Since design, construction, and maintenance practices can have a significant effect on their environmental surroundings, measures can be taken to either lessen negative impacts or improve previously contaminated sites (i.e. brownfields). Generally speaking, strategies involving the management of runoff and erosion can prevent the worsening of water quality, while the use of reflective roofing materials can mitigate the so-called ‘heat island effect’ that affects microclimates. Other sustainable site work practices can include the minimization of natural disturbance—not only caused by the building itself, but also the construction (and continued presence) of its access roads, parking, and other features.
Expanded polystyrene insulation
Carefully considering land use can lower a building’s effect on local flora and fauna, while also leading to reduced demands on municipal infrastructure services. The specification of certain systems employing plastic products can help a project achieve related goals. For example, the National Association of Home Builders (NAHB) promotes frost-protected shallow foundations (FPSFs) not only because of their quicker construction and cost reduction capabilities, but also due to their environmental benefits, which include resource conservation and soil-disturbance reduction.1
Expanded polystyrene (EPS) is used in FPSFs for buildings located in moderate and cold- climate areas. While traditional foundations are protected from frost-heave damage by placing the footing below the frost line, an FPSF can be placed just 305 to 406 mm (12 to 16 in.) below-grade even in the most severe climates. Its insulation is strategically positioned to raise the frost depth around the construction site and direct the building’s heat loss downward. When required in colder climates, ‘wing’ insulation extends outward horizontally from the footing. (The colder the climate, the further the wing insulation is extended.) Expanded polystyrene insulation is acceptable for both horizontal and vertical installation, which can lead to a reduction in excavation work and in the use of concrete, along with the associated costs.
Advanced stormwater-control assemblies include a mechanism so runoff can be cleaned before entering the municipal storm sewer system. One way this can be accomplished is via the passage of water through an oil/water separator unit. Frequently made from high-density polyethylene pipe (HDPE), these units are designed to reduce the velocity of water flow—allowing the grit, sediment, and other solids, toxins, and heavy oils to settle and remain in the unit while the clean effluent is discharged.
For smaller sites, such as convenience stores and gas stations, these oil/water separators can be ideal. A compact system that also cleans the water is important for the environment and can help communities comply with National Pollutant Discharge Elimination System (NPDES) Phase II demands. The U.S. Environmental Protection Agency (EPA) regulation (40 CFR 122.34) requires permittees to develop, implement, and enforce a stormwater control program designed to reduce the discharge of pollutants from the municipal separate storm sewer system (i.e. MS4) to the maximum extent practicable. This stormwater management program must include six minimum control measures:
- Public education and outreach on stormwater impacts.
- Public involvement/participation.
- Illicit discharge detection and elimination.
- Construction site stormwater runoff control.
- Post-construction stormwater control in new development and redevelopment.
- Pollution prevention/good housekeeping for municipal operations.
Extruded polystyrene (XPS) can also have a positive role in stormwater control, both in terms of rate and quantity. Garden roofs (i.e. vegetated systems) using XPS can help slow and reduce stormwater from entering storm sewers, while also helping to reduce heat build-up due to energy-absorbing exterior surfaces. There is also an opportunity for XPS insulation in conventional roofing designs with white roof membranes. Many of the green building rating systems encourage the construction industry to reduce ‘heat islands’—the thermal gradient differences between developed and undeveloped areas. extruded polystyrene can potentially help buildings achieve recognition for sustainable sites relating to roof construction.
1 For more information on these shallow foundations, see “Frost-protected Shallow Foundations,” by Elizabeth M. Steiner in the November 2004 issue of Modern Materials.