EPCs rarely recommend window replacements as a first measure because the efficiency gains are typically limited when compared to the high cost of installation.

While the EPC assessment does record window data in detail—including the width and height of each glazed unit, orientation, frame material, glazing type, age (if known), and the glazing gap—this information is primarily used to calculate overall heat loss rather than to justify replacement.

In most cases, the RdSAP 10 software wont recommend window replacements as replacing windows delivers a relatively small improvement in the property’s SAP score. Given the cost threshold that each recommendation must meet to be considered cost-effective, window upgrades are usually outperformed by measures such as improving insulation, upgrading the heating system, or adding heating controls. As a result, more impactful and cost-efficient improvements tend to appear first in the EPC recommendations list.