i don't know what i wrote early this morning, must be the beer talking. yeah, in response to snowbird.. actually the solar tint does block out sun radiation. and curtains do block out sun rays, hence no radiation transmission. in fact, air is a poor conductor of heat, heat is mainly transmitted into the house via radiation. another example is your car under the hot sun. keep stuff in the boot (where there is no window / no radiation) is better than leaving it in the front seat of the car.
When the interior of the house gets very hot from the sun's direct rays is because of greenhouse effect.
When the sun's rays heats up the windows and walls, the heat is transfer by thermal radiation into the room. Curtains and any fixtures nearer to the windows absorb all this heat and when the room get cooler in early evening, the heat is release which is why when you return early evening, the room is still very warm despite the sun already set.
Your example of the heat in the car is exactly the result of greenhouse effect.
Solar film offers effective deflection of the sunlight but after an hour direct sunlight, the glass panels continue to get heated up, thermal radiation take place.
Also, please take note that solar films has a very short life span of 4-5 years and needs to be replaced for effectiveness. However, solar film does reduce sun glaring and some protection to curtain colour fading.
To reduce the greenhouse effect, try not to close all the windows, leave some top-hung windows slightly open to allow ventilation to let the hot air dissipate out when the day get cooler.