Yes they should be cleaned. (They could have asked any HVAC Engineer to look it up in ASHRAE for them!)
Simply, haze in the atmosphere scatters light and reduces the amount of Solar radiation reaching the earth. Dust on a panel has the same effect! (They could also have asked any photographer that uses a yellow filter on tele-photos).
Index the world's information, organize it and use it!
Simply, haze in the atmosphere scatters light and reduces the amount of Solar radiation reaching the earth. Dust on a panel has the same effect! (They could also have asked any photographer that uses a yellow filter on tele-photos).
Index the world's information, organize it and use it!