A few obvious factors come to mind when high-rise building owners and managers think about preparing for and recovering from a natural disaster: creating emergency plans, establishing reliable back-up power, forming business continuity strategies to preserve data … and the list goes on.
But as New York continues its recovery from Hurricane Sandy, the recommendations released in a report from Mayor Michael Bloomberg and City Council Speaker Christine Quinn are a good reminder that there are other things to think about when preparing your facility for a possible disaster.
The report, which created by the 200-member New York City Building Resiliency Task Force, outlines steps that will strengthen New York’s buildings and standards/codes.
This panel of experts was assembled at the request of Bloomberg and Quinn after Hurricane Sandy struck in October 2012. In the report, they make 33 recommendations that address resiliency for commercial facilities, multi-family housing, and hospitals. These recommendations are being proposed to help existing New York facilities withstand natural disasters, as well as to ensure that future buildings can do the same.
While some of the recommendations made by the Building Resiliency Task Force may seem obvious, these four factors stand out as issues you might not typically associate with disaster readiness … but should.
New York City regulations currently mandate light-colored roof coatings for flat roofs; however, dark (non-compliant) coatings are still being sold. The Building Resiliency Task Force recommends that this code be expanded to include pitched roofs as well, and that it also prohibit companies from selling dark roofing materials to commercial building owners.
But how do light-colored roofs relate to disaster preparation and recovery? Because white or light-colored roofs reflect light and heat back into the atmosphere instead of transferring it to the building below, they help cool buildings and cities.
Not only can dark roofs contribute to the urban heat island effect (which is an increase in ambient air temperature in urban areas), but these warmer air temperatures can increase cooling demands in buildings and affect indoor comfort during warm months.
In case of a natural disaster that leads to a utility failure, tenants and occupants may need to shelter in place for several days. For this reason, commercial buildings, hospitals, and multi-family housing facilities need to be designed to maintain habitable temperatures for as long as possible. White or light-colored roofs can help keep indoor temperatures at comfortable, livable levels longer than dark roofs.
The goal of this new code proposal is to reduce urban heat island temperature impacts so that electricity use is minimized during times of peak demand (which could also help reduce blackouts), and to minimize the negative impact on indoor temperatures.
Some studies have shown that roofs painted with commonly used elastomeric acrylic white exterior paint can lose up to half of their solar-reflectance capabilities within several years (most likely due to dirt and particulate build-up).
Regular washing of white roofs is beneficial to keep them performing as efficiently as possible. But because of how difficult this task can be, the Building Resiliency Task Forcereport recommends that building owners and managers consider self-cleaning cool roof coatings that can prevent light-colored roofs from darkening over time.
R-Values of Roofs, Walls, and Windows
Because of the direct connection between the level of insulation and air sealing in a building’s façade and the internal temperature of a building, the Building Resiliency Task Forceis looking into a code recommendation that would require all building envelopes in new construction projects to achieve the following minimum R-values and airtightness levels:
- Wall R-values of R-25
- Roof R-values of R-50
- Window assembly R-values of R-4.3
- Airtightness of less than 1.5 ACH (air changes per hour) at 50 Pa (pascals)
According to panel experts on the Task Force, when outdoor temperatures reach levels below the freezing point, interior temperatures can plummet by 15 degrees within hours in a poorly insulated facility with high infiltration rates and a heating system that isn’t running. Within a number of days, interior temperatures can reach near-freezing levels, which poses a problem for tenants and occupants who may need to shelter in place.
If a building has single-pane glazing, suffers from air leakage through windows, has improper amounts of insulation, or features large areas of glass without window film or other insulating coatings, these internal temperatures won’t stay habitable for very long.
The report also recommends other ways to improve air sealing and insulation in existing buildings:
- Sealing open elevator shaft vents.
- Sealing passive stairwell vents.
- Sealing accessible side wall penetrations through the building envelope.
- Weather-sealing loading docks to restrict infiltration when vehicles are parked in the doorway of the loading dock.
- Requiring vestibules at all entrance doors, including lobby doors.
In a natural disaster, storms can cause localized flash flooding of buildings and streets. Because of this, the Building Resiliency Task Forcereport recommends that sidewalks be designed in a way to help capture stormwater. Although New York City has rigorous stormwater standards in place for buildings that add new sewer connections, the Task Force says stormwater from existing buildings must still be addressed.
Because sidewalks make up eight percent of New York City’s land area, the Task Force believes that creating a single sidewalk standard that includes permeable strips and water storage capacity would have an enormous cumulative effect on stormwater discharge and potential flooding in commercial buildings.
The Task Force’s recommended proposal suggests that sidewalks include a continuous permeable strip at the curbside. The permeable strip would have a width of at least one-third of the sidewalk width, and be no less than three feet wide along the curbside length of the sidewalk from lot line to lot line. Within this strip, no turf grass would be permitted. Plants could consist only of native meadow plantings and low herbaceous grasses or native ground covers, except the three-foot mulch bed at the base of street trees.
These recommendations would also require the outer third of all sidewalks to be permeable with at least two feet of structural soil below (creating a “linear tree pit�?). Because structural soil is 30% void, it would serve as a repository for stormwater. If New York City experienced a storm that produced two inches of rain, almost all of that rainwater would be captured by the sidewalks if they were designed to the proposed specifications.
Ultimately, this sidewalk design would reduce sewer, subway, building, and roadway flooding. It would also reduce the pollution carried into waterways.
In disaster situations, trees can overturn during high winds if the soil they’re planted in rapidly becomes saturated with moisture. The right tree selection and planting methods can help reduce the possibility of trees overturning and damaging overhead utility lines or infrastructure during major storms.
For this reason, the Task Force is advising that guidelines be put in place to recommend that trees be selected for planting based on wind tolerance, soil characteristics, proximity to structures and utility wires, etc. Proper tree care and planting can also affect a tree’s ability to withstand a natural disaster and high wind speeds, so practices to address proper upkeep would also be recommended as part of these guidelines.
“Hurricane Sandy made it all too clear that, no matter how far we’ve come, we still face real, immediate threats,�? says Mayor Michael Bloomberg. “These concrete recommendations for how to confront the risks we face will build a stronger, more resilient New York … this is urgent work, and it must begin now.�?