Residential additions require a building permit. An addition to your home can include a sunroom, a family room, a bedroom or 2nd storey addition etc.
Any addition that is attached to the building/house will require a building permit.
If the addition includes a washroom or alterations to existing plumbing fixtures, a plumbing permit is required. furthermore, if your home is serviced by an on-site private sewage disposal system, a septic permit may be required.
If the are of the addition exceeds a certain percentage, an HVAC (Heat Ventilation and Air Conditioning) Permit will be required, an HVAC Permit involves heat loss calculations, ventilation details, and the duct layouts.