How to calculate the usable area of the house?

The calculation method of indoor area is length times width times higher than room area, and the method of indoor area is room area. After the renovation of the new house, indoor air pollution includes formaldehyde and other gases harmful to the human body. It is suggested that some flowers can still be placed after 2~4 weeks of window opening. For example, green plants such as chlorophytum, tiger tail orchid, ivy, aloe, chrysanthemum radish, etc. are conducive to absorbing harmful fine gases and purifying the air. Generally, chlorophytum can absorb more than 80% of indoor harmful gases and formaldehyde.