Polystyrene Uses in Construction

Often encountered in daily life as a packaging material, polystyrene—a synthetic aromatic hydrocarbon polymer—has transcended its common uses to establish itself as a mainstay in the construction industry. When asking ‘what is polystyrene?’, one discovers that it is not simply a plastic material but rather a multifaceted thermocol known in various forms including polystyrene foam, often referred to as styrofoam. However, styrofoam vs polystyrene debates clarify that Styrofoam™ is a trademarked brand of closed-cell extruded polystyrene foam owned by The Dow Chemical Company, and whilst colloquially, people may refer to polystyrene foam products as Styrofoam, technically this is not accurate.

Properties of polystyrene such as its lightweight nature, durability and thermal insulation capabilities have led to diverse polystyrene uses in construction. The query ‘is polystyrene waterproof?’ is met with an affirmative, as it exhibits moisture-resistant properties, further enhancing its viability in the building sphere. Questions surrounding its safety such as ‘is polystyrene flammable?’ or ‘is polystyrene plastic?’ are addressed with careful consideration regarding its form and usage, ensuring compliance with safety standards. Its expanded form, expanded polystyrene (EPS), demonstrates a broad utility range, from insulated panel systems to efficient packaging solutions.

With construction professionals consistently utilising this lightweight, durable, and easily mouldable material, it’s clear that the uses of polystyrene in the construction industry are manifold and continuing to grow as technologies advance.

Key Takeaways

• Polystyrene is a versatile construction material beyond its common use in packaging.
• Its properties include being lightweight, moisture-resistant, and an excellent thermal insulator.
• Expanded polystyrene (EPS) is widely used in construction for insulation and packaging due to its durability and cost-effectiveness.
• Safety and environmental considerations are paramount when using polystyrene in construction projects.
• The construction industry favours polystyrene due to its multitude of advantageous attributes and applications.

Understanding Expanded and Extruded Polystyrene

In the realm of construction materials, there exists a duo of polystyrene types, each with distinct qualities and applications. Expanded Polystyrene (EPS foam) and Extruded Polystyrene (XPS foam) have emerged as prominent solutions for modern building requirements due to their versatile properties and cost-effectiveness. Ascertaining the differences between these foam plastics is fundamental for architects, builders, and engineers deploying these materials in their projects.

Both EPS and XPS possess foam plastic characteristics, but their manufacturing processes and resultant structural variations render them suitable for distinct construction needs.

EPS foam, often spotted as the white material within protective packaging or coffee cup insulators, is characterised by its lightweight and insulating features. Made by expanding spherical beads in a mould with heat and pressure to fuse them together, it comprises 96-98% air, giving it the buoyancy and thermal resistance beneficial in expanded polystyrene insulation.

Conversely, XPS foam—famous for its vibrant hues like pink, blue, and green—offers a consistency that boasts superior thermal insulation and high compressive strength. It is crafted using a continuous extrusion process that fortifies its cell structure, making it robust and nearly impervious to water—qualities that make extruded polystyrene foam particularly apt for moisture-resistant applications.

• EPS polystyrene is exemplary for large-scale insulation, from roofs to floors.
• XPS foam excels in demanding situations, including foundational barriers and below-grade insulation.

Concrete form tubes in the UK, including those for columns and footings, can be constructed with EPS, utilising its mouldability and strength-to-weight ratio. Both EPS and extruded polystyrene are integral in creating thermal envelopes for buildings, ensuring energy efficiency and compliance with stringent building regulations.

In conclusion, both EPS and XPS are indispensable foam plastic materials that respond to the various demands of the construction industry. Whether it’s for insulating a suburban home or fortifying the foundation of a towering skyscraper, these polystyrene variants stand as pillars of modern building techniques.

Expanded Polystyrene for Insulation

When addressing the question of ‘is polystyrene good for insulation?’, experts concur that expanded polystyrene (EPS) stands prominently in the realm of insulation materials. The remarkable features of EPS, such as its thermal efficiency and long-term durability, make it a preferred choice for construction and renovation projects globally. In this section, we’ll explore the properties of EPS that lend to its effectiveness as insulation, its benefits in flooring applications, and how it compares with other insulating materials.

