By
Kimberly Vermeer
In a few short years, green building has gone from being an interesting
but not well-understood concept to being the expected best practices
for affordable-housing developers. The Federal Home Loan Bank of
Boston (the Bank) has been a leader for a number of years in encouraging
Affordable Housing Program participants to consider smart growth,
energy conservation, and green design in projects it has funded.
As more lending programs offer bonus points for green building elements,
require energy conservation and healthy housing components, or ask for “LEED
certifiability” in order to qualify for funding, affordable-housing developers
are realizing that the time has come to go green. Success in green building
requires developers to use new approaches to the development process,
especially “integrated design,” and new tools such as
energy modeling.
The two most common programs offering guidance for affordable-housing
developers are the U.S. Green Building Council’s (USGBC) Leadership
in Energy and Environmental Design program (LEED) and the Enterprise
Green Communities Initiative. The original LEED standard is suitable
for larger-scale projects, while the LEED for Homes program is designed
for use in single-family and low-rise multifamily residential projects.
A program leader for the affordable-housing industry is the Enterprise
Green Communities Initiative (GCI) offered by Enterprise Community
Partners (formerly the Enterprise Foundation). GCI emphasizes mandatory
criteria as well as points earned from optional criteria. The GCI
program offers grants and financial incentives directly or through
state partnerships.
A goal of the program scoring systems is to encourage “integrated
design” so that green building goals balance energy and water
conservation, healthy indoor environments, and the larger environmental
impact in a cost-effective way over the project’s life cycle.
This green building buzzword means having the whole team − architects,
engineers, property managers, and often community members or potential
residents − participate in goal-setting and preliminary design
development. In practice it means having the engineers − civil,
structural, mechanical, electrical, and plumbing − involved
much earlier in the design process than they have been.
Energy modeling is an important tool that helps with the integrated
design process and supports the case for first-cost investments for
long-term savings. Many project sponsors have used the Energy Star
Homes Program for single-family and low-rise multifamily housing
and are familiar with the Home Energy Rating System Program (HERS)
upon which it is based.
A more sophisticated tool for larger multifamily projects is DOE
2.0-based energy modeling. These models are tied to ASHRAE 90.1,
a design standard for commercial buildings and a key benchmark in
both the LEED and GCI programs.
HERS uses energy models such as REMRate that benchmark a proposed
building against a hypothetical home built to the International Energy
Conservation Code (IECC). The system is built on a 100-point scale
where 100 equals the energy consumed by the home built to the IECC
and zero equals a home that consumes no net energy. A home must score
at least an 85 − in other words be at least 15 percent more
efficient than the IECC benchmark home − to qualify as an Energy
Star Home. One limitation of this system is that the model does not
convert the score to dollars and budgets, making it difficult to
calculate paybacks or life-cycle costs.
DOE 2.0 models are built on an energy model originally developed
by the U.S. Department of Energy. Software products such as Visual
DOE and E-Quest make the models more user-friendly, although use
of the models is still a specialized skill. Other DOE 2.0-based software
such as TREAT is useful for evaluating existing properties scheduled
for rehabilitation. These energy models take the basic building geometry,
size, footprint, orientation, and envelope and system characteristics
such as amount of insulation, percent of glazing on each façade,
and efficiencies of boilers, and estimate the energy consumption.
Then the modeler can check the impact of changing the building orientation,
adding more insulation, using better windows, or installing advanced
lighting on the predicted energy performance. With cost information
it is possible to estimate paybacks and life-cycle costs.Using these
models, developers and design teams can understand what it takes
to achieve energy performance 20, 30, or 50 percent better than local
energy codes or the ASHRAE 90.1 standard.
The design development for the rental and retail building at the
Kasanof Bakery site in Roxbury, Massachusetts, a green project under
development by Nuestra Comunidad Development Corporation (NCDC),
offers an example of how this works in practice. NCDC decided to
participate in the GCI and to use the Green Communities Criteria
as the project benchmark. The entire team met for a charette-style
workshop to compare the preliminary design to the GCI criteria and
see where the proposed project met the standards and where additional
steps were needed.
A set of green goals was developed, including the goal of using 50 percent
less energy than allowed by the Massachusetts Energy Code, to be achieved by
a combination of building envelope, systems, lighting choices, and onsite renewable
energy. Another green goal was to incorporate an active fresh-air delivery
system for the apartments for superior ventilation and indoor air quality.
The design team and consultants worked together to develop three advanced performance
scenarios for the energy modeler to evaluate.
Scenario one, primarily improvements in insulation levels and boiler
efficiencies, approximated the Energy Star Homes standards and was
estimated to be about 22 percent better than code.
Scenario two added energy recovery to the ventilation system, changed
the heating and cooling from fan coils to water-source heat pumps,
and assumed advanced lighting, a traction elevator, and premium efficiency
motors and pumps. This scenario predicted performance 42 percent
better than code.
Scenario three included an upgrade to a ground source heat pump,
increasing the estimated building performance to 48 percent better
than code. A proposed 50-kilowatt photovoltaic system, made possible
through a joint Massachusetts Technology Collaborative (MTC)/ MassHousing
grant program, brought the total energy performance estimate to 53
percent better than code. The cost analysis indicated that scenario
two would have the biggest impact on operations, but that the additional
cost to move to scenario three would have a 12-year payback, a worthwhile
investment for a long-term owner and operator like Nuestra Comunidad.
Energy modeling is an essential tool for green building, but it does
add another set of experts and costs to early project planning. For
some projects the analysis and technical support offered at no or
low cost from the Energy Star Homes program will be enough. Nuestra
Comunidad was able to offset much of the extra design and consultant
cost from grant sources through GCI and the MTC/MassHousing program.
Utilities may also offer some funding to offset these costs. By supporting
integrated design, energy modeling helps affordable-housing developers
to succeed at building green. T
Kimberly Vermeer is principal at Urban Habitat Initiatives, a
consulting and development
company dedicated to sustainable design, energy efficiency, environmental
consciousness, and occupant health in housing and communities. |
