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SmittyNYUSA 06-19-2009 07:21 AM

Acorn Windows are HORRIBLE - Aluminum
I have (ugh!) Acorn aluminum single hung windows. Many have broken glass. Acorn is out of business, which is good cuz their windows SUCK!

They have a "thermal break" which works very badly or not at all. I get heavy frost and condensation inside the window when it's cold outside.

Did a search and didn't see anything on Acorn on DIY so I thought I would add this to the knowledge base.

The upper unit in single hung can't even be removed.

I am looking into replacements. I can't beleive the prices have gone up so much in 13 years!


Melendez 12-04-2010 11:36 AM

I agree - Acorn Atherm Windows suck!
We have the same problems with our Acorn Atherm slider windows. Our master bedroom is 10 degrees colder than the rest of the house, and condensation builds on the windows so bad that mold and mildew grows on the walls in the winter and spring. I'm glad to know they are out of business. We didn't buy them, but we bought our house 3 years ago, and it's time for them to go!

DangerMouse 12-04-2010 12:15 PM

Here's an idea.... write down the needed sizes and call around to builders/window suppliers in your area and ask if they have any mis-measured windows 'out back'. I got 14 brand new windows for my home for under $800 this way. Of course, I framed and installed them all myself, but you may be able to find exactly what you need if you take a few minutes to call around.

My sidelite windows for my front door cost me $15.00 for the pair (brand new in the box) at a yard sale.

Good Luck Hunting!


mrgins 12-04-2010 02:55 PM


Originally Posted by DangerMouse (Post 545329)
Here's an idea.... write down the needed sizes and call around to builders/window suppliers in your area and ask if they have any mis-measured windows 'out back'. I got 14 brand new windows for my home for under $800 this way. Of course, I framed and installed them all myself, but you may be able to find exactly what you need if you take a few minutes to call around.

My sidelite windows for my front door cost me $15.00 for the pair (brand new in the box) at a yard sale.

Good Luck Hunting!


Thats a great deal, DM. You must have hit it just right.

polychrome 10-04-2013 01:21 PM

Those windows were fairly well made...
If yours are Acorn from the UK, a company still in business, then this reply is unrelated to your windows. If Acorn/A-Therm from the USA then read on...

My A-therm windows are 34 years old, and they haven't failed. Acorn/A-therm failed more than 20 years ago, so your windows are probably older than you think. At 34 years almost 1/2 of my sealed insulated glazing units have had to be replaced but half alive at 34 years is very good for sealed thermal units, the single sealed stuff from china at the big box stores is will all fog and fail within 15 years. (BTW Acorn Homes is still in business, but they didn't make windows they bought their windows from Wabash (now defunct) until the 80's then Pella. )

Broken glass is easily replaced. The glazing units are all 5/8 thick (3/8" space 2 x 1/8" glass). If you will live there a while you want double sealed edges. Low E glass and Argon fill are up to you. After removing the panels you can disassemble them at the corners, or let the local glass company do it all. You will probably find the seal pile (brush, fuzzies, etc) are worn or full of gunk and should also be replaced. the vinyl channel the glazing units are wrapped with should be changed when the glass unit is replaced. The steel screws that hold the fixed panels will have corroded to nothing, and should be replaced with same size aluminum or stainless steel screws from your local hardware store. The rollers can be best lubed with white lithium spray grease from an auto parts store, and any that don't roll or wobble should be replaced. Most hordware stores have rollers and some big box stores do too.

Where I live is as cold as anywhere in NY state. There is indeed condensation despite the thermal break in the window frame and sash parts. If you live in a cold enough place, and bathe or take hot showers, you will not find a window that won't have condensation. Its important to keep indoor humidity down so its intermittent, since it will also be condensing inside the walls. It also helps to use moisture tolerant material around the window interior. M.R. board and real plaster rather than common drywall and joint compound, or if a wood sill, use oil based urethane on all 6 sides/edges/ends of the sticks. The aluminum window itself doesn't care about the water, but its important to keep the water drainage channels to the outside open so the window channel isn't perpetually full of water because the glazing unit seals block water vapor well, and liquid water much less well.

That said, the simple 3/8" air gap glass spacing of the 70's has been improved on. You can get better thermal seperation in the framing with multiple breaks, and in the glass with triple glazing, low-e glass and argon fill, none of which were available 34 years ago. Replacement aluminum windows don't have a flange to seal against the exterior sheathing plywood. The cost of a true improvement, that isn't leaking air around it into the walls, will include some siding work as well. A replacement window is just sealed with caulk. 100% Silicone caulk might last 10-20 years if the house doesn't shift and open a gap, but pros hate 100% silicone because it smells, irritates, and sticks to your skin, so they use latex or latex with silicone which will shrink and fail in 2 to 5 years, no matter what 30 year fairy tale they print on the tube.

BettyVt 06-14-2014 09:17 AM

Anyone know how to install the screens for these windows? In a new place with these installed. Thanks.

polychrome 03-31-2015 11:49 AM

To install screen, with screen parts info.

Originally Posted by BettyVt (Post 1363529)
Anyone know how to install the screens for these windows? In a new place with these installed. Thanks.

You probably installed yours already, but most of us do it the wrong way at first. They are also probably deteriorating, and information about the components parts is below.

The screen cannot be installed with the inner (moving) window panel in place. (On the largest windows (over 2' x 3' panels) the screen can be flexed and installed with the moving panel in place, but the screen frame gets bent/bowed out of shape and fails to keep small bugs out.)

