Commissioning and Envelope Leakage: Using HVAC Operating StrategiesTo Meet Design and Construction Challenges

摘要

Successful HVAC design and efficient operation are inescapably linked to a "successful"building envelope design. From the HVAC system standpoint, a successful envelope must resistthe transfer of heat and moisture and minimize the exchange of air across its boundary. Whileintuitive, these goals are often relegated to second place in favor of creating an aestheticallypleasing structure or making an architectural statement. The construction industry oftenpresumes that if no water penetrates the building envelope, then the integrity of the system issatisfactory. But, scientific analysis and practical experience demonstrate that infiltration canlead to frozen pipes, condensation, and occupant discomfort.This paper contains an overview and examples of design and construction issues that leadto envelope leakage problems. The discussion includes identification techniques used to locateand quantify the leakage, operational ramifications associated with the leakage, and solutions tomitigate the leakage using HVAC operating strategies. For two of the examples, a test wasperformed based on ASTM-E-779-99 (Standard Test Method for Determining Air Leakage Rateby Fan Pressurization) to quantify the leakage rate and assess its impact on buildingpressurization. The results of these tests and other field experiences indicate that achieving acompletely airtight envelope is practically impossible. Thus, the architectural design andconstruction details targeted at providing an airtight envelope need to be supported by HVACdesign and operating strategies that will mitigate the impact leakage that will inevitably occur.