Life Cycle Cost Analysis
Low Slope Roofing Life Cycle Cost Analysis
Conducted by Ducker Research Company
Research Highlights - May 4, 2005
Research Objective
Ducker Research Company conducted an in-depth case study analysis of 36 roofing systems across the United States in 2004. The primary purpose of the research was to compare three different types of low slope roofing systems – metal, asphalt, and single-ply systems – on three different measures: total service life, life cycle cost, and maintenance costs.
Secondary goals of the research focused on gaining a better understanding of the purchase criteria and purchase decision process for roofs, as well as the various aspects of roof maintenance.
Respondents
Based on 41 interviews with building owners and managers, case studies of 36 roofing systems were drawn from the western, northern, and southern regions of the country. Twelve were metal roof case studies, twelve asphalt and twelve single-ply roofs. The 36 case studies represented four different types of construction: office, retail, institutional, and warehouse/ industrial buildings.
Roofs Under Study
As reported by Ducker in its 2004 report, the typical roof in the research had been in service for over ten years at the time of the study. Owners and facility managers, therefore, had a good base of experience on which to estimate roof life expectancy.
The average size of the roofs in this study is 92,000 square feet. Typical metal roofs were 24 gauge standing seam roofs using standard fasteners and PVDF coating. Asphalt roofs were typically 3-4 ply. Single-ply roofs were typically 45 mil non-reinforced membrane.
- Based on a study conducted by Ducker in 2003, metal roofs have a significantly longer expected service life than either asphalt or single-ply roofs. According to Ducker findings, metal roofs are expected to last 17 years longer than asphalt and 20 years longer than single-ply. A summary of expected roof life for each material is presented in the table below:
| Expected Roof Life | Years |
|---|---|
| Metal | 40 |
| Asphalt | 23 |
| Single-ply | 20 |
- According to Ducker’s 2004 research study, the life cycle cost of a metal roof is significantly less than an asphalt or single-ply roof. The expected life cycle cost of metal roofs reported in this study is 30 cents per square foot per year, asphalt is 37 cents per square foot per year, and single-ply roofs is 57 cents per square foot per year.
- Owners and property managers report performing little or no regular maintenance on their metal roofs in this study. A comparison of maintenance costs over the life of the roof for metal versus asphalt and single-ply shows that owners of metal roofs spent approximately 3 1/2% of total installed costs on maintenance, versus 28 1/2% for asphalt roofs and 19% for single-ply roofs.
- The majority of all roof types have experienced roof leaks, including metal roofs. However, none of the metal roofs have leaked as a result of material failure, as compared to 30% of asphalt roofs and 56% of single-ply roofs. Leaks in metal roofs are due primarily to contractor installation problems and secondarily to “other problems” such as grommet deterioration, flashing problems and people walking on the roof.
Verbatim Comments (Maintenance)
“Price was a little high at the time but it was fair I think. The roof has held up great and there is almost no maintenance.” – Metal roof, retail/shopping structure, southern US.
“I am extremely satisfied with the value because of the low maintenance and durability of this metal roof.” – Metal roof, retail/shopping structure, northern U.S.
“Once a year we sweep the entire roof. Spring and fall we clean the gutters and while we are up there, we inspect the roof, the fasteners, etc. Sometimes we use seam patches.” – Metal roof, manufacturing/industrial, western US.
“We do very little maintenance. Once in a while we will sweep PVC compound off of it when we have been blowing it into silos.” – Metal roof, manufacturing/industrial, southern US.
“None! The only thing I have done is to replace the grommets, and that was five years ago! The only other thing I do is to check for and remove any garbage on the roof because that could clog the drains.” – Metal roof, office/bank, western US.
“Metal roofs don’t need comprehensive maintenance like other roofs (BUR, modified bitumen) do.” – Metal roof, manufacturing/ industrial, northern US.
“Our roof is 39 years old and does not really require maintenance.” – Metal roof, manufacturing/industrial, southern US.
