The raid happened on Friday, December 7, shortly before 10.30pm on Atlas Mill Road, when the robbers entered the property wearing balaclavas, some carrying weapons.
They made threats to the occupants and demanded money.
They took cash and fled on foot, onto Owler Ings Road, past The Bridge public house and down a canal towpath into Owler Ings car park.
From there it is thought they drove off in a white VW Golf, away from the town centre.
The suspects were described as male, wearing casual clothing and balaclavas.
Anyone who witnessed the incident or has any further information is asked to contact Calderdale CID via 101, quoting crime reference number 13180614134.
Information can also be passed to Crimestoppers, anonymously, on 0800 555 111.