Your Old Windows, Part 3:
Restoring Your Old Wood Windows

Back in the day, windows were designed for longevity, endurance, and durability. Now, they are engineered for energy efficiency, with a long service life being a lesser consideration. This focus has drastically changed how windows are designed and manufactured — and how long they last.

Most modern windows have an expected lifespan of about 15-25 years — some of the best may reach 40 years, some of the worst only 5-10 years. Twenty years is about the average. The problem is not that the windows are poorly made. Many of today's windows are very well made. The problem is the engineering and the materials used. They just don't last like old wood windows. And, when they break, they cannot be easily repaired.

New Window Construction

A comparison of old and new sash balances, for example, illustrates this basic difference.

If you raise the sash of an old double hung window, it stays in place at whatever position you leave it. This is possible because the weight of the window sash is counter-balanced by two iron weights that ride in pockets built into the wall alongside the window, attached to the sash by ropes. The mechanism is simple and works by gravity. And gravity, at least so far, has never failed.

There is nothing in an old window that can fail except the ropes1 and these can be easily replaced. Once replaced modern sash ropes last between 50 and 100 years, (or even 200+ years if bronze chain is used in place of rope).

Modern, self-contained, replacement windows cannot use sash weight pockets built into the wall, so different balancing mechanisms had to be developed. These are all some form of metal spring. The tension in a spring is what holds the sash in place when the window is open.

Spring ballasts, however, unlike simple iron weights, are complex mechanical devices prone to breaking. Metal springs themselves are subject to metal fatigue which can cause the spring to lose tension over time or even fail completely. We have replaced some worn out spring balances less than four years old.

Other Voices

National Trust for Historic Preservation

Click to Read the Report

"...Given that an average house has between 24 and 30 windows, and the typical replacement window unit costs between $500-1,000 each, does an investment of $12,0000 or more make sense? On the flip side, the cost to restore an existing window and add storm windows (where appropriate) will generally be much less…

Many window replacement manufacturers claim greater savings than actually occur. Since windows account for at most 25% of heat loss, the payback and time to recoup your investment in terms of energy savings could take between 40 and as much as 200 years, based on various studies. A study from Vermont shows the saving gained from replacement windows as opposed to a restored wooden window with a storm is only $.60. The added problem is most replacement windows will not last as long as 40 years, much less over a hundred years. And, some are being replaced only after 10 years of service."

National Park Service

Click to Read the Report

"[We recommend] the retention and repair of original windows whenever possible. We believe that the repair and weatherization of existing wooden windows is more practical than most people realize and that many windows are unfortunately replaced because of a lack of awareness of techniques for evaluation, repair, and weatherization. Wooden windows which are repaired and properly maintained will have greatly extended service lives while contributing to the historic character of the building. Thus, an important element of a building's significance will have been preserved for the future." (Emphasis supplied).

Vinyl (PVC) Frames

Vinyl is another culprit

Vinyl expands and contracts nearly twice as much as wood with changes in temperature and seven times more than glass. This amount of expansion and contraction makes it hard to keep gaps from developing between vinyl components of the windows.

The Canadian Natural Resources Consumer Guide from 2005 states “The disadvantages of vinyl framing material is that vinyl expands and contracts with temperature, opening up cracks for air leakage.” The Canadian Center for Mineral and Energy Technology study of long-term performance of operating windows2 concluded that “Air Leakage in vinyl windows increases 136%, significantly more than aluminum or wood. Un-reinforced PVC profiles have a lack of rigidity and a high coefficient of expansion; PVC profiles are subject to distortion.” The studies found that vinyl windows have a tendency to bend, distort, and even crack, especially in "regions of Canada that experience cold winter months". (What regions of Canada don't experience cold winter months?)

Vinyl also deteriorates when exposed to ultraviolet (UV) rays. Those of us of a certain age remember well how vinyl dashboards in the old Chevy used to crack and split after only a few years exposure to sunlight. The vinyl is better these days. UV inhibitors retard deterioration, but nothing can stop it entirely. Vinyl window parts, especially the thin, flexible vinyl used in balance mechanisms, will deteriorate over time with repeated use. After a few years, they become brittle, break and need to be replaced.

