Here is how you can know how good your windows are even if the builder says they are Energy Star windows.
First of all - we need some definitions. Lots of buzz words and catch phrases get thrown around.
Energy Star - this has been around since 1992, a program introduced by the EPA as a voluntary program, first to rate computers and monitors for efficiency standards. It has since grown to include many appliances, electronics, windows, doors and other home/office products. Different areas of the country have different standards for many things due to differences in climate, temperature, etc. Standards change all the time, and when products have an Energy Star label on them they have met the most recent standard for that product.
U-Factor - this measures the window's ability to insulate against heat transfer. The number is between 0 and 1. The U-factor is divided into 1 to show the R-value (Resistance Value) of the window. A lower U-factor would mean a higher R-value, and better insulation.
Solar Heat Gain Coefficient (SHGC) - this tells you how well the window blocks the heat from the sun. Typically windows range from .12 to .80. A lower number indicates a better blocking ability, and less heat would be felt when the sun shines on the window.
Visible Transmittance (VT) - this tells how much light the window lets in. Numbers for windows are usually between .20 and .80. The higher the number the more light is let in.
Low-E (Low Emissivity) - a very thin layer of metallic particles is spread usually on the interior of the outside pane of a double-pane window. This layer acts as a filter to keep out the harmful long wavelengths of light, and allowing in the shorter wavelengths. Different coatings do different things - create lower U-factors, protect against fading, etc. And adding an inert gas inside, like argon, further increases window efficiency. Almost all windows now have Low-E characteristics.
Click this link to see what the Energy Star standards are for windows in your area.
On a pre-drywall inspection I asked my client if this was a an Energy Star house. She said yes, according to the contract. So I pointed out that the windows were not Energy Star rated for Virginia.
Windows have an energy sticker on them, called the NFRC label (the National Fenestration Rating Council).
This is a fictional sticker but similar to what a window company would put on its window.
To qualify as Energy Star in your area there would be a map that so indicates. The map would color in the states that consider that window to be Energy Star rated.
Some windows are very good.
They qualify everywhere.
The windows that do not qualify would have no such map.
My client asked me to wait to listen to what the supervisor had to say on her walk through. She wanted to make sure that she wasn't fed any lines.
To be truthful, I needed really high boots to protect me from all the barnyard filth being thrown around! I couldn't believe it.
The exchange regarding the windows went like this:
"My contract says this is an Energy Star house, but the windows are not Energy Star for Virginia."
"We build our houses strictly to Energy Star standards." Um, this is not the same as being an Energy Star house - that is a certification given by another organization and it is NOT determined by the builder.
"But the sticker on the windows says they don't meet those standards."
"All our windows are Low-E and see, they are Energy Star" (pointing to the symbol here). Not only does that not answer the question, but that Energy Star Partner sticker only means that the window company does produce Energy Star windows, but not that these windows meet any criteria. This answer was complete pap.
"But what about these windows?"
"Well, I don't know. It might be that when they picked out these windows for your house that was the standard and it has changed since." What?!! It was getting too thick to stand much longer and I was really biting my tongue.
But I couldn't stand it any more. For the first time on a pre-drywall inspection, I spoke up. "There have been no changes to Energy Star standards in Virginia for many, many years. These windows come no where close to Energy Star standards. The sticker you pointed to is meaningless. The standard is to change later this year, to be more stringent and to indicate the best products of the best."
And then the weakest statement of all - he said, "Well, these are the same windows we use on all our houses. I'll look into it."
To that I could only roll my eyes. If you want to read about these new standards, click here.
My recommendation: sometimes the bull flies thick and fast. This was not the only thing he said to my client that was phony or incorrect! I was truly amazed. But, nonetheless, you MUST have a pre-drywall inspection on new construction! To put it simply, we don't know what we don't know!