If it cannot be moved
The north-west is the corner of movement, and the tradition wants worship settled rather than in transit. Where the room is fixed, the altar goes in its north-east corner and the space is kept free of storage.
What the ವಾಯವ್ಯ governs
The north-west — Vayavya — is the air corner: movement, circulation, things that come and go. Guests, storage in transit and utilities sit here easily, and nothing meant to be permanent does.
Where the ಪೂಜಾ ಕಕ್ಷ belongs
The pooja room belongs to the light half of the plan. The tradition puts it where the first sun falls and keeps it away from anything heavy, wet or waste-carrying — including sharing a wall with a bathroom, which matters more than the compass point.