Air leakage through the building envelope into the building interiors has a considerable impact on the energy loads and consequently energy demand and energy costs of buildings. This phenomenon known as infiltration happens through various openings and venues in the building envelope varying from large openings such as doors and windows to minute cracks and crevices. In addition to impacting building energy loads, infiltration impacts indoor air quality and can result in moisture accumulation problems in the building envelope. A generalized review of infiltration that includes evaluation techniques and models, quantification, and interaction with other heat transfer phenomena is presented in this article.

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Purpose The public nature of water and wastewater construction capital projects has rendered design-bid-build (DBB) as the delivery method of choice for such projects over the past years. Shortcomings inherent to DBB have had a negative effect on the key performance indicators (KPIs) of these projects. Numerous studies have been published about the benefits offered by integrated project delivery (IPD) in improving the delivery of DBB projects. Links correlating IPD principles to improvements in KPIs of DBB construction projects have not been established scientifically, thus leaving owners with no guidance on which IPD principle(s) to implement in order to improve a particular project KPI. The paper aims to discuss this issue. Design/methodology/approach Actual data were collected from 43 water and wastewater construction projects – including two control projects with full implementation of selective IPD principles – and used to compute major projects KPIs. Regression analysis and a focus group are then utilized to determine the effect of each implemented IPD principle on various project KPIs. Findings Implementation of open communication was found to have a significant effect on reducing project cost overrun, and the co-location of teams significantly reduced the time to respond to RFIs. Collaborative decision making significantly reduced the cost of field rework. Other IPD principles showed less-significant effects on project KPIs and were concluded to be ineffective at improving the projects’ performance. Practical implications An implementation framework is developed that can guide utility owners on which IPD principle(s) to implement in order to improve specific project KPIs. Originality/value This study demonstrates that not all IPD principles will result in performance improvement of a project. A selective and cost-effective implementation of certain IPD principle will have to be based on the nature of the project and the particular KPIs targeted for improvement.