April 06th, 2020

Joinery - Keeping the elements out

External windows & doors need to be durable to keep the weather out of your home.

With the right type of glass, joinery can keep warmth in & allow the right amount of light transmission to make your home livable throughout the year. Insulation in the walls work wonders as well to keep the warmth in, but choosing the right type of joinery and glazing, will help increase your homes energy performance and reduce annual energy costs. This also helps reduce the amount of condensation that occurs inside your home during winter. The right glazing on the joinery helps keeps your home cools during summer and warm during winter.
 
Joinery Types
Aluminum
The most common & affordable type in New Zealand is aluminum joinery because it is light, durable and low on maintenance. Most aluminum joinery companies have a range of colours to choose from but some companies offer special anodized colours as well. The powder coating process on aluminum joinery makes them maintenance free but they will fade over time due to UV radiation. Aluminum joinery has lower thermal conductivity and as a result loses heat quickly; this can be overcome by using thermally broken or insulated aluminum joinery.

Aluminum Joinery

uPVC
uPVC joinery is made of a type of rigid plastic that is reinforced with metal inserts that is lighter than & more efficient that aluminum.  uPVC joinery is more expensive than aluminum since it is mostly imported and the manufacturing process varies in different countries. It is best to chose uPVC frames that have a titanium dioxide in their frames to act as a sunscreen to protect the frames from damage from UV radiation. uPVC windows do not require painting and require no maintenance other than a periodic wash to keep dust & dirt at bay.

uPVC Joinery

Timber
​Timber joinery is a popular choice among homeowners since they are the most energy efficient and look the best. But timber is a perishable product and requires regular staining or painting to protect and maintain its surface, else it could lead to rotting from water that pools from condensation. Timber joinery is rather expensive due to the intense labour and level of craftsmanship required during the manufacturing process. The advantages of timber are that they can be painted any colour you want, they look great on your homes, are extremely energy efficient and available in a range of styles to choose from.

Timber Joinery

Glazing
Depending on the choice of glazing you can increase the thermal performance of your joinery. The layer of glass that are installed between the frame of a window to seal out the elements is commonly referred to as glazing. In the past it was standard practice to use only one pane of glass, which was known as single glazing. This option of glazing does not meet NZ standards and is not used in any living areas of the home. The standard today is double glazing which is two layers or glass or in some cases it can also be triple glazing, which is becoming more popular since it further reduces the amount of heat loss through the window. Double & triple glazing have a layer of insulating air/gas trapped between the panes of glass, because they are poor conductors of heat and reduce the amount of heat lost through the window. Other benefits of double & triple glazing include lower energy bills and reduced noise transmission from the outside.
 
Low E glass is another form of glazing that can further boost energy efficiency of double or triple glazing. It makes use of a special coating on the glass to help increase the thermal performance of a window.

Single vs double glazing

Thermal Performance
Thermal performance is measured if rate the effectiveness of glazing in keep the warmth inside your house. The measure is called “U Value”, the higher the U value the lower the efficiency, which means more heat is lost through the window. Single glazed windows will have higher U values compared to triple glazed windows.
The chart below compares single glazing with double-glazing to show how effective the insulation in different forms can be

Making a choice
Choosing the right joinery comes down to the type of look you want your house to have and how deep your pockets are. Double glazed joinery is normally enough to keep your house comfortable, warm and energy efficient. Triple glazing is better suited for colder regions of the country and areas that have high levels of ambient noise.
 
References:
Website: Window & Glass Association NZ https://www.wganz.nz/guides/