When Conditions are Extreme
Imagine you are sitting at home this evening and you hear the wind start to howl outside your door. You look out the window and see tree branches bending under the force of the wind. Your neighbor's trash can goes rolling on down the street.
How you react to this might depend upon where you live. If you live in the Midwest, as I do, and the sky is sort of a funny shade of green, you head for the basement. In the Midwest we get tornados. They are not as big as hurricanes and their path of destruction is usually not nearly as wide. But we also usually do not have as much notice that they are coming as weather forecasters are able to give for hurricanes. So if there is any doubt, you try to find a safe haven.
Since I have never lived in a hurricane-prone region I don't quite know how you respond to the pending approach of one of those. I suppose either you gather up your entire family, including any pets, and head for what is considered to be a safer location; or you bunker down and hope for the best.
Even the fact that the building you are in has survived extreme weather events in the past is not necessarily a guarantee that it's a safe haven this time around. In Illinois a few years ago a building that was over a hundred years old was flattened by a tornado. Many of the residents in the small town where the tornado had occurred sought shelter in the basement of this building, assuming that since it was so old, it had withstood these types of events before and therefore would again. Some survived, others did not.
HURRICANES AND HIGH WIND EVENTS
Although the International Codes and ASCE 7 do not attempt to address tornados, they do attempt to address hurricanes and other high wind events that are anticipated to occur within a one hundred year cycle.
To design a building to withstand these forces, one must start with the framing system itself. Like the skeleton in the body, if the framing system cannot withstand the forces that act upon it the remainder of the object (whether a building or body) will not be able to, either.
Once a framing system that can withstand the design wind pressures is established, the focus turns to the building envelop. The building envelop maintains the integrity of the building and protects its interior-like the skin over the body that is framed by the skeleton.
If the building envelop is compromised, the integrity of the building is compromised, as well. In some cases, depending upon the direction that the wind is coming from relative to the compromise (opening) of the building envelop, an opening in the building envelop can actually result in a change in the forces-which the building must still withstand. These changes can be significant and could, if conditions are right, result in failure of not just the building envelop, but of the framing system as well and hence, the entire building.
For example, if the garage door of a single family home gives way during a hurricane, the forces of the hurricane can enter the home through the garage and, in some cases, basically blow up the house like a big balloon. The result is that components of the home's exterior walls and roof are scattered in all directions-siding, insulation, framing; all blow away in the wind. And the contents of the home are subject to the wind and rain of the hurricane. For this reason the 2006 International Residential Code and 2006 International Building Code now require vehicular access doors and garage doors to meet the criteria of DASMA 107 or ANSI/DASMA 108.
The walls and roofs themselves are also required to be built to resist the design wind pressure. Section 1609 of the 2006 IBC contains provisions for the design of all components of the building, including roofs and walls, for all design wind speeds currently prescribed in the U.S. The prescriptive provisions of the 2006 IRC for wall and roof construction are to be used in areas where the design wind speed is less than 110 mph, or in hurricane-prone areas where the design wind speed is less than 100 mph. In areas that exceed these design wind speeds, the American Forest and Paper Association Wood Frame Construction Manual for One- and Two-Family Dwellings (WFCM), the Southern Building Code Congress International Standard for Hurricane Resistant Residential Construction (SSTD 10), ASCE-7, the American Iron and Steel Institute (AISI) Standard for Cold-Formed Steel Framing-Prescriptive Method For One- and Two-Family Dwellings(COFS/PM) with Supplement to Standard for Cold-Formed Steel Framing-Prescriptive Method For One- and Two-Family Dwellings or concrete construction that complies with the provisions of the IRC are to be used.
Similarly, all editions of the IRC and IBC (2000, 2003 and 2006) require windows and some doors to be tested and labeled to the joint AAMA/WDMA standards for these products. The 2000 editions of the IBC and IRC required windows and glass doors to be tested and labeled to ANSI/AAMA/NWWDA 101/I.S.2 - 97. The 2003 edition required these building components and skylights to be tested and labeled to either that edition of the standard, or to ANSI/AAMA/WDMA 101/I.S.2/NAFS/02. The 2006 edition of the International Codes requires windows, sliding glass doors and skylights to be tested and labeled to AAMA/WDMA/CSA 101/I.S.2/A440-05.
Both the 2006 IRC and IBC require side hinged doors to both be tested and labeled in accordance with ANSI/AAMA/WDMA 101/I.S.2/A440/05, or tested in accordance with ASTM E330-02. During the most recent ICC code change cycle WDMA submitted a code change proposal (S141) that would have required all side hinged exterior doors to be tested and labeled to ANSI/AAMA/WDMA 101/I.S.2/A440.
AAMA/WDMA/CSA 101/I.S.2/A440 requires the component being tested (whether a window, skylight or door) to be tested for resistance to uniform wind pressure in accordance with ASTM E330, which is consistent with the other requirements of the International Codes for fenestration of exterior walls. It also requires, however, a battery of other tests, including testing for resistance to water penetration in accordance with ASTM E331, resistance to air leakage in accordance with ASTM E283 and forced entry resistance in accordance with ASTM F588 (windows), ASTM F842 (sliding doors) and AAMA 1304 (side hinged doors).
MUCH DISCUSSION REMAINS
The question this raised was whether it was really necessary, practical or cost effective to require all exterior side hinged doors to be tested and labeled in accordance with ANSI/AAMA/WDMA 101/I.S.2/A440. Many of the door jobbers who are members of the Association of Millwork Distributors argued that it was not. In many cases these types of doors are assembled by these jobbers on a project by project basis. They do not provide a "stock" product. For jobbers, the implications of certifying their products appear to be overwhelming and quite threatening. AAMA has been working with some members of AMD to try to develop a component-based certification program for these types of products, with the goal of accommodating the concerns of the door jobbers. The intent of a component-based certification program would be to allow the door jobbers to put together a door assembly that meets the intent of the code for third party certification, by combining an appropriately rated slab with appropriately rated hardware, in an appropriately rated frame and following methods that have been approved by the certifying agency.
But as yet such a program is not in place. Getting such a program up and running to the level that would be needed to respond to a provision that required all exterior side hinged doors to be tested and labeled, were such a requirement to be placed in the 2009 International Codes, would be a daunting task. When S141 was heard during the ICC Code Development Hearings in Palm Springs, AAMA offered a modification that limited the application of the testing and labeling requirement for side hinged doors to the more "critical" cases where the design wind speed was 110 mph or greater, the door served a habitable area (as opposed to an area such as a garage, which is considered a non-habitable area) and the door was not protected by an overhang.
In the end the proposal was disapproved by both the IRC-Building and Energy Committee and the IBC-Structural Committee. But the questions remain, and will remain-"What is the appropriate criteria for exterior side hinged doors?" and "What is the most practical, cost effective way to provide assurance to the code official (and perhaps the homeowner or building owner?) that the opening in the building envelop for exterior side hinged doors have been adequately secured against high wind and rain events?"
There are no easily answered questions. It appears that our industry will be wrestling with them for some time. In the end, of course, it all comes down to what is adopted into the local codes and enforced by the code official. Eventually some decisions will be made and the whole situation will stabilize. In between should be some rather interesting discussions.