The roof that an organization puts on its building – be it a small firm working in a residential-type house or a skyscraper – is one of the most important factors in determining energy efficiency.
Roofs play into energy efficiency in a number of ways. At the highest level – no pun intended – roofs are the major barrier against hot or cold air from entering or escaping the structure. The three key elements controlling this are simply whether there are gaps or holes, the material of which it is made and its color.
Steel and other metals often are used for roofs. This week, Bob Zabcik, the Director, Research and Development at NCI Building Systems, posted a commentary at Building Design + Construction that looked at metal roofs. There are, he said, three reasons that metal roofs are a good choice for buildings: They offer installation advantages, have a longer life expectancy than other options and can moderate the temperatures – and thus cooling needs – in the structures they cover.
A second and somewhat less commonly known advantage of metal roofs that Zabcik points out is that it improves the performance of the solar panels:
This is because PV modules get very hot in the sun, and this heat increases the electrical resistance of the circuit they power, reducing total efficiency. By using Cool Roofing, this effect is reduced.
It is not surprising, judging from its name – the Steel Market Development Institute – that this link provides a lot of reasons that steel is a good construction material for buildings. They fill the bill by offering 13 reasons that metal is drives efficiency. One of the most compelling is that cool metal roofs are not just for new construction:
Cool metal roofs are an excellent option for commercial retrofit applications because they can be efficiently installed with above-sheathing ventilation, allowing heat to dissipate through the ridge vent in hot weather while acting as an insulating layer when it is cold. Metal roofs can result in as much as a 30 percent reduction in heat gain through the roof.
The other reasons presented must, of course, be verified elsewhere. They do seem compelling. For instance, the list points out that metal roofs are resistant to damaging micro-organisms and shed dirt more easily than other surfaces.
Of course, there are arguments to be made for all sorts of roofing materials. Different materials simply have different attributes. There also are a wide variety of buildings. Buildings.com points to pitched and flat roofs as two variations that might tilt the scales to one material or another. And there is no shortage of metal approaches. Eric Skoog mentions cold-rolled steel, zincalume, painted steel, painted aluminum, copper and zinc. There no doubt are others.
The color of the roof appears to experts to be about as important as the material itself. It is a clear choice: Light colored roofs reflect heat — and thus are more appropriate for hot climates — and dark roofs absorb heat and are best for colder areas. Metal roofs seem more likely to truly differentiate themselves when it comes to the length that they last and what may be a greater ability to withstand damage from storms and other environmental hazards. Metal simply is stronger than most other materials.
The roofing market, driven by new construction and the rebound from the bad economy earlier in the decade seems to be healthy. Companies constructing new buildings or replacing the roof on an old one should pay very close attention – and perhaps attend or follow Metalcon, which will be held during the last week of October in Baltimore.