Window updating

[bail432]

Just purchased a condominium in Lewistown, Montana. It is the old Fergus County High School. It is part of a historic preservation district and the exterior cannot be tampered with. One wall has seven of the original windows. 34 inches wide and 68 inches high. They are double hung windows. The window frames and jambs are in good shape. Just need some attention.
Now the question. These windows face south and are single glazed. I know you can get new windows that would be able to reflect the heat, but is there some kind of retro-fit that I could use?

Chuck in Montana

[Rich]

You might be able to contact a glass manufacturer and get some replacement panes with a PPG coating on them for reflecting UV. There are many different levels of shading coefficients and UV reflectance ranges - whoever you find to do the glass will know what it needs for Lewistown.
Damn I miss Montana :)

[Link]

Look into Marvin Tilt Packs -- get Low E double pane sashes and keep the existing frames. Sounds like a good fit for your application.

[mjpliv]

Do you want to reflect the heat back in or keep the heat out?

Here is a copy/paste from a newsgroup posting I made a few weeks ago -

Conductive heat loss through a thermopane occures because the interior air heats the interior glass, which heats the air in the middle which heats the outside glass. Heat transfers easily through air molecule because it is not an inert gas meaning the molecules absorb the heat energy and move faster thereby transfering the heat energy between window panes. Argon gas (as well as the new krypton glazing) slows the conductive heat loss because these inert gases do not tend to absorb
the heat energy.

These gases also slow down the convection cycle happening inside a
thermopane window as well. As the gas layer against the inside pane
warms up it rises to the top of the thermopane cavity. When it curls
over the top and contacts the outside pane it cools, causing it to sink
to the bottom. And around and around it goes. The coldest surface of
your windows will always be at the bottom of the glazing areas. That is
why, when condensation or frost occures, it always starts at the
bottom. While the convention cycle with a normal air filled thermopane
is quite brisk, the argon and krypton gases are not prone to rapid
temperature changes (because, again, they are inert) so the cycle slows
to a crawl. This will help raise the temperature of the inside pane
relative to the outside temperature.

You will find some people who say that Low-e glass is a two way heat
mirror or that it keeps the heat out in the summer and in during the
winter. This is not really true.

Lo-e glass is a molecules thick metalic coating generally applied only
to the inside surface of the outside pane of glass. It can be difficult
to see the difference between a high quality Lo-e glass and plain clear
glass. Cheaper grades of low-e glass have a brown or blueish tint when
viewed from certain angles.

There are really two types of radiant heat at work when discussing
Low-e glass. The sun generates heat in short wave form. This type of radiant heat energy will pass between the molecules of metal on the Low-e glass (or about 85-90% of it). This allows the heat to enter your home
heating the floor, the chairs, the walls, the kids and the family dog.
When this heat is released from these things it is released in a long
wave energy form, the same type of radiant heat energy your heating
system creates. When this long wave energy will be reflected back into
the room (or 85-90% of it) because it cannot pass easily between the
molecules of metal coating the glass.

In the summer, direct sunlight will again pass through the glass, but thankfully, at that time of year, the sun is high and most will reflect of the surface of the glass. However, it will bake your car and your driveway as well as the garage roof and the roof of your neighbor. Again, when these surfaces release the heat energy it will be in a long wave form meaning the Low-e glass will reflect 85-90% back outside.

Another advantage of using Low-e is the reduction of ultra-violet light
entering your home. This is the stuff that fades the carpet and the
furniture. One sheet of low-e glass reduces ultra-violet light by 50%.
Using double low-e (both panes coated) will reduce it another 50% for a
total of 75% reduction. So even in warm, sunny locations, Low-e has its
advantages.

[bail432]

I'll look at Marvin. I want to keep the heat out.