Thermal Comfort/Technical Data
Whether there is direct sun on a window or not, heat is still pouring through a conventional glass window.
Heat can travel in three ways:
1. Radiant heat is felt from the direct sun.
2. Convection is the transfer of heat by a current of air (e.g. either ‘natural' convection - warm air rises, or 'forced' convection - a breeze by a window, both of these can result in a draught by a window).
3. Conduction is heat moving through an object (i.e. heat will travel through an aluminium, or steel frame more easily than through a timber or PVC frame).
Understanding Thermal Ratings
When evaluating what options there are to improve the effectiveness of your windows in neutralising temperature extremes, the following double glazing system measures should be considered:U – Value
represents the heat transfer through a window irrespective of direct sunlight. For example, heat still moves through a closed window at night-time. The U-value is specific to windows and glass and is the inverse of the commonly used R-value, which is used for insulation properties of walls and other building materials. For this reason the lower the U-Value the better the insulation performance. The U-value is important for measuring the heat transfer both in and out of the window. The more heat transfer that the window can resist the better an insulator it is. It can either stop the heat from coming in on a hot summer day (MAG-01-03) or stop the heat escaping on a cold winter evening (MAG-01-01).Solar Heat Gain Coefficient (SHGC)
is a fraction that is used to indicate the amount of radiant heat that can travel through a window. This coefficient is largely affected by direct sunlight, which is radiant heat. The lower the SHGC, the better the material will stop solar heat coming into the building through the window. A low SHGC is like having a very effective shade over the window, except that the view will be less restricted. In the summertime it is important for this number to be as low as possible as we are trying to minimise unwanted solar heat gain. In a winter climate we are trying to keep this number as high as possible as it is important to let the solar heat in but not let it out.Summary:
Winter
In winter the ideal situation is to let in as much of the sun's heat and then trap it inside to maintain a comfortable environment in your home or office. This will also greatly reduce heating costs and directly relate to money savings. The ideal window for winter will have a high SHGC to let the sun's heat in and a low U-Value to prevent the heat from escaping. Clear windows without shading films are better suited for winter climates.Summer
In summer the ideal situation is to minimize the heat coming in from outside and prevent the cool air inside from escaping through the window. This will make your home more comfortable and reduce your air-conditioning costs. The ideal window for summer, or for a large west-facing window, will have a low SHGC to limit the heat from the sun's direct rays, as well as, a low U-Value to prevent the heat in the air outside from moving through the window and warming the cool conditioned air inside. It is better to have a shading film on the first (outer) glass pane to limit the heat that enters the double glazed unit.The Comparisons
*The following information is extrapolated from studies conducted by the Australian Window Association in conjunction with their work on the Window Energy Rating Scheme (WERS)
Table 1.1 - Magnetite Window System vs. Single Glazed Windows
| Cooling Stars | Heating Stars | %Improvement on household cooling | %Improvement on household heating | U-Value | %Improvement on U-Value | SHGC | %Change on SHGC | |
|---|---|---|---|---|---|---|---|---|
| Aluminium frame & clear glass |
2% | 0% | 7.4 | N/A | 0.77 | N/A | ||
| Timber frame & clear glass |  |
 |
20% | 24% | 5.5 | 25.7% | 0.69 | 10.4% |
| Aluminium frame & clear glass with Magnetite |
|
 |
35% | 58% | 2.9 | 60.8% | 0.67 | 13% |
| Timber frame & clear glass with Magnetite |
 |
|
39% | 62% | 2.5 | 66.2% | 0.66 | 14.3% |
| Timber frame & ultra tint glass with Magnetite |
|
|
74% | 37% | 2.4 | 67.6% | 0.19 | 75.3% |
*%Improvements are compared with the generic base case 3mm aluminium window from WERS
It is clear that the addition of Magnetite double glazing systems will give the ideal window system for either winter (clear Magnetite added onto the existing window) or summer conditions (clear Magnetite added onto a window with solar control film).
With the addition of Magnetite to a basic window you can outperform conventional windows and films due to the superior sealing power of Magnetite combined with the insulating air cavity and insulating acrylic panels.
Did you know?
WERS test results confirm that the combination of Magnetite and low-e film can reduce U-value to 1.8 and SHGC to as low as 0.20. This combination can also reduce heat gain by up to 76%, which can achieve up to 6 cooling stars.Magnetite vs. Double-Glazing – What the experts say!
Ideal Systems for Winter
Table 2.1 Magnetite retrofit double glazing vs. traditional double glazing
| Cooling Stars | Heating Stars | %Improvement on household cooling | %Improvement on household heating | U-Value | SHGC | Air infiltration | |
|---|---|---|---|---|---|---|---|
| PVC Double Glazed 3/12/3 IGU (insulated glass unit) |
|
|
40% | 51% | 3.0 | 0.61 | 5.0 |
| Timber frame & clear glass with Magnetite clear panels (MAG - 005 -10) |
|
|
39% | 62% | 2.5 | 0.66 | 0.50 |
*%Improvements are compared with the generic base case 3mm aluminium window from WERS
Compared with conventional double-glazing Magnetite double glazed windows can get better results for cold climate areas such as the Adelaide Hills, Blue Mountains and Tasmania.
Magnetite's clear acrylic window panels still allow the direct heat from the sun's rays to enter the building and then once inside Magnetite works better at retaining that heat. Magnetite's superior magnetic seals give them an advantage over conventional operating windows.
Ideal Systems for Summer
Table 2.2 Magnetite retrofit double glazing Vs. traditional double-glazing
| Cooling Stars | Heating Stars | %Improvement on household cooling | %Improvement on household heating | U-Value | SHGC | Air infiltration | |
|---|---|---|---|---|---|---|---|
| PVC Double Glazed 5/6/5 supertoned glass IGU (insulated glass unit) |
|
|
55% | 37% | 3.3 | 0.41 | 5.0 |
| Timber frame & ultra tint glass with Magnetite clear panels (MAG - 005 - 07) |
|
|
74% | 37% | 2.4 | 0.19 | 0.50 |
*%Improvements are compared with the generic base case 3mm aluminium window from WERS
Again Magnetite double glazing system outperforms conventional double-glazing according to the nationally accredited Window Energy Rating Scheme. Simply adding Magnetite over an existing window with reflective film will give better summer heat control than a double glazed window with supretoned glass.
The Magnetite system stops the conduction and convection of heat better than glass windows giving superior results for summer conditions. Combined with a film or a shading device Magnetite is the ideal solution for the hot Australian conditions.
Click here to view pdf version of Magnetite WERS test result.
