Project Overcoat - An Exploration of Exterior Insulation Strategies for 1-1/2-Story Roof Applications in Cold Climates

Stacey Rothgeb, Stacey Rothgeb (NREL Technical Monitor)

Research output: NRELSubcontract Report


The development of an alternative method to interior-applied insulation strategies or exterior applied 'band-aids' such as heat tapes and ice belts may help reduce energy needs of millions of 1-1/2 story homes while reducing the risk of ice dam formation. A potential strategy for energy improvement of the roof is borrowed from new construction best practices: Here an 'overcoat' of a continuousair, moisture, and thermal barrier is applied on the outside of the roof structure for improved overall performance. The continuous insulation of this approach facilitates a reduction in thermal bridging which could further reduce energy consumption and bring existing homes closer to meeting the Building America goals for energy reduction. Research favors an exterior approach to deep energyretrofits and ice dam prevention in existing homes. The greatest amount of research focuses on whole house deep energy retrofits leaving a void in roof-only applications. The research is also void of data supporting the hygrothermal performance, durability, constructability, and cost of roof-only exterior overcoat strategies. Yet, contractors interviewed for this report indicate an understandingthat exterior approaches are most promising for mitigating ice dams and energy loss and are able to sell these strategies to homeowners.
Original languageAmerican English
Number of pages74
StatePublished - 2013

Bibliographical note

Work performed by NorthernSTAR, St. Paul, Minnesota

NREL Publication Number

  • NREL/SR-5500-56145

Other Report Number

  • DOE/GO-102013-3751


  • exterior insulation
  • external insulation
  • fully vented pitched attic assembly
  • high-R roof
  • ice dams
  • rigid foam
  • roof membrane
  • SIP roof retrofit
  • spray foam exterior


Dive into the research topics of 'Project Overcoat - An Exploration of Exterior Insulation Strategies for 1-1/2-Story Roof Applications in Cold Climates'. Together they form a unique fingerprint.

Cite this