What kind of windows are the best windows for winter? The answer is windows built with Low-E Glass.
That’s the answer. Didn’t expect the answer right out of the gate, did ya? Well we don’t like to drag our feet. This is important stuff after all! Just because it’s almost February doesn’t mean we’re out of the winter clear yet.
So now that we know the answer is Low-E, let’s figure out what exactly that is. Well, for starters,l the E stands for emissivity.
Emissivity is defined by Merriam-Webster as “The relative power of a surface to emit heat by radiation.”
So how likely radiation is to pass through a certain substance. In our world, it’s measured in a ratio of radiant energy a surface gives off that emitted by a blackbody of a similar temperature.
When it comes to windows, then, the best way to sum it up is how likely radiation is to pass from one side of the surface to the other. This is important for your windows, because heat both enters and leaves your window in the form of radiant energy.
Low-E glass is created at the point of manufacture (regular glass can not be retro-fitted as Low-E, however tinting could be an alternative). It is made with a metallic material coating it on a microscopic level. You can not see this coating, so visible light passes through but radiation does not.
Keeping out vs keeping in
A lot of people tend to think of winterizing and heating as keeping the cold air out, which is definitely part of it. As we’ve discussed before winterizing to insulate windows and doors is an important part of energy efficiency. When it comes to the windows themselves, however, the goal is to keep warm stuff in.
In colder climates like that of the Midwest, Plains and the Northeast United States, the Low-E glass is manufactured with the low-e side facing inward. This allows radiant energy from sunlight (aka heat) to come in, but not leave (we call it Hotel California glass in the biz…okay, it’s just me that calls it that and I’ve been shunned by my co workers for doing so).
You know those winter days where it looks like it should be 75 degrees or so outside with all of the sunlight? Well all of that wonderful sunny heat is able to move through the exterior facing side of the glass into your house. When it attempts to bounce right back out, however, the tiny metallic surface of the Low-E glass crosses its arms and waits for the charge.
Meaning you get to keep the warmth. Sorry, outdoors, it’s not coming back.
Why isn’t everything made of Low-E glass, then?
Great question! I mean we should be using this stuff everywhere if it’s as incredible as it sounds. There are a few reasons that have prevented Low-E from becoming the glass standard of the developed world.
The most common issue is the cost. Low-E glass can be 3 – 4 times as costly as regular window-glass. While most households will make this money back on savings from heating and cooling, the initial cost can sometimes be out of budget for window buyers.
As window and glass technology advance, however, the cost comes down and every year more efficient ways to develop and manufacture specialized glass are discovered.
To discuss your options for Low-E window installation, contact us today!