One of the greatest features of the Ironwood Home is its inherent fire, seismic and wind safety. As a homeowner these are features everyone wants and needs. Now, fire safety and a strong structure which goes beyond current building code requirements, will be a major consideration by financial institutions and insurance companies. It will certainly be a consideration how much it costs. This home is designed to address these issues. It may make a difference between getting construction loans and mortgages and not.
Fire resistance starts with the building materials. If it doesn’t burn it won’t burn down. For this reason, light-gauge steel is the best option for framing, particularly for fire resistance from interior fires. A fire from the interior will not burn the wall studs and structural framing. In a wood-frame home, an interior fire has a high-probability of burning through to the wall and structural studs, possibly losing the entire home. A wood frame home can be made much more fire safe from external sources by employing the same principles used for metal framing, however the reality is most home fires are started from internal ignition sources. A wood-frame Ironwood Home is just as susceptible to interior fires as any other wood-frame home.
When we use non-combustible siding and roofing and maintaining a proper defensible zone around the home it is easier to prevent fires from external sources. Especially when designed with operable exterior shutters and vent screening designed to prevent embers from getting in. Exposure of combustible surfaces are minimized if the embers do get in. Along with non-combustible exterior materials, the Ironwood Home uses a layer of rigid insulation board as part of the energy-efficient design. This material is specified to be a Polyisocyanurate foam board. Polyiso materials do not burn when used in a non-combustible assembly so it protects rather than contributes to the fire like a Polystyrene foam board would. It also has a zero Ozone Depletion rating in production, bonus!
Besides better insulation, the exterior insulation layer helps protect the framing from heat during a fire. Metal framing may not burn but it will lose its strength when exposed to high temperatures for an extended period of time. Non-combustible exterior insulation, siding, trim and roofs + metal framing + protected openings + a defensible zone = a highly fire-resistant home.
Just using non-combustible materials is not enough. You need high-quality workmanship. Poor construction may leave voids and gaps which can give burning embers a place to smolder. Prefabrication of wall and roof sections improves quality from the shop to on-site assembly improving overall construction quality.
Strength
Each structural frame is considered a “stand-alone” structure. One frame is not dependent upon another but when combined with other frames the entire structure is much stronger and exceeds structural requirements of traditional framing methods. This is true for gravity, seismic and wind loads.
When structural frames are stacked, the shear panels are aligned and stacked directly on top of each other. This creates a continuous load path from the roof to the foundation. Because the floor trusses are set between the frames, there is no break at each floor level.
Shear Panels are connected at each floor level creating a continuous path from roof to foundation.
At the foundation level, Anchorage is designed to receive the Seismic and Wind loads of the entire structure.
Roof designs have more options and can be specifically designed for areas where high-wind conditions can be expected. The roof trusses only carry loads directly to the structural framing below which directs all loads down the shear panels into the foundation. Roof trusses do not carry interior loads like MEP and insulation or sheetrock. These are carried by the frame. The roof truss is not required to provide horizontal shear at the top of the home either. Roof trusses can be made light yet strong and specifically designed for high-wind event areas.
This home can be built on slab-on-grade, footings with crawlspaces or over a basement. Foundations are designed to carry the building loads directly from the shear panels so these areas of the foundation are made to be heavier and stronger. Otherwise, foundations are the same as most other homes.
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