Whether or not the property is valued as housing depends on whether the property is suitable for use as a year-round dwelling. The Tax Administration will base its approach on whether or not the property is registered as a year-round dwelling in the country's central property register (the land register). What you use the property for is of no significance.
If you are able to provide information which indicates that the property is no longer suitable for use as a year-round dwelling, the property must be valued as a holiday home. Examples of factors that will be taken into account are the standard of the dwelling, water and sewage conditions and access to the property.
If you provide information indicating that the property does not have running water, mains electricity or an integral water closet, the Tax Administration will assume that the property is a holiday home. You must be able to document/substantiate this information upon request from the tax office.