However, there are also some potential drawbacks to using a duvet cover without the insert. For one thing, without the insert, the duvet cover may not provide as much warmth or insulation as it would with the insert For one thing, without the insert, the duvet cover may not provide as much warmth or insulation as it would with the insert For one thing, without the insert, the duvet cover may not provide as much warmth or insulation as it would with the insert For one thing, without the insert, the duvet cover may not provide as much warmth or insulation as it would with the insertcan you use a duvet cover without the insert. This could be especially problematic during colder months or in areas with harsh winters. Additionally, if you have allergies or respiratory issues, using a duvet cover without the insert could expose you to more allergens and dust mites that may be present in the filling.