Aluminium Windows and Doors

Granted that aluminium doors and windows are available in a wide range of options and sizes. However, before getting down to choosing them for your dream house, it is extremely essential that the science behind heat retention is understood so that your home is a more comfortable one irrespective of which season it is.

Simply put, thermal performance refers to the amount of heat that is dissipated by a building into its surroundings. It is taken into consideration when determining how well a structure will respond to the flow of heat from inside to outside and vice-versa.

Thermal performance is measured in terms of heat loss which can occur by three modes – conduction, radiation, and convection. Let us first understand each of these terms.

Radiation – refers to the transfer of heat between two bodies owing to the difference in temperature

Convection – a process wherein heat transfer takes place between two bodies using a medium which can be in solid, liquid, or gaseous state. Such a form of heat transfer involves movement by circulation.

Conduction – in this case, transfer of heat takes place between two bodies which are in direct contact with each other.

In essence, heat transfer takes place whenever there is a difference of temperature between two bodies from the one which is at a higher temperature to the one at a lower temperature. To prevent this from happening, insulation products are used to prevent the transfer of heat from one body to the other.

What is Thermal Insulation?

Thermal insulation as mentioned earlier refers to the process of preventing heat from escaping. This is essential when designing a building which includes aluminium doors and aluminium windows to prevent heat from escaping from the interior to the exterior. This is beneficial as it prevents heat from escaping during winter and keeps a house cool during summer. Thus, the better the thermal conductivity of the insulant, the better will be the insulation.

U-Value

U-value is also known as thermal transmittance is used to measure the amount of heat transferred through walls, windows, floors, roofs, and aluminium sliding doors of varying sizes. Its unit is Watts per square metre per degree Kelvin or W/m2K.

Measuring Thermal Performance

There are three types of values which are used for measuring the U-values of aluminium doors and windows –

Uf – means the U value of just the window frame
Ug – means the U value of the glass portion in the window
Uw – refers to the U value of both the frame and the glass

To calculate the U-value of a door or a window, we need to know both Uf and Ug values. Uf value depends on the design and material used including the number of glazing and weather gaskets. Ug value, on the other hand, depends on the type and thickness of the glass used, the size of the gap between the window panes, the type of spacer bar used, and in case of double-glazed windows, what is used for filling the space between the glass panes.

The lower the Uf value, the more insulated a building is whereas a higher value indicates that the building does not offer good thermal protection.

Reducing U-Value

Here are a few pointers for reducing the U-value of aluminium doors and windows

  • Slimmer doors and windows have lower Uf values
  • To lower Ug values, use low-e coating, argon, or xenon between the glass panes
  • Increase the glass area as Ug value is generally lower than the corresponding Uf values