Properties of EPS Insulation

EPS insulation boards are renowned for their high R-value per inch, providing superior thermal resistance. Formulated with air as the primary constituent—totaling up to 98%—it exudes a low density, denoted in units of g/cm³ to kg/m³, that belies its high-impact resistance properties. A thermal insulation engineer would prise EPS for its dimensional stability, which remains unaffected by environmental shifts, ensuring consistent performance throughout its lifecycle.

Benefits in Floor Insulation Applications

In the context of flooring insulation, EPS is an exceptional contender. It is implemented as under slab insulation and under floor heating boards, improving the energy efficiency of the space above. High-density polystyrene underpins passive house standards by acting as a thermal barrier, minimizing heat loss and contributing to a building’s overall warmth. Additionally, suspended floor insulation employs EPS to protect against cold arising from unheated areas such as garages.

Flooring Application	Brief Description	Benefits of EPS
Under Slab Insulation	Insulation positioned beneath concrete slabs.	Decreases heat loss, enhances comfort.
Under Floor Heating	Insulation designed for heated flooring systems.	Improves heat distribution and energy efficiency.
Suspended Floor Insulation	Insulation used within the cavities of suspended floors.	Prevents heat escape, ideal for renovations and new builds.

Key Differences Between EPS and Other Insulators

Distinguishing EPS from other foam plastics such as Styrofoam—a brand-specific, extruded polystyrene foam—sheds light on its unique advantages in construction. Unlike XPS which may lose insulating capacity over time due to its blowing agent, EPS retains its thermal insulation characteristics indefinitely. Its structure offers impressive compressive stress resistance, which is essential for load-bearing flooring insulation applications. This solidifies EPS’s role as a trusted and sustainable insulation solution in the building industry.

• Closed-cell, high-density structure conducive for heavy loads.
• Consistent R-value reinforcing long-term thermal efficiency.
• Adaptability to a variety of flooring insulation requirements.

Polystyrene in Modern Building Envelope Solutions

Unveiling the adeptness of polystyrene in revolutionising building envelope technologies, insulated panel systems don the architectural world with enhanced energy efficiency. Widely recognised for its thermal properties and structural diversity, high impact polystyrene emerges as a driver for innovative facades, walls, and roofing solutions.

Striking a delicate balance between durability and lightness, polystyrene boards excel in high-impact zones, harnessing resilience against environmental stressors whilst assuring energy conservation. The adaptable nature of this material extends its benefits, enabling ease of customisation and facilitating tailored, high-performance building envelopes.

Polystyrene’s formidable character finds its expression in insulated panel systems. The lure of modularity, paired with simplified installation processes, empowers constructors to achieve set thermal performance goals without compromise. Consequently, polystyrene board becomes the keystone in constructing sustainable and energy-efficient buildings.

Feature	Advantages	Applications
Thermal Efficiency	Minimising energy consumption through superior insulation	Facades, Wall Systems, Roofs
High Impact Resistance	Withstands severe weather and mechanical effects	High Traffic Areas, Defensive Exterior Layers
Customisation	Flexible shaping and sizing for bespoke design solutions	Custom Architectural Features, Modular Constructions
Lightweight Properties	Facilitates ease of handling and reduces structural load	Elevated Structures, Retrofitting Insulation

Traversing the myriad uses of polystyrene reveals its capacity to fortify building envelopes against energy loss. Its proficiency as an insulation medium reflects in insulated panel systems that couple resilience with economical value, presenting an approach to construction that is as sustainable as it is architecturally sound.

Ultimately, it is the versatility in polystyrene boards that architects and engineers harness to engrain efficiency at the core of modern constructions. Through adept applications of polystyrene, the industry propels towards a future where building envelopes are not only protective shells but also active participants in energy conservation.

Application of Polystyrene in Wall Systems

Within the vast domain of building technologies, polystyrene serves as a robust ally, particularly due to its commendable insulation properties when used in external wall systems. Incorporating polystyrene, notably expanded polystyrene (EPS), into the construction of exterior walls or as cavity fill significantly elevates the structure’s thermal performance. Through its aptitude for insulation, EPS improves the building’s energy efficiency while simultaneously driving down operational costs—an accomplishment that aligns with the stringent demands for sustainability in contemporary building practices.

