Building Materials & Construction

 

Abstracts of research conducted by students & faculty

New Insulation for Retrofitting Existing Buildings

Student: Ellann Cohen

Buildings consume too much energy. For example, nearly 14% of all the energy used in the United States goes towards just the heating and cooling of buildings. Many governments, organizations, and companies are setting very ambitious goals to reduce their energy use over the next few years. Because the time periods for these goals are much less than the average lifetime of a building, existing buildings will need to be retrofitted.

There are two different types of retrofitting: shallow and deep. Shallow retrofits involve the quickest and least expensive improvements often including reducing infiltration around windows, under doors, etc and blowing more insulation into the attic. Deep retrofits are those that involve costly renovation and typically include adding insulation to the walls and replacing windows. A new, easily installable, inexpensive, and thin insulation would move insulating the walls from the deep retrofit category to the shallow retrofit category and thus would revolutionize the process of retrofitting homes to make them more energy efficient.

For my thesis, I am working on the development of a new, easily installable, inexpensive and thin insulation. The basic design idea for this new insulation is to have a silica aerogel (the lowest thermal conductivity material known today) based insulation that will have superior insulative properties as compared to conventional insulations. It will also be thin enough that it can be installed on the inside walls of buildings while still adding substantial R-value.

Composite Materials for Building Envelopes

Principal Investigators: Leon Glicksman, Leonard Morse-Fortier, Lorna Gibson, John S. Crowley

Sponsors: Alcan International Ltd., Dow Chemical USA, GAF Corp., Hoechst-Celanese, Macmillan Bloedel Ltd., Miles Chemical Corp., USG Corp., Certaineed Corp., GE Plastics and Weyerhauser Co.

Traditionally the envelopes of houses are site-assembled from basic components with separate materials serving as the structural members, the weather shield, and the thermal insulation. In this recently completed project composite materials were developed that combined these separate functions. In addition, a construction system well suited to automated fabrication and simple field assembly is being developed. A proof-of-concept roof system, the first product of this research, is based on innovative design and analysis strategies and is compatible with conventional systems while minimizing house-specific design. The roof components include thin-ribbed stress-skin panels, a multi-function ridgebeam and a spline-connection scheme.

Advanced Thermal Insulations

Principal Investigator: Leon Glicksman

Sponsor: U.S. Department of Energy

New buildings and renovated existing buildings, as well as appliances, can be made more energy efficient by the use of insulations which are more compact for the same level of performance. Recently completed research on closed-cell foam insulation improved its insulating performance and at the same time allowed it to be manufactured with elements which are not hazardous to the environment (in particular which do not deplete the ozone layer). Advanced insulation, which includes a composite of foam and vacuum technology, was also developed.

Thermal Insulation for Developing Countries

Principal Investigators: Leon Glicksman and Les Norford

Sponsors: ICI Polyurethanes, American Society of Heating, Refrigerating and Air-Conditioning Engineers

In a number of resource-poor developing countries, buildings are constructed of masonry material without thermal insulation. In winter, these buildings are uncomfortably cold or even uninhabitable. MIT is developing a low- cost thermal insulation for such countries. The feedstock for the prototype insulation is straw, a by-product of wheat threshing. The investigations have focused on straw density, the type and amount of binder needed to make straw panels, thermal and structural tests, and means of attaching the panels to stone walls and applying a surface finish. MIT students have made on-site surveys and prototype tests in Pakistan.

Identification and Promotion of Locally Sustainable Building Construction Methods for Latter-stage Slum Improvement

Principal Investigator: John E. Fernandez Sponsor: 3M Innovation Award

Slum-improvement strategies are a result of conclusions drawn from the most successful projects that have addressed city-center squatter communities. While the factors that need to preside in successfully addressing the needs of the residents of these settlements are complex and necessarily mutable depending on location and overall purpose of the project, it has been recognized by a wide range of organizations that the upgrading, as opposed to physical removal, of slums is a better long-term solution. The creation of mechanisms, financial, political and institutional, that provide a well-conceived ‘package’ of service infrastructure and the establishment of land tenure are the most important first steps in alleviating the health risks and economic hardships that the residents endure. Later, the sustainability of these improvements should lead to an increased desire to upgrade the physical quality of the dwelling units themselves. This project proposes the identification of locally sustainable methods of construction for dwelling upgrade as a strategy for catalyzing the development of viable income producing activities within and adjacent to the confines of the slum itself. This promotion is in the service of establishing a sustainable process of continual slum-improvement after the work of this project has been completed. The identification of construction methods and the consideration of innovative materials and assembly systems will contribute to a realistic proposal for a set of building components to be used in the upgrade of dwelling units. The location of the project is to be determined.

Center for Sustainable Materials and Building Envelopes

Principal Investigator: John E. Fernandez

Sponsor: Department of Energy

The study of sustainable materials necessarily involves an extremely large set of scientific and economic criteria to reasonably establish a productive comparative analysis. While a number of systems have been proposed and developed, none has secured a clearly predominant position over all others. Therefore, it is necessary to glean from a great number of sources the necessary information and rating criteria to offer a current and productive assessment of the state of rating materials for their sustainable value. This proposal offers to study the available literature and tools for determining the sustainability of construction materials for the purpose of:

  1. Establishing the state of the art of ratings systems and their attendant criteria,
  2. Identifying the most recent and important innovations in sustainable material technologies, and identifying key areas for further research.

