If there's one thing studios have to fear this year, it's opening against a horror film.

'Insidious: Chapter 2' continued the genre's hot streak at the box office this weekend, exploding into an otherwiselifeless month with an estimated $41 million gross in the U.S. and Canada. The ultra-low-budget sequel distributed by FilmDistrict cost only $5 million to make and has taken in more than triple the openingweekend gross of the original 'Insidious' in 2010, once again proving horror movies are the closest thing today to a safe box office bet.

Second place went to the weekend's other new release, 'The Family,' which drew older audiences and grossed $14.5 million. The movie, starring Robert De Niro as a former Mafia don who moves his family to France as part of the witness-protection program, cost $30 million to make and was released by Relativity Media LLC and eOne as a bid to appeal to different moviegoers than 'Insidious: Chapter 2.'

The tactic, known in the industry as counter programming, apparently worked, with the movies attracting very different crowds. About 83% of the audience for 'The Family' was over the age of 25, whereas only 38% of the audience at 'Insidious: Chapter 2' was.

'We always thought there was room for both pictures to simultaneously succeed,' said Kyle Davies, president of world-wide distribution at Relativity.

The 'Insidious' sequel benefited from a PG-13 rating and a Friday the 13th release date. The audience for the 'Insidious' franchise has grown since the first one performed well on home video, said Jim Orr, president of distribution at FilmDistrict.

The horror genre is having a banner year using a model forged 14 years ago by 'The Blair Witch Project,' a 'found footage' horror movie that grossed $140 million on a budget that would be a rounding error on most studio productions. That trend picked up again when Viacom Inc.'s VIAB -0.34% Paramount Pictures released the surprise hit 'Paranormal Activity' in 2007, and has been on display this year since January, when 'Mama' from Comcast Corp.'s CMCSA +1.10% Universal Pictures grossed $71.6 million domestically on a $15 million budget.

The low-budget, high-return formula is most closely associated with Blumhouse Productions, the company behind the 'Paranormal Activity' and 'Insidious' franchises and 'The Purge,' a summer release from Universal Pictures that grossed $64.5 million domestically on a $3 million budget. The company's next movie, 'Paranormal Activity: The Marked Ones,' is a Latino-focused spinoff of the blockbuster franchise due in January.

The success of the genre has upended a releasecalendar that once relegated horror movies to the winter months and Halloween season, proving they can compete with summer spectacles and break out of the traditionally quiet September.

'If you have a great film and you market it aggressively, I don't know if you have to wait until October for a horror film,' said Mr. Orr.

'Insidious: Chapter 2' director James Wan also directed 'The Conjuring,' a haunted-house summer release from Time Warner Inc.'s TWX -0.38% Warner Bros. that outperformed several summer 'tentpole' productions with a $135 million domestic gross.

'James Wan has just mastered the scary movie,' said Mr. Orr.

That success with horror genre movies has gotten Mr. Wan a higher-budgeted gig: He is directing the 'Fast & Furious 7' sequel due from Universal next July.

In other box office news, third place at the box office went to Universal's 'Riddick,' which saw its gross fall 63% from last weekend to $7 million. It has grossed $31.3 million so far. Weinstein Co.'s 'Lee Daniels' The Butler' passed the $100 million mark in its fifth week in release, and so did 'This Is the End' from Sony Corp.'s Sony Pictures in its fourteenth week of release.