materials _ whole building design guide

Fig. 1. Wood quoinssymbolize stone

by Phoebe Crisman, Assistant ProfessorUniversity of Virginia School of ArchitectureLast updated: 06-16-2010

The term "materials" refers to all the physical substances that are assembled to create the interior and exterior of abuilding. Today most buildings are constructed from a multitude of materials, each with very specific functional demandsand complex assembly requirements. For instance, an exterior wall assembly contains materials that keep the rain andwind out, thermally insulate the inhabitants from exterior temperatures, structurally support the building and theassociated enclosure system, and provide desired interior and exterior finishes. In addition, windows, doors, vents, andother apertures connect to the interior and exterior of the building. The list could go on, but this example should serve toillustrate the complexity and importance of the material selection process in building design. These decisions should bebased on a number of carefully considered issues as described below, including symbolism, appropriateness, physicalproperties, and technique.

A. Symbolism

Particular materials carry specific connotations within cultures and regions. Terms such asnatural or artificial, eternal or ephemeral, austere or opulent, describe a few suchassociations. We often refer to the enduring qualities of stone, or the ephemeral nature ofglass or paper. In some cases, the material associated with a desired symbolic expressionis not available or too costly, and another material is substituted to replicate that materialand achieve the desired effect. Mount Vernon, the home of George Washington, illustratesthis situation. The symbolic solidity of stone was imitated in the carved and painted woodenconstruction of the house exterior. See Fig. 1.

B. Appropriateness

There are three primary areas that must be evaluated in selecting appropriate materialsand assemblies.

MATERIAL COMPATIBILITY WITH CLIMATIC, CULTURAL, AND AESTHETIC CONDITIONS

Climate is one of the most important factors to consider in material and assembly selection. Too often we see buildingsthat have not taken local environmental conditions into consideration, by either replicating the same prototypical designfrom Alaska to Arizona, or by designing a building for a specific site that ignores climatic issues. The result is a buildingthat performs poorly—failing to keep inhabitants comfortable without excessive energy expenditures and near completereliance on mechanical systems to rectify poor construction decisions (see High Performance HVAC ).Materials also must be compatible with specific regional and local cultural and aesthetic conditions. For example, theSouthwestern adobe and flat roof residential construction would not export well to New England, where the widespreaduse of wood framing, clapboard siding, and pitched roofs is climatically appropriate, as well as culturally embraced.

APPLICABILITY OF MATERIAL TO OCCUPANCY AND SIZE OF BUILDING, INCLUDING DURABILITY,STRUCTURAL, AND FIRE PROTECTION REQUIREMENTS

Material choices are often legally limited by the building type and size, in order to protect public health, safety , and welfare . For instance, a

detached single-family house has far fewer limitations than a high-rise office building or a federal courthouse, from which hundreds of inhabitants must be evacuated in case of emergency. In general,

buildings with large occupancy numbers (especially assembly occupancy such as theaters, lecture halls, andrestaurants) and greater enclosed square footage require more fire-resistant construction and more complex fireprotection systems . Another concern is the added wear and tear on a densely inhabited

d i t l d b ildi h bli h l h it l h

Materials

INTRODUCTION

DESCRIPTION

Materials | Whole Building Design Guide http://www.wbdg.org/resources/materials.php?r=dd_architecture

1 / 4 2010/12/21 17:33

and intensely used building, such as a public school or hospital , wherematerial durability is a major concern.

ENVIRONMENTAL IMPACT OF OBTAINING RAW MATERIALS, PROCESSING AND FABRICATING BUILDINGMATERIALS, TRANSPORTATION IMPACT, AND RECYCLING ISSUES

In addition to the easily quantifiable issues above, the long-term ecological footprint of material production is equally important and must be analyzed holistically. For example, a number of

questions must be raised and answered.

Where did this material come from? Ideally materials should be obtained from renewable sources, such as woodharvested from sustainably managed old growth forests.How was it processed or fabricated? The energy and resources expended in material preparation, sometimestermed "embodied energy," must be taken into account.How did it arrive on-site? Transportation impacts and expenses should be minimized, with locally availablematerials often making a better choice than those imported from afar. For example, if building in Vermont, selectlocally quarried stone rather than specifying imported marble from Italy.How long will it last? How will it eventually be disposed of? Materials should be selected with durability and lifespan in mind. Recycled materials should be chosen when possible. Consider designing easily dissembled buildingsthat may be reused and recycled in the future.How will this material impact the environment while in place? For example, many paints, carpets, acoustic ceilingtile, vinyl flooring and wallcoverings, and adhesives contain volatile organic compounds (VOC's). Avoid usingmaterials embodying VOC's, and select low toxicity building materials to avoid off-gassing after constructioncompletion.How can the use of a particular material minimize construction waste? Choose construction materials that don'thave a lot of by-products. For instance, building with reusable formwork for cast-in-place concrete constructionavoids plywood and wood formwork waste on-site.

