Wintertime window condensation problems were reported on the top two floors of a five-story, multi-unit residential building in central New York (7200, base 65° F heating degreedays ). Initially built as a five-story brick hotel at the turn of the century, the building was rehabbed into low-income apartments in the early 1990s. Ventilation in each unit consisted of operable windows and a single bath exhaust. Condensation on windows was severe enough to support fungal contamination in the first winter of occupancy.

Blower doors are used to measure the airtightness and air leakage of building envelopes. As existing dwellings in the United States are ventilated primarily through leaks in the building shell (i.e., infiltration) rather than by whole-house mechanical ventilation systems, quantification of airtightness data is critical in order to answer the following kinds of questions: What is the construction quality of the building envelope? Where are the air leakage pathways? How tight is the building? Tens of thousands of unique fan pressurization measurements have been made of U.S.

CO2-based demand-controlled ventilation (DCV), when properly applied in spaces where occupancies vary below design occupancy, can reduce unnecessary over ventilation while implementing target per-person ventilation rates.

Sealed attic construction, by excluding vents to the exterior, can be a good way to exclude moisture-laden outside air from attics and may offer a more easily constructed alternative for air leakage control at the top of residential buildings. However, the space conditioning energy use and roof temperature implications of this approach have not been extensively studied. A computer modeling study (Rudd 1996) was performed to determine the effects of sealed residential attics in hot climates on space conditioning energy use and roof temperatures.

A simple duct system was installed in an attic test module for a large-scale climate simulator at a U. S. national laboratory. The goal of the tests and subsequent modeling was to develop an accurate method of assessing duct system performance in the laboratory, enabling limiting conditions to be imposed at will and results to be applied to residential attics with attic duct systems. Steady-state tests were done at a severe summer condition and a mild winter condition. In all tests the roof surface was heated above ambient air temperatures by infrared lights.

Attic ventilation 1/150 and 1/300 rules of thumb were established to avoid problems from indoor moisture. In cold regions another strong reason to ventilate roofs that slope to cold eaves is to prevent the formation of problematic icicles and ice dams. Building heat, not the sun, is responsible for the large icings that cause such problems, and roof ventilation is a direct and effective way of solving them. The authors have instrumented buildings to determine attic ventilation needs to minimize icings and have developed design guidelines for natural and mechanical ventilation systems.

This study established a research facility where airflow velocities, temperature, and differential pressures could be measured at the ridge of an attic. Following the construction of a test building, sensors were constructed, calibrated, and installed inside the attic. Paired tests were performed for three different ridge vent treatments; two were rolled type vents and one was a baffled vent.

Current methods for designing exhaust stack height and exit velocity are based on avoiding contamination of the roof, walls, and nearby ground surface of the building on which the stack is located. Usually, no account is taken of the effect of adjacent buildings that add turbulence and increase dispersion if they are located upwind and may be contaminated themselves if they are downwind of the emitting building.

A three-dimensional computational fluid dynamics (CFD) analysis has been used to predict airflow patterns in laboratory fume hoods. The simulation includes bypass fume hood primary operational features including the top and bottom bypasses, front airfoils, and rear-slotted baffles. All results were validated experimentally, and the simulation was found to adequately predict fume hood airflow patterns. The results indicate that fume hood flow patterns are highly dependent on inlet flow boundary conditions so that the computation must include the near field room airflow.

Many methods of estimating energy savings from measured weather-dependent energy consumption data attempt to compensate for varying weather conditions between the pre- and post-retrofit periods by identifying an empirical model of pre-retrofit energy consumption and outdoor air temperature. Even though the pre-retrofit model may include a balance-point or change-point temperature, savings determined using this method implicitly assume that the indoor air set-point temperature and internal heat gains are the same during the pre- and post-retrofit periods.