Asphalt is an aliphatic compound and in almost all cases a byproduct of the oil industry. Some asphalt is manufactured from oil as the intended purpose, and this is limited to high quality asphalt produced for longer lasting asphalt built-up roofs. Asphalt ages through photo-oxidation accelerated by heat. As it ages, the asphalts melt point rises and there is a loss of plasticizers. As mass is lost, the asphalt shrinks and forms a surface similar to alligator skin. Asphalt breaks down slowly in water, and the more exposure the more rapid the degradation. Asphalt also dissolves readily when exposed to oils and some solvents.
There are four types of roofing asphalt. Each type is created by heating and blowing with oxygen. The longer the process the higher the melt-point of the asphalt. Therefore, Type I asphalt has characteristics closest to coal tar and can only be used on dead level surfaces. Type II, is considered flat and can be applied to surfaces up to 1/4 in 12 slopes. Type III, is considered to be “steep” asphalt but is limited to slopes up to 2 in 12, and Type IV is “special steep”. The drawback is, the longer it is processed, the shorter the life. Dead level roofs where Type I asphalt was used as the flood and gravel adhesive has performed nearly as well as Coal Tar. Asphalt roofs are also sustainable by restoring the lifecycle by making repairs and recoating with compatible products. The process can be repeated as necessary at a significant cost savings with very little impact on the environment.
Asphalt BUR is made up of multiple layers of reinforcing plies and asphalt forming a redundancy of waterproofing layers. The reflectivity of built up roofs depend on the surfacing material used. Gravel is the most common and they are referred to as asphalt and gravel roofs. Asphalt degradation is a growing concern. UV-rays oxidize the surface of the asphalt and produces a chalk-like residue. As plasticizers leach out of the asphalt, asphalt built up roofs becomes brittle. Cracking and alligatoring inevitably follows, allowing water to penetrate the system causing blisters, cracks and leaks. Compared to other systems, installation of asphalt roofs is energy-intensive (hot processes typically use LP gas as the heat source), and contributes to atmospheric air pollution (toxic, and green-house gases are lost from the asphalt during installation).
A bitumen is a term applied to both coal tar pitch and asphalt products. Modified Bitumens were developed in Europe in the 1970s when Europeans became concerned with the lower performance standards of roofing asphalt. Modifiers were added to replace the plasticizers that had been removed by advanced methods in the distillation process. The two most common modifiers are APP (attactic polypropylene) from Italy and SBS (styrene-butadiene-styrene) from France. The United States started developing modified bitumen compounds in the late 1970s and early 1980s. APP was added to asphalt to enhance aging characteristics and was applied to polyester, fiberglass, or polyester and fiberglass membranes to form a sheet good, cut in manageable lengths for handling. Usually applied by heating up the underside of the roll with a torch provided a significant fire hazard and was outlawed in some municipalities when buildings caught fire and some burnt to the ground. Another problem developed when a lack of standards allowed some manufacturers to produce goods with amounts of APP insufficient to enhance the aging characteristics. SBS is used as a modifier for enhancing substandard asphalt and provides a degree of flexibility much like rubber. It also is applied to a myriad of carriers and produced as a sheet-good in rolls that can be easily handled. SEBS – (styrene ethylene butadiene styrene) is a relatively new formulation increasing flexibility of the sheet and longevity.
Turbo Seal is a self healing gel like membrane that never cures. Made of 45% recycled tire rubber, it goes on top of existing tar (asphalt) roofs then capped with a sheet membrane.
COAL TAR PITCH BUILT UP ROOF
Coal Tar Pitch is a known carcinogen, forbidden by code in some areas. When installing and patching existing coal tar roofs, worker and building occupant exposure should be avoided, or minimized to the maximum extent possible. Coal Tar fumes are hazardous and provisions must be made during application to prevent fumes from getting into the building. Workers should wear protective equipment and clothing, and commonly get higher compensation (Pitch Pay) for exposure to the health risks.