Vinyl softens at temperatures greater than 165°/F, and it's not that uncommon to see such temperatures in the unventilated space between window panes on a bright, sunny day. Excess heat can also cause vinyl to warp and twist. While vinyl window manufacturers say they have that problem under control, few manufacturers actually warrant vinyl windows against warping, twisting or cracking, and those that do limit the warranty to just a few years.

Leaking Insulated Glass Units

Double- and triple-pane glass in thermal windows are manufactured in what are called Insulated Glass Units (IGUs). Spacers between the glass panes not only separate the panes but seal in the gas between the panes. Air between panes of glass must be very dry. If the spacer holding that two panes of glass together springs a leak, moist room air will get between the panes and condensation will form, which may lead to mold, mildew and other nasties inside your IGU where you cannot get at it. There is no cure for this problem. It cannot be repaired. The entire unit has to be replaced.

Seals are much better now than they were when first IGUs were first marketed in the 1930s as Thermopane®. Still, no one has yet invented a seal that does not leak. All spacers are going to leak eventually. Some leak sooner, some later, but they all will leak someday. The environment that spacers have to survive is brutal. Temperatures can be as hot as 180° in summer, plummeting to -30° in winter, or even worse. It's very hard to come up with an adhesive that works for a long time in that kind of environment. It is common to find spacer leaks even in very good windows within 10 years of installation and in some poorly made windows within one or two years.

One-Piece Window Sashes

Like today's Integrated Glass Units, modern window sashes are often single units that cannot be taken apart for repair. They can only be replaced using a new sash supplied by the original manufacturer. You have to hope the window manufacturer (1) is still in business and (2) still makes the part. Plus, you can expect the replacement parts to cost nearly as much as a new window. The manufacturers have a monopoly on replacement parts for their own windows and are not at all bashful about charging what the market will bear, and a little more.

Old Windows: Built to be Re-Built and Re-Built and Re-Built and…

The Sinclair Inn Museum in Annapolis Royal, Nova Scotia can claim what is possibly the oldest double-hung wood window in North America. Built sometime between 1690 and 1710, it was probably recycled from a still older building.

After 300 years, it still works.

Unlike modern windows, old wood windows were made to last for many generations, so they were built to be repaired, over and over again if necessary. The old-time craftsmen knew that their windows would last a good long time, but not forever. So they built windows that could be easily fixed when something finally did give way.

There are no exotic materials in an old window, just wood, glass, iron, rope and a little bronze or brass for the hardware. No vinyl, no unpronounceable chemical compounds, just basic stuff available almost anywhere that has a lumber yard and a hardware store.

There is no chance the parts won't be available even 200 years from now, unless we simply run out of trees — which, despite the hysterical alarms of the more radical elements of the environmental movement, is not all that likely.

Anyone with some basic carpentry tools, a little understanding of how windows work, and decent eye-hand coordination can restore an old window.

Restoring Window Function

Unlike modern windows, old windows rarely break. They may stop working, but the culprit is seldom the window itself. It is (1) broken pulley ropes and (2) accumulated layers of paint that have glued the sashes to the frame. These are easy fixes that usually take less than 2 hours to complete. Freed from decades of paint, with new pulley ropes, and with a little scraping and sanding, most old windows work like new.

First, with light taps with a hammer on a painter's 5-in-1 tool inserted into the gap between the window frame and sash, break the window free of the paint that has glued it shut. The window will then move up and down.

This will take time and a little elbow grease, but it's not hard and does not require great skill. Keep the taps light and watch out for the upper sash when it breaks free. These have a tendance to just drop, mashing fingers, etc.

Step two is to replace the pulley ropes. These join the window sash to the counter-balancing iron weights, and are known in the trade as "sash cords". Without the weights, the window will not stay up. With the weights and sash joined with new cords, they will work just like new. The cotton cord used when the window was made had a life expectancy of about 25 years. The amazing thing is, that after nearly 100 years, most are still working. But, some are not, and in either case, it's past time to replace them, broken or not.

Replacing a Broken Sash Cord
Popular Science Monthly, December 1928

What is the quickest and easiest way to replace sash cord?

Few defects around the house cause greater annoyance than a broken window cord. Yet, like many other things that go wrong, it may be easily remedied without calling in the aid of a mechanic, if you approach the task with confidence and have some degree of ability to use your hands. Few tools are required.

