Thursday, March 24, 2011: 6:00–7:30 pm

Next Generation Roofs and Attics: Some Design Guidelines

William 'Bill' Miller, Ph.D., Program Manager, Energy and Transportation Sciences Division, Oak Ridge National Laboratory

 Dr. Miller is a specialist with 30 years of experience in vapor compression refrigeration systems, absorption heat and mass transfer and building science technologies. He has a Ph.D. in Mechanical Engineering, serves as a Research Professpr for the College of Engineering at the University of Tennessee and he works for the Energy and Transportation Sciences Division of the Oak Ridge National Laboratory. As Program Manager, Dr. Miller coordinated a team of engineers with the setup of four 50% energy saver homes. He completed two PIER funded cool roof color studies in collaboration with Lawrence Berkeley National Laboratory. He is investigating above sheathing ventilation for the Metal Construction Association and the Tile Roof Institute. He investigated the impacts of low-emittnace roofs for the Cool Metal Roof Coalition and has completed research with Louisiana Pacific and PolyFoam Corporation. He has also conducted studies for SPRI Inc. and for a consortium of metal industries to quantify the energy savings for highly reflective roof products as compared to dark absorptive roof systems in different geographic regions of the U.S. He has expertise in numerical heat conduction for application to forced convection, natural convection and mixed convection finite-difference simulations.

Manufacturers, builders, suppliers and code officials need to be familiar with the best available materials and construction methods available that reduce energy bills sufficiently and justify for the homeowner the economics of higher up-front material and installation costs. For instance, the most common roof and attic assembly found on single family residential buildings has dark heat absorbing asphalt shingles that are nailed to a wood deck, which in turn is attached to a wooden truss system with blown-in loose-fill fiberglass insulation.

Three different prototype residential roof and attic assemblies were constructed that reduce both the energy consumption and peak demand of the attic 90% compared to the traditional attic assembly. The prototype assemblies are highlighted in a DOE Building Technology (DOE BT) report Guideline for the Design of Roofs and Attics in Hot Climates. The assemblies exhibited attic air temperatures that did not exceed the peak day outdoor air temperature. Field results were benchmarked against an attic computer tool and simulations made for the ASHRAE climate zones.

Field data and validated computer simulations are reviewed to better understand energy and economic tradeoffs for the next generation of attic systems in terms of reflective roof covers, the type and placement of insulation, the use of above-sheathing ventilation, attic ventilation, thermal mass, radiant barriers and the location of ducts.

Objectives:

• Cite prototype roof designs using various roof and attic strategies to reduce the heat flow penetrating into the conditioned space.
• Present the trade-off between attic insulation, solar reflectance and thermal emittance for heating and cooling dominated climates and show the positive impact of sub-roof venting on the heating penalty associated with cool roofs.

Continuing education credit is available for architects, building officials, and others. Seating is first come first served. Q&A session will follow presentation.