It has been three years since the renovation. Why does it smell when it's hot?

The release of formaldehyde at home mainly comes from the formaldehyde-containing glue in the board, in which formaldehyde can be stored for up to 3- 15 years. Especially in summer, when the temperature rises and the house is stuffy, it will accelerate the release of formaldehyde and cause harm to the human body. According to your description, this is probably the case in your family.