Just how much do density and green space affect urban energy use? It
depends on where you live.

Date:
November 9, 2021
Source:
Drexel University
Summary:
Tree cover, paved surfaces, the spacing of buildings and green
spaces all affect how much energy it takes to offset the 'urban
heat island effect.' But the relative contribution of these urban
form factors has been a matter of debate. Researchers seeking to
clarify the matter presented a method for measuring the impact of
each of these factors -- and revealed that their contribution to
building energy use varies between cities.



FULL STORY ==========================================================================
In the battle to mitigate "city heat" and conserve the energy it takes to
keep folks comfortable inside, recent research has shown the importance
of urban planning. Tree cover, paved surfaces, the spacing of buildings
and green spaces all affect how much energy it takes to offset the
"urban heat island effect." But the relative contribution of these
urban form factors has been a matter of debate. In a recently published
journal paper, researchers in Drexel University's College of Engineering, seeking to clarify the matter, presented a method for measuring the
impact of each of these factors -- and revealed that their contribution
to building energy use varies between cities.


========================================================================== Buildings contribute more than half of greenhouse gas emission of North American cities, due in large part to the energy they use for heating
and cooling. In recent decades, climate scientists have identified the
heat- amplifying effect of surfaces like paved roads, parking lots and
building roofs, as a prime culprit behind the steady increase in cities'
energy use.

"Form, through the layout and orientation of urban blocks, vegetation
and high albedo materials, and the shading effect of surrounding blocks, changes the microclimate within building networks," the researchers
wrote in the journal Buildings.

Managing the microclimate to avoid excess heating is becoming a priority
for cities as they continue to change and grow. But countering urban
heat island effect isn't as straightforward as planting more trees,
building parks and increasing green space between new buildings. Perhaps counterintuitively, research in the last few years suggests that
increasing urban density - - packing people more closely in rowhomes
and apartment buildings -- may reduce energy use, by comparison to a
more sprawling layout.

To understand the relative energy-saving benefits of a few more units
in an apartment building versus a few more trees next to it, Drexel's
Nariman Mostafavi, PhD, who led the research, and his collaborators,
gathered public geospatial data on surface temperature, tree cover
and impervious surfaces; U.S. Census population data; and open-source information on building characteristics (i.e. type, age, value) and
housing unit layouts in several U.S. metropolitan areas that track and
report building energy use.

The team looked at 12,700 buildings situated in areas with five
different levels of density located in Washington, D.C., New York City, Philadelphia, Chicago, Seattle, Minneapolis and Austin, Texas. Using
a step-by-step method to analyze progressively larger groupings of
buildings in each type of density level, the team was able to tease out
the distance within which buildings share a microclimate pertaining to
building energy consumption.



==========================================================================
"The first question we wanted to answer was what distance from a
building shall be taken into account when the impact of urban density
on building energy is of concern," Mostafavi said. "Secondly, we wanted
to understand what the relationship was between different urban form
parameters and building energy use, in different cities." Their efforts
aimed to reveal how far from a building vegetation, or pavement, or other buildings could be located and still influence its energy use, also to determine which factors had a larger impact on building energy use.

The results suggest that in sprawling cities, like Austin, the morphology within a 1.5-kilometer radius better explains the urban form effect on
energy use; while in a more densely packed city, like New York City,
the radius of impact for urban form is more relevant within half a
kilometer around a given building.

But the most significant finding, according to Mostafavi, might be
that the relationship between urban form/density and energy use varies
across cities.

"These findings show that energy use is related to density but it's city specific and distance specific," Mostafavi said. "The important thing is
that this methodology we developed is a way for each city to understand
the impact of urban form and density within their city and incorporate
it in future development plans." Of all the form factors included in
the study, tree-cover area, impervious surface area and building density
showed a more consistent impact across all urban areas studied.

To get a clearer picture of the factors that affect building energy use,
the researchers suggest, more cities should track energy use data and
compile datasets on building stock. While they were able to obtain energy
use data for the seven cities studied, the research could have been much broader if more cities made this information available, or if reporting
was standardized in urban areas across the country.

"With the current trends of urbanization and the expected
2.5 billion people urban population growth projected globally
through 2050, energy demand of cities will only increase in the
future. Cities are a big problem for us when it comes to energy
consumption and carbon emissions, but at the same time they could
also be the solution," Mostafavi said. "If we want to address the
environmental crisis -- in a way that will have a big impact --
reducing the energy consumption of cities is a great place to start." ========================================================================== Story Source: Materials provided by Drexel_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Nariman Mostafavi, Mehdi Pourpeikari Heris, Fernanda Ga'ndara, Simi
Hoque. The Relationship between Urban Density and Building
Energy Consumption. Buildings, 2021; 11 (10): 455 DOI:
10.3390/buildings11100455 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211109120329.htm

--- up 9 weeks, 5 days, 9 hours, 25 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)