Everywhere you turn nowadays, energy efficiency and renewable solar are in the news. It’s been a long time coming, but I think we would all agree that they are here to stay. The problem with this, though, is it appears that most promotional efforts are directed toward new construction, which misses the 80 percent of the total construction market: renovation projects.
Other things you see are daylighting, upgraded HVAC, vegetative roofs and the sort. The truth is our existing buildings consume about 70 percent of all energy produced annually in the U.S., which includes transportation. And, of the total, almost $32 billion is wasted due to roof inefficiencies. So, shouldn’t we focus on reducing heat gain/loss in our 82 billion square feet of existing building inventory?
It is quite simple actually. When a building is re-roofed or retrofitted, increase its thermal resistance by adding high-performance insulation and dynamic ventilation systems to meet minimum recommended Model Energy Code standards. Since we have not been focused on saving energy in our construction planning for decades, the majority of our building roofs have very little thermal resistance. Many have as little as an R-5 or R-6 rating compared to what should be a minimum of R-30 to R-38 today, depending on occupancy type.
And it doesn’t matter if a building is temperature controlled or not. For those that are, it’s a no-brainer to increase the R-value, but for those that are not, adding insulation can create a more pleasant and productive work environment much needed in manufacturing and warehousing buildings nationwide.
Adding Insulation-When proposing a retrofit metal roof system over an existing flat or sloped roof, increasing the building’s energy efficiency should not be an option; it should be mandatory. Think about it: What else can you do with a roof replacement that actually can turn an expense into an investment through energy savings?
Your options are abundant in adding thermal resistance, and can be broadened if renewable energy sources are included in the roof replacement plans. Any flat roof retrofit can include fiberglass batt/blanket or blown-in/loose fill fiberglass or cellulose
(recycled paper fiber) insulation to a thickness that obtains maximum performance.
This is when you decide how much insulation based on the occupancy type. For retrofits over existing sloped roofs, fiberglass batts or rigid polyisocyanurate can be integrated into the roof assembly. With both of these, reflective radiant barriers can be incorporated as well. There have been retrofits over sloped roofs that have obtained an R-50 rating. Several of these are very near net zero facilities now.
Dynamic Ventilation-All roofs should be ventilated to reduce temperature differentials between the outdoor ambient temperature and the building’s interior space. What’s interesting today is ventilation has taken on a whole new meaning when it comes to metal roof applications.
For more than six years, the Metal Construction Association
(MCA) and Oak Ridge National Laboratories (ORNL) have conducted research on ventilated metal roof assemblies with some very impressive results. The research includes actual constructed roof assembly lanes equipped with sensors that measure heat flow and a host of other things over one year. Data is recorded 24/7 and then analyzed by the U.S. Department of Energy.
This bank of research is known as Above Sheathing Ventilation and compares various components installed between the roof deck and bottom side of the new metal roof. The comparisons include different types of insulation, varying depth of airspace above insulating layer, radiant barriers, phase change materials and other technologies. The research is reported by the MCA and ORNL on an ongoing basis.
Renewable Solar-Incorporating renewable energy technologies into a retrofit roof application comes down to the decision of the building owner. This is usually based on the energy demand of the building. If the building has a large electricity demand, photovoltaic (PV) equipment may be a good solution when installed on the new metal roof. This technology comes in two different types for metal roof applications.
First is surface-mounted mono or polycrystalline modules, and the second is thin film, which also is known as building integrated photovoltaics (BIPV).
If the building has a large hot water demand, a solar thermal hot water/air system can be installed in the cavity to assist in preheating boiler water and domestic hot water, radiant space heat and the hot water necessary for the manufacturing or whatever operations the building does. These systems are very efficient and cost effective, and can provide a return on investment in less than five years.
Through 2016, all roofs installed with PV and/ or solar thermal systems will receive a very attractive dollar-for-dollar federal tax credits up to 30 percent of the entire assembly, including labor and materials. In a retrofit application, this can include the framing and new metal roof. To help the building owner, there are many state and local incentives that include grants and funding.
Mark James has more than 40 years experience in the retrofit and metal construction markets, working for leading manufacturers and executing great projects. Currently, he is president of RetroSpec LLC, a consulting company offering direction and deep knowledge of the retrofit business for manufacturers and contractors. James can be reached at mark@retrospecllc.com.
