Jim Chanos and Carson Block, two of Wall Street's biggest short sellers, fired shots at Sunrun , saying the residential solar company is not as "green" as many investors think.
"This company is the aluminum siding of the 21st century for those who are old enough to know what I'm talking about," Chanos, founder of Kynikos Associates, said at CNBC's Delivering Alpha Investor Summit in New York City Wednesday.
Aluminum re-sidings were prevalent in the 70s and 80s but they fell out of favor as the material was susceptible to scratches and dents.
Muddy Waters Capital CIO Carson Block said he has a short position against Sunrun, taking issue with the way the company deals with tax subsidies from the government.
"Muddy Waters has its 'facts' wrong.