See the Sustainable design objective section for a comprehensive discussion of sustainable building design, includingfundamental principles, implementation strategies and sustainable building material links.

C. Physical Properties

A number of physical properties must be taken into account in the material selection process. While certain propertiesare inherent to the material and unchangeable, other qualities can be determined in the fabrication or finishing process.The following outline lists only primary considerations, since each material possesses a unique combination ofproperties.

STRENGTH

Material strength quantifies resistance to compression, tension, and other types of loading on a given material. Forinstance, masonry performs most effectively as a load-bearing or compressive material, while steel is a more suitablechoice for greater spanning and tensile requirements.

MASS AND THICKNESS

After an initial material selection is made, the dimensional thickness of each material must be based on requirementsfor durability, strength, and aesthetic considerations.

PHYSICAL AND VISUAL DENSITY

Often a particular tactile density is desired, ranging from heaviness to lightness in degrees of opacity, translucency, ortransparency. See Figs. 2 and 3.


2 / 4 2010/12/21 17:33

From Left to Right:Fig. 2. Masonry solidity, Fig. 3. Glass translucency, Fig. 4. Smooth glasssurface

TEXTURE

Many materials may be finished to different textures, either during off-site production or while finishing materials on-site.Smooth to rough, soft to hard, and a range of surface finishes—matte, satin, polished, and so on—are possible. SeeFig. 4.

COLOR

Selection of a building color palette must consider the surrounding context, as well exterior and interior light qualitiesunder which the colors will be viewed. The cool diffused light of Seattle will render colors quite differently than the hotclear light of Phoenix. Colors may be light absorptive or light reflective, warm or cool, while the palette may bemonochromatic or polychromatic. See Figs. 5 and 6.

Fig. 5. (left): Brick pattern in color and line and Fig. 6.(right): Brick pattern in relief

TEMPERATURE

The tactile qualities of architecture are of utmost importance, especially those surfaces that building inhabitants touchon a regular basis, such as door hardware, work surfaces, and floor materials. Metal surfaces quickly registertemperature change, while stone more slowly absorbs ambient temperatures and retains temperature much longer.Thus, material thermal conductivity is an important consideration in the comfort of occupants

.

PATTERN

Material patterning must be designed at two scales: the individual elements themselves, such as bricks or glass panes,and the composition of these elements into larger assemblies. For example, at the individual element scale the inherentpatterning of wood grain or stone marbling must be considered. The creation of larger patterns occurs when thematerial is assembled into building facades. See Figs. 7 and 8.


3 / 4 2010/12/21 17:33

Fig. 9. Prefabricatedsunshading

Fig. 10. Exposed steeltruss

Fig. 7. (left): Stucco patterning and Fig. 8. (right): Patternedglass

D. Technique

The methods of material fabrication and assembly are a complex aspect of the constructionprocess. Technique includes the fabrication process, the detailing of how materials and systemsare joined and erected, and the craft employed to execute the work.

FABRICATION

Fabrication refers to how a material was created, processed, and assembled. Fabricationtechniques range from handcrafted to mass produced to prefabricated. Materials carry traces oftheir making and assembly that can be used to create surface modulation and richness. See Fig.9.

DETAIL

Construction details determine how individual material elements orsystems are joined. Common methods of joinery include various types ofmechanical fastening (nails, bolts, rivets...), welding, adhering, and soon. Construction details should relate to the overall architecturalintentions of a building. Attention to detail is evident in a well-resolvedand finely executed building, such as the elegant assemblage of woodand concrete systems in Fig. 10.

CRAFT

The quality of design and construction workmanship is crucial to the success and longevity of a project. Theemployment of well-trained and experienced trades people is the best way to assure a high level of building craft. SeeFig. 11.

WEATHERING

The passing of time has an immense impact on the appearance and life span of building materials. Thus, futureweathering must be carefully considered during material selection, building detailing, and construction. See Fig. 12.

Fig. 11. (left): Careful craftmanship and Fig. 12. (right): Exquisitely weatheredstone wall

The application of particular building materials and systems is discussed in numerous sections of the Whole BuildingDesign Guide. Particularly refer to the Products and Systems category and theSustainable design objective sections for more detailed information.

Building codes limit the allowable materials for a particular building, based on building occupancy type and zoning

APPLICATION

RELEVANT CODES AND STANDARDS


4 / 4 2010/12/21 17:33

materials _ whole building design guide

Documents