The Glass Masonry vs. Traditional Brick

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  • Date August 29th, 2011 18:42
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  • Designers often prefer the aesthetics of clear glass block. Apart from obviously different appearances and light properties, what are the ecological and performance advantages and differences between glass masonry and traditional bricks? To answer this question, our Research Team did a deep dive on both.

    We used the following categories to differentiate these materials: Raw Materials, Size, Price, Thermal Conductivity, Strength, and Recyclability.

    Raw material
    Visible raw material differences between traditional bricks (clay, shale or shale) and glass bricks are fairly obvious from their names. Though, these distinctly different materials trace back to similar origins: all are from non-renewable ores and minerals that are locked up in the earth's crust. All materials require excavation to source (unless reclaimed materials are sourced). The embodied energy (sourcing, transit, production, transit, assembly) of glass and traditional brick also differs greatly. Traditional bricks tip the energy meter at around 5000 MJ/m3 while glass bricks consume a whopping 37,500 MJ/m3. From an energy security standpoint, there is a clear argument for glass reclamation (notably glass also retains its physical properties when recycled, furthering the argument for closed glass loops).

    95 Brick. This is what the industry calls standard bricks: 240x115x53mm. Also common, 85 Brick shrink to a final size: 240x105x43mm. There is less consensus for glass block - with 3 commonly available square sizes: 190x190x80mm, 190x190x95mm, and 240x240x80mm. Sadly, there are currently no overlapping sizes of masonry and glass block. This is likely because masonry bricks can be used for load bearing applications and are sized to meet construction and strength dimensional requirements. Glass block is not load bearing and is typically installed with aligned joints. Note that during construction, glass blocks should be braced by a frame if joints are aligned.

    Shale and fly ash bricks are best for those on a tight budget, ranging from 30 to 80 rmb/m2. Clay bricks tend to have higher price points, around 150 to 300 rmb/m2. (This may be partly attributed to simple rules of supply and demand - clay bricks are being used less and less, in favor of other options). Glass block tops the pricing charts, weighing in around 10 to 25 rmb per block which is equivalent to 250 to 650rmb/m2.

    Thermal conductivity
    The thermal resistance of masonry bricks is not typically notable, though masonry is an excellent material for thermal massing design strategies. Conductivity coefficients typically range from 0.58-0.70 W/ (m·K) for clay brick and 0.47-0.58 W/ (m·K) for fly ash.

    Glass block (if hollow), however, can contribute to better insulation performance. Glass block is typically made from 6 sheets of glass which are fused together to form a hollow center. This air space provides some extra insulation muscle - hollow glass block typically has a thermal conductivity coefficient around 0.36W/ (m·K). This is not to say that designers should start using glass block in their insulation strategies. Insulation values of XPS usually measure around 0.03W/(mK). Note that lower K-values (or higher R-values) reflect better insulation.

    Generally, the compression resistance of glass block measures between 6-7.5Mpa, while traditional brick is 10-30Mpa or higher. Therefore, glass block cannot be used in load bearing applications! Full glass block walls are self supporting and can be used for walls that do not carry any weight.

    You read earlier about the positive impact recycling can have on both glass or masonry industries. We especially appreciate the definitive benefits of recycling glass (energy and extraction). The good news: glass is already being recycled and reclaimed glass can be sourced as a raw material. Manufacturers who are interested to source reclaimed glass should be careful not to commingle colors. Colored glass can ruin an entire batch of recycled glass - unless murky colors are the goal. Reclaimed brick can be reused for infill walls, slag, or paving. If non-toxic, bricks will inertly degrade.

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