Construction Today - January 2017 - 15
How Does a Project Like the
Distillery Get There?
Through radical simplicity and rigorous
attention to detail, a Passive House project
combines a super-insulated, airtight envelope with an intelligent ventilation system
and passive solar strategies. Collectively,
these integrated measures substantially
minimize heating and cooling loads by 80 to
90 percent, reducing overall energy demand
by up to 50 to 60 percent and realizing extreme thermal stability.
The Distillery is designed to incorporate
these principles carefully through traditional building methods and readily available
products. The building is podium construction - a wood-framed (Type 5) building
over a concrete and steel (Type 1) deck. Four
stories of panelized wood construction -
with wood stud walls and prefabricated
open web trusses - sit above two levels of
garage and commercial space. This standard
construction methodology is employed with
careful emphasis on the components critical
to realizing a Passive House project:
1. Thermal Protection - The building envelope's walls, roof and
floor are designed with enhanced insulation both within cavities
and continuously at the exterior to minimize thermal bridging. The
2x8 wood stud walls filled with cellulose insulation are augmented
with three inches of rock wool on the exterior for an R-value of 37.
At the roof, two inches of minimum continuous EPS sits on top, and
the open web roof truss cavity is filled with cellulose for an R-value
of over 70. At the separation between the parking and commercial
space and the residences above, six inches of continuous EPS provide an R-value of 30.
2. Air Tightness - A continuous airtight barrier carefully wraps
the entire Passive House envelope. Zip sheathing at the walls and
roof is tied to both liquid applied air barriers at elevator shafts and
a continuous poly vapor barrier at the floor. Joints are lapped and
taped. With air tightness, the products are simple, but the attention
to detail and the sequencing become critical to ensure continuity
and, therefore, performance.
3. Windows/Doors - As the largest penetrations in a thermal/airtight envelope, appropriately sized and quality windows are fundamental. Thermally broken, triple-glazed windows and doors within
the PH envelope ensure an optimal envelope. The percentage and
location of glazing are carefully considered, and shading is provided
to ensure appropriate amounts of solar gain when needed.
4. Continuous Ventilation - With infiltration all but eliminated,
the incorporation of heat recovery or an energy recovery ventilator
(ERV) is essential. Not only does it continuously supply filtered air
and exhaust stale air, but by passing incoming and outgoing air
through this heat exchanger, it also minimizes the temperature delta
of the incoming air. In the Distillery, each unit has a small ERV in a
closet at the exterior wall, which minimizes the insulated intake and
5. Heating/Cooling: Minimal active heating or cooling systems
are then required, and provided in the form of individual air source
heat pumps at each unit.
CPHC Associate is an
architect, planner and
urban designer who
combines optimism and
pragmatism to design
that strengthen communities and celebrate the
uniqueness of place. She
has worked on a broad
array of project types and
scales, from large, multiphase master plans and
design and construction
of new multifamily developments to strategic
infill, adaptive reuse and
Her work has achieved
LEED certification at
numerous levels as
well as one of the first
Passive House certified
multifamily projects in
New England. She is
a frequent speaker on
topics including Building
Reuse and Passive House
design. She received a
B.A. from Dartmouth and
an M.Arch and Master of
City Planning from MIT.
Radical But Realistic
While the enhanced thermal envelope and detailing can be a premium, this is offset by much reduced heating and cooling equipment
and associated ductwork. When we take into account a substantial
life-time reduction in operating cost, any initial cost premium
should see a payback of only a few years. Should renewable energy
be an option, Net-Zero or Net-Positive becomes easily feasible.
In the context of properties that will be owned and managed for
years to come, this makes particularly eminent sense. Coupling the
lifetime of savings in energy use and associated operation costs with
the substantially higher level of comfort and indoor air quality, the
Passive House standard would seem to be ideally suited for multifamily housing and any other long-term assets.
JANUARY 2017 CONSTRUCTION-TODAY.COM
per gallon of our buildings, as heating and
cooling typically comprise roughly one half
of a building's total energy use. Air tightness
is critical to energy but is also fundamental
to building durability and moisture control.
Primary energy represents our true carbon
footprint, taking into account not only all
energy used on site, but also how we source
our energy and what is lost in translation.
Together, these three criteria ensure that
we are building true value - high-quality
buildings that are intended to endure and
to perform optimally both for the occupants
and the owners. While the specific numbers
associated with each of the criteria may be
difficult to digest, their exceptional nature
becomes clearly apparent in comparison.
Relative to these criteria, a Passive House
building typically performs four to five times
better than its code-compliant counterparts,
and still two to three times better than comparable LEED Platinum projects.