Double-glazed windows are usually made from pre-fabricated glass panels.  Although this is a good design to reduce the cost and complexity of manufacture, there are drawbacks.  For example, if a double-glazed window is broken, replacing it may be very difficult and expensive due to custom sizes, discontinued models, and companies going out of business.  Most double-glazed windows are only expected to last 10 years in moderate climates, and less where there are temperature extremes due to the seasons, which is reason enough to be able to maintain a window.

The design shown below is a true DIY double-glazed window.  It can be built and maintained by a person of modest skill; and at minimal cost.  If someone breaks the glass, it can be replaced with readily available glass sheets from a home-supply store.  If it begins to collect moisture, the seals can be replaced and new desiccant can be added.

One often-mentioned disadvantage of an air-gap (instead of noble-gas filled) double-glazed window is the convective loss due to air circulating around in between the sheets of glass.  Other gases may lower the convective losses due to higher mass, which leads to slower diffusion.  However, I think that most older windows have long since lost whatever special gas filling they may have once had.  Air-filled windows have the advantage that a normal person can replace glass and replenish desiccant without any special equipment.

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Step 1: Making the frame

The sash of the window is the trick to this design.  It acts as the spacer between the sheets of glass; it  provides a place for the O-rings that seal the glass to the frame; it provides a place to add trim, which holds the glass in place; and it provides a structure that supports the glass.

The air gap is created by using the wood of the sash.  I used a 1/2-inch gap.  Note that the thermal performance of this window sash is improved by not using a metal spacer between the layers of glass.

I designed my frame to accommodate 1/8" glass and 3/8" trim.  The O-ring groove is 1/8", which is a poor choice because there were no available  O-rings with the appropriate diameter.  You should find the O-ring and let that determine the width of the groove.  The O-ring should be chosen based on it's cross-sectional area.  That area should match the cross-sectional area of the groove.  See the selection at http://www.mcmaster-carr.com.  I was surprised at how much some of these materials cost.  Find something weather-resistant so the UV-radiation doesn't destroy it immediately.  For my prototype, I used silicon calk, which was cheap but will make the glass very difficult to remove.  DO NOT USE CALK!!

The wood that I used for this demonstration is pine from framing-grade 2"x4" lumber.  When I do this for a larger project, I will use something much nicer.  I've read a lot about windows and there doesn't seem to be a consensus on what wood is best for windows.  I would use white oak, but most any hard or soft wood can be found in commercial use, so I guess it doesn't much matter.

When you're cutting this profile, make sure that you produce enough for your project.  Measure the outside perimeter of the windows and add 10% to the total for all of the windows.  If you are making a frame for a very large window, or if your stock is short pieces, you may have to be more careful about the exact amount of stock.  Also, for a window larger than 3'x3', you'll want to make something more sturdy than the design presented here.  Just a thought, Mr. Fox.

One of you will want a drawing of the cross section---I just know it.  I've decided not to provide a technical drawing because the point of this article is to demonstrate a concept; it's not a engineering consultation.  You'll know the difference because concepts are free.  The other comes with a fee---and usually 10% up front.

