Choose by where the air gets through
The Department of Energy treats these materials as complementary, not competing upgrades. One window may need weatherstripping where its moving sash meets the frame and caulk at a fixed frame joint. Describe the exact leaking joint before choosing a product, rather than assuming everything around a drafty window needs the same treatment.
Prioritize large leaks, including hidden ones
DOE recommends addressing the largest air leaks first. Its home-energy checklist warns that major trouble spots are often not windows and doors: they can include utility openings, gaps around chimneys and recessed ceiling lights, and unfinished spaces behind cupboards or closets. An obvious door draft is worth fixing, but it does not establish where the house loses the most air.
For widespread discomfort, ask a home-performance professional to assess the whole house before undertaking a room-by-room caulking campaign. Areas near flues, chimneys, wiring, or ceiling fixtures belong in a qualified contractor’s scope, not an ordinary homeowner sealing project. These locations can require special materials and fire-safety details; identifying a gap is not enough to specify its repair.
Make a safe, simple leak list
Inspect accessible doors and windows for missing or damaged seals and gaps at fixed joints. DOE describes a simple check: close a door or window on a piece of paper. If the paper can be removed without tearing, that indicates leakage. Check several locations, without forcing the window or putting fingers near hinges.
Treat that check as a clue, not a measurement of the home’s total leakage. Record whether each suspect joint moves, stays fixed, or is hidden behind trim. Note whether the door or window closes and latches normally. This gives a contractor a useful starting list without removing trim, opening electrical boxes, entering an attic, or deliberately changing pressure inside the house.
Use weatherstripping where parts must still move
Weatherstripping should make a continuous seal around the appropriate moving joint while allowing normal operation. For an exterior door, perimeter weatherstripping addresses the sides and top; a suitable door sweep addresses the bottom. Caulking the door to its frame is not an alternative. Federal building-science guidance calls for compatible materials and a continuous perimeter gasket.
Before shopping, photograph the existing seal and note how the door or window operates. Follow the replacement product’s fit and installation instructions. Afterward, check that the unit opens, closes, and latches without unusual force. If it already binds or will not latch, ask a window-and-door repair professional whether adjustment or repair should precede new seals.
Use caulk for appropriate small, stationary gaps
Caulk belongs at fixed joints, not across an operable window’s moving edges. Gap width matters: DOE weatherization job aids identify 1/4 inch as a gap many caulks and sealants can span, and call for backing or another infill material when caulking wider gaps. That is guidance, not a universal limit for every product.
Check the label for compatible surfaces, gap dimensions, preparation, application conditions, and curing. Do not assume a larger bead will solve a large opening. If the suspected leak is inaccessible, repeatedly reopens, or would require removing surrounding materials, ask an air-sealing contractor to identify the actual air path and specify the repair before covering another visible seam.
Philadelphia PECO tip before you buy caulk or weatherstripping
If you are a PECO customer in the Philadelphia area, PECO Connection’s February 25, 2026 cold-weather tips specifically recommend caulking around doors, windows, and openings for utility services, and note that reducing air leaks around floors, walls, ceilings, ducts, fireplaces, doors, windows, vents, and plumbing could cut an average monthly energy bill by about 10 percent. Use that local tip as a prompt to fix the largest accessible leaks first—matching DOE’s checklist priority—rather than caulking every visible seam.
Ask for testing when the problem is bigger than one joint
For persistent or widespread drafts, seek a home-performance assessment with blower-door testing rather than simply requesting more caulk. Ask which leaks have priority, what materials each repair requires, and how results will be checked afterward. Building America guidance calls for blower-door testing before whole-house air-sealing work and notes that fibrous insulation is not an air barrier.
Also ask who will evaluate ventilation and combustion safety. If the home has natural-draft fuel-burning equipment, the guidance calls for a combustion-safety test after air sealing to check for backdrafting or combustion-gas spillage. Have qualified professionals perform those checks and any necessary equipment or venting work; do not attempt to diagnose combustion safety with a household draft test.
Related HomeFix guides: programmable or smart thermostat savings in a drafty older house · drafty original wood windows: repair or replace · home energy assessment before windows or insulation · attic insulation enough for winter.