To remove it, open it until it is 2 to 3 inches less than totally open. In that location (only) it is possible to lift the moving panel. With the moving panel lifted clear of the bottom frame rail, tip the bottom of the moving unit into the room just far enough to lower the panel out of the upper frame rail.

[At this point you have good access to both sides of both glazing units and the frame. Cleaning the rolling channel, frame, and glass, is easy at this time. You can clean and lubricate the rollers. You can inspect the pile (the replaceable fuzz strips). Pile is how all movable windows seal the sliding parts. Replacement pile is available by its width and thickness dimensions and if and how many plastic fins are also in the pile. Searching on Amazon or Prime-Line products is productive if you want to do it yourself. Crushed pile with broken fins is 90" of why an A-Therm window leaks air and the frames get condensation, or frost, in some places and not in others although its inevitable if it gets cold enough, the frame need not frost/condense before the glass area does too. Pile generally needs replacing every 10 or 15 years depending on if and how often you open the windows, but it crushes anyway even if you never open the windows. If you have someone come do it, don't let the window repair people bamboozle you and sell you windows you don't need. Aluminum doesn't age and the rollers and pile are widely available. Replacement windows will rely on strips of the same pile. Replacement windows will not have flanges to seal to the sheathing, they will rely on latex caulk that's good for about 3 years. They are generally made of vinyl or wood with a 10 to 20 year maximum life. Thicker glazing units with the same number of layers don't insulate notably better, they let you stuff more drying agent inside the spacers and use a cheaper 1 layer butyl edge seal that doesn't resist water well instead of a 2 layer seal with butyl topped with silicone that keeps water from softening the butyl. Argon gas is nice, but none of the sealing systems can keep it in place. The thing that does work that wasn't available when A-Therm was in business (and can be used for replacement glass units) is infrared blocking (low-e) glass. UV blocking glass to reduce fading is also new but A-Therm windows are commonly found in cooler climates and the 2 layers of glass block enough UV that fading is an uncommon complaint.]

The screen was originally supplied with a lift tab at the center bottom and four rotating tabs to hold it in place. Without the moving window directly place the screen in position with the lift tab at the bottom and the rotating tabs toward the inside. Rotate the tabs enough for the plastic tab to enagage the slot in the frame.

At their present age, the original plastic parts may have seen many years of sushine and become brittle. The tabs break when turned, the lift tab tears off when you try to install or remove the screen. The original style A-Therm rotating tabs with zero-offset and bent handle can be found as Prime-Line PL-7920 (white) and the lift tabs (dark) as Prime-Line L-5687. There are other colors of rotating tab cataloged and probably other sources as well. There are similar turn latch parts available at hardware stores, but they are straight handles, over-long over thick latch tabs, and/or not zero-offset. If you have the skills, tools, and drive to modify them rather than wait a week for mail order parts, you probably aren't sitting around reading this.

The old rotating tab rivet is removed using a 1/8" drill only to remove the head then push the rivet stub into the frame and let it drop in and stay there. The stub can only be removed when replacing the screen cloth, by opening the frame corner. Don't use the screws that come with the PL-7920 rotating tabs, they are too long, won't hold, and a dissimilar metal would corrode the aluminum frame every time it got wet and drop out in a year or two anyway. They should be attached with a 1/8" diameter x 3/16-1/4" (grip range) aluminum blind rivet (pop rivet). If you must use a screw, find #4 x 1/4" (or 5/16" or 3/8" it won't matter) aluminum sheet metal screws. If an aluminum screw won't hold you can use a toothpick to put a glob of epoxy around the inside of the hole, put a little grease or Crisco or whatever else is handy on the tab to prevent the epoxy from sticking to the tab then screw it it and if clamp it place with a clothes pin while the epoxy sets up. It won't be terribly strong but the screw is not being tugged on once the screen is installed.

Replacement lift tabs are installed in the spline channel behind the spline and are supplied with instructions.

vinrossgmailcom 05-13-2015 01:15 PM

Atherm Window replacement parts
2 Attachment(s)
I have old Atherm windows as well. My local glass repair has companies that will replace the paines of glass with the new argon gas double pain windows. However the windows to do not move smoothly. Can these rollers be replaced? If so does anyone know where I would find replacement parts? The local company here claims they cannot get them.

Desh123 11-20-2015 12:05 PM

Acorn Windows
I am trying to figure out if I have the ACORN Atherm windows or the ACORN windows from the UK.
The only identifying thing I see on a single hung window is the word ACORN on the center latch. They are brown aluminum.

Anyway, even if they are the A-Therm, they seem to be holding up OK after 28 yrs except the spring loaded sliding latch that holds the top of the window in its track have broken/failed.

Any idea where replacement parts might be found or foraged from?

The suggestions for the screen tabs and rotating latches are good ideas.

Thanks for any suggestions.\

dd57chevy 11-21-2015 08:16 AM

Parts are available from Blaine Window Hdwe .

Depending on your location (climate) , it might be wise to consider replacing them with a properly installed high-performance vinyl window . Aluminum conducts heat out very quickly .

DonnaPal 11-23-2015 08:17 AM

Another source for old Acorn replacement hardware is here:

jxmos 10-18-2016 04:33 PM

Re: Acorn Windows are HORRIBLE - Aluminum
You don't need to replace Acorn with new windows. All the parts are available from many window parts suppliers. Last year I replaced all the springs that support the sliding window. This year I had a local window shop build the window units and I replace all the south facing glass myself. We replaced 24 window units (12 single hung windows) for $2500. That's a lot cheaper than replacement windows. DIY is best!

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