Coal Tar is an aromatic hydrocarbon and a by-product from the coking process of the coal industry. It is historically in abundance where coal is used in steel manufacturing. It ages very slowly through volatilization and is an excellent waterproofing and oil resistant product. Roofs are manufactured by heating the coal tar and applying between layers of coal tar saturated felts. It has limitations to application on dead level or flat roofs with slopes less than 1/4 in 12. It has a tendency to soften in warm temperatures and “heal” itself. It is typically ballasted with gravel to provide a walking surface, however a mineral surface membrane is available. Coal Tar provides an extremely long life cycle that is sustainable and renewable. It takes energy to manufacture and to construct a roof with it but its proven longevity with periodic maintenance provides service for many years, with ages from 50 to 70 years not uncommon, with some now performing for over a century. Currently, there are cold process (no kettle is used) coal tar pitch products that almost eliminate all fumes associated with its typical hot process version.
Coal tar pitch is often confused with asphalt, and asphalt with coal tar pitch. Although they are both black and both are melted in a kettle when used in roofing, that is where the similarity stops.
EPDM is an extremely durable synthetic rubber roofing membrane (ethylene propylene diene terpolymer) widely used in low-slope buildings in the United States and worldwide. Its two primary ingredients, ethylene and propylene, are derived from oil and natural gas. EPDM is available in both black and white, and is sold a broad variety of widths, ranging from 7.5 feet to fifty feet, and in two thicknesses, 45 and 60 mils. EPDM can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system sealed with liquid adhesives or specially formulated tape. Typically, there are three installation methods.
1.) Ballasted at 1,000 lbs/sq or 10 lbs/sq.ft. with large round stones.
2.) Mechanically attached is another method and is suitable in some applications where wind velocities are not usually high.
3.) Fully adhered is the most expensive installation method.
PVC (Vinyl) MEMBRANE ROOFING
Polyvinyl Chloride (PVC) membrane roofing is also known as vinyl roofing. Vinyl is derived from two simple ingredients: fossil fuel and salt. Petroleum or natural gas is processed to make ethylene, and salt is subjected to electrolysis to separate out the natural element chlorine. Ethylene and chlorine are combined to produce ethylene dichloride (EDC), which is further processed into a gas called vinyl chloride monomer (VCM). In the next step, known as polymerization, the VCM molecule forms chains, converting the gas into a fine, white powder – vinyl resin – which becomes the basis for the final process, compounding. In compounding, vinyl resin may be blended with additives such as stabilizers for durability, plasticizers for flexibility and pigments for color.
Thermoplastic is heat-welded seams form a permanent, watertight bond that is stronger than the membrane itself. PVC resin is modified with plasticizers and UV stabilizers, and reinforced with fiberglass non-woven mats or polyester woven scrims, for use as a flexible roofing membrane. PVC is, however, subject to plasticizer migration. (a process by which the plasticizers migrate out of the sheet causing it to become brittle.) Thus a thicker membrane has a larger reservoir of plasticizer to maintain flexibility over its lifespan. PVC is often blended with other polymers to add to the performance capabilities of the original PVC formulation, such as KEE – Keytone Ethylene Ester. Such blends are referred to as either a CPA – Copolymer Alloy, or a TPA – Tripolymer Alloy.
Vinyl roofs provide an energy-efficient roofing option due to their inherently light coloring. While the surface of a black roof can experience a temperature increase of as much as 90 degrees under the heat of the full sun, a white reflective roof typically increases only 10–25 degrees Fahrenheit.
Vinyl membranes can also be used in waterproofing applications for roofing. This is a common technique used in association with green, or planted, roofs.
It worthy of note that many Green Building organizations recommend not using PVC roofing due to significant environmental hazards from the toxicity of the manufacturing process as well as the noxious compounds released in a fire such as hydrochloric acid fumes and byproducts including dioxin, a potent carcinogen. Installers should also be informed of possible hazardous fumes while installing PVC membranes and where personal protective equipment.
