Basic Documentation

Siemens Industry, Inc. Page 11 of 14
Document No. 149-488
Terminal Leakage
Air distribution systems for buildings are large,
custom, sheet metal structures built under tight cost
constraints. Typically, they leak. Leakage can waste
energy. When the supply ducts leak, conditioned air
gets lost on its way to the rooms. It adds to the total
energy load, without accomplishing a result. When
exhaust ducts leak, air is drawn from interstitial
spaces or other areas without improving air quality in
the zones.
Duct systems may leak where sections or
components are joined. They also leak through
certain components. Airflow control terminals have
openings for shafts, pipes, and access panels. Each
opening is a potential leak. Depending on the
intended application, terminals are built to varying
leakage standards. In a laboratory built to meet
sustainability goals, it is appropriate to select
terminals with Ultra Low leakage. These terminals
pass less than 1cfm at a static pressure of 1 in. WC,
compared to 3 cfm leakage from terminals with
"standard" construction. The incremental cost of
tighter terminal pays for itself in 3 to 5 years, early in
the useful life of the building.
The amount that an air system leaks depends
largely on the attention the mechanical installer pays
to sealing it. If you need well-sealed ducts to
conserve energy, you need to communicate that to
the mechanical contractors so they can select the
appropriate materials and construction processes.
Water Efficiency
Our use of water is recognized as another important
way a facility affects the environment. The LEED
rating system includes five points specifically for
water efficiency, covering landscaping, wastewater
treatment and overall reductions in water use. (Two
more ID points are expressly described for
‘exemplary performance’ in water conservation.)
Attention to the issue reveals opportunities for
efficiency: some particularly related to laboratories,
some more generally applicable.
High-Purity Systems
The work in many chemistry and biology laboratories
demands a grade of water more pure than municipal
tap water. Tap water typically contains particles,
dissolved organics and dissolved inorganics that can
disrupt laboratory research or analyses. Water
treatment systems remove these contaminants,
through a combination of technologies, including
reverse osmosis, deionization, UV photo-oxidation,
ultrafiltration, and microfiltration.
Today these treatment technologies are replacing
distillation because of the enormous energy savings.
To purify the same amount of water, it still may
consume 20 times as much energy as reverse
osmosis system. This fact eliminates distillation as
an option for sustainable facility.
In order to produce purified water for the lab, these
processes convert some of the tap water to
wastewater that flushes away the contaminants.
This “reject rate” can affect the overall water
consumption for facilities that require large volumes
of high-purity water. In the proposed standard,
16
ASHRAE limits the reject rate for laboratory
treatment systems to 60% or less. This target affects
equipment selection and system design.
Facilities that use large volumes of purified water
have the strongest reason to minimize the reject
rate. They often apply centralized, engineered water
treatment systems that can be optimized for low
water reject rate. Compared to systems that serve a
single room, central systems are more complex to
design, install and operate. Long term water
efficiency depends on regular maintenance by
specialists trained on the equipment. This is a good
approach for organizations that can realistically
commit to maintaining performance.
For smaller users, a trade-off in efficiency is often
made so that a simpler system can be installed.
Small reverse osmosis systems, sized for a single
laboratory, are designed with high reject rates to
eliminate the need for pre-treatment of the tap water.
Between the largest and smallest systems, there is
an intermediate class of equipment sized for multiple
labs (200 lph) that can be applied with reject rates
below 50%. Designers can choose a modular,
scalable approach, rather than a fully centralized
system. This combination of efficiency and flexibility
expands the possibilities for designers.
Rain Water Usage
Green design teams see rain water as a resource to
apply, reducing the load on municipal water utilities.
The system may be as simple as a collecting tank
that uses gravity to irrigate landscaping. Teams with
more ambitious goals apply more highly engineered
rain water catchment systems. Specific functions
16. ASHRAE, BSR/ASHRAE//USGBC/IESNA Standard 189P.