A few people will paint their attic white just because they think it looks better or think that it makes the attic look brighter when the attic lights are on while putting holiday storage boxes in the attic.
Attic fire and / or smoke evidence
Attics may be painted white to cover over evidence of a fire in the attic or home. After a fire has been put out by the fire department they may say the house is basically safe structurally or that it is not safe and the city building inspector checks the house for safety.
Roof rafters or trusses that have been exposed to a fire or very high heat may have lost part of their structural integrity. Home inspectors and buyers usually look for structural damage evidence such as cracked or sagging rafters or trusses. They may step outside and look at the roof for signs of bowing or sagging.
Attic rafters, trusses and roof sheeting (plywood, OSB, etc) often gets covered with smoke, soot or the wood gets charred in a attic fire. Usually badly damaged wood or sheeting will be replaced with new wood for structural integrity. Other framing member may be discolored or charred a little, but still be structurally sound.
Look bad – smell bad
These charred or smoke covered wood framing members do not look good to the average viewer. Worse yet, they often give off a smoky odor or smell.
Homeowners will often paint the wood framing members; rafters, trusses and roof sheeting to make the attic area look better and to encase or seal the wood so that the burnt smoky odor is eliminated or sealed.
If there has been a house fire or attic fire there is often an insurance claim. Usually this insurance claim will show up in a CLUE report.
PAINTED FOR FIRE PROTECTION
Painted with Intumescent Fireproofing Paint for Passive Fire Protection
Occasionally an owner may paint his attic for increased fire protection, but not because there has been a fire in the attic. There are some products, i.e. intumescent fire proofing paint that provides extra fire protection to wood framing members and sheeting.
In existing residential homes you usually will not see intumescent fireproofing paints because they are usually not required by the building department and are expensive.
These paints when exposed to a fire can expand by a factor of 50 to 70 times their original thickness. Doing this generates an ash-like char layer on the wood which provides a degree of fire protection
Occasionally trying to cover mold
Under some circumstances an attic will develop mold, often due to poor ventilation. Some owners may paint over what they perceive as mold and think that paint, or a special paint, will kill the mold which generally does not work. In the end, the majority of the time the painting of an attic involves capsulation of smoke odors.
Painting an attic white or some other color after being exposed to a fire or smoke is not unusual. It improves the look of the attic but the main reason is for encapsulating the smoke odor.