TPO (Flexible Thermoplastic Polyolefin Single-ply Roofing)
TPO is “Flexible”-retains flexiblilty “Thermo”-can be reheated again and again, does not cure”. “Polyolefin”-a polymer produced from a simple olefin. Flexible Thermo Poly-Olefin is the exact physical and chemical name given to the product “TPO” Thermo Plastic Olefin. Although TPO exhibits the positive characteristics of other Thermo Plastics, it does not however have any “plasticizers” added to the product like other Thermo plastics. This mis-categorization made sense when the product was introduced in the early 1990s and was unproven in the industry. TPO was categorized with thermo plastic membranes that were similar in look and performance but were far from there real chemical and physical characteristics of the TPO membrane.
TPO was formulated to fix all the problems associated with other Thermo plastic membranes. Having no plasticizers and chemically being closer to rubber but having better seam, puncture, and tear strength, TPO was touted to be white weld-able rubber of the future.
From 2007-2012 reported sales of TPO roofing products by all six major U.S. manufacture’s report materials and accessories sales quadrupling all other flat roofing materials. Gross sales of TPO membrane roofing in U.S. exceeds all other flat roof types combined. TPO’s rapid market acceptance over the last twenty years by contractors, architects, engineers, and the market in general shows it is living up to its original purpose and it’s here to stay. TPO is also being touted as the green solution as it is safer for installers and recycles 100% with out chemical byproduct. Flexible Thermo Polyolefin will soon replace the Thermo Plastic Polyolefin as the correct abbreviation for the TPO membrane roofing category
This roofing material can be fully adhered, mechanically fastened, or ballasted. TPO seam strengths are reported to be three to four times higher than EPDM roofing systems.
This is a popular choice for “Green” building as there are no plasticizers added and TPO does not degrade under UV radiation. It is available in white, grey, and black. Using white roof material helps reduce the “heat island effect” and solar heat gain in the building.
FIBERGLASS GRP ROOFING
A GRP roof is a single-ply GRP laminate applied in situ over a good quality conditioned plywood or OSB3 deck. The roof is finished with pre-formed GRP edge trims and a coat of pre-pigmented topcoat. The durability and lightweight properties of GRP make it the ideal construction material for applications as diverse as lorry aerofoils and roofs, boats, ponds and automotive body panels. GRP is also used in hostile industrial settings for applications such as tanks and underground pipes; this is due to its ability to withstand high temperatures and its resistance to chemicals. Unlike other roofing materials, GRP has properties that render it ideally suited to small craft construction. As well as being an inexpensive material, it is robust, flexible and will never corrode.
Roof coatings are seamless and when installed correctly, can solve roof leaks on almost any type of roof substrate.
Field-applied reflective roof coatings can extend the useful life of nearly every roof substrate keeping a roof surface cool and providing a level of protection from the sun and weather.
Roof coatings can add 25 years to the service life of a roof and reduce the amount of discarded roofing materials that end up in landfills. The infrared image on the right shows “175°F” on the uncoated (black) section of the modified bitumen roof. The coated (white) section is “79°F”. Field studies have shown that cool roof coatings can lower rooftop temperatures and reduce air conditioning bills.
Most flat roofs are not perfectly sloped, causing water to puddle in some areas, in particular around the drains and scuppers. Many roof coatings are not rated or warranted for “Ponding Water”, and thus might fail pre-maturely if exposed to standing water over long periods of time. Serious consideration should be given to the performance and limitations of the coating being selected. Some manufacturers will warranty their coatings including ponding water. Typically, manufacturers for acrylic roof coatings do not include warranties for ponding water, while some polyurethane roof coatings manufacturer will warranty.
A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproof membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. Rooftop ponds are another form of green roofs which are used to treat greywater.
Green roofs serve several purposes for a building, such as absorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower urban air temperatures and mitigate the heat island effect. There are two types of green roofs: intensive roofs, which are thicker and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are covered in a light layer of vegetation and are lighter than an intensive green roof.
The term green roof may also be used to indicate roofs that use some form of green technology, such as a cool roof, a roof with solar thermal collectors or photovoltaic panels.
Species, with only the hardiest surviving varieties selected for installation on the roof
Green roofs are used to:
- Reduce heating (by adding mass and thermal resistance value) A 2005 study by Brad Bass of the University of Toronto showed that green roofs can also reduce heat loss and energy consumption in winter conditions.