Thermal Performance with EPS in Exterior Walls

Employing EPS-based exterior wall insulation (EWI) is a strategy embraced to increase the thermal efficiency of buildings. The EWI boards act as a formidable barrier against temperature fluctuations, markedly bolstering a building’s insulation system. The EPS, formed into various shapes such as polystyrene cubes, can be tailored to suit diverse architectural requirements. Innovations within the UK construction sector, such as the utilisation of resin molds UK, enable precision in shaping and reinforcing EPS, adding flexibility to its application in complex wall assemblages. The enhanced insulation brought forth by EPS contributes to maintaining desired interior temperatures, denoted in degrees in latex, which translates into both energy conservation and cost savings.

Using EPS for Structural Insulated Panels (SIPs)

The construction landscape has been revolutionised by the integration of Structural Insulated Panels (SIPs)—pre-fabricated panels that are synonymous with efficiency and swift assembly. EPS is extensively adopted as an infill material for these panels, predominantly due to its lightness and outstanding thermal insulating capacity. This fusion of EPS within SIPs fortifies the panels’ innate ability to maintain internal climates while pre-empting excessive energy expenditure. Through the collective efforts of the XPS group, a consortium that specialises in extruded polystyrene products, and the rising adoption of EPS in SIPs, building designs are enviable blends of thermal control and structural fortitude.

Another aspect of modern construction that involves EPS is the symbolic fork and glass symbol, which refers to the material’s compliance with food safety regulations—a testament to the versatility and safety standards met by utilising EPS in construction applications. Thus, EPS’s role in creating robust wall systems is replete with examples of cost-efficiency, energy savings, and a keen adherence to industry specifications.

Polystyrene for Roofing Solutions

The construction industry continues to embrace polystyrene for its lightweight, thermally efficient attributes, particularly in roofing applications. Builders and architects opting for roofing insulation materials that are not only effective in temperature control but also practical, find an invaluable resource in polystyrene variants such as EPS sheets and insulated roofing panels.

Thermal insulation sheets crafted from EPS are engineered to cater to a range of roofing needs, whether being installed atop domestic dwellings or commercial edifices. These sheets are highly adaptable, allowing customisation to fit the unique configurations required by differing roof structures.

Moreover, the ease with which they can be cut to specification on-site reduces waste and underscores their efficiency. Aptly coined as ‘cut-to-fall’ capabilities, these polystyrene solutions facilitate an expedited installation process, especially in situations that necessitate a tapered approach to ensure effective water drainage and eliminate the potential for ponding on flat roofs.

Roofing Characteristics	Polystyrene Variant	Benefits
Flat Roofs	Cut-to-fall EPS Panels	Prevents water accumulation, enhances thermal performance
Tapered Roofs	Custom EPS Sheets	Adapts to roof gradient, offers tailored insulation
Commercial Buildings	Insulated Roofing Panels	Large scale energy efficiency, durability under heavy use
Domestic Settings	EPS Insulation Boards	Cost-effective, straightforward application

In addition to their installation advantages, EPS sheets exhibit an intrinsic resistance to moisture ingress. Their structure maintains the thermal resistance needed to provide continuous insulation throughout the year, hence playing a pivotal role in the long-term reduction of heating and cooling costs.

Conclusively, roofing insulation with an EPS core not only instantaneously enhances a building’s thermal performance but does so with a mindfulness towards economic and environmental efficiency. The dexterity with which insulated roofing panels handle the challenges of modern construction cements their status as a decidedly rational option in progressive building practices.

Innovative Use of Polystyrene in Civil Engineering

The adoption of polystyrene, particularly Expanded Polystyrene (EPS) and Extruded Polystyrene (XPS), has become a game-changer in the realm of civil engineering. With advancements in material science, these lightweight polymers have redefined traditional civil projects through their application as EPS geofoam and clayfill, becoming integral to modern engineering solutions. Their role in innovations such as lightweight concrete fill and the execution of complex designs using large foam building blocks is transforming the ways engineers approach both the practical and ecological impacts of construction.

Benefits of EPS Geofoam in Civil Projects

Lauded for its remarkably low density yet superior load-bearing capacity, EPS geofoam stands tall among lightweight fill materials. This versatile product has taken precedence in projects where reducing soil stress and eliminating the need for extensive earthworks are crucial. From forming the base of landscape structures to acting as a reliable substrate in uneven terrain, EPS geofoam has been instrumental in simplifying construction phases and driving down costs.

