Windows, The Weak Link

In the history of man, it's been only a little more than a millenia that we've had the luxury of seeing out of our shelter without the frigid blast of winter or furnace wave of summer filling the abode.

But the technology of glass, or other transparent building material has come to a virtual stand still. Yes, there are single, double and even triple pane windows - with or without inert gas or films applied. But with all of these minimal changes made to the making and use of glass, it is still the weak link in keeping a house heated and cooled.

And yet, we have increased its use substantially. 20 years ago, the general rule was for window space to be 10 % of your floor space. So if you had a 1000 sf home, you would require 100 sf of window space. That number has jumped to 15% - 18% and many homes approach a phenominal 30%. The problem is, with every 3% increase in window space, a 2% reduction in heating and cooling efficiency is realized.

How Weak

Beyond that, walls account for 30% of all heat loss from a home, but are easily 3 times the surface area of windows. Windows account for 20% of all heat loss - using 1/3 the space of the walls, they accomplish a heat transfer at least 60% more efficient than the walls. This is an efficiency we can ill afford.

Another way to look at this idea is that walls are now insulated to at least an R-20. Windows, on their own, max out at R-4.5. This is with the most expensive and most efficient windows on the market today. Hardly what the majority of homes have.

There are several things you can do to improve the R-value (there's a thing called the U-value, but I'm not going to confuse this discussion even more) of your windows. Curtains and drapes aren't really helping you. Unless they are an actual window cover that fits tightly within the window's woodwork, they are little more than - oh - window dressing!

I'll try to organize the suggestions in an order that is from least to most extreme, with many of them being equal.

Metal Windows

Metal windows are by far, the most inefficient beast man has made. The metal frame is the most effective "cold bridge", even over cold air itself. It conducts heat and cold (don't fight with me physics folks, I know) so efficiently, that it's a wonder anyone considered metal frames a great idea.

You must make a barrier for these windows both inside the wall and inside the living space. Inside the wall, place rigid foam or expanding spray foam so it is covering the entire metal frame - or the wood that surrounds it, so that it doesn't touch any other aspect of the wall - drywall or wood. This will block it from conducting heat or cold to the surrounding wall space. Outside the wall, but within the living space, make a plexi or rigid plastic "storm window" with a rubber or foam gasket that will cover the entire window space, and the gasket covering the entire outer edge of the metal frame. This will accomplish the much needed air space and block the metal from conducting the cold to the interior of the room

All Other Windows

Air Spaces

The more air spaces you have, the more insulating ability you have. This includes windows, blinds and drapes. You can add a storm windows or shutters (that are more than decoration) to the outside of the home. You can add a plastic film, blinds, shutters, shades, drapes and rigid foam inserts to the inside. They all must make direct contact with the window frame to be of any use, but with that simple rule, you can achieve a great deal with any, or all of these ideas.

Blinds

All types of blinds are very effective at creating an airspace between the living area and the window. But again, they must be a good fit, which often means the must be custom made. Metal blinds aren't effective, due to the conductivity of heat and cold, but they have long since gone out of style, and are most likely not made anymore. So no worries.

Shades

Some shades are good, if made of a tight-weave fabric or of segmented wood. The types made out of sea grass or reeds are too loosely woven to be effective at making that air space.

Drapes

Again, these must be made of a tight weave, or have a liner made of a tight weave and must make a solid connection to the wood frame surround all 4 sides of the window. If not, the air is free to move. With the air cooling between the drape and the window, a strong current is established, making a very effective air conditioner during a season you least want it.

Insulated drapes are another step within using drapes. You can purchase these in stores or catalogs or you can make them yourself. The more layers within each drape - again for the highest number of air spaces - the better they will work for you.

Shutters

Interior and exterior shutters will work virtually the same, except exterior can protect the glass during a storm, and bring partial or full shade to the glassed area, cutting down on the green house effect during the summer. For heating purposes, they must be create a tight bond covering the glass space.

Rigid Foam

These can be made of any thickness rigid foam insulation you find at the home improvement store. It should be cut to size for each window, so that it fits snuggly within the window frame. It would be put in palce and removed just as curtains are drawn or opened on a daily basis.

This suggestion is the most extreme and I would only recommend this for the coldest of homes or buildings that have many rooms unused for much of the week. It's laborious and these fillers take up a significant amount of space and need to be stored during the day or pleasant weather. Again, for the buildings with many unused rooms, these are also appropriate during the summer, to keep heat OUT.

Radiant Barriers

Radiant barriers can be used individually or incorporated into any of the above suggestions. The material can be styled like mylar, can be a bubble-style insulation with the radiant barrier on one or both sides, or can be similar to material, with nylon strands incorporated within it. You can find these materials online or in home improvement stores. Since it works like it says, it will radiate (or reflect) the heat back to wherever it came from. This can be outside during the summer, or inside during the winter. When used in walls, it has a 97% reflectivity rating, making it incredibly effective in maintaining the temperature in a house. Which means, it can be similarly effective with your windows!

Storm Windows

Most of us already have storm windows on our homes, if not the ever-coveted replacement windows. But if not, seriously consider them. They are a cheaper alternative to replacement windows and most likely will do more good since the air space is larger.

Savings

And while it truly depends on which of these suggestions, or even which combination of suggestions you choose to use in your home as to how much heat you save. Count on it being at least 5%, which is often enough to pay for any of these suggestions within 2 years.

Note

Note that I did not suggest replacing your windows. Unless they are metal framed or the rope-sashed windows, it's difficult to advocate replacing them. Adding storm windows, if done properly, is as effective, due to the larger air space between window panes. Many people are unable to afford replacement windows, and so feel they have no options to save money. But they do. And if you have been able to replace your windows, you still have much to do to make those windows as efficient as they should be. They are not stopping the heat from escaping from your house. They're just slowing it down a little bit compared to your old windows.