E. Gregory McPherson

Impacts of vegetation on residential heating and cooling

Computer simulation has been used to test the effects of irradiance and wind reductions on the energy performance of similar residences of 143 m2 in four U.S. cities — Madison, Salt Lake City, Tucson and Miami — representing four different climates. Irradiance reductions from vegetation were modeled using SPS, which simulates shade cast from plants on buildings, and MICROPAS, a microcomputer-based energy analysis program. Space cooling costs were found to be most sensitive to roof and west wall shading, whereas heating costs were most sensitive to south and east wall shading. Irradiance reductions were shown to substantially increase annual heating costs in cold climates (

Effects of Three Landscape Treatments on Residential Energy and Water Use in Tucson, Arizona*

128 or 28% in Madison), and reduce cooling costs in hot climates (

Geometric solids for simulation of tree crowns

249 or 61% in Miami). Dense shade on all surfaces reduced peak cooling loads by 31% – 49% or 3108 – 4086 W. A 50% wind reduction was shown to lower annual heating costs by

16. Functions of buffer plantings in urban environments

63 (11%) in Madison, and increased annual cooling costs by

A community forestry planning process: Case study of citizen participation

68 (15%) in Miami. Planting designs for cold climates should reduce winter winds and provide solar access to south and east walls. This guideline also applies for temperate climates, however it is also important to avoid blocking summer winds. In hot climates, high-branching shade trees and low ground covers should be used to promote both shade and wind.

RAINFALL INTERCEPTION BY SACRAMENTO'S URBAN FOREST

Abstract Vegetation can reduce the cooling loads of buildings in hot arid climates by modifying air temperature, solar heat gain, longwave heat gain, and heat loss by convection. However, savings from reduced mechanical cooling may be offset by increased irrigation water costs. In this study, three similar 1 4 -scale model buildings were constructed and surrounded with different landscapes: turf, rock mulch with a foundation planting of shrubs, and rock mulch with no plants. Irrigation water use and electricity required to power the three room-sized air conditioners and interior lights were measured for two approximately week-long periods. Electrical energy consumed for air-conditioning by the rock model was 20 – 30% more than for the turf and shade models. Factors accounting for these differences in energy performance include dense shade that substantially reduced solar heat gain for the shaded model, a 16% difference in longwave radiation flux between the rock and turf treatments, and a maximum drybulb depression of 4 °C over the turf compared with the rock. Air-conditioning savings exceeded water costs for shade treatments that were simulated to receive moderate and low amounts of irrigation water. These preliminary findings suggest that the localized effects of vegetation on building microclimate may be more significant than boundary layer effects in hot arid regions.

BENEFIT-COST ANALYSIS OF MODESTO'S MUNICIPAL URBAN FOREST

Abstract Geometric solids are used to simulate tree crowns and their shadows. If real tree crowns cannot be accurately modelled by standard geometric shapes, inaccurate estimates of shadow-pattern location can result. This error may cause substantial inaccuracies in subsequent calculations of tree shade effects on space heating and cooling costs, as well as in estimates of crown volume and leaf surface area. This study found no statistically significant difference between formula- and photoestimated tree crown profile areas when open-grown trees were assigned geometric shapes with a template in the field. Less than 10% mean difference was found between the measures for three crown shapes; parabaloids, vertical ellipsoids and horizontal ellipsoids.

EFFECTS OF TREE COVER ON PARKING LOT MICROCLIMATE AND VEHICLE EMISSIONS

Abstract Buffer plantings are linear strips of vegetation that have been either retained or purposefully planted in urban environments. As biologically diverse ecosystems interspersed among much simpler systems, buffer plantings function as environmental regulators that help stabilize the urban ecosystem while simultaneously separating incompatible land uses and providing visual amenity values. Sensitive land planning integrates existing buffers and new plantings into the urban fabric to maximize potential benefits. Mandatory tree protection and planting programs provide planners with a means of promoting the use of buffer plantings to enhance the livability of our cities. A comprehensive program would restrict the removal of existing vegetation, provide protective measures for vegetation not removed during development, and require planting of additional buffers with new developments. Standards that offer developers a variety of options to achieve a specified level of performance are currently preferred by most planners and developers. Further research is needed to help designers to design buffers that provide the functional benefits required, and which are relatively inexpensive to plant and maintain.

ENERGY CONSERVATION POTENTIAL OF URBAN TREE PLANTING

Abstract Efforts to manage the urban forest may be hampered by inadequate budgets and unsympathetic politicians. Public involvement may reduce these obstacles by cutting operating costs and increasing opportunities for program funding. This paper describes a community forestry planning process that was implemented by citizens with little previous urban forestry experience. Major components of the process are described and illustrated using a case-study example.