Three-dimensional Fiber Textile Composites for Use in Construction

Principal Investigator: John E. Fernandez

Three dimensional fiber composites have resulted from a search for viable alternatives to 2D composite laminates. As a result of increasing concern regarding the difficulty with which 2D composites have been able to address delamination from impact, in-plane shear stresses and transfer of axial and bending stresses between adjacent composite elements, 3D fiber textile composites (FTCs) have recently received greater attention. For many reasons, the industrial application of 3D FTCs has lagged far behind the use of 2D composites in high-performance industries such as aerospace and large-scale marine structures. However, several isolated yet noteworthy applications have been implemented in less demanding performance scenarios for civil and architectural structures. The lower level of performance requirements makes the use of 3D FTCs a possible way in which to lighten and strengthen typical structural and non-structural components used in civil and architectural structures. In addition it is possible that 3D FTCs may provide a versatile medium for the inclusion of specialized fibers for a variety of enhanced properties. One particularly interesting possibility arises from the inclusion of smart or responsive fibers within the architecture of the 3D FTC.

Natural Fiber Reinforcement of Large-Scale Composite Polymer Panels

Principal Investigator: John E. Fernandez

Recently, natural fibers (NF) have been investigated as filler materials capable of serving as localized tensile reinforcement and volume fillers within several types of polymer matrices. A number of natural fibers have been under continued investigation for use in natural fiber reinforced polymer composites (NFRC); including wood fiber, jute, sisal, kenaf, flax, wheat straw and bamboo. These fibers have been coupled in a matrix primarily composed of two commodity plastic matrix materials: polyethylene (PE) and polysytyrene (PS). While specific mechanical properties of natural fibers vary according to the particular fiber, the overall performance of natural fibers lies within a relatively tight range as a result of similar molecular composition. An increasing amount of interest has developed over the past few years for NFRCs because of their ease of production, subsequent increase in productivity, cost reduction, lower density and weight and use of renewable resources. The automobile industry has begun to apply NFRCs in a variety of exterior and interior panel applications. The significant weight savings and the ease and low cost of the raw constituent materials have made NFRCs an attractive alternative material to glass and carbon fiber reinforced polymer composites. However, further research needs to address significant material and production obstacles before commercially available NFRCs are widely used in architectural and civil works.

Fiber Reinforcement of a Composite Exterior Wall Panel for the Purpose of Resisting High-velocity Impact Events

Principal Investigator: John E. Fernandez

The introduction of fiber reinforcing into the exterior finish component of an exterior wall assembly may aid in preventing catastrophic failure of the integrity of the wall during events in which high-velocity impact is likely. The most important events to address are those conditions caused by naturally occurring high winds and blast events. During these events, it has been observed that a wide range of objects become lethal projectiles that pose significant hazards to both personal injury and property damage. While layered polymer composites have demonstrated an increasing level of resistance to projectile impact, significant difficulties remain that require further research. In particular, delamination from low and high velocity impact has been a major problem that threatens the structural integrity of the panel. The use of composites for exterior sheathing is a growing area for research and architectural and civil applications in the US, and especially in Europe and Japan. For the advancement of the use of large-scale composite panels for exterior sheathing, further research regarding resistance to impact should be undertaken.

Self-healing Smart Fiber Inclusion into an Air/vapor Barrier Textile Substrate Material

Principal Investigator: John E. Fernandez

Self healing fibers have received a significant level of interest primarily with applications for inclusion in reinforced concrete as a crack management strategy. These “smart fibers” have been added as discrete elements within the concrete matrix. The self-healing fibers are primarily fluid-filled hollow capillaries that contain a bonding agent that, when released, slow or prevent the spread of a crack through the concrete matrix. Self-healing fibers have also been proposed as a strategy for addressing debonding events between the concrete matrix and reinforcing bars. Another application is proposed for this type of smart fiber. The management of the transfer of heat through an exterior wall is an important aspect of the thermal performance of that envelope; one that is substantially compromised by air infiltration and exfiltration. Standard building practice, especially in residential construction, usually requires that a membrane be applied to the building volume to reduce the movement of air between the interior and exterior. Any discontinuities in this membrane may allow for the passage of air to and from the exterior. Self-healing fibers, as an inclusion within the weave of an air/vapor barrier textile, will be studied as a strategy for passively sealing the miscellaneous discontinuities that arise during the application and lifetime of the membrane.

Incorporation of a Smart Fiber Network within a 3D Fiber Textile Composite Near-net Preform Structural Member for Remote Structural Monitoring

Principal Investigator: John E. Fernandez

3D fiber textile composites are a type of fiber architecture that allows for the inclusion of a variety of fiber types within a three-dimensional near-net preform network. The inclusion of monitoring “smart fibers” within the architecture of the woven material allows for the through-member permeation of a fibrous sensor material. Typical fiber materials used for stress and strain monitoring are optical glass fibers linked to a central processor. In this way it is possible to gather important information regarding the health of a structure during construction and during its lifetime from a remote location. The study proposes to evaluate fibers for inclusion within a 3D FTC structural member as well as propose various sensor network architectures most productive for the applications listed. The materials chosen need to conform to the stresses inherent in the pultrusion and weaving processes during the production of the standardized structural forms.


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