ASHRAE Journal - June 2019 - 62

2019

ASHRAE TECHNOLOGY AWARD CASE STUDIES

Perimeter
Radiant
Panels
Automated
Interior
Shading

Underﬂoor
Air
Distribution
FIGURE 1 A creative UFAD, plus radiant system design eliminated typical fan powered
boxes, ductwork and reheat.

The lighting design uses high efﬁcacy continuously
dimming ﬁxtures that are controlled based on available
daylight. The lighting design achieved a lighting power
density of 0.66 W/ft2 (7.1 W/m2). The result is a 57%
reduction over the ASHRAE Standard 90.1-2007 baseline
building's lighting energy consumption.
These energy conservation features combine to reduce
the annual energy cost of the Marine Way building by
40% over a Standard 90.1-2007 baseline building. The
ﬁnal energy model predicted the building's EUI to be
41.2 kBtu/ft2·yr (467.9 MJ/m2), before accounting for
renewable energy production. The building's 385 kW
roof-mounted photovoltaic system further reduces the
annual energy cost, resulting in a 55% annual cost savings over the Standard 90.1-2007 baseline, as well as
achieving a 24% renewable energy fraction.
Twelve months of measurement and veriﬁcation
(M&V) has recently been completed for the project,
which has revealed that the building is performing very close to what the energy model predicted.
The building is provided with an array of end-use
submeters, which allow trending of HVAC, lighting,
and receptacle consumption. Figure 2 compares the
measured against predicted consumption, showing lighting and HVAC consumption slightly below
predicted, while receptacle loads are either slightly
above or below predicted, depending on the month.
From an annual perspective, the building is consuming 5% more energy than predicted by modeling software, resulting in an actual EUI of 43.26 kBtu/ft2·yr
(491.28 MJ/m2·yr).

Indoor Air Quality

The UFAD system enhances IAQ by delivering low

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The Marine Way headquarters is Intuit's ﬁrst LEED Platinum Certiﬁed building.

velocity air directly to the occupied zone, which provides the highest ventilation efﬁciency possible (1.2),
per Standard 62.1-2007. The project pursued and
achieved the Increased Outside Air credit (EAc2) under
LEED v2009 by providing 30% more outside air than is
required by Standard 62.1-2007. The base requirement
was for 26,540 cfm (12 525 L/s) of total outside air, while
the design provides 44,235 cfm (20 877 L/s). MERV 13
ﬁltration is provided at the air handlers for both outside
and return air.
Because cool air is supplied from the ﬂoor and relieved
from above the occupied region, stratiﬁcation occurs
between the occupied zone and the unoccupied zone
above the occupants' heads, which efﬁciently removes
pollutants and reduces remixing into the occupied zone.
The UFAD system uses adjustable swirl diffusers in the
ﬂoor, which are reconﬁgurable based on changing ﬂoor
plans or an individual's request. ASHRAE Standard 55
recognizes that users with direct control over their thermal environment are more accepting of a wider range
of thermal conditions. Thus, this design approach aided
in achieving the Controllability of Systems-Thermal
Comfort LEED credit (EAc6.2).
The operational setpoints for both heating and cooling mode were designed to comply with the criteria set
forth in Standard 55, using air temperature setpoints of
74°F (23°C) for cooling and 70°F (21°C) for heating. The
CBE Thermal Comfort Tool was used to demonstrate
that these setpoints are acceptable for both men and
women wearing typical ofﬁce attire (summer clo of 0.96
and 0.67 for men and women, respectively). The mean
radiant temperature is simulated at approximately
2°F (1.1°F) below the air temperature to account for the

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ASHRAE Journal - June 2019

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