Final Report: Design Support for Green Building in the Wildland-Urban Interface to Enhance Sustainability and Fire ResistanceEPA Grant Number: SU836125
Title: Design Support for Green Building in the Wildland-Urban Interface to Enhance Sustainability and Fire Resistance
Investigators: Bormann, Noel E
Institution: Gonzaga University
EPA Project Officer: Page, Angela
Project Period: September 1, 2015 through August 31, 2016
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2015) RFA Text | Recipients Lists
Research Category: Sustainability , P3 Challenge Area - Built Environment , P3 Awards , Pollution Prevention/Sustainable Development
The purpose for this project is threefold: First, the project will encourage the development of a more sustainable community throughout Okanogan County, especially in the Wildland-Urban Interface (WUI). Second, the project will support positive and proactive residential development that promotes community resistance to and resiliency in response to future wildfires. Third, the four projects will reduce the amount of solid waste generated from wildfire destruction and rebuilding of structures. To achieve this purpose, the project accomplished four objectives. The first objective was to work within the local regulatory paradigm to develop effective techniques to improve fire resistance. Second, the team is preparing to present educational tools that will empower the community to build and operate their homes in a more sustainable manner that is less vulnerable to wildfires and with increased energy efficiency. Historic fire data were used to develop a Monte Carlo model to estimate the damage costs and wastes avoided if the various proposed design guidelines are followed. Third, team members have designed three sample building-enveloping systems that each offer different advantages over typical residential construction in the area when evaluated for fire resistance, sustainability, and affordability. For the fourth objective, team members designed a system for mechanical shutter systems suitable for incorporation with each respective envelope system to prevent fire penetration at window openings. The team is planning to provide Okanogan County groups access to the outputs from these four objectives via educational seminars and demonstrations. The project incorporated the efforts of a multidisciplinary team of civil engineering students, mechanical engineering students, and environmental studies students assisted by a group of expert local partners in Okanogan County.
Literature for wildfires in the Wildland-Urban Interface (WUI) reveals that homes typically ignite from embers, flames, and heat transfer to the building envelope. Firewise prevention practices reduce the access of flames to the house. The two common ways that fire penetrates to the interior of the house are either the breaking window glass or embers that may blow onto flammable features of a house (such as decking, fencing, or clutter) or be carried into an attic through soffit vents. The team developed an innovative method to provide attic ventilation without soffit vents, and incorporated fire resistant methods with green building concepts into wall designs. The team also developed innovative protective shutters to reduce window failure during wildfire. Protective shutters range from simple sheeting with a fire retardant gel to fabric shutters that deploy automatically when exposed to fire temperatures. In the Okanogan County area, demographics suggest that many residents are constrained from spending for fire resistant or energy saving building alternatives; this characteristic emphasized the need to create affordable fire-resistant solutions with appropriately sustainable materials and techniques. A Monte Carlo simulation provided a method to make a statistically based estimate of the damages avoided if design changes are implemented. The Monte Carlo damage simulations also yielded an estimate of fire waste prevented and the construction wastes prevented when reconstruction is not necessary. The statistical prediction estimated that the expected number of houses burned by wildfire was 22 per year in this area.
Significant reductions in damage, cost, and waste generation are possible. The reductions depend on the level of implementation of Firewise prevention activities and the level of fire resistant methods adopted. Using a house with no Firewise prevention and no recognized fire-resistant methods as the traditional base case, damage reduction (i.e., house loss) ranges from 48% of base 5 to 12% of base. Because waste generation is in proportion to houses lost, waste generation is also 48%-12% of the base case. The wall designs selected implement non-flammable exterior siding and the innovative soffit vent replacement in addition to energy efficiency improvements. Three options were developed: a Standard wall, an Advanced wall, and a Net-Zero Ready wall, which improved fire resistance and energy efficiency the most. The Okanogan area has remarkably low costs of electricity, with residential rates between $0.04-$0.05 per kWh. At these rates, the amount of energy savings that can be used to partially offset increased construction costs is lowered. Estimates of energy cost savings are approximately $20 per month for the Advanced wall design. The monthly payment to finance the cost of the Advanced wall is approximately $50 per month. Based on these estimates, approximately half of the monthly cost of improved energy efficiency and fire resistance is offset by just the energy saving, not counting the savings of fire resistance. The fire resistant features include three innovative shutter systems that reduce windows breakage due to heat and flames during a wildfire. The cost of shutters over vinyl window frames is estimated to be less than the cost of using metal or fiberglass frames. The cost of shutters is also less than using tempered glass as a method to reduce window breakage. The Monte Carlo estimate of house damage losses indicates that at least $2.27 million in house losses could be avoided annually over a long-term average if Firewise and fire-resistant construction were to be implemented in Okanogan and neighboring Ferry and Chelan counties. The second phase of this investigation is to refine wall and shutter designs and test those designs in full-size flame exposure tests to confirm the ventilation and fire resistance meets building code requirements.