Building energy use compilation and analysis (BECA). Part C - Conservation progress in retrofitted commercial buildings.

Data on energy use was compiled for 223 retrofitted US commercial buildings and analysed for average savings, average retrofit costs, correlation between cost and savings, type of retrofit attempted etc. Dominant building types were schools and offices. Nearly all buildings included operations and maintenance changes as part of the retrofit. 89% of the buildings which saved energy by retrofitting achieved a payback (simple) in less than 3 years. 9% of the buildings failed to save (generally because of improper maintenance). Average savings for the entire sample were 20%. About 60% of actual savings exceeded predictions. Data on 15 buildings for savings achieved over a number of yearsfollowing the retrofit showed that in most cases the savings persisted and even increased.