The R-ETRO System offers building owners a simple yet effective way to attach the best performing insulation product to an existing building and then serves as a fastening point for finish materials.Expanded Polystyrene (EPS) is the most effective thermal insulation because of its inert properties: EPS has no nutritional value for plants, animals or micro-organisms. It will not rot and is highly resistant to mildew. EPS will not decompose or decay and its R-Value will not decrease with age. Unlike batt insulation, there is no sagging or settling. EPS offers the lowest cost per unit of R-Value compared to any other insulation material. No additional framing is necessary so thermal bridging is minimal.When done in conjunction with other scheduled maintenance or rehabilitation, insulation is a cost-effective way to improve the building envelope performance in terms of conductive heat loss or gain and air infiltration or exfiltration. In the case of un-insulated basements, the addition of interior insulation also makes basement space more comfortable and useable.