The potential for urban open spaces to convey therapeutic benefits is increasingly substantiated. Others have considered more specifically how low impact designs to manage stormwater such as bioswales perform in this context. We found only three studies investigating the effects of ecoroofs on human health. Here, we report on an NIH-funded pilot study addressing: 1) the effects of ecoroofs on visitor stress as indicated by salivary cortisol levels and 2) factors determining whether a hospital has an ecoroof. We utilized a mixed methods approach that encompassed phone interviews of hospital ecoroof managers as well as analysis of national hospital databases. We also conducted behavioral observations on a hospital ecoroof in Portland OR. At this same location, we collected cortisol samples from roof visitors over a time interval of a minimum of 15 minutes. We compared these to patients, staff, and caregivers who were waiting indoors.
Results/Conclusions
Initial salivary cortisol levels varied significantly by ecoroof visitor type, ranging on average from 0.09µg/ml for caregivers to 0.30 µg/ml for patients. Declines were highest for patients although no significant treatment effect on stress level change was found in our study. This could be explained by low replication. Alternatively, these pilot data may indicate a gap in horticultural therapy theory vs practice. Behavioral observations demonstrated a wide array of different uses of the ecoroof space such as cell phone use and passing by. Our interviews with hospital ecoroof practitioners nationally indicate that roof design, maintenance, and programming around horticultural therapy can vary. Understanding what motivates decision makers to install hospital ecoroofs as well as barriers could help explain this variation. Our analysis of a national hospital database identified two factors which significantly predict whether a hospital has an ecoroof: the number of Medicaid patients and hospital type (non-profit, government, and privately owned). Qualitative analysis indicated that internal champions as well as external service providers can also increase the likelihood of hospital ecoroof installation. We conclude that therapeutic effects may vary by user type and activity and depend on roof design and goals. We further provide suggestions on how the design process could be expanded to promote stress reduction in the hospital environment through ecoroofs.