The Retrofit Roofing Game:
Increasing Energy Efficiency
Mark James ,
Posted
10/29/2012
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.