New double-hung windows change a house in ways you feel every day: rooms stop roasting in summer, hallway drafts disappear, and the front of the house actually looks intentional. Most installers can swap a typical home's worth of windows in one to three days, so the disruption is short. The bill, though, lands all at once, which is why a short-term plan matters more than picking the right brand of glass.
Early autumn is the sweet spot for booking. Trades slow down after Labor Day, schedules open up, and you catch the tail end of any late-summer discounts before the holiday rush. Get two or three written quotes from licensed installers in the same week so the numbers actually compare. A quote that is 20% lower than the others usually means something is missing, not that you got lucky.
The 15-month intro period is a deadline, not free money. If any balance is still on the card when month 15 closes, interest starts charging on whatever is left at the card's regular APR, and it gets applied back to the original purchase date, so the cost of the windows can jump fast. Set a payoff reminder for month 13 and pay the rest down well before the window closes.