Resilient Design, Part 1
The recent Christmas-week ice storm and the arctic temperatures that followed here in Down East Maine make it a particular good time to talk about the concept of “Resilient Design,” specifically in our homes. According to a working definition from the Resilient Design Institute (RDI) “Resilience is the capacity to adapt to changing conditions, and to maintain or regain functionality and vitality in the face of stress or disturbance.” Resilient Design applies those principles to the buildings we rely on to provide us with shelter and other vital services. It goes beyond just having plenty of drinking water and firewood on hand, though those are both extremely important. It’s about modifying our existing houses and designing new ones to provide the necessities, and to some extent the luxuries, when we are hit with natural and/or man-made disruptions and catastrophes—ranging from localized power outages to hurricane winds that challenge the ability of these buildings to continue to stand. The events of the past few years—hurricane Katrina, super storm Sandy, and the Fukushima earthquake, tsunami, and subsequent nuclear reactor meltdown—all carry the message that we need to make our homes more resilient.
A house can be broken down into a series of interrelated “systems.” Let’s examine those systems and see how Resilient Design can affect them:
-Structural, including roof and walls: If a house is to provide shelter and safety it is important that it stay intact, and not have its skin opened or its structure fail due to the extreme weather or other disasters.
-Water, including both supply and waste: It is important that we have available in our homes an adequate supply of potable water and a sanitary means of disposing of waste water regardless of disruptions to services linked to the home.
-Heat: We need a means of providing a safe, comfortable temperature, even in the event of a temporary loss of access to offsite fuels.
–Electricity: These days we rely on electricity for so many things. They are often key components in our water and heating systems. Ideally we should have a way of providing on-site production of some electrical power for at least some services (heat, water, refrigeration) for during periods of interruption.
-Communications: These days being in touch with the outside world and being able to communicate with it is also vital. At least one communications system—preferably a two-way one—should be able to stay up and running.
Over the next few weeks I’ll look at how we can incorporate Resilient Design into each of these systems. In this blog entry, I’ll start with the structural system.
There are three major threats to the integrity of a home’s structural system: wind, flooding, and earthquake. While we do get earthquakes here in Maine, they are not considered a major threat. Wind and floods are.
There are two ways to deal with flooding: Site the house above the 100-year flood line, or raise it above the flood level on piers specifically designed to withstand the pressure of rising water and the debris that may be in it. This applies both to new homes and existing ones. Obviously moving or raising existing homes is extremely expensive, but given the new rules concerning flood insurance, that may be the best way to deal with the situation.
With wind, the situation is both easier and more complicated. It is easier in that overall the work to make a house resilient to the wind is much cheaper. But there is more to it than just raising or moving the house.
Wind can affect every part of a building, from the windows and doors, to the walls, to the framing. Whether you are having a new home designed or planning major renovation for your existing home, at least some of the most important aspects of Resilient Design should be considered, especially if you live in an area with high winds.
Windows: In high winds, flying debris or, in particularly extreme conditions, the wind itself will break windows, allowing wind and water into the house. In some cases, the subsequent changes in pressure in the house can lead to failure of the entire structure. Anyone living on the coast or in some other high-wind area should consider replacing existing windows with specially designed, wind-resistant windows. Many of the major window manufacturers make them. While they are more expensive, they can be lifesavers. Also, check with your insurance company: You may get a break on your premiums if you have these wind-resistant windows.
Doors: The situation with doors is similar to that of windows. Larger doors, such as garage doors, are particularly vulnerable. Again, most major manufacturers have wind-bracing upgrades available.
Framing Reinforcement: Strong winds can find weakness in any of the major connections between framing members—from the eaves to the basement—and pull them apart. Over the past couple of decades, specialized hardware has been developed to strengthen the various framing connections. Starting at the eaves, “hurricane clips” attach the rafters to the wall plates. Metal straps connect the plates to the wall studs, and the studs of the second floor to the first floor. Other straps can connect the first-floor studs and mud sill to the foundation. All of these can be retrofitted whenever you expose any part of the existing framing of a house during renovations. The hurricane clips can often be retrofitted in open attics at any time, and may be the most important form of framing reinforcement, since roof eaves are particularly vulnerable to high winds. Some types of mud-sill straps can be easily installed in open basements. This sort of hardware is made by Simpson Strong-Tie and other manufacturers and is readily available at building supply outlets. You may wish to consult an architect or builder as to which ones would work best for your particular circumstances, as well as how and where to install them.
Foundation Tie-Downs: “Tie-downs,” which are specialized hardware that connect the first floor framing to the foundation, are your best protection in this area, though you’ll need to expose the plate and a fair amount of the stud to install them. They are widely available at building supply outlets. Again, it may be a good idea to consult a builder or architect.
Bracing Wall Panels: The exterior walls of our houses have to resist the forces of the wind—in particular, wind shear, which is the lateral force of wind on a wall. This requires the wall framing and sheathing to be fairly extensive and connected. Yet we need and want to put large holes in our walls to accommodate our windows and doors, and sometimes these openings seriously compromise the ability of walls to resist wind shear. In that case, we can incorporate bracing panels on the specific solid portions of the wall. Bracing panels are a specific combination of tie-downs, additional sheathing, and extra nailing that strengthen the wall. Whenever you have a wall that has many and/or large openings in it, bracing panels may be called for. They should be designed by an architect or an engineer.
The next post will review resiliency in water systems.