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Winbloks: Pre-Cast Modular Concrete Window Frames

By Rain Noe - March 12, 2013

in Architecture

Winblok is a South African construction innovation by inventor Al Stratford, former president of the South African Institute of Architects. Intended to be used in buildings constructed with masonry, it's essentially a modular, pre-cast concrete window frame that negates the need for sills, reveals and the like; you just brick right up against it (and over it) and you're done. A reveal on one edge is fitted for a window, and the architect specs out which way the Winbloks face, providing options for having the window flush with the inside wall or the outside wall. A variety of different window styles are designed to fit within the system, as well as louvres and burglar bars.

Winbloks are made in different heights for reasons of passive solar management. By cross-referencing the latitude of the building site, the architect can choose the appropriately-sized Winblok to create a "solar cut-off angle," blocking direct sunlight while allowing in the ambient light. This is to lower cooling costs and obviate the need for additional shades and overhangs.

I'm not sure why these haven't gained much traction outside of South Africa; any practicing architects want to chime in? While it's designed for masonry construction and not, say, the dimension lumber platform-frame construction prevalent in much of the U.S., there's plenty of places that use masonry construction in the American Southwest, so I'd imagine I'd have heard of this system before. Because it definitely isn't new—Stratford used it to build his own house shortly after prototyping it, and that was back in 1980. Winblok hit the marketplace in 1985, and today Stratford's company, Wintec Innovation, is still a successful venture.

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John Lawlor

11 years ago

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Any links to the Winblok product with a built-in thermal break?
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Gary Murray

11 years ago

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Thanks for the feature on the Winblok.

With the new legislation in South Africa regulating thermal performance in buildings we are currently developing an improved Winblok with a thermal break.

We have also launched a new product - the Winslot - a horizontal precast louvre/sill system which allows for the same passive solar management.

@Gustavo - the Winbloks used in Brazil are the originals, using moulds that were obtained from Al Stratford - the inventor who assisted in establishing the business in Brazil in 1993
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Edward

11 years ago

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They also produce these with a thermal break..
www.wintecinnovation.co.za
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Gustavo Petinati

11 years ago

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We do use those here in Brazil. The company, by the way, is Winblok. I always tought it was local. They work great.
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Andrew Moore

11 years ago

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A few thoughts off-the cuff. Judging from the website, Wintec makes a nice set of building products. As you note, I suspect that part of the explanation for the limited use in the US is the target construction type - these types of products are made for load-bearing masonry walls (a rare type in many parts of the country, except for low-end construction like bid-box retail). Another consideration is the through-wall nature of the Winbloc that doesn't lend itself to a thermal break. In cold-weather climates, a thermal break is particularly important for comfort and energy efficiency. Finally, by its very nature, precast concrete lends itself to economies of scale based on repetition. Note the limited numbers of sizes available and relatively small scale (the largest rectangular window is approx. 24"x30"). Although the modular, pre-set sizes are not necessarily a negative, they do dictate a certain approach to design that some architects may find overly restrictive.

I am interested in what others think.

Andrew Moore, AIA
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Daniel

11 years ago

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I like the product, but I don't think it will see much use here in Denmark, because of the problem with thermal bridges. Concrete conducts heat 10 times better(or worse depending on pov) than wood for example. The heat loss would be very significant, and increase risk of problems with moisture and mold.
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