Buying replacement windows without being sold to

Buying replacement windows is unusually hard to do well, because almost every source of information is someone selling them. Here is what actually decides whether the job goes right.

Read the label, not the brochure

Every certified window carries a rating label. Five numbers, and only three of them are required to be there.

Full-frame or insert — and why it is not really a price question

An insert, sometimes called a pocket replacement, drops a new unit inside the existing frame, keeping the old frame, the sill and the interior trim. Full-frame removes everything down to the rough opening. Inserts run roughly $100 to $400 a window; full-frame runs roughly $180 to $1,500.

The salesman's version is that inserts are the cheap option. The real distinction:

• Insert is correct when the existing frame is sound, square and dry, and you do not want to disturb interior plaster or exterior brick mould.
• Full-frame is mandatory when the frame is rotten, warped or out of square, when you are changing the size, and — this is the one — whenever the original window was never properly flashed and the opening needs a sill pan tied into the barrier. An insert cannot fix a missing flashing detail. It conceals it.

Inserts do cost you glass area. How much depends entirely on the existing frame; the only hard published figure we could find is a National Park Service comparison putting replacement of narrow steel casements at about twenty per cent of glazed area lost, which is an upper bound for an unusual case rather than a universal number. Anyone quoting you a precise percentage for your house without measuring it is guessing.

The two rules that ruin orders

Safety glazing

The code names seven locations where tempered glass is required, and ordering “the same window we had” into one of them is one of the most common and most expensive mistakes on a replacement job.

Order the same window you had, from a big-box store, into one of these locations, and you get annealed glass where tempered is required. Tempered runs two to three times the glass cost and a longer lead time, so finding out at installation is expensive.

Egress

Every sleeping room, every basement and every habitable attic needs at least one operable emergency escape and rescue opening.

Frames

Vinyl — the volume choice, and the range within it is enormous. Fails by sash warp on large or dark units, by hardware and balance failure, and occasionally at the welded corners. Fiberglass — least thermal movement of anything, so its failures are hardware and glass rather than frame; the premium is real and so is the product. Wood — the best-looking and the most maintenance, rots at the bottom rail and sill where the paint or putty failed. Clad wood — a wood window with a weatherproof skin, which fails in the one place you cannot see: at the joint where water gets behind the cladding and cannot get back out. Aluminium — conducts cold straight through unless it is thermally broken, and the published life expectancy of fifteen to twenty years reflects exactly that.

Glass

Low-e coatings come in two families. Hard-coat is high-solar-gain, made for cold climates and passive solar. Soft-coat is solar-control, made for hot ones. Neither is right everywhere on the same house, which is why orientation belongs in the conversation.

Argon versus krypton: krypton performs better — up to about 27 per cent improvement against argon's 16 — and costs up to forty times as much with poor supply. For residential double glazing it is not a rational purchase. Standard specification is a 90 per cent argon fill.

The argon leakage myth. You will be told argon escapes and the windows stop working in ten years. The testing standards permit up to one per cent loss a year; measured real-world rates are far lower, around half a per cent a year on small specimens and around a tenth of a per cent on a large unit, and the rate slows as the partial pressure difference falls. The failure that actually matters is total seal failure, not slow permeation.

When the glass fogs

That permanent haze between the panes is a failed seal, and the causes are mostly fabrication-side: edge pressure, sealant voids, poor corner sealing, desiccant left exposed too long before the unit was closed. Three things you can do about it:

• Defogging services drill and vent the unit. It clears the visible fog. It does not restore the seal, the gas fill or the desiccant. It is cosmetic.
• Replace the glass unit only, keeping the frame and sash. This is the real repair, and on a first-generation vinyl window from the nineties whose frame is still sound it is very often the honest recommendation.
• Replace the whole window, which is only necessary when the frame or sash has also failed.

Most manufacturers warrant the sealed unit separately from the frame and finish, usually on shorter and often prorated terms, and glass breakage and reflected-solar damage are typically excluded. Read which component the number applies to before you compare two warranties.

What replacement windows will not do

They will not pay for themselves. EPA's own modelling for this climate zone puts the saving at about $493 a year replacing single-pane glass with ENERGY STAR windows, and about $253 replacing older double-pane. Against a real job in this market that is a payback measured in decades, and the industry's own resale report puts window replacement at the bottom of the exterior projects it tracks, recouping under seventy per cent.

That is not an argument against replacing windows. It is an argument against the reason you are usually given. Replace them because they are failing, because the house is uncomfortable, because you are tired of painting them, or because you want the house to look different. Those are good reasons and they are honest ones. And if the goal really is energy, there is a cheaper option with a better payback that almost nobody in this trade will mention.

Sources: energystar.gov · efficientwindows.org · co.routt.co.us · shapeproducts.com · efficientwindows.org · nachi.org · glassed.vitroglazings.com · thisoldhouse.com · windowanddoor.com