Hya. I need to replace the glass in front door ( double glazed) &amp; have been told v difficult with beading etc could you advice me? Thanks<br>
<p>Sorry, I don't know you well enough to give good advice. To DIY or not is a philosophical question. I default to DIY and re-consider based on danger, cost, and availability of free time.</p>
<p>Hello,I have a question I would like to attach a plastic panel for shading to a timber window frame, the panel is about 12 kg. Is there any adhesive that I could use to glue the panel to the frame? If not, could I screw somehow the window frame, without create a thermal bridge? Thank you!</p>
<p>With good preparation and the right adhesive, you can do it without fasteners. Of course, if you do everything right, it's fairly permanent. If you use shorter screws, they won't be a very good thermal bridge. I've heard 7-lbf per thread so you can get away with fairly short screws. If you want some redundancy, use 8 instead of 4.</p>
<p>Thank you for you answer! I was also thinking an adhesive, but do you have any idea of a product-adhesive that could perform well for two different materials, wood(porous) with plastic?</p>
<p>A word of advice- spending a bit more on your glass cutter will make a hell of a difference. Good glass cutters will have a reservoir for the oil and work far better. Never make more than one pass with the tool, it will end in disaster. If you do it properly, with a good cutter, you won't need much force to either score or snap the glass. </p>
<p>Since I wrote this, I've used a quality diamond-tipped cutter. It's amazing. If you use the hardware-store cutter, you need a lot of pressure and a good jig. The one I used here is not very easy to use.</p><p>The thing about cutting 2x... If your cutter isn't making the right sound, you're not pressing hard enough and you can usually cut again. I've sometimes had a successful second cut in really thick glass but it's a last-ditch work-around type move, at best.</p>
I have a crazy, cooky question.<br><br>I want to make a permanent greenhouse, attached to a shed sized building. I was thinking about doing 16 inch center framing, solid and insulated bottom 2 1/2 feet, then windowed up to the roof line, and making the windows fit inside the framing, instead of building the framing to the size of the windows. <br><br>One, would something like your design concept work for my idea, and two can I do this with clear acrylic sheeting instead of glass?<br><br>Thank you so much!
<p>Sure. Do look up the angle of the sun and get the orientation right before you start building. </p><p>The issue with windows on 16-in framing is that 2x4s cast a giant shadow when the sun isn't straight on. This highlights one of the major problems with passive solar design---if you aren't careful, you can easily take up 10-20% of the area with framing. The other problem is that 16&quot; centers is a code designed for 5/8&quot; plaster board and has to do with sagging between supports. Structurally, you can get away with a lot less wood, even up here where we have 50 lb/sqft snow load requirements. Taken together, these issues argue for wider windows and metal framing for maximum effect. Still, we're all constrained by our own budgets and available material.</p>
Hehehe you are either going to laugh at me or call me crazy, but this is an idea for my THOWs I'm designing (Tiny house on wheels for the uninitiated). I want to have the last 6-8 feet of my tiny house to be a green house with acrylic windows and the clear ish roof panels. I like the idea of fixable Windows, and building it myself so ican have it to my specs. <br><br>Am I totally crazy for thinking this will work?
<p>I think it's a good idea. Read through the other comments while you're thinking about making windows water tight. There's details about how to paint to seal the glass into the frame, etc. </p><p>Do us all a favor and make an instructable when you get around to making the windows. I'd really like to see what you dream up for 2.0!</p>
<p>Yes, you can absolutely use acrylic. (To be as obnoxious as possible, call it polymethylmethacrylate....poly-methyl-methac-ryl-ate. Has a nice ring to it, doesn't it?) </p>
<p>Thank you for this fantastic instructable. May I suggest that some woods are better than others in two respects: dimensional stability, and rot resistance. SPF (Spruce Pine Fir) is a decent wood with reasonably long lasting qualities. However, I believe the wood of choice would be Tamarack or Larch, which has both qualities in spades. Regrettably it is not generally available as dimensioned lumber so you may have to look around for a source, and a sawmill to cut it for you.</p>
<p>Hi,</p><p>Nice article.. really informative..</p><p>http://www.lancetglass.com/</p>
You suggest trying not to paint over the screws, you could always paint the parts first.
