Remember kids, think first before you take action.

[WindexGlow]

That's what I had done, kept throwing a chair at the door until the other chair started showing.
Than I started throwing the chair on the other side (wouldn't actually be thrown, but would move around)

I was able to open the door enough to finally open it. I than went into the vents and discovered that

Spoiler below!

the special picture-frame in front of the vent near that door

Wish I had figured that one out myself instead of cheating =[