Unintended Infiltration in buildings is responsible for a significant portion of the global housing stock energy demand. Today, the fan pressurization method, also known as blower-door test, is the most frequently used measurement method to evaluate the airtightness of buildings and determining the total air change rate of a building or a building element. However, the localization and quantification of single leaks in the building envelope remain difficult and time-consuming. In this paper, an acoustic method is introduced to estimate the leakage size of single leaks in buildings. Sound transmission measurements and measurements of airflow have been conducted in a laboratory test apparatus. The objective of this investigation is to compare acoustic measurements with airflow measurements of leaks under the same boundary conditions. The test apparatus consists of two chambers, which are separated by a test wall. This test wall represents a single characteristic air leakage path in the building envelope. Various types of wall structures with different slit geometries, wall thicknesses and insulation materials have been investigated. The acoustic measurements have been performed with a sound source placed in one chamber and ultrasonic microphones located in both chambers. The results of the acoustic measurements were compared to airflows through the test wall measured using a flow nozzle to provide estimates of the uncertainty in the acoustic approach.

We estimate postmeter methane (CH₄) emissions from California's residential natural gas (NG) system using measurements and analysis from a sample of homes and appliances. Quiescent whole-house emissions (i.e., pipe leaks and pilot lights) were measured using a mass balance method in 75 California homes, while CH₄ to CO₂ emission ratios were measured for steady operation of individual combustion appliances and, separately, for transient operation of three tankless water heaters. Measured quiescent whole-house emissions are typically <1 g CH₄/day, though they exhibit long-tailed gamma distributions containing values >10 g CH₄/day. Most operating appliances yield undetectable CH₄ to CO₂ enhancements in steady operation (<0.01% of gas consumed), though storage water heaters and stovetops exhibit long-tailed gamma distributions containing high values (∼1-3% of gas consumed), and transients are observed for the tankless heaters. Extrapolating results to the state-level using Bayesian Markov chain Monte Carlo sampling combined with California housing statistics and gas use information suggests quiescent house leakage of 23.4 (13.7-45.6, at 95% confidence) Gg CH₄, with pilot lights contributing ∼30%. Emissions from steady operation of appliances and their pilots are 13.3 (6.6-37.1) Gg CH₄/yr, an order of magnitude larger than current inventory estimates, with transients likely increasing appliance emissions further. Together, emissions from residential NG are 35.7 (21.7-64.0) Gg CH₄/yr, equivalent to ∼15% of California's NG CH₄ emissions, suggesting leak repair, improvement of combustion appliances, and adoption of nonfossil energy heating sources can help California meet its 2050 climate goals.

Light commercial buildings, one- and two-story with package roof-top HVAC units, make up approximately 50% (of the number of buildings) of the non-residential building stock in the U.S. Despite this fact little is known about the installed performance of these package roof-top units and their associated ductwork. These simple systems use similar duct materials and construction techniques as residential systems (which are known to be quite leaky). This paper discusses a study to characterize the buildings, quantify the duct leakage, and analyze the performance of the ductwork in these types of buildings. Over the 1996 and 1997 cooling seasons, this study tested twenty-five packaged roof-top systems in sixteen different buildings located in northern California. All of these buildings had the ducts located in the cavity between the drop ceiling and the roof deck. In 30% of these buildings, this cavity was functionally outside both the building’s air and thermal barriers. The effective leakage area of the ducts in this study was nearly 3 times that in California residential buildings [ELA25 (cm’/m’ floor area) 3.7 for light-commercial compared to 1.3 for residential]. For these systems, the average supply-side leakage rate was 26% of the system flow rate. This paper looks at the thermal analysis of the ducts, from the viewpoint of supply effectiveness. Conduction effectiveness gauges the fraction of the capacity available at the supply-air plenum that is delivered to a supply-air register. Effectiveness calculations are done on a register basis and include the length of a cycle, and whether the fan is always on or if it cycles with the cooling equipment. Combining effectiveness and leakage numbers yields delivery efficiency. The ten systems tested in 1997 had an average delivery efficiency of 65%.