Q: I was outside over the weekend and noticed that a small area of my home’s vinyl siding appears to be melting. My husband believes that the melting is being caused by a reflection off our neighbor’s window. Have you ever heard of this happening?

melted siding

A: Thank you for your question. Yes, we have encountered this situation from time to time. Vinyl siding is an amazing product in many ways. It is often less expensive than alternative siding options, can be virtually maintenance-free, and is much more energy efficient compared to the old wood and aluminum siding choices. With that said, unfortunately, with a perfect storm of variables, your vinyl siding could be at risk for melting from a window reflection. This is especially true with older and normal grade types of vinyl siding.  Thankfully, higher quality types of vinyl siding are created to resist higher temperatures.

So let’s take a closer look at how windows can melt siding. Windows these days are extremely energy efficient.  Energy Star windows are so energy efficient that they have materials like titanium zinc-dioxide and crystalline structures to help reflect sunlight from the windows.

This will keep the Solar Heat Gain Coefficient (SHGC) down, designed to increase energy efficiency in the summer months when a home has its air conditioning running.  The problem with this is that the solar heat has to go somewhere.   And anyone who has been sunburned at the beach knows that reflective sunburn can be just as brutal at the beach if not worse than a day out in the park.  That reflective solar heat at certain parts of the day can be directed right at your home.  And if your vinyl siding cannot withstand that heat, it will warp and melt.  There are a few ways to fix this problem to help ensure that it will not happen again.

6 Ways to Prevent Your Vinyl Siding from Melting

  1. Placing a Full Screen over the window – The full screen over the glass will break the solar energy apart and create what’s called solar diffraction by the threads of the woven screen creating less energy coming from the sun to the focal point. You can ask us which neighbor’s window will need this if necessary.
  2. Using a PTI screen or film – PTI is a material made by Protect Industry and MFG to help with solar glare and solar heat issues on windows.  The concept is exactly the same as putting a full screen on the window.  The difference is this material is connected to the window pane, not the window frame.  This is the perfect alternative if a casement window is causing your vinyl to melt and you want to be able to keep it functional. Homeowners can have an exterior screen on the glass while the window can still swing outward.
  3. Homeowners can also cover the low-e windows with awnings to keep the sun off.
  4. Replace the low-e glass with a different type.  There are many different glass package options out there.  Ask us to see what type of windows are right for your situation.
  5. Plant a landscape buffer between homes to prevent the reflections from hitting the vinyl siding.  Plants can be an attractive method of helping to solve a problem while also adding to the beauty of your home’s landscaping.
  6. Replace your siding with vinyl siding that is resistant to high temperatures above 250 degrees F.  Higher end vinyl sidings are worth the investment if this is a common issue that will need to be addressed year after year.

What Homes Are Most Susceptible to Pinpoint Beams?

The Vinyl Siding Institute (VSI) states that temperature ranges beginning at 160-165 degrees Fahrenheit can soften normal grades of vinyl siding. Also to note, darker colors absorb more heat and can soften before lighter colors of siding. The heat generated from sunlight from double paned low-e windows measures around 250-300 degrees Fahrenheit, but this doesn’t always result in a damaging reflected sunlight incident. You need to have a combination of contributing factors before the effect causes damage to your vinyl siding. As I said above, you need the perfect storm of combinations for this to occur as it is a rare occurrence.

  1. You need to have the presence of the concavity in the double glass panes  (the primary cause of the heat generation) combined with the angle of the sun.
  2. A low angle of sunlight like in late fall, winter, or early spring, is more likely to produce the effect.
  3. Proximity to the adjoining house, wind speed, air temperature, and the presence of buffering foliage are all additional contributing factors.

Bottom Line:  If you want to experience the freedom from maintenance with lifetime labor and warranty on vinyl siding, make sure your siding is resistant to high temperatures and you use the preventative measures listed in this column to avoid melted siding.

Choosing the right vinyl siding can be a challenging experience, but rest assured we are here to help!  Coastal Windows & Exteriors can help you choose your style, color and configuration along with a FREE estimate.  If you have any questions, call us today by calling 978-304-0495 or e-mail svanderbilt@mycoastalwindows.com.