Sorry for that UT A&M article, its a tough read but in the conclusion, does refer to energy loads. This one Iam linking to now is more appropriate, informative and easy to read. Author John Straube needs no introduction in the building science community. Its a good article for anyone building a home that explores air infiltration impacts on homes other than energy use. On infiltration's impacts to energy use related to HVAC, he agrees with wickipedia too: 1/3. Verifying Airtightness with blower doors saves energy, prevents rot and helps ensure we have CONTROL over mechanical ventilation. Manual J is an amazing tool. Its incredible how accurate it can be in the hands of a skilled user. I dont think Manual J or other energy software results are being used appropriately when extremely detailed outputs from limited samples involving many variables with built in fudge factors are being used to talk the community into building below energy code minimums. Here is a link that might be useful: Building Science.com link; Air Leaks--How they rot homes and waste money This post was edited by Brian_Knight on Tue, Feb 5, 13 at 22:19

Efficient windows for a pool room. Interior moisture will be an issue in the pool room. A good choice for the MOST energy efficient windows would then be either triple-glazed vinyl or aluminum. If you are in the northern 80% of the country, the best choice would be vinyl. A very good - and more economial - choice is double glazed vinyl. Regardless of what you choose, make sure the glazing has both low-e and argon. www.efficientwindows.org is a very good resource.

Buy American, Try PGT Windguard products. Florida based product. These guys stay on the ever changing codes. They are a Florida company. I use there products in my business. They stand behind there products. If you have any problems do they have service techs in N.C? Here is a link that might be useful: PGT Windows

How did a discussion about windows turn into a cultural disagreement and charged political discussion? Left, right or wrong, please save the personal attacks. That said...I have an old (circa 1840s Greek Revival home with 6 over 6 double hung windows. Unfortunately, I had to replace them because they were in just too bad of a shape to restore economically. The closest I found in an affordable stock size and style was Brasco Boston 6 over 6 ADL (authentic divided light) windows (sash replacement kit--sash and balances only, no frame). A local mill was able to make custom wooden storms to match an original storm I found in the barn when I purchased the house. The windows cost a little over $100 each, the storms about $85.00. With a little ingenuity, I was able to make the Brascos fit into the original openings (the size difference was only about a 1/2 inch or so). From the outside, the house looks the same as it did in the photos I found at the local hisrorical society. The only drawback is the balances, which are vinyl with a spring mechanism. I was able to hide those with some creative interior trim work that doesn't look out of place. The net result is my heating bill has dropped significantly and my home is a lot less drafty. In the back turn of the 20th century addition that I had to completely rebuild due to structural issues, I bought pricey (stock) Marvin low E with argon 6 over 6 SDL's (simulated divided light windows--(prices ranging from $500 for a single unit to $1,100 for a mulled unit). The muntons are about an 1/8th of an inch thicker than the Brascos which matched the originals, but not noticeable since they are consistent on that portion of the house. Net net...The Marvins look great, operate smoothly (thanks to the quality balances) and are tight and completely draft free, but expensive. The Brascos look very close to the originals and with the storms seem to be as efficient. If I were in the position of the original poster, I would probably get removable interior storms and only put them in during the coldest months. The good ones don't look too bad and are a lot less expensive than replacing the windows. And my guess is the energy savings would pay back the cost within a few years or so. Perhaps Oberon can do the cost recovery calculation for you.