Windows fitted to the opening, not just the order

Two numbers matter more than the marketing. Solar heat gain coefficient measures how much of the sun's heat gets through — lower is better here, and it matters more in this climate than almost anywhere. U-factor measures heat transfer. Low-emissivity coatings on the glass are effectively standard for Arizona west and south elevations, and it is reasonable to specify differently for different sides of the same house.

Retrofit fits a new window into the existing frame, which is faster, cheaper and less disruptive. Full-frame removes everything back to the opening, which costs more but is the only honest option when the existing frame or the surrounding structure has deteriorated. Retrofitting into a compromised opening hides a problem rather than solving it, and we will say so.

They generally help, and on a house with old single-glazed windows and west-facing exposure the difference can be substantial. We will not put a percentage on it, because the honest answer depends on your insulation, your air conditioning system, your shading and how you use the house. Anyone quoting you a guaranteed saving is quoting a sales figure, not an engineering one.

That is the part of a window job that shows, and it is where cheap installations fail. Cutting a window out of a stucco wall means the flashing, the weather barrier and then the stucco patch all have to be reinstated correctly and the texture matched to a wall that has weathered for years. We do that work ourselves rather than leaving it to whoever comes next.

Like-for-like replacement often does not, but changing the size of an opening does, because it is structural. The threshold varies by jurisdiction. We check before starting rather than assuming, since the cost of getting that wrong lands on the homeowner at resale.