Window Frame Materials Compared

What the survey says

A 2026 This Old House survey of 1,000 homeowners who completed a replacement reported these national averages per installed window [W1]:

That is a $111 spread from cheapest to dearest, against an overall average of $517 per installed window and an average total project of $7,183 [W1]. These are national survey averages, not Wisconsin prices and not quotes. The quality range inside each material is wider than the gap between materials, so "vinyl" on its own tells you very little.

Vinyl

Vinyl (PVC) frames are hollow extrusions, usually with internal chambers and sometimes with insulation in them. They do not conduct heat well, which is what you want, and they need no painting.

The things that separate good vinyl from bad vinyl are not visible in a brochure: wall thickness, whether the corners are fusion-welded or mechanically fastened, how many internal chambers there are, and the quality of the hardware and weatherstripping. Vinyl also expands and contracts more than other frame materials across a Wisconsin temperature swing, so welded corners and good installation detailing matter more here than in a mild climate. Dark colours absorb more heat and are harder on the material.

Vinyl cannot be refinished, and the colour is what you get for the life of the window.

Fiberglass

Fiberglass frames are pultruded glass-fibre and resin. The property that matters is that fiberglass expands and contracts at close to the same rate as the glass it holds, which puts less stress on the seal over years of thermal cycling. It is strong, so frames can be slimmer for the same glass area, and it can be painted.

It was the most expensive material in the survey, at $564 per installed window [W1], and fewer product lines and colours are available than in vinyl.

Wood

Wood frames insulate well, can be refinished, and are often the right answer on a pre-war house where the interior trim and sightlines are part of the building's character. Most wood replacement windows sold now are exterior-clad, with aluminum or a composite skin on the weather side and wood inside, which removes most of the maintenance problem.

Wood averaged $544 per installed window in the survey [W1]. Unclad exterior wood needs paint or stain on a cycle, and in Wisconsin the south and west elevations weather fastest. On a historic house, check with your local building or historic preservation office before ordering, because some districts have requirements about appearance.

Composite

"Composite" covers several different products: wood fibre and polymer blends, fibrex-type materials, and various proprietary mixes. They are generally pitched as wood-like appearance with lower maintenance, and they averaged $513 per installed window [W1].

Because the category is not standardised, compare the actual product rather than the word. Ask what it is made of, what the warranty covers, and for the NFRC label figures on the exact unit.

Aluminum

Aluminum was the cheapest in the survey at $453 per installed window [W1], and it is the one to be most careful with in a heating climate. Aluminum conducts heat readily. Without a thermal break, an aluminum frame is a cold bridge: the interior frame surface runs cold, and condensation and frost collect there in a Wisconsin winter.

Thermally broken aluminum frames exist and perform far better. If aluminum is being quoted for a house, ask specifically whether the frames are thermally broken and ask for the whole-window U-factor from the NFRC label, not the glass U-factor. Aluminum is much more common and better suited to commercial work and to large spans where frame strength is the priority.

Choosing, in practice

1. Start with the glass and the label, not the frame. U-factor and SHGC are measured for the whole window assembly, so they already account for the frame. See energy-efficient windows.
2. Then the house. A 1920s bungalow with deep interior casing and a 2004 colonial have different constraints.
3. Then maintenance. Be honest about whether you will repaint anything.
4. Then budget, across all the windows rather than a showcase few.

If a rebate is part of your plan, the Focus on Energy programme specifies ENERGY STAR Version 7 Northern Climate Certified models and a participating Trade Ally contractor, with a reservation approved before purchase [W2]. No frame material is excluded or favoured by the programme; the certification is what matters. See the rebate page for the dates and caveats.

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