cold and doesn’t need maintenance.

The other side of the coin is Solar Heat Gain Co-efficient (SHGC)

SHGC measures how much solar energy gets through the windows and doors.  It is a number between 0 and 1. The lower the SHGC is, the less heat that it transmits.

The SHGC will be relevant to different elevations in Canberra.  I would recommend a high SHGC on the north side provided there is an eave or shading in place for summer.  You want to get as much sun through the glass that you can in winter.  East and West would have a low SHGC and south won’t see any sun so you want to make sure that the uValue is very low.

SHGC can be reduced by applying selective low E (low emissivity) coating to glazing.  It can reduce heat loss in winter as well as solar gain in summer.

Glazing Calculator

If you are building a new home or extending an old one, a glazing calculator will need to be submitted to your Certifier and both the uValue and the SHGC will be required.  The figures are entered into the calculator on each orientation of the home along with shading and a green tick or a red tick will appear in the spreadsheet.  If you get a green tick you are home and hosed, if you get a red tick you need to change your windows/door or glazing.

Solace Creations at 17 Townsville Street Fyshwick and will be able to help you with these considerations and is available on 02 6260 1621.  www.solacecreations.com.au

Karen Porter is now a Board Member of the Australian Window Association

Karen Porter, Managing Director of Solace Creations has served as a Board Member of the Australian Window Association (AWA).  Karen will represented suppliers on the east coast of Australia for a 2 year period.

Karen was an integral part of the AWA and provided a greater focus on energy efficient windows and doors so that they become a standard feature of new construction.

Karen ensured that the Canberra Community was well represented at the meetings along with uPVC and double glazing.

Energy Efficient Windows in Canberra

Windows have traditionally been treated as just any another building material.  They are sourced as cheaply as possible and the same traditional style is put into the design and the build.  What a lot of builders, architects and home owners don't take into account is that they provide a massive opportunity to improve the insulation of the home.  

They provide light into the home along with fresh air but they also provide the opportunity to save heat loss in winter and heat gain in summer.  The frames play just an important part of the insulation process as the glass.  These are the best frame materials for energy efficient homes:

1. uPVC frames
2. Timber frames
3. Thermally broken aluminium frames

Combine the insulated frames with double glazed units and you will experience comfort, cheaper energy bills and still have light coming into your home.

Australia has a wide range of Climate Classes.  Canberra is a heating climate and is in Zone 7.  In Canberra we want to draw the sun into our home and then trap it there to benefit from free solar heating.  In summer we want to keep the heat out but be able to open our windows to benefit from the air flow.

In Canberra we want our windows to have a low U-value and high solar heat gain coefficient (SHGC) (see below).  It is important to ensure that each window and elevation (N,S,E and W) are considered to ensure they let the sun in during winter and keep the sun out during summer.  www.wers.net show the ratings of all rated windows and you should consider these when selecting your windows and doors.  Solace Creations provides a wonderful advisory service on new plans and existing homes to help you to select the best windows for your home www.solacecreations.com.au.

When you are building a new home or extending an existing home, ACT Government requires that a glazing calculator is completed or an energy audit to make sure that the required star rating is achieved.  The U-value and SHGC are important factors for the calculations and can be found on www.wers.net or from your window supplier.

What is a U-value

Wall insulation such as batts have an R-value rating.  This best batts for insulation is as high a rating as possible.  Windows and doors have U-values and for Canberra you want a low rating.  The U-value is a measurement on how well the windows and doors prevent heat from escaping.  Ratings can be from 2.0 to 10.  This should include the frame, glass, seals and spacers.  If a window such as ours has a U-value of 1.8, that means that 1.8 watts per metre is lost per hour.  Some aluminium windows are rated at 5.8. This shows that those windows lose heat much quicker than those with a lower U-value.  You can double glaze standard aluminium but the frame will still leak a lot of your heat.

What is Solar Heat Gain Co-efficent (SHGC)?

SHGC is a measure on how well the windows and doors block heat caused by sunlight.  This measure is a combination of how much sun is directly transmitted towards the window, absorbed by the window and ultimately released inwardly.  The SHGC is a number between 0 and 1.  The lower the number, the less heat it transmits.  The low ratings are excellent for the west side, however, you need to remember that if you have a low SHGC in summer, it will also be a low SHGC in winter meaning that you won't get as much of that lovely afternoon sun through your windows and doors in winter.  You can't beat natural shading from a tree or an awning for the summer westerly sun.

Orientation

Nothing beats perfect orientation and more aspects of energy efficient homes will be discussed in further blogs.  If you orient your home correctly, seal up the whole building envelope with insulation (including windows and doors) then you will not have to rely on heating or airconditioning.  This will save you $$$ on your bills and you are contributing to our planet.

Picture source:  www.wers.net

17 Townsville Street Fyshwick www.solacecreations.com.au