Passive house considers the performance of a house against the amount of energy that is needed to create a comfortable healthy home. Reducing heat loss is one of the key areas that needs to be considered if we want to achieve maximum home comfort level with the minimum amount of energy required to achieve it.

Windows in a house construction are the weakest thermal element. It is the element we rely on for natural light, natural ventilation, connection to the outside and solar gains. It is the element we need to secure the most and the part of our homes that loses the most heat. The window arrangement (or fenestration in Architectural Terms) plays a large role in the design aesthetic of the building.

Through considered design, we can make this critical building element work for us in the best way, by balancing all the requirements of this window with the least desired outcome namely heat loss.

Here are a few things to consider about windows to your home.

We have moved from single glazed aluminium to double glazed and now thermally broken aluminium frames. However, this is not a magical fix, and there are much better options out there. The window frame is the weakest link in the window element and usually made from Aluminium. Metal is a great conductor of heat. By adding a PVC thermal break or using Wooden, PVC or other composite frames can help reduce the amount of heat loss.

Similarly, the design of the window counts. Windows with the same area but orientated vertically with a low sill allow more solar gain than windows with a high sill.

Mullions (vertical pieces in a window frame) and transoms (horizontal pieces) contribute to the heat loss of a window but are needed for structural reasons and to create opening panes. Carefully creating openings and reducing Mullions and Transoms go a long way in improving the thermal performance of a window.

Windows loose heat, mostly at night, regardless of which side of the building they are located on. Considering a larger amount of window space on the Northern walls and a smaller amount to the Southern walls, increases the percentage of window area able to give you passive heat gains.

Double glazing is commonplace now, however that is not a magical fix either. By filling the area between the panes with gases such as Argon and using Low E surfaces we can increase the thermal resistance (ability of the pane to resist heat loss), but the trade-offs are lower clearness (gas and thickness dependant) and less ability to allow the suns heat to reach the interior of the building when it is required.

Another element is the installation. Gaps around and badly installed windows mean the benefits of the cost and thought that has gone into the design can be lost through leaking heat. By carefully considering your builder, doing the work needed around the window in a retrofit situation and investing in other supporting systems that are needed for an airtight window installation, means you can enjoy the benefit of better preforming windows.

The difference between a design that looks good and one that preforms well too, is understanding the detail and investing in the right considerations, calculations, and construction.

It's all about Architectural Design with People and Planet in mind. That’s the mission statement at Smart Living Spaces.

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Architectural Design services for Waikato, Cambridge, Raglan, Hamilton, Morrinsville, Matamata and Te Awamutu.

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Offsite NZ Member    Licenced Building Practitioner    New Zealand Green Building Council Passive Designer Homestar Designer
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