Replies

1. GBA Editor
   Martin Holladay | Sep 09, 2010 03:22pm | #1

   John,
   Q. "Is it practical for a DIY builder on a tight budget to build their own high-R-value windows for use in a cold NE climate? Openable? Non-openable? With exterior storm windows?"

   A. When it comes to operable windows, it's possible but not especially practical -- unless you are a cabinet maker who enjoys high-quality cabinet work. Even then, it will be hard to develop a window with adequate air seals, proper tolerances, and wood that stands up to moisture. Manufacturers can buy hardware cheaper than you can, and they can use composite materials that are much cheaper than teak or red cedar.

   In the past, I have built wooden storm windows for clients. It's do-able, but I wouldn't want wooden storm windows on my own house.

   I've also built plenty of site-built fixed windows. They were all the rage during the 1970s, when we were all building passive solar houses. They're not too hard to build if you know what you are doing, although most DIY windows are terrible -- with rotting sills and bad details for setting the glass into the wood.

   Q. "Using plastic sheet or film instead of, or in addition to, glass?"

   A. I wouldn't want to have such windows in my house, but you can buy Plexiglas (acrylic) at any hardware store.

   Q. "Are single panes of low-e glass available?"

   A. Sure, You can order hard-coat low-e glass through any storm-window shop.

   Q. "Is there such a thing as low-e plastic?"

   A. Never heard of it.

2. 
   Riversong | Sep 09, 2010 07:27pm | #2

   John,

   I concur with Martin except on the "single panes of low-e glass". The low-E coating is a few molecules thickness of metalic oxide and very vulnerable to damage, so all low-E coatings are on one of the inner surfaces of a double or triple pane sealed glazing unit. You cannot buy a single pane of lowE glass, but you can buy lowE double or triple-glazed factory sealed units of almost any size and shape (the larger the thicker the glass, and after a certain size tempered glass is required).

   But a relatively inexpensive way to create double-glazed lowE fixed windows is to buy patio door replacement glass units. They are mass produced in a few standard sizes and are far less expensive per square foot than custom-sized units.

   However, as Martin suggests, it's important to build a fixed window correctly. The glazing units must be set on ¼" rubber setting blocks cut to the thickness of the unit, two per window, at the one quarter and three quarter points along the bottom edge. Both outer and inner glass surfaces along the edges need to have self-adhering butyl tape applied, against which the wooden stops are applied, leaving an 1/8" gap for silicone caulk, at least on the outside if not both. Outer sills should be beveled for drainage and have a drip kerf cut into the bottom lip. Alternatively, simply use picture-framed outside casing as the outer stop (no sill), set the taped glass unit tight to the casing from the inside, and apply wooden stops to the rough frame on the inside and then trim.

   There are now many varieties of lowE glazing, so make sure you get what is appropriate for your design and location: solar shading glass for hot climates, high solar heat gain glass for passive solar, or simply lowE² (two coatings) for additional insulation value.

3. GBA Editor
   Martin Holladay | Sep 10, 2010 05:19am | #3

   Robert,
   The type of hard-coat (pyrolytic) low-e glass I'm talking about is routinely used for storm windows. It differs from glass with a soft-coat (sputtered) coating.

   Hard-coat low-e coatings are durable enough to be used for storm windows -- that is, a single piece of glass that is routinely touched.

   It is not only possible to buy a hard-coat low-e storm window; it is also possible to buy hard-coat low-e glass. If DIY tinkerers want to assemble their own low-e windows, they can -- although I don't recommend it. It's much easier just to buy insulated glazing units.

4. 
   user-872446 | Sep 11, 2010 10:50pm | #4

   Thank you, Martin and Robert, for your responses to my questions. Windows are very expensive items, but it seems you get what you pay for.

5. 
   Robert Hronek | Sep 12, 2010 11:43am | #5

   I think the risk of failure would out weigh cost saving of a DIY even if someone could do it.

   When is comes to DIY many times the time spent learning, designing and building would be put to better use doing the tedious chores that make or break a job.Things like spending the time air sealing etc. Things that take a lot of labor but not a lot of skill, things that the hired help likes to skimp on.

6. 
   Michael Chandler | Sep 12, 2010 02:51pm | #6

   It is possible to get "IR TwinWall" polycarbonate greenhouse glazing panels up to 4' x 12' (=$116.80 @ CharleysGreenHouse.com ) with an IR sun control coating that gives it a U-0.48 with a VT of 66, no info on SHGC. We've used it for rolling shop doors to let in light while controlling heat. It is translucent, not transparent but the price and weight are very attractive. Lexan ThermoClear and Solexx are alternative brands and non-IR control HeatSaver TripleWall is also available as panels and Solexx is available in twin-wall non-IR semi rigid rolls up to 8'x40' which we use for landscape structures and trellis roof covers.

   For all but well protected transoms the issue is rot on the frames and pre-mature failure. For the doors we made we ended up cladding the exterior wood in light-gauge galvanized steel and we have also site-clad wood doors in copper with good results. I imagine it would be pretty easy to do the same with aluminum or vinyl coil stock. The old-school solar solution was to use sliding glass door replacement panels and tremco glazing tape on greenhouse mullions. Not operable but it might still be a solution for what you are trying to do. Just understand that there is a good chance that you will be facing a do-over in a few years.