There are some comments worth reading by &quot;TheWindowMan&quot; in the UK at this link. http://www.thewindowman.co.uk/misty-wood.htm <br> <br>Here are a few of his remarks: <br> <br>&quot;The biggest problems with wooden frames arises because (unlike PVC-U and Aluminium) the sealed units are not drained, and the perimeter of the sealed unit is not ventilated&quot; <br> <br>&quot;Sorry if I seem to go on about double glazing sealed units not lasting in wood windows, but this is what I see in real life almost every other day! <br> <br>&quot;Sealed units fitted in wooden frames MUST in my opinion have near a quarter inch gap between the glass and the wood at the bottom of the frame AND slotted holes to allow both drainage and ventilation. If sealed units are fully bedded and puttied into wood frames (even with non setting butyl putty) this is what you can expect, usually showing signs of failure between 6 and 8 years at most from new.&quot; <br>
<em>&quot;One often-mentioned disadvantage of an air-gap (instead of noble-gas filled) double-glazed window is the convective loss due to air circulating around in between the sheets of glass.&quot;</em><br> The primary factor in&nbsp;convective loss due to circulation is the thickness of the spacer. Noble (Argon etc..)&nbsp;gases are less conductive than air, but you'll still get circulation losses if you go over about 16mm (I think). As long as you keep the gap between the panes less than 16mm you should be fine.<br> Where&nbsp;I work we make double glazed fridge doors, and the widest spacer we use is 14mm, with or without Argon.<br> Looks good though. I'm looking at doing something similar and would really like to see a finished unit.<br> Once sorted&nbsp;you could design a custom router bit to cut the profile in a single pass.
Oh. Well thanks for posting. I'm mainly going off the information I could find on the mighty interwebs, which I trust less than real experience.<br><br>You could certainly get a shaper bit that cuts the profile. I don't think it's terribly expensive. If you could spread the cost over enough windows, it'd probably work out really well.<br>
Great job<br>
Please explain to me the function of the &quot;O-ring&quot; and how can the desiccant be added to the window without looking odd as it can be seen from outside. Kindly also show the picture of the O-ring that you used. My email address is owais40@gmail.com
owais40, when you put the windows together make !!sure!! it is low humidity or you will get condensation in between. boatboy
http://www.mcmaster.com/#o-ring-cord-stock/=bkfvyc<br><br>The o-ring keeps additional moisture from getting into the window. I don't have a picture of this because I haven't started building my custom windows yet and the one shown here was just a proof of concept. <br><br>The desiccant is added through a hole in the top of the frame. It must be plugged with something air tight. I did not use desiccant in the prototype, so you do not see the hole in my pictures.
Thanks for your quick response.<br><br>How many O-rings will I've to put on one side of the window for one glass for best results. Also in my opinion the diameter of O-ring should be slightly more than the cross-sectional length of the groove, while keeping its height equal to the O-ring dia., for the O-ring to be able to seal the glass to the frame. Please tell me if I'm correct.<br>
You should probably just buy the cord stock. Otherwise, you'll have to account for axial stretch and, if you're making several windows, you may have to order several o-rings---and they usually come in multiples. They're already an expensive part of the project, so I doubt you'll want to have a bunch of extra inventory.<br><br>For a better seal, you could use a set of concentric seals... hadn't thought of that. Well, it will be more expensive, but it might be worth it.<br><br>If you match the areas, the o-ring will protrude above out of the groove. For a low-pressure application like this, it might not matter if the o-ring material bulges out of the groove when you tighten down the glass. Well, I suggest you use equal areas. If you do something else that works, let me know.<br><br>
Got a great suggestion to use knurled brass thumb screws with threaded inserts for parts that can be disassembled. Sounds like a really great idea. I can't wait to give it a try.<br><br>
One thing to say: Awesome !!! Is what I needed
If you make any windows, post a picture, so we can see your interpretation.
You bet. I hope not to let down the pros, but I'll try. cheers
This is a good idea, and have been thinking about doing it for awhile.&nbsp; I've been trying to install a solar air heater first before the winter hits here in Ohio.&nbsp; Have you had any experience with these?<br /> I think I&nbsp;found a really neat one at solarairsystems.com. &nbsp;<br />
For solar gain, you generally want single-glazed windows for maximum thermal gain.&nbsp; Remember to use 1-way valves in the ducting to prevent cooling at night.&nbsp; There are some great resources on the web that can help you calculate the amount of mass and window area you need.&nbsp; My favorite is <br /> <br /> http://www.builditsolar.com/Projects/SolarHomes/PasSolEnergyBk/PSEbook.htm<br /> <br /> <br />