  1. Inspect the cords of both upper and lower sash. If one is broken and one or more are worn and frayed, it will be an obvious economy to replace them at the same time.
  2. Obtain a good grade of braided sash cord from the hardware store. It will be more economical to buy an entire hank if several cords are to be replaced, but if only one or two, you can figure roughly how much you need by allowing 5 ft. for each cord of any window of ordinary size.
  3. We will assume that only one cord is to be replaced and that in the lower sash, for that is more likely to give trouble. Remove the sash by the method described in a previous reference sheet (Nov. 1928). If there is a broken cord on each side, remove both stop strips, but if only on one side, the other side need not be disturbed.
  4. If but one cord is broken, swing that side of the sash out and place a kitchen chair, bot, or other support under it. The lower sash may be pushed under one end of the upper sash to help hold it, as suggested in Fig. 1. It is, however, the best and safest practice to take the good cord out of the sash, tie a knot in it, and allow it to run up to the pulley as in Fig. 2, and then set the sash aside.
  5. Remove the pocket facing. It may be necessary to take out the parting strip to do this. Lift the weight out of the pocket as in Fig. 3, cut the rope away from it and dig out the knotted end from the sash as at A of Fig. 1. Observe how each of the knots is tied and fastened, for the new cord may be fastened the same way.
  6. The easiest way to put the new cord through the pulley is to make a “mouse.” Wrap several narrow pieces of thin sheet lead around a piece of strong, flexible line perhaps 8 ft. long, as in Fig 4. Pound lightly, or press each piece of lead so it stays in place about as shown. A piece of chain, a bent nail, or other light weight will answer the purpose as a makeshift. A 4-in. length of sash chain makes a particularly convenient “mouse.”
  7. Tie a knot near one end of the cord like Fig. 2, and tie the long end of the mouse line to the other end using half hitches as in Fig 5. Push the mouse through the pulley from the front; allow it to drop down the pocket behind the pulley stile until it can be reached from the pocket opening. Pull out the mouse through the opening and at the same time coax the cord through the pulley from the front. Pull the cord down until the knot (Fig. 2) stops it. Remove the mouse line and tie the end of the cord to the weight with a knot that will not slip. Use the knot shown in Fig. 6, for example, or use the same knot that was on the old cord. Nearly every workman has a pet knot for this purpose, but any knot that does not allow the cord to pull directly over the axis of the weight will permit the latter to turn and swing clear of the back side of the pulley or the sash cannot be closed, though the stretch of the cord will soon make it right if not more than 1/2 in. has to be gained.
  8. To find the length of the cord, pull the weight up until it strikes the back of the pulley. Untie the slip knot (Fig. 2) and swing the sash back again until it is as nearly as possible in place. Hold the cord against the edge of the sash and cut it off 6 inches below the hole at A, Fig. 1. Lay the cord in the groove, tie the knot and push it into its hole. Drive a small nail through the knot, if necessary to hold it there and push the sash into its place. Raise the sash, put the pocket face in its place, fasten it, and put the stop strips on.
  9. It is obvious that if the upper sash is to have new cords, they must be put in before those of the lower sash. In this case, remove the lower sash entirely and do not merely swing it around and attempt to hold it as suggested in operation No. 4 above. Pull the upper sash down, take out one or both parting strips, pocket facing, and weights as may be required. Put the cords in by the methods already described, being sure the cord of the upper ash is not too long or the sash may not stay up. The lower end of the weight should swing at least 3 inches above the window stool when the upper sash is in place to allow for the stretching of the cords. Replace the parting strips, pocket facings, and stops.

The sash cords we use today are not the ropes of 100 years ago. The new nylon/cotton cords last up to 100 years. If you want the repair to last nearly forever, use bronze sash chain instead of rope. Some people don't like chain because it's noisy, but considering that a properly installed sash chain never has to be replaced again, the trade-off is, in our humble opinion, a no-brainer. One caveat is that chain cannot be used with pulleys originally intended for cord, so if you are migrating from cord to chair, you will also have to replace the pulleys.

Repairing Deterioration

The next step is to check for rot and deterioration. Water is a window's worst enemy. Although poor design, sloppy installation, wood-loving insects and baseball-loving kids can contribute to a window's demise, the usual culprit is wood rot caused by standing water.

