External solar shading intercepts sunlight before it reaches the window glass, while internal shading controls light after it has passed through the glazing. If you want to reduce indoor heat, external shading, such as vertical awnings, is therefore generally more effective.
Internal shading, such as Venetian blinds, roller blinds and curtains, is mainly used to control light, glare, room darkening and privacy. A patio awning also provides external shading, but primarily shades an outdoor space. Many households combine external shading to reduce heat with internal blinds or curtains for blackout when needed.
