By Calgary Roofers - GENERAL ROOFING SYSTEMS CALGARY

03/21/2010
Calgary Flat Roofing

A Critical Investment
The roof is a vital part of the building and thus a substantial and critical investment. Whether you're considering the environmental benefits of green roofing, “cool roofs”, a conventional new roof, or are looking for ways to extend the life of an existing roof, our expertise and commitment to quality will ensure your roof is built to last, and will extend the life of your building.

We believe in an educated client, it is our hope that the following guide to roofing choices will assist your organization with considerations that you may be tasked with in the process of managing your roof investment.

Re-Roofing or Retro-Fitting
No roof will last forever – not even the very best roof. Re-roofing or retro-roofing can help maintain a healthy building and your investment.

Re-roofing, or full-removal of the existing roof, involves removing the roof surface, membrane, and insulation right down to the roof deck to enable the new roof to be installed.

Retro-fitting, or re-covering, covers an existing roofing system with a new system. This process requires that all wet or deteriorating insulation be removed prior to the new system being installed. Both systems are appropriate for roofs that can no longer be repaired through regular maintenance, are showing signs of deterioration, or are beginning to leak.

Re-roofing requires special attention to detail. In most cases, the building is occupied while the installers are working. We take special care to make sure the building tenants stay safe and are inconvenienced as little as possible.

As with all roofing projects, we strive to exceed industry standards for safety and quality. Your roof is an investment and proper application of a re-roofing or retro-fitting system will extend the life of your roof for years to come.

New Roofing
Roofs are not installed in a controlled environment - projects encompass many variables. The type of material, the way it's applied, job-site conditions, and weather all affect a project. But even with all those variables, we strive to deliver a top-quality roof.

In addition to our own standards for quality, we adhere to the guidelines set out by the CRCA's recommendations for roofing and flashing details.

We also pay close attention to safety. Our safety practices are designed to ensure that our staff and the other trades working on-site stay safe and healthy for the entire project and return home to their family safe and healthy every day.

Working Together
Our management works with project consultants, designers, membrane manufacturers and general contractors to achieve the best roof assembly possible at the most competitive price.

Once a contract has been agreed to and executed, we carefully review construction schedules and project details with the owner and the applicators before the project begins.

Environmental Solutions
From green roofs to solar installations and day-lighting, our environmental solutions can help your business utilize your roof as an effective way to generate energy and find cost savings.

Roof Types
Following is an exhaustive guide of roofing applications available to the commercial, institutional, and industrial marketplace.

1. Built up Roofing (BUR)
2. Singly Ply Membrane Roofing
a. EPDM
b. TPO
c. PVC
3. Modified Bitumen (SBS) Roofing
4. Metal Roofing
5. Liquid Applied Roofing
6. Green Roofing (Garden Roofs)

1. Multiple-Ply or Built up Roofing (BUR)
Traditionally, flat roofs have been installed by setting 3-4 layers of asphalt-saturated felt (“tar-paper”) in a mopping of hot asphalt. Typically, the surfacing is gravel set in a flood-coat of hot asphalt. This is generally referred to as “conventional built-up roofing (BUR)”.

2. Single-Ply Membranes
Over the past 30 years, a wide variety of roofing membranes have been developed, using various forms of synthetic rubber and vinyl. The membrane is manufactured under controlled conditions in the factory. The seams are typically formed on site, using adhesives, tapes, or hot-air welding. Some are available in different colors, and can be manufactured in wide rolls to minimize the number of seams.

2a. EPDM (Ethylene Propylene Diene Monomer)
EPDM is a low cost single ply roofing system composed of a rubber membrane for small to large commercial and industrial projects. Applied using a fully-adhered glue system, loose-laid with gravel (ballasted), or mechanically fastened - all require no open flame. The environmentally friendly considerations are; it involves reduced emissions from equipment, fewer petroleum based products, and less waste in landfills. The system can lower heating and cooling costs with proper insulation. The product is available in white or black. Competitive life cycle costs. Less cost than a complete re-roof and is a less intrusive installation than other systems.

