Thermal Performance of Curtains, and other retrofit options

A couple common questions:
“What is thermal resistances of window film with an air gap, and curtains?”

  • Timber framed window, single glazed (baseline)
    • R0.2
  • Timber frame, single glazed, with drapes and pelmet
    • R0.3 $0-$150/m2
  • Timber frame, single glazed, with window film
    • R0.4 $5/m2
  • Alu frame, thermal break, double glazed, low-e
    • R0.4 $450/m2
  • (Higher R values mean less heat loss)

“What are good retrofit options for my home”?
Reducing heat loss is one important strategy.  (Another is maintaining ventilation)
Good strategies mean picking the most reduction in heat loss, for the least cost.  This chart can help.

Bishop, T. W. (2009). Heat Losses and Gains in Residential Housing in Southern New Zealand (Thesis, Master of Science). University of Otago. Retrieved from

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