Whatever their material make-up, external building envelopes need to have one thing in common: they must provide protection from the weather to the structural members beneath. In so doing, they need to be able to withstand excessive moisture, adverse wind-loading and also incorporate some energy performance. In addition, any material selected in the modern construction agenda needs to embody real sustainability and, of course, carry the right documentation to prove its compliance.
Produced by blending wood fibres with resins to create a homogenous, inherently strong yet relatively lightweight board, MDF’s advantage lies in its convenience. It is light and easy to cut, rout and machine to create any variety of shapes and designs. It is also a cost-effective alternative to solid timber. Yet the nature of the material, made from wood fibres, means it is not a long-term option for moist environments, or even outdoor applications.
However, the use of acetylation technology has changed this and now architects and specifiers can blend the convenience of MDF with the performance of the very best tropical teak with none of the associated cost or environmental issues. Acetylation technology alters the chemical structure of wood, significantly reducing its susceptibility to the effects of moisture. MDF manufactured using this wood, Medite Tricoya, is extremely durable and withstands wet conditions without warping, expanding or twisting. This performance, with all the inherent sustainability credentials of locally sourced, FSC certified timber, is being utilised within building envelope systems that are helping to change the way MDF is specified.
Large format, extreme durable MDF panels were selected for the façade of a technical college in the Netherlands. Clever detailing using 45° angle joints between each panel junction has helped to achieve the appearance ofconcrete clad façade. The external envelope of the newly refurbished ROC Central Netherlands also features a climbing wall, so the selected material had to be exceptionally strong in order to meet the demands of this function, in addition to the usual requirements of a building envelope.
Architects for the Stirling Prize shortlisted Limerick University, have used the same material in a different way, to create infill, spandrel panels that protect and conceal the concrete beam flooring system and insulation components from view. We required a durable panel that would stand the test of time and harsh weatherconditions, explained Michael Carew from Carey Glass. After speaking with the architect, who wanted a matt finish to match the timber windows as opposed to a spandrel glass panel, we decided that laminated timber or marine plywood would not give us the same confidence that Medite Tricoya could. We laminated two 12mm sheets of Medite Tricoya together to get the desired thickness and it was extremely successful.
It is being used in regeneration projects too. A similar consideration led to the specification of the material for a new façade for the scout hut on Walthamstow’s Wood Street. The 14th Group Scout Hall, a part of the Wood Street Project, is one of many public projects that seeks to enhance the character of the area: restoring heritage buildings, providing new planting, signage, street furniture and shop frontages. Funded by London Borough of Waltham Forest and the Mayor’s Outer London scheme, the renovation program aims to increase the vibrancy and growth of high street places across London.
Installed over the existing garage structure of the scout hut, durable MDF panels were used to create a smart white façade, forming the base for paint stencilled or vinyl signage. The panels were also transformed into large fascias and installed in patterns derived from the Scout logo. This Fleur de Lys and diamond/triangle motif, also found in the scouting uniform and its distinctive scarf, provide a smart external decoration. The refurbished building now presents a trustworthy welcome to the Scout hall.
We required a panel that would stand the test of time in an external application, potentially in harsh weather conditions, explained Tomas Klassnik, architect at Klassnik Corporation, We had a precise geometric design for the façade which we needed to produce on site, to fit over the existing structure. Medite Tricoya was chosen because it is relatively lightweight, can be machined on site and provides a smooth finish for painting. The 50-year product guarantee gives us reassurance that the new façade will last for many years to come.
The robustness, yet light weight qualities of the material have been used to provide real protection on a much more visceral level too. Fabricated in Ireland, prefabricated homes constructed from Medite Tricoya were last year deployed to families in hurricane-torn areas of New York.
Housebuilders and specifiers can also take advantage of the clear benefits the material delivers, by using a timber rainscreen-style cladding system that replicates the look and feel of real timber, with none of the maintenance issues. Manufacturers are coming to the fore by offering cladding, as well as fascia boards, soffits, window beads and bespoke envelope products, including doors, to deliver dimensionally stable, low maintenance yet sustainable systems that carry a service life of 60 years. With a fair face, these products can also take paint or other surface finishes with ease.
Where MDF has been favoured for its versatility, thanks to new technology and the ingenuity of product and system manufacturers, together with the foresight of specifiers, it is now becoming a reliable material for successful integration into building envelopes.
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