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.

The goal of this work is to better understand the influence of window U-factor and solar heat gain coefficient on residential space heating and cooling energy use in the United States. We calibrated our simulation models with residential energy use data and evaluated the affect of window U-factor and solar heat gain coefficient on space heating and cooling energy use. U-factor and solar heat gain coefficient have a comparable impact on heating energy use, whereas U-factor has a minor impact and solar heat gain coefficient has a strong impact on cooling energy use.

A small commercial building was monitored before and after energy-saving retrofits to study the impact of retrofits upon ventilation rates, humidity, building pressure, and air-conditioning energy use. Duct airtightness testing identified severe duct leakage as a significant source of uncontrolled airflow. Differential pressure and infiltration measurements using tracer gas indicated an attic exhaust fan as another significant source of uncontrolled airflow. Duct repair resulted in a 31% drop (30.5 kWh/day) in cooling energy and an increase in relative humidity from 72% to 76%.