A porous organosilicate glass (OSG) film: Si.sub.vO.sub.wC.sub.xH.sub.yF.sub.z, where v+w+x+y+z=100%, v is 10 to 35 atomic %, w is 10 to 65 atomic %, x is 5 to 30 atomic %, y is 10 to 50 atomic % and z is 0 to 15 atomic %, has a silicate network with carbon bonds as methyl groups (Si--CH.sub.3) and contains pores with diameter less than 3 nm equivalent spherical diameter and dielectric constant less than 2.7. A preliminary film is deposited by a chemical vapor deposition method from organosilane and/or organosiloxane precursors, and independent pore-forming precursors. Porogen precursors form pores within the preliminary film and are subsequently removed to provide the porous film. Compositions, film forming kits, include organosilane and/or organosiloxane compounds containing at least one Si--H bond and porogen precursors of hydrocarbons containing alcohol, ether, carbonyl, carboxylic acid, ester, nitro, primary amine, secondary amine, and/or tertiary amine functionality or combinations.