Internal solar shadings allow the protection of interior space from direct radiation. The user should close the shading when direct solar radiation is entering the building in cooling seasons, while in heating seasons shadings should be opened to permit that solar radiation and natural light enter the building.
Reduce internal temperatures in cooling seasons
Increase internal thermal loads in heating seasons
Reduce the use of cooling and heating systems
Internal solar shadings are not as effective as external shadings because they allow that solar radiation enters in the interior space
The cost is zero, although it is convenient to train and inform properly users on these issues. It reduces the costs associated to HVAC system.
References and best practices
An overview on solar shading systems for buildings: researchgate