- Reduce cooling (by evaporative cooling) loads on a building by fifty to ninety percent, especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir – a concentration of green roofs in an urban area can even reduce the city’s average temperatures during the summer
- Reduce stormwater run off — see water-wise gardening
- Natural Habitat Creation — see urban wilderness
- Filter pollutants and carbon dioxide out of the air which helps lower disease rates such as asthma — see living wall
- Filter pollutants and heavy metals out of rainwater
- Help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies
- If installed correctly many living roofs can contribute to LEED points
- Increase agricultural space
- With green roofs, water is stored by the substrate and then taken up by the plants from where it is returned to the atmosphere through transpiration and evaporation.
- Green roofs not only retain rainwater, but also moderate the temperature of the water and act as natural filters for any of the water that happens to run off.
Many green roofs are installed to comply with local regulations and government fees, often regarding stormwater runoff management. In areas with combined sewer-stormwater systems, heavy storms can overload the wastewater system and cause it to flood, dumping raw sewage into the local waterways. Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. It has been found that they can retain up to 75% of rainwater, gradually releasing it back into the atmosphere via condensation and transpiration, while retaining pollutants in their soil. Elevation 314, a new development in Washington, D.C. uses green roofs to filter and store some of its storm water on site, avoiding the need for expensive underground sand filters to meet D.C. Department of Health storm-water regulations.
Combating the urban heat island effect is another reason for creating a green roof. Traditional building materials soak up the sun’s radiation and re-emit it as heat, making cities at least 4 degrees Celsius (7 °F) hotter than surrounding areas. On Chicago’s City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically 1.4–4.4 degrees Celsius (2.5–8.0 °F) cooler than they are on traditionally roofed buildings nearby. Green roofs are becoming common in Chicago, as well as in Atlanta, Portland, and other United States cities, where their use is encouraged by regulations to combat the urban heat-island effect. Green roofs are a type of low impact development. In the case of Chicago, the city has passed codes offering incentives to builders who put green roofs on their buildings. The Chicago City Hall green roof is one of the earliest and most well-known examples of green roofs in the United States; it was planted as an experiment to determine the effects a green roof would have on the microclimate of the roof. Following this and other studies, it has now been estimated that if all the roofs in a major city were greened, urban temperatures could be reduced by as much as 7 degrees Celsius.
Green roofs also provide habitats for plants, insects, and animals that otherwise have limited natural space in cities. Even in high-rise urban settings as tall as 19 stories, it has been found that green roofs can attract beneficial insects, birds, bees and butterflies. Rooftop greenery complements wild areas by providing stepping stones for songbirds, migratory birds and other wildlife facing shortages of natural habitat.
The main disadvantage of green roofs is the higher initial cost of the building structure, waterproofing systems and root barriers. The additional mass of the soil substrate and retained water can require additional structural support. Some types of green roofs do have more demanding structural standards especially in seismic regions of the world. Some existing buildings cannot be retrofitted with certain kinds of green roof because of the weight load of the substrate and vegetation exceeds permitted static loading. Depending on what kind of green roof it is, the maintenance costs could be higher, but some types of green roof have little or no ongoing cost. Some kinds of green roofs also place higher demands on the waterproofing system of the structure, both because water is retained on the roof and due to the possibility of roots penetrating the waterproof membrane. Another detractor is that the wildlife they attract may include pest insects which could easily infiltrate a residential building through open windows.
A metal roof is a roofing system made from metal piece, or tiles. It is a component of the building envelope.
- Steel roofs can rust, and need maintenance to prevent corrosion.
- Copper and lead roofs can be targeted by metal thieves.
- The high heat conductivity of metals (particularly copper and aluminum) requires careful incorporation of insulation into the roof structure.
- Cellular and radio reception may be negatively impacted.
Metal roofing can be used for residential or commercial buildings. The same material used for metal roofs can be used for siding as well.
Metal roofing in retrofit applications
Metal roofing can be applied over an existing roof.
