Window Replacement

In a cooling climate the number that matters is not the one on the sticker people quote.

Windows get sold on U-factor, which measures how well a window resists heat flow and matters enormously in a heating climate. Houston is not a heating climate. For most of the year you are trying to keep the sun's heat out, and the number that governs that is different.

The number to look at here

Solar Heat Gain Coefficient, or SHGC. It measures how much of the sun's heat the window lets through, from 0 to 1. Lower is better in Houston. A window with an excellent U-factor and a high SHGC will still cook a west-facing room all summer.

Low-E coating is what delivers a low SHGC. It is a microscopically thin metallic layer on the glass that reflects infrared while letting visible light through. There are different Low-E formulations tuned for hot and cold climates, so the question to ask is not "does it have Low-E" but which one.

Impact rated glass

Laminated impact glass has a plastic interlayer bonded between two panes, so when it breaks it holds together rather than leaving an opening. On the Gulf Coast that matters for two reasons. It resists windborne debris, and it keeps the building envelope closed, which prevents the pressurisation that lifts roofs off houses in high wind.

Whether your address is in a windstorm-designated area with specific requirements depends on where you are in the region, and that is worth confirming before you buy, because it changes what is permitted rather than merely what is advisable. It can also affect your windstorm insurance. Ask your carrier and your local authority, not a salesman.

Full frame or insert

Insert, sometimes called a pocket replacement. The new window goes into the existing frame. Faster, cheaper, less disruption to siding and interior trim. It only works if the existing frame is completely sound, and you lose a little glass area to the doubled frame.

Full frame. Everything comes out down to the rough opening. More expensive and more disruptive, and it is the only option when there is rot in the frame or the sill. It is also the only way to correct flashing that was wrong from the start.

In Houston, rot around window openings is common enough that we check before recommending an insert. Fitting a new window into a rotted frame is putting a good window on a failing wall.

The part that decides whether it leaks

A window is a hole in your wall. The window unit itself is rarely what leaks. What leaks is the joint between the window and the wall, and that joint is made with flashing, not caulk.

Done properly: sill pan flashing under the unit so any water that gets in is directed back out, jamb flashing lapped over the sill pan, head flashing over the top lapped under the housewrap above. Every layer sheds onto the one below, the way roof shingles do. Caulk is the last line, not the first.

A window installed with expanding foam and a bead of caulk around the outside will pass a rain test for a couple of years and then rot the wall below it quietly. That is where a lot of our rot work comes from.

What we do

Check the condition of the frame, sill and the wall below before recommending insert or full frame.
Specify glass for orientation. West and south elevations carry the heat load and deserve the lower SHGC.
Remove carefully, and deal with any rot found rather than covering it.
Flash the opening correctly, sill pan first, in the right order.
Set, shim and fasten the unit square, checking that it operates before anything is closed up.
Insulate the gap with low-expansion foam, which will not bow the frame.
Trim, seal and paint, inside and out.

What to be sceptical about

Energy savings claims are the most oversold thing in this trade. New windows in a Houston house do reduce cooling load, particularly on sun-facing elevations, and the payback period on energy savings alone is usually long. Buy them because the old ones are rotten, draughty, painted shut, single glazed or unsafe. Treat the energy saving as a benefit rather than the justification, and be wary of anyone presenting a payback calculation as the reason.

What it costs, and how you can check

Every job on this page is priced Cost Plus. You see the supplier invoice for the materials, the crew hours at our published rate, the permit and disposal at what they actually cost, and one service fee of 20 to 30 percent set by job complexity and locked before anything starts. There is no second number and no change order conversation after the fact. The full breakdown is here.

Common Questions

What should I look for on the window sticker in Houston?

Solar Heat Gain Coefficient, and lower is better here. U-factor matters much less in a cooling climate than in a heating one, and it is the number most salespeople lead with.

Do I need impact rated windows?

It depends on where your address sits relative to windstorm designation, which affects what is required rather than just what is sensible, and it can affect your windstorm coverage. Confirm with your local authority and your carrier before deciding.

Can you replace windows without disturbing my siding?

An insert replacement usually can, if the existing frame is sound. A full frame replacement disturbs the trim and sometimes the siding, and it is the only correct answer when there is rot or the original flashing was wrong.

Will new windows lower my electricity bill?

On sun-facing elevations with a properly specified Low-E glass, they reduce cooling load measurably. They rarely pay for themselves on energy savings alone in a reasonable period, and anyone telling you otherwise is selling.

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