Step One: Open One Window and Look at the Sill
Before anyone measures anything, pick the window on the weather side of the house that looks worst and spend ten minutes on it. Everything downstream comes from what you find here.
What Soft Wood Feels Like
Press a small screwdriver into the sill at both outside corners. Sound wood takes the tip and stops. Punky wood accepts it like cork, and the tip comes out with fiber on it. Do the same under the interior stool at the ends and along the bottom edge of the exterior brickmould. Paint can look perfect over wood that has been wet for six winters, so trust the probe, not the finish.
Where the Water Is Getting In
Look for the actual path while you are there. Failed glazing putty on an old wood sash. An open joint where the exterior stop meets the sill. Siding or J-channel butted tight against brickmould with no gap for drainage. A sill that has weathered flat or, worse, back toward the house. Any one of those means the next window will do what the last one did unless the detail changes.
Step Two: Measure the Frame Three Ways
An insert has to fit inside what is already there, so the frame has to be measured like a machinist would.
Width jamb to jamb at head, middle and sill. Height head to sill at left, center and right. Then both diagonals inside the jambs. Write down all eight numbers per opening. The smallest width and the smallest height are what an insert has to live inside; a quarter inch gets deducted from each on most orders.
Read the spread, not just the smallest number. Under a quarter inch of variation is normal for any house past middle age. Half an inch or more means the opening has moved, and an insert will telegraph that as a wedge of caulk down one side for the rest of its life. That is a full-frame signal even when the wood is sound.
Two more numbers belong on the sheet. Measure the existing daylight opening, glass edge to glass edge, so you can compare it directly against the daylight opening of whatever gets quoted; that is the only honest before-and-after. Then measure jamb depth from interior stop to exterior stop. Under about three and a quarter inches, a lot of insert frames will not fit until the old jamb liners come out, and the quote should say who is doing that and what it does to the finished sightline.
Step Six: Price Both, on One Written Scope
The Line Items to Insist On
Send every bidder the same sheet: the opening count, the sizes, which openings are bedrooms, and a request for both a pocket price and a full-frame price. Ask each to state removal depth in plain words, whether a sill pan is included, who handles interior patching and paint, and the daylight opening size of the units they intend to order.
Handling the Rot Contingency
Nobody knows what is behind the trim until it is off. Have the contract carry a per-opening unit price for sill replacement and a separate hourly rate for framing repair, plus a rule that you approve anything over a set dollar figure. That single clause is the difference between a discovery and an argument.
Lead-Safe Work in Pre-1978 Ingalls Homes
A tear-out disturbs far more painted surface than an insert does, and a great many central Indiana homes predate 1978. Federal renovation rules require lead-safe work practices when painted surfaces are disturbed in housing of that age: containment sheeting, HEPA vacuuming, controlled debris handling and a written cleanup. Ask whether that is included or excluded, because it is a real line item and a bid that ignores it entirely on a 1940s house is telling you something.
Step Three: Do the Glass Loss Math
Small Windows Lose the Most
An insert typically costs about two to three inches of width and two and a half to four inches of height. On a wide living room unit that is a rounding error. On a 24-inch bath or stair window it is a tenth of the width, and the room reads darker afterward. Take the smallest three windows in the house and subtract the numbers on paper before you decide, because that is where the regret lives.
The Egress Check on Ingalls Bedrooms
Sleeping rooms and finished basements have a minimum opening size for escape and rescue. The usual figures are a net clear opening around 5.7 square feet, a minimum clear height near 24 inches and clear width near 20 inches, with the sill no higher than about 44 inches off the floor. Local adoption and grade-floor allowances vary, so confirm with the Ingalls building department rather than a brochure. If an opening is already close, an insert can push it under, and the only way back is a full-frame unit or a larger rough opening.
Do the arithmetic on the sash that actually opens, not on the frame. In a double-hung only the lower sash clears, so a 32 by 54 unit with a 28-inch daylight width and roughly 24 inches of clear height gives about 4.7 square feet — already under the usual threshold before an insert takes anything. The same rough opening fitted with a casement swings clear of nearly the whole hole and passes with room to spare. That one difference pushes a lot of bedroom openings toward a full-frame unit in a different style rather than a like-for-like insert, and it is worth knowing before you fall in love with matching sashes across the front of the house.
Step Five: Read the Outside Wall
The exterior decides how invasive a tear-out actually is. Vinyl or lap siding comes off and goes back with almost no scarring, and the flashing can be tied properly into the water barrier. Brick veneer means working to the rough opening behind the brick and leaving the veneer and lintel alone, which is slower but clean. Stucco and synthetic stucco are the ones to think hard about, because the finish has to be cut and patched and the patch will show.
While you are outside, check whether the existing units have a nail fin buried behind the siding. Newer subdivision homes almost always do, and that changes a full-frame job from carpentry into siding work.
Step Seven: Sequence It With Everything Else
The order of operations saves real money. If siding is being replaced within two years, do windows full-frame at the same time and the flashing labor is nearly free. If the interior is getting painted anyway, the trim damage from a tear-out costs almost nothing extra. If neither is planned and the frames are sound, inserts in late winter or early spring usually price better than the summer rush.
What happens if you do nothing for another year? Sound frames stay sound and you lose only heating dollars. Soft frames do not hold still — a sill that reads slightly punky in one autumn generally probes noticeably worse the next, because the freeze and thaw cycle works the same joint open every winter. That is the one situation where waiting has a compounding price.
Step Four: Decide What the Interior Trim Is Worth
A full-frame tear-out takes the casing, stool and apron with it. In a 1990s house with finger-jointed colonial casing, that is a shrug and a trip to the lumberyard. In an older Ingalls home with plaster returns, wide fir casing and bullseye rosettes, it is the thing that makes the room, and it does not come back the same.
Walk the house and sort openings into two piles: trim you would miss and trim you would not. It is common to end up with a front room and a stair landing in the first pile and everything else in the second, which is a perfectly good reason to run a mixed scope.