&nbsp;This is really an interesting idea. Thanks for posting it.<br /> I have been thinking about a&nbsp;similar&nbsp;project, but have not gotten any further than thinking about it yet.<br /> <br /> My first thought when looking at this design is: I really like the o-ring idea. But I see a possible flaw in it. Without the use of glazing compound water will be able to get between the glass and the sash. Only a small area of it, but over time this could possibly be an issue.<br />
Good point.&nbsp; Hadn't thought of that.&nbsp; Maybe you could calk or glaze it after installing the outside trim.&nbsp; As long as the putty is on the outside, it would be accessible and possible to remove.<br />
&nbsp;Yes, I think glazing the exterior would be a good idea.&nbsp;<br /> <br /> I just had an other thought too. Instead of an o-ring I wonder if screen spline would work. (that grey or black rubber used around aluminum window screens)<br /> It is available in a couple different&nbsp;diameters&nbsp;and is&nbsp;readily&nbsp;available at most hardware stores.<br /> <br /> <a rel="nofollow">.200 screen spline on Amazon 500' for $20.61</a>&nbsp;Just under a quarter inch and enough to do a ton of windows.<br />
I think the main issues are the diameter and hardness.&nbsp; You can choose dimensions of the groove to match the spline, so that's not a big deal.&nbsp; But I've found that the spline material is rather hard, so it may be difficult to seal the window without cracking the glass.&nbsp; I found that the corners are particularly sensitive... You'd have to tighten down the trim slowly and evenly around the whole frame---like a head gasket.&nbsp; Also, remember that wood screws are only good for about 7 lb/thread, so the length of the screws may have to be longer to accommodate the harder seal.<br />
wait, you used silicon caulk instead of an o-ring? How big in diameter is this o-ring? Or are we talking about long round strings of rubber?<br /> <br /> When I was sorting out how to do this in my head, I was thinking the way to do this would be to step the frame, and thus have one piece of glass maybe 1/4 inch bigger all around. I would have also used glazing points to hold the glass in place. I've never tried silicon instead of glazers putty, but I&nbsp;don't see why it would not work.<br /> <br /> I'd probably give the frame two coats of &quot;curb-shopped&quot; exterior grade paint, especially if I was adding desiccant, before putting in the glass<br />
Right.&nbsp; Don't use calk if you ever want to get the glass out.&nbsp; Being able to remove the screws and tip out a single sheet of glass is the most important feature of this design.&nbsp; But my wife wanted to see that the air gap would work as promised, so ordering 10' of tubing would have only added un-necessarily expense.&nbsp; <br /> <br /> The O-ring cross section should have an area equal to the cross section of the groove.&nbsp; Otherwise, it will bulge out and crack the glass or get pinched or cause the space shuttle to explode or something equally horrible.&nbsp; You can buy tubing stock that isn't connected at the ends, and lay that in the groove.&nbsp; Where the tubing ends butt together, a dab of calk would be needed to keep the inside of the window dry.<br /> <br /> Glazing putty can be a bear to get off.&nbsp; The old stuff was lime and linseed oil and maybe some clay.&nbsp; But the new putty is something else that is sometimes a real chore to get off.&nbsp; If you use putty, you'll have a hell of a time getting it out.&nbsp; Remember, you can't just push on the other side of the glass---there's two layers.<br />
I thought about doing something similar to this in older windows, but never got around to it.&nbsp; Are you seeing/feeling any advantage?<br />
If you have oddly-sized windows, or have many fixed windows, the advantages are greater.&nbsp; But this type of window retrofit may only be economical if you have more time than money and already have a table saw and a goodly selection of tools.&nbsp; The part that's shown here is but a small fraction of the work involved.&nbsp; If it's a retrofit, much more effort is required to ensure that windows will fit into the existing frames.&nbsp; Various hardware and weatherstripping can take a lot of effort.&nbsp; But for new construction of large non-moving windows, I think this would be a really good way to do it.<br />
For new construction, I've seen plenty of high quality replacement windows that were special ordered but measured wrong. They turn up at the ReStore that's run by Habitat for Humanity.&nbsp; As long as you can be flexible with the window size in the new construction, you can rough in whatever you have managed to scrounge up.<br /> <br /> Something like this really shines when you have an old wooden window in good shape, but with a busted or rotten frame. <br />

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