Corrugated Galvanized Steel
This describes the original product that was wrought iron–steel sheet coated with zinc and then roll formed into corrugated sheets. This product is still used today in most areas. The newer push of modern architecture and “green” products has brought these products back to the foreground.
A blend of zinc, aluminium and silicon-coated steel, sold under various trade names like “Zincalume”, “galvalume”,etc. Sometimes left in the raw zinc finish, but more widely used as a base metal under factory coated colors.
Available for harsh conditions and/or as a distinctive design element. Usually roll-formed into standing seam profiles.
Copper roofs offer corrosion resistance, durability, long life, low maintenance, radio frequency shielding, lightning protection, and sustainability benefits. Copper roofs are often one of the most architecturally distinguishable features of prominent buildings, including churches, government buildings, and universities. Today, copper is used in roofing systems, flashings and copings, rain gutters and downspouts, domes, spires, vaults, and various other architectural design elements. Copper could be reused because of its high value in recycling and its variety of potential uses.
One of the longest-lasting metals, but somewhat expensive compared to steel products. Aluminum roofs are very lightweight, corrosion-resistant, have high natural reflectivity and even higher natural emissivity, increasing a building’s energy efficiency. Aluminum products with Kynar paints easily last over 50 years. The newest innovation is anodizing of the aluminum coil stock for use in architectural details and standing seam panels. The anodized layer is intimately bonded to the metal and is not normally subject to weathering and wear.
Stone Coated Steel
Panels made from zinc/aluminium-coated steel with acrylic gel coating. The stones are usually a natural product with a colored ceramic coating.
A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. It has elastic properties that allows it to stretch and return to their original shape without damage.
Typical roof coating dry film thickness vary from paint film thickness (plus or minus 3 dry mils) to more than 40 dry mils. This means a roof coating actually becomes the top layer of a composite roof membrane and underlying system. As such, the roof coating is the topmost layer of protection for the membrane, receiving the impact of sunlight (both infrared and ultraviolet (UV), rain, hail and physical damage.
Roof Coatings should not be confused with Deck Coatings. Deck Coatings are traffic bearing – designed for waterproofing areas where pedestrian (and in some cases vehicular) traffic is expected. Roof Coatings will only waterproof the substrates but will not withstand any kind of on going use by people or vehicles (such as walkways, patios, sundecks, restaurants, etc.).
Metal Roof Coatings
Several different types of coatings are used on metal panels: anti-rust, waterproofing, heat reflective. They are made of various materials such as epoxy and ceramic.
Untreated Metal roofs absorb and retain heat which causes high building envelope heat loads.
Can be applied on metal roof materials to add heat reflective characteristic. Most ceramic coatings are made from regular paint, with ceramic beads mixed in as an additive. Although an average ceramic coated roof material reflects 75% to 85% of solar radiations, performance drops by over 30% after a few years due to dirt build-up. Their composition and thickness (from 500 to 1,000 micrometres) can cause cracks to appear, and the color selection is generally limited to white matte finish.
Coatings are sometimes applied to copper. Clear coatings preserve the natural color, warmth and metallic tone of copper alloys. Oils exclude moisture from copper roofs and flashings and simultaneously enhance their appearance by bringing out a rich luster and depth of color. The most popular oils are Lemon Oil, U.S.P., Lemon Grass Oil, Native E.I., paraffin oils, linseed oil, and castor oil. On copper roofing or flashing, reapplication as infrequently as once every three years can effectively retard patina formation.
- A metal roof graded “AG” or “Utility” will need recoating once the factory finish wears off, or corrosion will occur. These paints are commonly acrylic or polyester based. Roof coatings are the preferred material since they are able to stay elastic and withstand the thermal cycling that occurs in metal roofs.
- Roofing materials made from stainless steel, zinc or copper will rarely require maintenance over their lifetime. Any required maintenance is usually due to design or installation mistakes. Otherwise, these materials commonly last over a century.
- Metal roofing with long life polymer coatings like Kynar should not normally require maintenance until the coating fails. These products have been used for over half a century now in the U.S. and few installations have failed. They should be considered lifetime products.