We find this primarily on the sashes and stool or sill of the window. It's not hard to fix. If the problem is minor, and exterior (which is where it usually is), then a little outdoor spackling and some new paint solve it. Otherwise, there are special two-part epoxy fillers that are — or so their manufacturers' say — even stronger than the wood being replaced. If the problem is even more serious we may splice in some wood or even remove and replace the deteriorated part with a new part made in our cabinet shop. If necessary, we can build an entirely new sash that duplicates the old one exactly. In 40 years we have had to do this exactly twice.


Now we need to look at weatherproofing. Over the years the wood in your window has dried out and shrunk a little. This is the reason your sashes may be loose in their frames and sometimes rattle in the wind. Since the sash is now smaller, air can creep around the sash.

The weatherstripping may also need attention. A lot of old window makers used bronze for weatherstripping, and it may be intact, but often it has come loose because the nails used in those days to attach the weatherstripping have worked themselves out — or the bronze may have been removed by some old painter too lazy to mask it off when painting. We use new spring bronze slipped around the sides of the sashes to eliminate air leaks, tighten them up in frame, and provide a nice slick surface for the sash to ride on. Horsehair felt made specifically for windows, or silicon bulb weatherstripping (but not rubber or plastic which do not last) can be used where the sashes meet the frame at top and bottom and at the meeting rail to bar air infiltration. Most of the time, however, these are not needed.

Insulating Around Windows

Once the weatherstripping is done, we look at the insulation where the window meets the wall and in the sash weight pockets. Even if you have had your old house insulated, the insulators usually miss that small 1/2 inch or smaller gap between the window frame and the wall stud. We seal this area with low-expansion foam.

Hopefully, your insulators did miss the sash weight pocket. If they did fill it with blow-in foam, cellulose of fiberglass, you just may have sussed out why your window suddenly stopped working. If it is filled with insulation, the weights don't move. If the weights don't move, the window does not work. But, the sash weights do not take up all of the space in the pocket, and the space they don't use can be insulated using a high R-value rigid board like polyisocyanurate (we don't try to pronounce it either — its "poly-EYE-so" to us) which has a rating of R-7.2 per inch. We use 2-1/2 to 3" of it in total together with expanding foam to arrive at a total R-value of R-18 to R-22 in the sash pocket — which is probably more than the R-11 to R-19 you have in your walls.

Replacing Single-Pane Glass

What we never do, and don't recommend, is replace single pane glass with double-pane IGUs. We used to try this, but it never worked very well. Old sashes are just not milled for the extra thickness of the dual pane glass, and the sash pulley/weigh system is not designed for the increased poundage of extra pane. There are also technical difficulties in installing the glass. New Integrated Glass Units are generally not installed in the same manner as the traditional single-pane glass. And, in the end, the gain in energy performance, if any, is tiny.

17 Steps to New Old Windows

There are seventeen steps required to restore a typical old wood window and put it back in working order. Not all of these will be required for every window. Non-typical repairs are indicated in red.

1. Remove sash stops. Reserve for reinstallation. Sash stops that cannot be reused are discarded and new sash stops fabricated in our door and window shop match the existing sash stop as close as possible. We do not have cutters for all of the heritage sash stop profiles, but we have most of them.

2. Remove the lower sash, cutting and removing any existing sash rope.

3. Remove the parting bead. This is usually destroyed when removed due to accumulated layers of old paint and will be replaced with a new parting bead. Parting bead is waxed to ensure smooth operation but never painted.

4. Remove the upper sash, cutting and removing any existing rope.

5. Remove any hardware (locks and handles) from the sashes for cleaning.

6. Inspect the frame for damage.

7. Strip all paint and varnish in our steam box. Steaming removes most paint and glazing compound and does no harm to the underlying wood.

8. Replace cracked or broken panes.

9. Replace glazing compound with acrylic silicon glazing compound. This compound remains flexible and does not harden over the years like the old linseed oil compounds.

10. Prime the exterior of all sashes.

11. Repair any broken or rotten sash parts: muntins, rails or stiles.

12. Repair any broken or rotten frame members.

13. Lubricate pulleys with dry silicon lubricant (does not attract dust to turn into goo. Replace missing and repair inoperable pulleys.

14. Replace existing sash ropes with Sampson3 Red Spot pulley ropes — the best available. Most old windows have a pulley access cut into the frame. If your windows do not, then we will need to remove the interior window casing to replace the ropes, and they reinstall the casing.

