New Tools Influence Window Design
Design Resources Facilitate Efficient Choices
By Nils Petermann and Kerry Haglund
Façade design begins in the early concept phase,
in which it may be difficult to conduct detailed engineering analyses
of the impacts on heating, cooling and lighting systems. But even rough
early assessments can help designers take steps toward balancing daylighting,
thermal performance and comfort considerations. To facilitate such assessments,
Lawrence Berkeley National Laboratory (LBNL) and the University of Minnesota
have developed online resources that designers can use to identify promising
façade designs and quantify the energy and comfort impacts quickly.
These resources include the Façade Design Tool (FDT) and the Commercial
Fenestration (COMFEN) energy simulation software.
The FDT is available free of charge on the recently updated Windows for
High-Performance Commercial Buildings website, www.commercialwindows.org.
This website, hosted by LBNL and the University of Minnesota, is a comprehensive
resource for performance data on the energy-efficiency, interior environment
and technical considerations that influence window design decisions. The
FDT gives designers the means to compare design strategies for glazing,
window area and shading quickly without the need for detailed input. Annual
energy use, peak demand, daylight illuminance, glare and thermal comfort
impacts are based on pre-simulated performance data specific to the climate
and façade orientation. This pre-simulated data assumes a typical
perimeter zone oriented in one of the cardinal directions. This allows
for a rough assessment, based on which designers can quickly narrow down
their options to the more promising ones and take note of likely impacts
on energy use, lighting strategies and HVAC design. To supplement the
quantitative assessments, the website also offers qualitative background
information on relevant performance considerations, design guidance, codes
and standards, as well as case studies.
Getting The Data
The FDT uses pre-simulated data for 17 cities that has been generated
with the COMFEN schematic design and simulation tool, available for free
download on http://windows.lbl.gov/software/comfen/comfen.html.
COMFEN is more versatile than the FDT.
It provides in-depth data and thus supplements the quick insights that
designers can gain by starting their analysis with the online tool. COMFEN
enables the architect or designer to do “what-if” scenarios on specific
façade, lighting and shading designs with the EnergyPlus simulation
engine. Because COMFEN focuses on a specific zone within a building, it
requires only limited input and allows its users to focus on the energy,
daylighting and comfort impact of fenestration options without having
to model entire buildings.
COMFEN also offers glazing contractors a tool for communicating the impact
of glazing choices to their customers. It presents the simulation results
in easily accessible graphics that help to visualize the benefits of glazing
and shading choices.
The FDT and COMFEN provide early information on how different façade
and daylighting choices may impact energy use and occupants. Even though
these early insights do not substitute for in-depth modeling, they allow
early assessments of façade performance and facilitate integrated
design considerations during conceptual design and design development.
Nils Petermann is a program manager at the Alliance
to Save Energy and a partner in the Efficient Windows Collaborative.
Kerry Haglund is a senior research fellow at the Center for Sustainable
Building Research at the University of Minnesota.
© Copyright 2011 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.