The EU project HOPE (Health Optimisation Protocol for Energy-efficient buildings) seeks to characterise those buildings that achieve good performance in both energy efficiency and occupant health and comfort. This project involved two stages of fieldwork: assessment of buildings by checklist and occupant questionnaire in the first stage, more detailed physical measurements in a subset of buildings in the second stage. In order to help with selection of buildings and measurement plans for the detailed measurements, a series of health hazard algorithms were designed, each based on an individual building health hazard (such as asbestos, carbon monoxide, fungi, etc). The criteria within the algorithms were based on the responses to the checklists and questionnaires, in order to highlight potential hazards. This paper briefly describes the fieldwork methodology used in HOPE, and explains the derivation of the health hazard algorithms and their use in the evaluation of health risks in buildings.