Roof cleaning is the process of removing algae, mold, mildew, lichen and moss from roofs. Also cleaning oxidation on metal roofs. Cleaning can extend the duration of a roof's ability to function. Algae and other types of build-up often form on the north and west parts of roofs that are shaded or receive less sun, and can reduce a roof's life expectancy. The presence of soot, dirt, or biomass can affect how much sunlight is absorbed by a roof and thus the amount of heat a building absorbs.
Cleaning may be accomplished with a bleach or sodium percarbonate solution, various cleaning products or commercial cleaning services. The Asphalt Roofing Manufacturers Association (ARMA) recommends using a 50/50 solution of 12.5% sodium hypochlorite (pool chlorine) and water to remove moss and algae. The addition of zinc strips near the roof's peak may reduce the regrowth of algae and moss.
Roof cleaning devices may use high-pressure water spray and rotary surface cleaners, and some have extensions to enable their use from the ground. Because of the high pressure, damage may occur with untrained operators. Soft washing is the most preferred by the roofing manufacturers because it is applied at a very low pressure, allowing approved soaps and solvents to kill the mold. Soft washing can be done by changing the tip on the pressure washer so that it drops the pressure down to around 500 psi (3,400 kPa) or less, or can be done using a 12-volt, air diaphragm, or gas-engine driven pump. Using a venturi setup at the end of the pressure line can use the principles and utilise the best of the low and high pressure setups. In Australia the use of higher concentrations of sodium hypochrlorite may rapid ly rust metal roof screws if the roofs have been rescrewed with lower grade screws.
Roof cleaning devices exist that may minimize the spread of airborne radioactive materials (in contaminated areas) and other harmful materials, such as asbestos. Specialized robots have been designed to facilitate cleaning roofs.
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- Fox59 4:34 p.m. EDT, August 28, 2012 (2012-08-28). "Stretching Your Dollar: Cleaning your roof for a good price". fox59.com. Retrieved 2018-06-08.
- Levinson, Ronnen; Paul Berdahla; Asmeret Asefaw Berheb; Hashem Akbaria (December 2005). "Effects of soiling and cleaning on the reflectance and solar heat gain of a light-colored roofing membrane". Atmospheric Environment. 39 (40): 7807–7824. doi:10.1016/j.atmosenv.2005.08.037. Retrieved 18 April 2013.
- "Sodium Hypochlorite, Sodium Percarbonate or Sodium Hydroxide for Roof Cleaning?". eClean Magazine. Retrieved 2017-06-29.
- "ARMA - Asphalt Roofing Manufacturers Association | Algae & Moss Prevention and Cleaning for Asphalt Roofing Systems". www.asphaltroofing.org. 2016-09-23. Retrieved 2017-06-29.
- Airborne Radioactive Contamination in Inhabited Areas - Kasper G. Andersson - Google Books, pp 223 - 229.
- ""We're Here to PUMP! You Up!"". eClean Magazine. Retrieved 2017-06-29.
- Elkmann, N; Felsch, T.; Sack, M.; Saenz, J.; Hortig, J. (2002). "Innovative service robot systems for facade cleaning of difficult-to-access areas". Intelligent Robots and Systems, 2002. IEEE/RSJ International Conference on. 1: 756–762. doi:10.1109/IRDS.2002.1041481. Retrieved 18 April 2013.