Especially useful in GeoFoam implementations, EPS geofoam is a steadfast solution for professionals grappling with challenges such as land heave or weak subsoil situations. The capacity of EPS geofoam to function effectively as a lightweight fill material is also reflected in projects where fluid dynamics, such as drainage and runoff, are essential considerations, ensuring long-term stability of the structures it supports.

EPS as a Lightweight Fill Material

The preference for EPS in civil engineering extends into its use as a lite alternative to traditional fills such as gravel or soil. When matters of logistics and practicality are paramount—be it in the UK concrete tube forms sector or within the broader context of infrastructural development—EPS stands out as resourceful. With products like lightweight concrete fill and large foam building blocks, tasks from landscaping to constructing acoustic barriers can be completed with unprecedented efficiency.

The featherweight character of EPS enables superior handling and lower transportation costs. This is evident in the UK, where xps foam has carved a niche for itself in the market, offering discernable benefits over heavier counterparts. The adaptability of EPS to suit varied applications reflects a robust versatility, thus catering to ever-evolving engineering ambitions.

Application of EPS	Significance
Retaining Structures	Geofoam provides lateral support to prevent land collapse
Bridge Abutments	Reduces weight and settling, minimising structural stress
Road Embankments	Facilitates stability on weak substrates and sloped terrains
Landscaping	Effortless reshaping of terrain without affecting underlying soil

In essence, the adoption of EPS and XPS within civil engineering signifies an inception of eco-friendly methodologies, merging cost-effectiveness with resourceful innovation. As this branch of engineering continues to explore sustainable prospects, polystyrene remains at the forefront, offering scalable and adaptable solutions to conundrums of the past and present.

Why Polystyrene Foam is Favoured in Construction

The affinity for polystyrene foam board within the construction sector is predicated on a combination of its quintessential characteristics which align seamlessly with industry requirements. The extensive anecdotal evidence from construction professionals highly praises polystyrene for its compression resistant nature, a crucial attribute in environments where structural rigidity and longevity are paramount. Not only does polystyrene foam offer a sturdy composition, but it is also hailed for its high shock absorbency characteristics, which are essential in the safeguarding and transportation of delicate construction materials.

The dimensional stability of polystyrene foam, crucial for maintaining the integrity of structured insulating systems, originates from precise foam runners sizing, ensuring that each application’s demands are met with bespoke solutions. Due to its remarkable lightweight quality, polystyrene foam has become a material of choice for situations requiring ease of handling and reduced labour impact during installation processes. Moreover, it’s the exceptional versatility of polystyrene that allows it to be deployed in a broad spectrum of construction projects, ranging from residential to large-scale commercial developments.

Proving its mettle against the pernicious effects of moisture, polystyrene foam’s inherent resistance to moisture adds another layer of utility in the unforgiving aquatic prospects of construction environments. This quality not only protects against water-induced damage but also extends the material’s life span, presenting cost-effective and enduring benefits to stakeholders. The durability of polystyrene foam further enhances its attractiveness, as it transcends the passage of time without succumbing to significant wear and tear.

Characteristic	Benefit
Compression Resistance	Ensures structural integrity, essential for load-bearing applications.
High Shock Absorbency	Protects materials during transport and handling, ideal for packaging.
Lightweight Nature	Facilitates easy and cost-efficient installation.
Moisture Resistance	Guards against water damage, extending the material’s usefulness.

In summary, it is the blend of resilience, strategic sizing, and insulation proficiency that render polystyrene foam board an invaluable component within the construction industry. Its ingrained capacity for durability and protective qualities embodies the innovation and efficiency driving the development of modern building practices.

The Stability and Lifecycle of Polystyrene Products

As the construction industry increasingly centres around principles of sustainability and longevity, expanded polystyrene (EPS) stands out for its stable lifecycle and enduring quality. EPS’s unrivalled thermal insulation capabilities make it a preferred choice over other types of solid insulation board, qualifying “is polystyrene a good insulator” with a resounding yes. Beyond its insulation properties, the sustainability of EPS is highlighted in its recyclability, contributing positively towards green building initiatives and environmental product declarations.

