Does Putting Foil on Windows Keep Heat Out?
As the summer months approach, many of us are looking for ways to keep our homes cool and comfortable. One popular solution is to cover our windows with foil, a method that is often touted as an effective way to keep heat out. But do we really need to wrap our windows in foil? In this article, we’ll explore the science behind this technique and provide an answer to the question: Does putting foil on windows keep heat out?
A Quick Look at Radiation and Heat
Before we dive into the science of foil and heat, it’s essential to understand a bit about how radiation and heat work. Radiation is the transmission of energy through electromagnetic waves, including visible light, ultraviolet (UV) radiation, and thermal radiation (heat). All objects, including windows, emit and absorb radiation. When a window is exposed to the sun, it absorbs and re-radiates this energy, causing the inside of the building to heat up.
Why Foil on Windows?
The concept of using foil on windows dates back to the 1970s, when people started applying aluminum foil to their windows to deflect the sun’s rays and keep their homes cooler. The thinking behind this method is that the shiny, reflective surface of the foil would reflect the sun’s radiation, reducing the amount of heat that enters the building.
The Science of Foil and Heat
However, the concept of using foil as a heat-deflecting material is flawed. Here’s why:
- Foil does not absorb heat: Unlike other materials, such as paint or coatings, foil does not absorb heat energy. Instead, it reflects it, which means the radiation bounces back out, potentially causing the window and surrounding area to heat up even more.
- Foil is not a perfect reflector: While foil is indeed reflective, its ability to reflect radiation is not uniform. It has low reflectivity in the near-infrared range (2-5 micrometers), which is where most of the sun’s radiation falls. This means that even with foil, a significant amount of heat can still enter the building.
- Convection and conduction: Foil is not a perfect insulator, and heat can still be transferred through convection (air movement) and conduction (direct contact with the window frame). This means that even with foil, heat can still seep into the building through gaps, cracks, and crevices.
The Bottom Line: Foil is Not an Effective Heat-Blocking Material
While covering windows with foil may have been touted as a quick and easy solution to keep the heat out, the science suggests that it’s not an effective method. Here are some key points to keep in mind:
- Foil does not absorb heat: It reflects radiation, which can increase, not decrease, heat gain.
- Foil is not a perfect reflector: It’s not effective in the near-infrared range, where most of the sun’s radiation falls.
- Foil has gaps and crevices: These can allow heat to seep in, making it even less effective.
Alternative Solutions for Keeping Your Home Cool
So, what are some more effective ways to keep your home cool? Here are a few options:
- Choose energy-efficient windows: Newer windows are designed to minimize heat gain and loss, making them a more effective choice for keeping your home cool.
- Install window treatments: Lightweight, translucent window treatments like shades or cellular shades can help block the sun’s radiation and reduce heat gain.
- Use solar screens: These can block 80-90% of the sun’s radiation, making them a more effective choice for heat reduction.
- Seal gaps and crevices: Properly sealing any gaps or crevices around windows and doors can help prevent heat from entering the building.
Conclusion
In conclusion, covering your windows with foil may have been a temporary solution for keeping the heat out, but it’s not an effective or long-term solution. The science suggests that foil is not an effective heat-blocking material due to its low reflectivity, ability to reflect radiation, and gaps and crevices. For a more effective and long-term solution, consider using energy-efficient windows, window treatments, or solar screens. With the right approach, you can keep your home cool and comfortable without the need for foil.