2b. TPO (Thermo-plastic Polyolefin Roofing Membranes)
A thermoplastic elastomer is a diverse family of rubber-like materials that, unlike conventional thermoset rubbers, can be reprocessed and recycled like thermoplastic materials. Thermoplastic polyolefins are in the thermoplastic elastomer family and are commonly referred to as TPO in the single-ply roofing industry.
TPO-based products have been used in various applications, including the automobile industry since the 1980s, and have seen their usage continue to expand. In 1989, TPO-based membrane moved into the roofing industry as a non-reinforced sheet. In 1993, the original non-reinforced TPO membrane was replaced with membranes containing reinforcing fabric. Since that time, the TPO single-ply roofing market has grown to hundreds of millions of square feet annually with TPO membrane comprising the fastest growing segment of the single-ply roofing industry.

TPO Composition
TPO roofing membrane is typically based on polypropylene and EP (ethylene-propylene) rubber polymerized together using state-of-the-art polymer manufacturing technology. This technology enables the production of TPO membranes that are flexible at low temperatures without the use of polymeric or liquid plasticizers. Unlike some other popular thermoplastic roofing membranes, the TPO polymer does not contain chlorine and no chlorine-containing ingredients are added during sheet production. This lack of chlorine has allowed TPO marketers to tout their membrane as an environmentally safe, “green” product.


The TPO resin is compounded with other components including a weathering package, fire retardants and pigments for color to create a product that can withstand the elements associated with rooftop exposure. The membrane is comprised of TPO based top and bottom plies encapsulating a reinforcing fabric that enhances the physical properties of the sheet. The combination of the fabric and TPO plies provide reinforced membranes with high breaking and tearing strength and puncture resistance. Sheet widths are available up to 3.66 m (12 ft) and membrane thickness is typically 1.1 or 1.5 mm (0.045 and 0.060 in.), however, membrane up to 2.0 mm (0.080 in.) is available.

Installation/System Types
TPO roofing membrane is typically installed using mechanical fasteners and plates placed along the edge of the sheet and fastened through the membrane and into the roof decking. Adjoining sheets of TPO membrane are overlapped, covering the fasteners and plates, and joined together with a minimum 40 mm (1 1/2 in.) wide hot air weld.

In the field of the roof, proper membrane width and fastener spacing is determined after calculating potential uplift loads based on building height, surrounding terrain and the wind zone in which the building is located. The fastener/deck combination must exhibit adequate pull-out resistance to withstand the fastener loading generated during uplift. The membrane and the welded seam must also resist the forces generated by wind uplift. The ability of a mechanically fastened system to withstand these forces is typically evaluated using a 3.7 x 7.3 m (12 ft x 24 ft) uplift table where the system may be pressurized until failure. Along the perimeter of the roof, where the highest wind loads are experienced, reduced width membrane (40 to 60 percent of the field sheet width) is installed to reduce the fastener and seam loading.

The membrane may also be fully adhered to an insulation or deck material using an adhesive. Insulation is typically secured to the deck with mechanical fasteners and the TPO membrane is adhered to the insulation.

This type of system is highly resistant to wind and its associated uplift forces. Since the sheet is 100 percent affixed to the substrate, the membrane does not flutter due to associated wind forces. With no sheet movement due to the 100 percent attachment of the membrane, the fully adhered system is ideal for very visible roofs such as domes or other high slope applications.

Weld-ability
One of the primary benefits of TPO membrane is the ability to fuse the sheets together with a hot air weld. The welding process results in a bond that is actually stronger than the sheet itself. Flashing details, such as exhaust vents, pipes and parapet corners are also completed using hot air welds and flashing material (typically non-reinforced).

When properly compounded, TPO membrane has a wide window of weld-ability, allowing the roofing applicator to complete hot air welds consistently in a broad temperature range. Since weld integrity is critical to the performance of the roofing system, it is imperative that the membrane welds properly in a wide range of ambient temperatures. TPO membrane can be welded at speeds up to 80 mm/s (16 ft/min) using a self-propelled hot-air welder, however, optimum welding speeds are 60 to 70 mm/s (12 to 14 ft/min) with the air temperature at the welding nozzle at approximately 540º C (1000º F). TPO is a thermoplastic material and does not “cure” on the rooftop once installed. This allows the sheet to be repaired with proper surface preparation after rooftop exposure.

Wide Sheet Technology
Another benefit that TPO membranes bring are wide width sheets. Currently, TPO membrane is available in the market in widths up to 3.66 m (12 ft). These wider sheets provide installed cost savings by reducing the total number of seams to be completed in the field and the labour associated with the seaming/welding process. Wider sheets also require fewer fasteners and plates for membrane to be secured, fewer rolls for the roofing applicator to handle on the roof, and less membrane being utilized in the seam overlaps.

