inside ases | chair’s corner
design Beyond Parking
How to build a garage for a future with fewer cars: Plan for conversion to higher-value use.
By JOHN REYNOLDS,
FAIA
John Reynolds, FAIA,
is chair of the American
Solar Energy Society
Board. Contact him at
chair@ases.org.
Note: This is my last column, as my long-time
friend and colleague Margot McDonald becomes
our new ASES Chair in
January. I look forward to
her contributions.
My least favorite part of today’s cityscape is the ubiquitous parking lot. Typically barren, often potholed, these gaps in our urban centers speak
of abandonment and neglect. They are ghosts of the buildings that were destroyed.
I want a canopy of trees in these urban mini-deserts.
Trees give welcome summer shade, provide oxygen and
bring a third dimension, creating a space, rather than a
void, in which to park. Trees bring a fourth dimension
as well: time. With their seasonal change, trees bring a
substantial organic presence to an otherwise unrelentingly
geometric environment. Maintenance folks object to the
dropped leaves and twigs, and trees harbor birds that drop
far worse. But trees remain an amenity that too few parking
lots have utilized.
Some parking lots now sport canopies of photovoltaic
(PV) arrays. These provide shade, and are less welcoming
to birds. They bring daily change of light, with tracking
PV modules. An example is the elegant PV canopy over
the parking lots at Springs Preserve in Las Vegas (springs
preserve.org). With many small, two-sided PV tracking
modules above and a white reflective sheet below, this
canopy creates an attractive and slowly varying shadow
pattern on the cars and pavement below. And what a great
potential service for parked electric cars!
John REynoldS
The Springs Preserve parking lot in Las Vegas uses single-axis tracking modules
to provide 409 kilowatts of
peak capacity.
With greater urban density, consider the many multi-story parking garages we have constructed. What if we
required new parking garages today to encourage future
renovation for other uses, rather than demolition? How
might we resolve the design struggle between today’s car
parking economy versus future office or residential daylighting and ventilation?
For efficient use of parking volume, sloped floors, rather than horizontal floors served by ramps, are often used
throughout parking garages. Eliminating ramps stores more
cars but makes renovation almost impossible. Low ceilings in parking garages require less overall building height
but produce poor internal daylighting when the building is
renovated. The higher the ceiling, the deeper the daylight
penetration, resulting in electricity savings for lighting. Low
ceilings also inhibit good interior air quality, making cross
ventilation more difficult and allowing fewer cubic feet of
air per occupant. This results in quicker fouling; think of a
goldfish in a small bowl versus a larger bowl.
One bright spot: Today’s typical concrete parking
structure promises excellent thermal mass for solar heat
and for passive cooling by night ventilation. And with
adequate ceiling height, the 60-foot (20-meter) width of
a parking bay converts readily to a central corridor, with
daylit offices or apartments with balconies on either side,
including possibilities for cross ventilation.
Some design guidelines for multi-story parking garages: First, strive for a building plan elongated along the east-west axis to maximize north- and south-facing windows. This
enables easier control of daylight and solar access. Next, provide horizontal parking floors, with ceiling heights proportional to floor width, optimizing daylight and natural ventilation. Roughly, if the floor-to-floor height is distance H, then
the maximum overall width of the parking floor is 5H. Thus,
in a 60-ft wide parking bay, a 12-ft minimum floor-to-ceiling
dimension is necessary. Even higher ceilings would give more
options for future renovation, such as a raised office floor to
accommodate forced air and utilities distribution.
Next, consider the future role of the ramps that serve
the parking floors. In an elongated central atrium, provide a
two-way ramp between two 60-foot parking bays. The overall
north-south width of such a structure would be, at minimum,
150 feet, allowing a 30-foot-wide central space that begins life
filled with ramps and transitions to a central daylit atrium as
ramps are gradually removed from the top down. However,
the higher the floor-to-floor, the longer the ramps needed
between them, and the wider the atrium needed, to assure
daylight to the lowest floors. The top floors become the first
to transition to offices or residences. The ramps themselves
could be made of recyclable materials, such as steel or aluminum grates, bolted in place for easy removal later. As ramps
above are removed, a glass atrium cover could protect the
air quality of the floors above from autos below. This cover
would also be lowered as ramps successively disappear.
And how might tenants be lured to move into the
top floors first? From the beginning, provide PV panels
overhead to shade the rooftop parking stalls. When cars are
banned here, sunny gardens and PV-shaded recreational
areas result. With the first renovation, tout the top floor’s
access to daylight and long-range view. Promise (
temporarily) guaranteed parking spaces on the floor immediately
below; after all, the highest floors are the last to fill in the
typical parking garage. Why promise parking in a transition-oriented building? Because the transition has just started,
justifying only one or two renovated floors so far.
Ultimately, such a building probably retains a ramp only
to below-grade floors, for limited parking and vehicular
deliveries. The central daylit atrium transforms to a central
social space with retail space at the atrium floor.