Sustained R-Value of EPS Products

EPS’s insulation efficiency is quantified by its R-value, displaying remarkable stability over time. The absence of chemical blowing agents in its makeup indicates that the material’s expansive air-filled cells maintain their shape and insulating properties. This consistent thermal resistance refutes any concerns surrounding the question, “is polystyrene recyclable?” Not only can it be recycled effectively, but it also ensures performance consistency throughout its lifecycle, making frequent replacements redundant. Such factors position EPS as the material of choice for achieving long-term energy savings and cost reductions.

Environmental Considerations in EPS Usage

Expanded polystyrene’s profile as an environmentally considerate material is increasingly recognised. With no reliance on toxic chemicals during its production and featuring a low global warming potential, EPS usage offers minimal environmental footprint. Its potential for being completely recycled and reused stands at the core of its environmental appeal, often seen contributing to significant LEED® credits for sustainable construction. Furthermore, with endorsements from UL Environmental Product Declarations, EPS features prominently within the lexicon of eco-conscious building materials.

Aligning with global directives for sustainable development, the construction industry can rely on EPS’s attributes for fostering environmentally viable growth. The dual guarantee of high insulating efficacy and a commendable environmental profile ensures EPS’s stable position in the future of construction materials.

Maximising Efficiency with Polystyrene in Construction

The integration of polystyrene, particularly expanded polystyrene (EPS), into construction processes heralds a new era of construction efficiency. Its lightweight and adaptable properties underscore its capability to expedite and simplify building practices, contributing significantly to project time reduction and overall construction cost savings.

Developers and constructors seeking versatile and efficient materials need not look further than custom EPS solutions. Engineered to fit specific design requirements, EPS facilitates a flexible approach to construction, allowing for rapid adaptation on-site, and swiftly responding to bespoke construction demands.

As a lightweight material, EPS can be easily handled by construction teams, reducing labour requirements and physical strain, which directly translates into speedier project cycles. By integrating EPS within a construction strategy, firms benefit from a material that is not only cost-effective to produce and purchase but also has a proven track record of reducing timelines on-site.

Construction Element	EPS Application	Impact on Efficiency
Insulated Panel Systems	EPS is used in walls, roofs, and floors for thermal regulation.	Minimises complexity in installation, leading to quicker project completion.
Formworks	Lightweight EPS formworks are used for concrete casting.	Enhances maneuverability and reduces strain on workers.
Packaging	EPS protects materials during transport, reducing damage-related delays.	Enhances logistics and handling, encouraging seamless project flow.
Geofoam Applications	EPS as lightweight fill in civil engineering projects.	Decreases the need for heavy machinery and streamlines construction phases.

Cutting-edge technology now also allows for custom EPS solutions to be crafted with precision, ensuring that the material’s insulating and structural properties are maximised to meet specific building codes and energy efficiency standards. The inherent qualities of EPS—such as its insulation prowess and moisture resistance—remain uncompromised, even when customised to fit irregular designs or complex architectural features.

When considering the entire lifecycle of a building, EPS further showcases its efficiency through its longevity and durability. Unlike traditional materials that may degrade or underperform over time, EPS maintains its form and insulating capabilities, thereby reducing the need for costly maintenance or replacement.

In conclusion, EPS emerges as a cornerstone of modern construction methodology. Its abilities to reduce project durations, lower expenditure, and provide tailored solutions without forfeiting performance make it a favoured choice for forward-thinking construction experts. Through ongoing advancements in EPS production and application methods, the construction industry continues to embrace this versatile material, poised to redefine efficiency and economy in the built environment.

Recycling and Sustainability Aspects of Polystyrene

In an age where environmentally friendly construction is not just a preference but a mandated responsibility, polystyrene emerges as a material that treads lightly on our planet. The vast potential of polystyrene for recycling has earned it a commendable place within the discourse on sustainable construction materials. Enterprises engaged in trade insulations increasingly advocate for the use of polystyrene owing to its impressive environmental credentials. Not only does it eschew the need for landfill space through robust recyclability but it also stands testament to the burgeoning philosophy that sustainability blends seamlessly with functionality and design.

Contribution of Polystyrene to Green Building

‘Polystyrene recycling near me’ – a query increasingly typifying the conscientious builder’s search for sustainable materials. The extensive recyclability of polystyrene is intrinsically linked to its virtue in green building conduct. Unlike many other materials, polystyrene offers the dual advantage of high-performance insulation and an end-to-end lifecycle that mitigates environmental impact. A building insulated with polystyrene not only conserves energy but also assures stakeholders that the material embodies the principles of environmental stewardship, from its creation to its repurpose.