Recyclability
TPO membrane, reinforced and non-reinforced, is 100 percent recyclable during the production process. During production, if the need arises, the membrane can be ground into “rework” and this regrind can be incorporated into the bottom ply during the extrusion process to produce new TPO product. This process results in 100 percent reuse of recycled product.

Reflectivity
Another important characteristic of TPO membrane is its high level of reflectivity. Because of this, white TPO membranes can meet and even substantially exceed ENERGY STAR performance levels. While TPO membranes typically display reflectivity ratings in the high 80 percent range when new (ENERGY STAR specifications require 65 percent minimum) and in the low 80 percent range after three-year rooftop exposure with cleaning (ENERGY STAR specifications require 50 percent minimum). TPO membranes are highly resistant to mold and algae growth, which can degrade the overall reflectivity of the roof and reduce anticipated energy savings.

Conclusion
Over the past decade, TPO membranes have succeeded in gaining strong roofing industry credibility based on their physical property characteristics, wide sheet technology and long-term rooftop performance throughout the world. The newly approved ASTM TPO specification adds credibility by providing definitive guidelines for minimum membrane properties, thus helping to ensure product quality, durability and longevity.

2c. PVC
Durability
PVC is amongst the most durable roofing and waterproofing options as proven through more than 45 years of service on roofs all over the world. Products that serve their intended purpose for a longer period of time without need for replacement are naturally more sustainable.
Recycling
PVC is the only single ply roofing membrane with an established end-of-life roof recycling program that converts the old membrane back into roofing membrane products.
Fire Safety
PVC out performs other single ply roofing materials regarding fire resistance. It is naturally fire retardant and will self extinguish with the removal of the flame source.

Energy Efficiency
Reflective vinyl roofs save energy by reducing the absorption of solar energy and its transfer to the building interior. Less heat transferred to the interior means less energy needed for air conditioning. Cooler roofs also minimize the degradation of insulation thermal efficiency that can occur at high roof envelope high temperatures. Vinyl roofing products were the first roofing products to be labelled under the EPA's EnergyStar® Roof Products Program that could also demonstrate 30 years (circa 1999) of demonstrated performance history. According to the EPA, white vinyl roofs may lower air conditioning utility expenses by as much as 50 % in some climates.

Resource Efficiency
Just 47% of the PVC resin's raw materials are derived from petroleum, less than any other single ply roofing membrane. The remaining 53% are derived from salt. Decreasing the United States dependence on foreign oil is universally accepted as a national Security and domestic policy prerogative. Vinyl roofing membranes are the most resource efficient roofing products because of their limited reliance on the hydrocarbon chain/petroleum.

Health & Safety
PVC roofing is inert and contains no dioxins. The plasticizers are highly stable and an integral part of the membrane. They have never been shown by any government body to be harmful to humans.

Code Compliance
PVC meets all applicable building codes. PVC roofing membranes also meet the cool roofing requirements of EnergyStar®, Green Globes™, and LEED®.

Air Quality/Green House Gases
Reflective roofs help to reduce the ambient air temperature in urban areas by decreasing the square footage of dark surfaces. As a result, they in turn help to decrease the formation of smog related pollutants that form when carbon monoxide interacts with warmer ambient air temperatures. Each square foot of dark coloured roof membrane replaced with a reflective PVC roof membrane reduces green house gas emissions. On average, vinyl membranes are carbon neutral after 1.7 years.

Water Quality
PVC roofing membrane is inert and does not contribute any chemicals of concern to storm water runoff.
[source: sarka sonifil]

3. Modified Bitumen
These membranes are still asphalt-based materials, but plasticizers have been added to improve strength, flexibility, water-resistance, etc. They can be incorporated into a conventional BUR, or applied as a single-ply membrane. Close cousin of the Built-up-Roof (BUR) designed for buildings with low-slope or “flat” roof structures. Engineered modified bitumen roofing membranes originated in Europe in the mid 1960's and have been used successfully in the United States and Canada since approximately 1975.

Increased resistance to brittleness at cold temperatures, greater flow resistance at high temperatures, and increased elasticity can be achieved by blending synthetic rubberized polymers with asphalt in lieu of modification by the blowing process used for BUR asphalt.

There are numerous surfacing options for this system which include a factory applied mineral surface, gravel surface, including “cool roof” coatings which are highly-reflective to save on building cooling costs. Mineral-surfaced products are typically furnished with white granules, but are also available in designer colors to match asphalt shingles or to otherwise compliment the building design.