Recycling wood window frames

One architectural feature that has always fascinated me is the ‘window’ in its multiple types and forms. Windows allow us to open out and connect to the world outside, bring in natural light and ventilation and at the same time, add an interesting aesthetic to a building. When designed well, they can be one of the most expressive features of a building.

The word ‘window’ originates from the Old Norse word — vindauga — vindr ‘wind’ and auga ‘eye’. They are the eyes of a building.

Traditionally, in India, wood and stone were used to create different types of windows. The use of glass in window shutters (the openable part of a window) was first introduced by the Romans around 100 AD. Although these were not transparent and could only be made in smaller pieces. ‘Shoji’ (paper) screens originated in China around the 8th century and were used in Japan and Korea in window shutters. In England, animal horn was used before glass took over in the early 17th century.

What works for you?

Irrespective of the shutters, the frames were mostly made of wood until the early 20th century when steel and aluminum became possible options. Today, a wide range of materials such as wood, UPVC, steel and aluminum are available for the frames making the choice a challenging one. Typically cost and aesthetics are the driving factors in selection. However, today we need to include another key factor when making the choice: environmental sustainability.

Environmentally, it is possible to evaluate these materials based on the following factors: embodied carbon or global warming potential (amount of greenhouse gasses released during production), embodied energy (energy consumed during its manufacture), recycling potential (amount of material that can be recycled), thermal transmittance (amount of heat that can transfer through the material).

1.  New wood: Although wood in general performs well with respect to environmental sustainability including thermal resistance, new wood necessitates cutting trees and hence not ideal in today’s environmental situation unless the trees are grown in certified and managed forests. Cutting trees also result in carbon emissions.

2.  Salvaged wood: There are multiple places today to buy windows that have been taken down from older buildings during demolition process. This wood will most likely be of higher quality than what is available today, well seasoned and eliminate the need to cut trees. If desired size is not readily available, these old wood frames can be reworked to customised sizes.

3. UPVC: Relatively new in the market compared to others, Unplasticised Polyvinyl Chloride (UPVC) windows are popular today for their rigidity, thermal and weather resistance, and relatively low cost. They are also leak proof and require low maintenance when compared to other materials. It is completely recyclable and relatively low in embodied carbon and embodied energy.

4. Aluminum: Popular for its relatively low cost and recyclability, aluminum however performs poorly when it comes to thermal transmittance, embodied carbon and also embodied energy.

5. Steel: Scoring high on strength and durability, steel windows are a good option. It compares much better than aluminum in embodied carbon, embodied energy and thermal transmittance. It is however prone to corrosion, making it difficult to maintain in areas along the coast.

To conclude, salvaged wood window frames require no manufacturing leading to zero embodied carbon and embodied energy and hence would rank the best in terms of environmental sustainability. However, it is imperative to choose non-toxic paints to finish these frames as otherwise they would result in carbon emissions.

The writer is the founder of Green Evolution, a sustainable architecture firm.