- Compared to asphalt and single-ply roofs, owners and property managers of metal roofs report the highest level of customer satisfaction with “value for price paid.” When owners and managers of asphalt, single-ply and metal roofs rated their satisfaction with “the value of their roof for the price paid” on a 1-5 scale (1 being not at all satisfied and 5 being extremely satisfied), metal roofs came out on top. Detailed ratings were as follows:
Satisfaction 1 - 5 Scale Metal 4.75 Asphalt 4.30 Single-ply 3.91
- When asked what material owners and managers would use for re-roofing, metal owners showed the greatest loyalty.
Would Use the Same Roofing Material Metal 92% Single-ply 58 Asphalt 46
- Maintenance activities play a critical role in the overall life cycle cost, as well as the building owner’s decision regarding material selection.
- Among ten criteria considered for the purchase of a new roofing material, “service life” was rated #1 and “initial cost” was rated #9. Importance ratings for each factor are shown below. (1 = not at all important, 5 = extremely important)
Factor Importance 1 - 5 scale Service life 4.78 Life cycle cost 4.63 Weatherability 4.61 Familiarity/past history 4.60 Low maintenance 4.53 Environmentally friendly 4.28 Annual maintenance cost 4.26 Energy efficiency 4.08 Initial cost 4.08 Appearance 3.10
Maintenance
- On average, the roof’s share of building owners’ annual maintenance budget is relatively small (less than five percent).
- Primary maintenance activities on all types of roofs, including the typical cost per foot for each type of maintenance, is shown in the following chart.
Cost/ft. Visual inspections .01 Picking up debris/cleaning .04 Patching .31 Repairing flashing .24 Cleaning drains .08
- Six in ten building owners and managers (61%) studied by Ducker believe that following a comprehensive maintenance schedule would prolong the life and decrease overall cost of a roof. Almost four in ten (37%) do not agree.
- Only one in five building owners and managers (22%) schedule professional roof inspections on a regular basis. Almost eight in ten (78%) do not.
- Only one in four (24%) have in place or have considered a roof assessment management program as a preventive measure for extending roof life. Three in four (76%) have not considered it.
Purchase Decision Process
- Almost eight in ten (78%) of building owners/managers characterize their involvement in the roof installation process as “extreme” or “average.” About two in ten (22%) have “little interest” or “no interest.”
- Building owners and managers believe that system manufacturers and architects/consultants – more than any other group – are responsible for educating them about their current product improvements and new products.
Percent Saying Each Group is Responsible
Manufacturer 54% Architects/consultants 51 Contractors 41 Associations 18 Conferences, engineers, distributors 13
Verbatim Comments (Education)
“The manufacturer needs to keep us appraised of new products. We go to trade shows and I do research on the Internet also. The architect will get information from a product promotion and then they will spec it not knowing the performance.” – Single-ply roof, institutional, western US.
“Butler the building manufacturer is who we talked to most about the roof. They manufactured the building and roof so they know the most.” – Metal roof, manufacturer/industrial, northern US.
Energy Efficiency
- Respondents believe that PVC and BUR are the most energy efficient roofing materials. When asked which materials are thought to be energy efficient, six common roofing materials were ranked as follows:
% Perceiving Each Material as Energy Efficient PVC 32% BUR 32 TPO 18 EPDM 14 Metal 14 Modified Bitumen 9
- Awareness levels are increasing regarding the importance of energy efficiency/reflectivity, though roofing material product selection based on reflectivity characteristics is still in its infancy.
Increasing Use of Solar Efficient Materials
- When asked if they plan to increase the use of materials that contribute to solar efficiency, 40% said “yes,” and 53% said “no.”
- Of those who said “yes,” the likely materials to be used to increase solar efficiency are as follows:
White PVC 33% White EPDM 20 White coatings 13 Hypalon 13 TPO 7
Re-Roofing
- When asked what material owners and managers would use for re-roofing, 68% would use the same materials used originally, 32% would use a different material.
