What is energy efficient roofing?

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The energy efficiency roofing question

In the context of energy efficiency, the roofing system needs to be insulated. The roof is a part of the building support structure. Walls support the roof above the ground and enclose the walled space. The roof frame supports the roof covering material that provides the building with weatherproofing.

 A usual and obvious feature of many rooves is their slope. The slope helps to shed water to prevent it from entering the building from above. The roofing systems come in many types from flat structures with asphalt rubber membranes to straw thatch, wood and slate shingles, clay and concrete tiles, composite and metal roofing systems. More recent developments incorporate solar tiles and roofs with solar panels to collect energy.

Steep and flat roofs give energy-efficient roofing

The slope of a roof can range from almost flat to steeply inclined. The “roof” is the all-weather cover to a building and can be made of many materials. A roof usually has a slope to encourage water to move off the roof under gravity. Steep-slope roof systems typically comprise individual installed tiered assemblies. That will make the steep roof as watertight as possible and shed snow. Steep slope roofing describes a water-shedding type of roof with a slope exceeding 14 degrees.

A flat roof can provide energy-efficient roofing. Most low-slope roofs need to have some waterproofing membrane material. The roofing membrane systems consist of materials and compounds like asphalt, bitumen, tar, rubber, ceramic tiling, plastic and other waterproof solutions. That membrane has three main components: Let’s start with a range of roofing solution items.

  • A Roof covering component that provides the weatherproofing to prevent water from entering from above.
  • Strengthening for dimensional stability and membrane puncture resistance. This provides a backup to the weatherproofing barrier.
  • A structural substrate and material system to increase protection of the membrane from weather, hail, sunlight, and fire. The substrate will add resistance to the abrasion of pedestrian traffic.

Asphalt continues to be a common roof membrane material for waterproofing a flat roof. About 40 years ago coal tar pitch was a common waterproofing membrane. Asphalt exhibits a particular problem if its oil solvent evaporates over time. The dry asphalt membrane becomes cracked and will leak at cracks where ponding occurs. Roofs with asphalt membranes require some slope to prevent the possibility of ponding. Provide some degree of slope to shed water from all low-slope roof membranes systems. Provide a slope for flat roof systems. Such rooves are sealed with modified bitumen, sprayed polyurethane plastic foam, roof insulations, and metal panels.

The roofing type: steep or low pitched

There are generic classifications of steep slope roof coverings. The thatch roof is the most low-tech roofing system. Thatch roofs will usually have a slope of 45 degrees or more. The thatch is not very watertight. The straw thatch is about 300 mm thick. The steep slope serves to have the water runoff. If the water did not runoff quickly it will penetrate and saturate the roof material.

Shingles and tiles are a steep roof covering. Shingles are flat pieces of material. The layered pieces help to shed water. Traditionally, shingles made from asphalt, stone, slate, or wood are roof covers. Slate shingles are heavy stone materials. It is a natural type of stone that splits into thin layers if hit with a chisel in the right way. Craftsmen produce thin waterproof stone tiles. The tiles overlap to form a roof. Slate roofing needs to have a sufficient slope. Water must run off the roof without trickling through the gaps. Stone roof tiles are not uniform in size and thickness. The split natural stone is not a highly waterproof roofing system. Roof tiles can be manufactured from clay, concrete, or metal and are uniform. They are suitable for a lesser steep slope above 14 degrees.

The roof must be durable

The energy-efficient roofing of the house must appear attractive, resist storm damage and be durable. In a cold climate with snow, the roof structure must be self-shedding or built to support snow loads. In warm climates, the roof insulation must keep the supporting structure cool if the day is hot. The insulated roof will help retain heat in cold climates. In windy locations, the roof must be able to withstand the horizontal and vertical wind loads. A roof needs to withstand wind loads, which can be extreme in some areas. The roof must accommodate the live weight of maintenance workers and materials traversing the area.

The metal roof system

Longer sheets roofing systems made from metal, synthetic materials, polycarbonate, and composites suit steep and flat roofs. Composite panels use a sandwich of metal sheet with polystyrene and gypsum board as a long span insulated lightweight roofing solution.

Metal sheet roofing systems are popular in educational, commercial, industrial and residential buildings. The roof material is light, strong, economical, and waterproof. Manufacturers make various profiles of metal sheets in a range of custom lengths. They use metals like mild steel, zinc, copper, aluminium and stainless steel. Steel roofing sheets need to be protected from corrosion. That occurs by coating the metal with a protective layer like zinc or paint. The roof sheets are relatively thin and require adequate uniform support. The sheets become part of the roof structure with efficient roof fixings. Adding effective insulation with the roof sheeting improves the thermal efficiency of the building.

The pros and cons of a metal roof

Metal Roof sheeting is an energy-efficient roofing system. Uniform profile metal sheets are cost-effective as a cover material and typically quick to install. Metal roof sheeting is a long-lasting, weather-resistant covering. If installed with a reflective coating it will serve to reduce home cooling costs. Where an insulation layer is below the decking sheet the efficiency of the metal roof improves.

Metal roof sheeting is thin and can be easily damaged/ dented. Direct pedestrian traffic over the roof to appropriate maintenance access ‘walkways’. The impact of hail or tree branches in storms can damage the roof surface. Metal sheets laid in long lengths are hard to replace compared with single tile or shingle types of roofing. That difficulty makes metal sheets more secure to prevent unwanted entry via the roof. Metal sheeting in long lengths is prone to expansion and contraction with temperature changes. There is movement and creaking noises that accompanies the changing effects of heating and cooling the structure.

Functional energy-efficient roofing

An efficient roof will provide shelter. The roof is a functional element of the building. It can be an aesthetic element of the design. The roof is a covering element to keep the building weatherproof.  Insulate the roof to minimise heat gain or heat loss. The insulation will reduce the environmental noise from penetrating the structure from above. The most efficient roofing system is the one that does its intended job for a long period with low maintenance. The roof looks good and moderates the above ceiling temperature within a habitable band of temperatures. The materials available to do that are many and various. The roofing systems improve year by year.

Roof designs provide shelter and more. Good roof structures materials include natural timber, metal or synthetic materials (like concrete, plastic and fibreglass). They can be clad with any of the natural or composite materials mentioned above. For some observers, the quality of the roof aligns with a particular aesthetic supporting their personal taste. Classical architecture may oblige a classical roof material and appearance.

Sufficient and energy-efficient roof

A sufficient roof will have the strength to support added features and some level of live loading. The design will cater for wind loading plus the occasional higher forces of nature, rain, snow or sun. Some locations have full seasons of extreme heat that might be part of the usual weather cycle and natural environment. An energy-efficient roofing design may become adorned with a solar PV panel that will generate electricity and a solar thermal panel for producing hot water.

The design will envision a construction period where some added loading must be considered. Designers must consider the deadweight of future solar panels, piping and wiring. The foot traffic of installers carrying that material to install roof appendages must be calculated. Designers may not know solar panels will be installed. After the building is erected the roof must carry live loads of installers and maintenance people. There will be people working on the roof at some time.

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