15. Install spring bronze strip weatherstripping at sides of sashes. This is the original 100-year weatherstripping. We use Dorbin 25B Bronze Spring Weatherstrip, made in the U.S.A. and the best available.

16. Reinstall sashes and hardware. Replace missing hardware with matching or complementary hardware as needed. Replace missing sash weights4.

17. Lubricate sash sides with bowling alley wax. (We recommend re-waxing every Spring — when the time changes from standard time to daylight savings time, so you will remember.)

A much better choice is to install a good storm window over restored sashes. Unless it's cracked or broken, leave the glass alone.

Lead Paint and Putty

Before April 2010 no special precautions were required, other than common sense, in dealing with old lead-based paint and glazing compound. Now, elaborate measures are mandated by the EPA, most of which are still, however, just good common sense.

Never grind off lead paint so that the paint particles discharge into the air. The best course is to use removal methods that do not produce dust, such as heat or steam removal. But, if you must grind (and you may have to grind out the old, hard putty), do it outside, and make sure any dust is captured in a HEPA (Not HEPA-like, but actual HEPA) vacuum. Cover the ground with heavy plastic.

Keep lead dust confined to the work area. Cover any doorway into the rest of the house with plastic, and seal all air intake vents in the room. Use reasonable care to ensure that lead particles are not tracked into other rooms on boots or shoes — usually, a brush left by the doorway for dusting off shoes is all that is needed. We hang ours on a string. Wear an N-95 dust mask. Vacuum thoroughly at the end of each day, and at the end of the project, fold the ground-cover plastic edge to center to trap dust particles, put the plastic in a heavy plastic bag, and tie the neck of the bag using a "gooseneck" tie.

Adding Storm Windows

If this seems like a lot of work, it is. But, restoring your old window is a fraction of the price of replacing it with a new thermal window, and wastes nothing. Old growth hardwood is saved from the landfill, and a lot of good old-time craftsmanship is preserved. A typical window can be restored for between $200 and $350. Of course, it is not yet as energy efficient as a new window. For that we are going to have to add a storm window.

A good quality painted aluminum storm window installed will run about $120. An upscale wood combination storm window from a company like Spencer Works will cost a bit more. If you already have storm windows, then you are just that much ahead. But, assuming you don't, your cost to repair your old wood windows and add a good storm window is about $470.00 vs. $1,100.00 and more to replace them with a good quality (not the best quality) replacement window. This is a savings of $12,600.00 in a 20-window house. For your investment, you get a window that will last for at least another 100 years, while a replacement window is doing very well to last 30 years. Your window performance is just as good if not slightly better than that of a modern thermal window, and you saved over 50% of the cost of installing replacement windows.

How to Really Save Energy Costs

Replacement windows are, according to most energy consultants5, high on the list of energy measures that don't work. The notion that new, thermal windows save significant amounts of home energy is a myth fostered primarily by those who sell replacement windows.

Independent studies starting in the 1980s have repeatedly shown that the most effective course of action for those with old wood windows in any sort of reasonable shape is to simply add a good storm window. If you already have a window/storm combination, your window system is already as energy efficient as a replacement thermal window.

If you really want to save energy costs, assuming your attic and walls are already insulated at least to code, your heating and cooling system is already very high efficiency and all your doors are weather-stripped, go buy a high efficiency water heater ($1,000), put $4,400 in the bank against a rainy day, and treat yourself to a really lavish steak and lobster dinner ($100.00), for being "energy smart". Just the water heater alone will save many times more energy dollars than a whole houseful of replacement windows.


1. Even the sash pulleys can fail and the window will still work, albeit stiffly and with effort.

2. Canadian Centre for Mineral and Energy Technology. A Study of the Long Term Performance of Operating and Fixed Windows Subjected to Pressure Cycling. Republished by CANMET Efficiency and Alternative Energy Technology Branch. Publication # M91-7/214-1993E. 1993.

3. Sampson Cordage is the oldest rope maker in the U.S., and the owner of the oldest registered U.S. trademark still in use.

4. Old sashweights are increasing difficult to find, but modern replacements are available from Smith Restoration Sash or Window Weights.

5. Michael Blasnik, Mythbusters: What Works, What Saves?, Proceedings of the 2008 National Energy and Utility Affordability Conference.

Rev. 02/07/18