New homes use styrofoam exterior moldings, how good are these?

Styrofoam, or expanded polystyrene (EPS), is often used as exterior molding or trim in new homes for its lightweight, durable, and cost-effective properties. The use of styrofoam molding has both advantages and considerations:


  1. Lightweight: Styrofoam is very light, making it easy to handle and install. This can be especially advantageous for construction and installation purposes.
  2. Insulation: Expanded polystyrene provides some level of insulation. While it may not be a substitute for proper wall insulation, it can contribute to energy efficiency to some extent.
  3. Resistance to Moisture and Rot: Styrofoam is resistant to moisture and does not rot. This can be beneficial in exterior applications where exposure to the elements is a concern.
  4. Versatility: Styrofoam can be easily shaped and molded into various designs, allowing for versatility in architectural details.
  5. Cost-Effective: Styrofoam is generally less expensive than alternative materials like wood or other synthetic trims, contributing to cost savings in construction.


  1. Vulnerability to Physical Damage: Styrofoam can be more susceptible to physical damage than some other materials. It may chip or break upon impact, potentially requiring replacement.
  2. UV Sensitivity: Direct and prolonged exposure to ultraviolet (UV) radiation can cause styrofoam to degrade over time. Manufacturers often include coatings or additives to mitigate UV damage, but long-term exposure may still affect the material.
  3. Fire Hazard: Expanded polystyrene is flammable, and in the event of a fire, it can contribute to the spread of flames. Fire-resistant coatings or treatments may be applied to address this concern.
  4. Aesthetic Considerations: Some homeowners and builders may have aesthetic preferences for traditional materials like wood or other synthetic trims, as these materials can offer a more natural or high-end appearance.
  5. Environmental Impact: Styrofoam is not biodegradable and can have a negative environmental impact. Some regions have restrictions on the disposal of styrofoam, and there is growing concern about its contribution to plastic pollution.

In summary, styrofoam exterior molding can be a cost-effective and versatile choice with some insulation benefits, but it also has vulnerabilities such as susceptibility to physical damage and UV sensitivity. The choice of exterior molding material often depends on factors such as aesthetic preferences, budget constraints, and regional building codes. It’s essential to consider these factors and consult with builders or architects to determine the most suitable material for a specific project.