EPS and EPP: Recyclable Materials for a Sustainable Future

Expanded Polystyrene (EPS) and Expanded Polypropylene (EPP) have risen as pillars of sustainable construction. Lauded for their 100% recyclability, these materials close the loop in resource efficiency, making them central to eco-conscious building systems. The sustainability narrative of EPS and EPP is further augmented by their inherent energy-saving properties, thereby fulfilling a multifaceted role within the construction industry. As the sector forges ahead to align with global sustainability goals, the environmental and practical excellence of EPS and EPP position these materials at the vanguard of a responsible building future.

FAQ

What is polystyrene and what are its properties relevant to construction?

Polystyrene is a synthetic aromatic polymer made from the monomer styrene. It comes in various forms, including expanded polystyrene (EPS) and extruded polystyrene (XPS). Key properties relevant to construction include lightweight nature, thermal insulation, moisture resistance, and shock absorptiveness, making it suitable for use in insulating walls, roofs, floors, and for packaging materials.

How does expanded polystyrene (EPS) differ from extruded polystyrene (XPS) foam?

EPS foam is typically white and is made by expanding polystyrene beads, resulting in a lightweight and effective insulator. XPS foam is often coloured pink or blue and has a process that creates smaller air pockets, which leads to superior thermal performance and moisture imperviousness. Both are used in construction, but for slightly different applications due to these distinctions.

Is polystyrene waterproof and flammable?

Polystyrene itself is water resistant, which makes it beneficial in construction applications where moisture is a concern. However, it is not entirely waterproof without proper coating or treatment. It is also considered flammable and will burn if exposed to a flame without flame retardants.

What makes EPS such a good material for insulation?

EPS insulation is popular due to its high R-value per inch, providing excellent thermal resistance. It is stable, maintains its insulating properties over time, and is resistant to moisture and environmental variations. Its closed-cell structure allows it to withstand compressive stresses, enhancing its suitability for insulation in buildings.

Can polystyrene be used safely in construction, considering its environmental impact?

Yes, polystyrene can be used safely and sustainably in construction. Its production has a low environmental impact, being free of toxic substances and using minimal water. EPS foam is recyclable, which aligns with green building practices and may contribute towards LEED® credits for environmentally responsible construction practices.

What sustainability and recycling measures are associated with polystyrene in the construction industry?

Polystyrene contributes to sustainability in the construction industry by being 100% recyclable, minimizing waste going to landfills. Recycled EPS can be used to create new EPS products or a variety of everyday items, leading to higher resource efficiency and reduced environmental impact. The use of EPS and EPP in construction supports energy savings and responsible resource use as well.

Are EPS and XPS both considered polystyrene?

Yes, both EPS (Expanded Polystyrene) and XPS (Extruded Polystyrene) are types of polystyrene used in construction for insulation and other applications. They differ in their manufacturing process and resulting physical properties.

How does EPS contribute to constructing efficient buildings?

EPS contributes to building efficiency by providing excellent insulation, reducing heat loss and energy consumption. Due to its lightweight and versatility, EPS can be easily installed and modified, speeding up the construction process and reducing overall costs, leading to more efficient building practices.

Does polystyrene insulation deteriorate over time?

Polystyrene insulation, particularly EPS, has sustained R-values over time since it does not contain blowing agents that can decrease its thermal resistance. Therefore, EPS insulation tends to maintain its performance throughout the lifespan of a building.

What are Structural Insulated Panels (SIPs) and how does EPS benefit them?

Structural Insulated Panels are high-performance building panels used in walls, floors, and roofs. They are fabricated using an insulating foam core sandwiched between two structural facings. EPS, when used as this core, ensures excellent thermal performance and contributes to the overall energy efficiency of the SIPs.

What are the environmental considerations in EPS usage?

EPS has environmental considerations such as being produced without toxic chemicals, having a low global warming potential, minimal water usage, and complete recyclability. These aspects are crucial for sustainable building and can contribute to green building certifications.

Source Links

• https://www.engineeredfoamproducts.com/industries/construction/
• https://hotwiresystems.com/what-is-polystyrene-eps-xps-different-uses-of-polystyrene/
• https://www.atlasmoldedproducts.com/blog/eps-construction