The House explodes at the end of the film
Photoshop, After Effects, and Lightwave 3D
The photo below is of the house and was the only photo used to create the explosion.
First I separated the treetops from the foreground and reversed the sky to make it dark. Cut out the house and cut holes in the windows so the explosions could be seen indoors. Darkened and blue-hued the foreground and snow to give it a night-time feel, also added snow to the roof. Next, I created lights and snowfall in lightwave 3d so that the explosions would light up the woods and front yard as they went off. Also added yard lights to shine up on the house. Finally, bought some great HiDef explosions from Detonation Films and layered them into the mix using AfterFX.
The final Effect can be seen in this clip.
To set it up for you, Alex has set up a chemical reaction to burn the house down but has spilled some of the reactant on his shirt.
Megan has knocked down a gas can with the intent to light it and destroy Alex along with the house.