Governments: prime customers for roofing materials and roof repairs
Editor’s note: No question about it, local, state and federal governments are major consumers of roofing materials.
A quick check on the BidNet bid library (www.bidnet.com) shows a total of 432 bid solicitations over the past three months from local, state and federal government agencies in the United States that are seeking bids on roofing materials or roof repair, replacement, sealing, renovation and other roof construction projects. BidNet is an online bid notification and market intelligence service based in Albany, N.Y.
The Energy Information Administration’s latest “Commercial Buildings Energy Consumption Survey (CBECS): Building Characteristics Tables” estimate that there are 635,000 government-owned buildings in the United States. The predominant roof materials found in a high percentage of those buildings, according to CBECS, are built-up, shingles (not wood), metal surfacing, and synthetic or rubber.
In addition, a good number of the government-owned buildings may be showing their age and may need roof repairs, with 25,000 constructed before 1920 and 67,000 constructed between 1920 and 1945. A whopping 99,000 were constructed between 1946 and 1959—the youngest in that last batch would be 50 years old.
Preliminary results from the newer 2007 CBECS survey will be available in mid-2009. Visit EIA for information: http://www.eia.doe.gov/emeu/cbecs/.
To help GovPro.com readers as they plan future roof repairs, we offer this analysis on metal retrofits.
Michael Keating, Senior Editor
Stretching your roofing dollars with metal retrofit
By Chuck Howard, PE
Consultant to The Metal Initiative
Industry sources suggest that some 30 billion square feet of roofs will be in need of major repairs in 2009. Adding a sloped metal roof to an existing flat roof can generate a strong return on investment in the form of lower energy costs and little or no maintenance for decades. In most circumstances, the slope addition can be accomplished without having to remove the existing flat roof.
A slope as low as ¼ inch per foot is sufficient to satisfy most metal roof warranties and can be achieved by installing light gauge steel columns in varying lengths. After the variable height columns are installed, steel purlins are positioned between each of the columns, and the necessary bracing is installed. A new metal standing seam roof panel system is then placed on top of the sub-framing system. When the job is completed, it’s almost like having a small metal building sitting on the original roof.
If properly maintained, the exterior surface should last at least 30 to 50 years. The exterior surface, whether painted or bare, can reflect up to approximately 80 percent of the solar energy that would normally penetrate the building. Adding un-faced fiberglass insulation in the newly created cavity can further increase the building’s ability to conserve energy used to control temperatures in interior spaces.
In today’s market, the cost of adding a sloped metal roof system over an existing roof is, in most cases, less than the cost of removing a flat roof, placing the removed materials in a landfill, and replacing it with a Built-Up Roofing or Modified Bitumen Roof with tapered insulation. (Tapered insulation is required by most code authorities to achieve a certain level of roof slope.)
Owners who may not be looking to add slope, but simply want to replace their existing sloped metal roof can do so without removing the original roof. It’s simply a matter of positioning a light gauge structural member, notched to span over the original roof’s ribs or corrugation, directly over the building’s framing system. The member is attached to the roof purlins through the bottom flange of the member and the existing roof sheet. A new standing seam metal roof is then attached to the new member. The cavity between the old and new roofs can be used to add insulation, which should allow the retrofit process to begin paying for itself quickly.
Another reason to consider re-roofing over an existing sloped system is if the existing roof fails to meet current code requirements for wind uplift. For metal roofs installed on pre-engineered buildings, the standard 5-foot purlin spacing often will not satisfy panel clip spacing requirements in edge and corner conditions necessary to satisfy design loads established in current building codes.
In metal roofs installed over solid metal decks, the panel’s clips are often misplaced to satisfy uplift loads and panel capacities. Placing the new structural member properly can correct those deficiencies.
A metal-over-sloped retrofit creates a cavity between the old and new metal roof surface that can provide natural convective cooling, known as Above Sheathing Ventilation (ASV). By providing a continuous air gap from the eave to a ridge and venting the warmer air, the energy efficiency of the new roof assembly can be improved. Tests at Oak Ridge National Laboratory have demonstrated that the natural ventilation can reduce heat flow into the building up to 30 percent. It costs practically nothing yet yields significant savings.
Other systems can be added to metal-over-sloped retrofits to reduce energy consumption. Solar thermal heat recovery systems, for example, use air heating and ventilation collectors integrated into a photovoltaic system. They use air as the heat transfer circulating fluid. Building owners that install such systems are eligible for federal solar energy tax credits up to 30 percent of the entire roof system, with no dollar limit. When combined with a special accelerated depreciation, the tax credits can pay for more than half of the retrofit improvements, which does not include the energy cost savings from the system. Solar water heating systems also can be integrated into a metal-over-sloped retrofit to serve the hot water requirements of the building and reduce energy consumption
Adding a structural metal roof to an existing building is an environmentally responsible choice because metal roofs are manufactured from recycled materials, and they are almost 100 percent recyclable. Moreover, they can accommodate additional insulation and solar panels, which, when used together, can help a metal roof pay for itself quickly and continue generating a return on investment for the building owner into the future. For most buildings, a new metal roof will be the last roof required.
Chuck Howard is a professional engineer and roofing consultant who has specialized in metal roofs for more than 30 years. He currently provides commercial roof consulting to contractors, architects, building owners and The Metal Initiative, the educational arm of the metal roofing and wall industry in North America. For more information contact The Metal Initiative at www.themetalinitiative.com or 847-375-4785.