One of the difficulties with producing more resilient designs, as I’ve discussed, is the lack of practical information available for designers. The U.S. Department of Energy and Environment for Washington, D.C., just published Resilient Design Guidelines (RDG). This document is intended to help planners, owners, and design professionals increase the resilience of both new and existing buildings. The guidelines are intended primarily for public projects, but many of the recommendations are applicable to private developments as well. Climate change is the focus of the document, with flooding and increased temperatures identified as the hazards that should be addressed, and resilient design is defined as “the intentional design of buildings, landscapes, communities, and regions in response to these vulnerabilities.”
However, the guidelines also only consider the building and site and specifically do not address social aspects, such as planning, emergency services, community resources, etc. The District of Columbia has identified that climate change will generate an increase in frequency and magnitude in certain hazards, predicting “more intense storms, increased precipitation, heat waves, and power outages.”
In last month’s column, I discussed the updating of climate dates in building codes worldwide, and how, at this time, the building codes use only historical data to estimate risks with no projections to account for changing conditions.
The newly published RDG provides tables for estimates of low- and high-end predictions of flood elevations and temperature increases, including predictions for multiple time periods to match the expected lifetime of a project. This is important since a temporary structure, storage facility, or pavement might only be expected to be in service for 20 years, maximum, while most buildings have a life span of 50 years or more. It doesn’t always make practical or economic sense to design all buildings for the same predicted climate-related conditions. Regarding flooding, the RDG considers three sources: riverine, sea-level rise, and interior flooding due to inadequate drainage or sewer capacity. The need for resilient design is not just from the primary hazard of high water levels and the potential need to evacuate but also due to secondary aspects such as mold growth and the introduction of pollutants into a building.
Specific recommendations range from general provisions, such as avoiding building in a flood zone and elevating the occupied space to very specific recommendations about reinforcing parts of the building to providing details for cladding rain screens. More specifically related to the building systems, the RDG suggests avoiding putting mechanical and electrical equipment in the basement or otherwise protecting it from flooding, ensuring access during and after an event, and installing sump pumps and sewer backflow preventers.
Similar recommendations are provided for dealing with extreme heat. In particular, the guide emphasizes passive measures, such as considering the building form and orientation as well as insulation and thermal mass to allow for better performance, even if there is a power shortage or loss. It is also recommended to consider alternative energy sources, such as solar panels, to provide some or all of the power requirements. The building performance should be looked at as a complete system with efficient HVAC systems and passive measures reducing the energy requirements and reliable on-site generation allowing for continued operation at some level.
One point of potential confusion is that the guide suggests a lifespan of approximately 20 years for mechanical systems, considering climate change effects over that period. However, in another section, the RDG recognizes that distribution systems, such as ducts and pipes, be sized for the required capacity over the entire life of the building, but this point could be lost without a careful reading of the document. At the end of the day, the RDG provides useful information for planning, designing, constructing, and operating buildings that are better able to cope with and adapt to changing conditions. Although only flooding and extreme heat are covered, along with some information about dealing with power outages, this document goes a long way toward generating more resilient buildings for most facilities. Obviously, there are other hazards that may need to be addressed, and some critical facilities may require more advanced analysis and evaluation to determine the best approach to increasing resilience, but the guide provides an important tool for engineers and architects and opens the discussion to consider other requirements.