How many vents should I put under my mobil home when I underpin it?
Also If it is not vented properly will it make the paint bubble?

how many vents should I put under my mobil home when I underpin it?
Also If it is not vented properly will it make the paint bubble?

Depending on what part of the country you are located in you want to have at least one vent for each wall. If you are in a colder climate you may look into the vents that close in the winter keeping the underside of the home warmer. If you live in a warmer climate you won't need the closing vents.

Also as far as not being properly vented - no, it will not cause your paint to bubble. Don't know what paint you are talking about as most mobile homes have vinyl siding nowadays. Also your material for properly skirting the home is usually made of vinyl as well. The vinyl skirting can be purchased with small air vent holes already in each panel or you can purchase the skirting solid with no air vents. What does matter though is what sort of preparation is made to the area under the home. Is there thick plastic sheeting being used to act as a vapor barrier laid directly on the ground and then covered with rough gravel? If so, then you don't need as much venting to keep the underside of the home free of too much moisture.

Sometimes mobile home owners like to use concrete blocks and make some sort of permanent foundation for the home to sit on. This is okay for colder climates to keep the cold out in the winter but that sort of configuation definitely needs at least 4 vents for moisture control.

Don't forget to leave an access panel for getting under the home in case of a water leak, etc. Two access panels are best versus just one.