This document is dedicated to exploring the options for increasing the SQFT of naturally ventilated spaces in Oregon. Because naturally ventilated buildings offer potential large reductions in energy, the goal of this site is to gather input from design professional on how to incentivize the building practice. You can freely edit the site here: http://natvent.wetpaint.com/ Savings Potential Typically incentives are in place to reduce energy consumption. Although predicted energy savings for natural ventilation is high, the predictions rely on a range of difficult variables. The following was published in the June 2006 issue of the ASHRAE Journal, "Few studies have evaluated energy-saving potential of "hybrid ventilation" in the U.S. to date, all of these studies have limitations. Emmerich, et al., carried out simulations comparing "hybrid ventilation" performance and conventional systems conditioning a five-story, 46,000 ft2 (4273m2) office building in five different U.S. climates during February, April, and July. They found that HV could dramatically reduce (>50%) fan energy consumption in all cities, except during colder months in the colder climates. The study also found major reductions (~50%+) in cooling loads in all but the hot and humid climates. On the other hand, HV moderately (~10%) increased heating loads in the colder climates." One of the more difficult design variables is predicting the acceptable indoor temperatures. ASHRAE Standard 551 published an adaptive temperature range for occupants where higher temperatures are acceptable in the summer. The outdoor air temperature is acceptable for a large number of hours in the Pacific Northwest(citation needed). Current Incentive Path Current incentives for naturally ventilated spaces require sophisticated energy simulation models to predict energy savings. The three primary incentive providers for energy reductions are the Oregon Department of Energy, the Energy Trust of Oregon, and the LEED Rating System (LEED does not specifically provide incentives but incentives are based on achieving specific LEED points). The incentives are based on the simulated electricity or natural gas savings. Although it is possible to estimate energy savings, there are several disadvantages to requiring all project teams to attempt this. First, it uses up valuable resources to perform the modeling and calculations. This time could be spent on more practical design issues that need to be resolved. There is no single all-in-one modeling software application. Modelers are forced to juggle between multiple software applications as well as hand calculations to approach reasonable projections. Finally, there is little modeling and design experience in the building community and designers open themselves up to liability when energy predictions are not realized. New Incentive Path The goal of a new natural ventilation incentive is to,
Characteristics for a new incentive might include:
Design The CIBSE Natural Ventilation guideline states, "Natural Ventilation systems need to be designed to achieve two key aspects of environmental performance:
Definitions Demand Control Ventilation: Automatic reduction of outside air below design rates when actual occupancy is less than design typically determined by occupancy indicators; such as, time-of-day schedules, a direct count of occupants, or an estimate of occupancy or ventilation rate per person using occupancy sensors such as those based on indoor CO2 concentrations. Local Stack Ventilation: A design strategy where the distribution of a window open area in the vertical plane induces ventilation; such as, low to high level windows. Mechanical Ventilation: ventilation provided by mechanically powered equipment, such as motor-driven fans and blowers, but not by devices such as wind-driven turbine ventilators and mechanically operated windows. (ASHRAE 62.1-2004) Mixed-mode Ventilation: Mixed mode ventilation stretches the performance of natural ventilation by using mechanical systems only when and where necessary. Mixed mode ventilation strategies include three distinct approaches; contingency, complementary and zoned. (CIBSE Guide F - 2008) Natural Ventilation: Ventilation design relying on a range of techniques which maximise the potential of the stack effect, using air passages through doors, windows, or other intentional openings at differing heights and wind effects. Passive Conditioning: Uses the building layout, fabric and form to provide thermal comfort and/or ventilation to a conditioned space using non-mechanical forms of heat transfer and air movement; such as chilled beams, solar heat gain, building mass, and stack effect. Passive Stack Ventilation: Ventilation by generating a column of air at higher temperature, creating pressure differences, and giving rise to air movement through design techniques; such as, shafts, solar chimneys, and atriums. (CIBSE Guide F - 2008) Passive Ventilation: Uses the building layout, fabric and form to provide natural ventilation to a conditioned space using non-mechanical forms of heat transfer and air movement; such as stack effect and cross ventilation. Ventilation: is the process of supplying air to and removing air from a space for the purpose of controlling air contaminant levels, humidity or temperature within the space. (ASHRAE 62.1-2007) Resources "Natural Ventilation in Non-Domestic Buildings" CIBSE 2005 "Wind-driven Natural Ventilation Systems" BSRIA 2005 "Natural and Hybrid Ventilation" ASHRAE Journal June 2006 SIGNED Tom Hudson - Green Building Services Mark Heizer - Interface Engineering Footnotes 1. ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy |