Insulating old windows or replacing them: which makes sense

What insulating an old window actually involves

Insulating an existing window usually means three things: replacing worn weatherstripping in the sashes, adjusting or adding ironmongery so the sash closes tightly, and sometimes fitting a secondary glazing panel or a removable inner sash for winter. None of this touches the glass or the frame structure.

The weatherstripping itself is cheap, a few metres of foam or brush seal costs very little, but fitting it well takes patience: every gap along the sash has to be found and sealed, and a sash that has warped over decades may need planing or packing before a seal will even sit against it.

Secondary glazing, an extra pane or perspex sheet fitted inside the existing window, does more for comfort than seals alone because it adds a second still-air layer, similar in effect to what a modern double unit does, without disturbing the original window at all.

What a full window replacement brings with it

Replacing a window means taking out the old frame entirely, fitting a new one, usually with double or triple glazing, insulating around the frame with foam, and fitting new trim inside and out. It is building work, not a repair.

A new window is airtight and thermally even across the whole unit, glass included, which an old single-glazed pane never will be no matter how well it is sealed. It also usually needs less maintenance for some years afterwards.

In a wooden house in Kalamaja or Nõmme, replacement raises questions an insulation job does not: whether the building or apartment association has rules about window appearance, whether the opening needs adjusting, and how the new window will look next to original joinery on the same façade.

Cost and comfort side by side

Weatherstripping a window is quick work, often under an hour per window once the ironmongery is sorted, and sits well within our hourly rate of 39 €/h. A full set of windows in a flat might be a half-day job.

Secondary glazing costs more because of materials and precise fitting, and a full replacement is the most expensive option by some margin, priced per window after we have seen photos or measurements, with a fixed quote valid for 30 days.

Comfort-wise, sealing stops draughts, which is often the complaint people actually have. Secondary glazing adds a noticeable drop in the cold coming off the glass on a frosty evening. Full replacement goes further still, but the jump from sealed-and-glazed to brand new is smaller than the jump from draughty to sealed.

When sealing and insulating is the sensible choice

If the frame and sashes are sound, sealing is nearly always worth doing first. It is inexpensive, reversible, and solves the draught problem, which is usually what prompted the complaint in the first place.

It is also the right call when the window itself has value worth keeping: original glazing bars, old glass with slight waviness, joinery that matches a protected façade. Sealing keeps all of that intact.

For a rented flat, or a house where a replacement is planned in a few years anyway, sealing buys comfortable winters in the meantime without spending money on something that will be pulled out later.

• Frame and sashes are structurally sound, no rot or deep warping
• The window has original features worth keeping
• A full renovation or replacement is planned for later
• Budget needs to stretch across several windows this winter
• The building is under heritage or façade rules limiting changes

When it is worth thinking about full replacement instead

If a window has rotten timber, glass that has lost its seal and fogged up permanently, or a frame so warped that no amount of weatherstripping will close the gap, sealing is treating a symptom on a window that is already failing.

Replacement also makes more sense than repeated patching in a room where the draught and cold-glass effect is a real problem, such as a bedroom or a child's room facing the prevailing wind, and where the household wants that solved properly rather than managed.

In new developments and panel flats without protected façades, there is usually no reason to hold onto an old window purely for its looks, so the comparison there is mostly about cost against how many years of comfort are left in the current one.

What we would suggest for a typical Tallinn home

For most wooden houses in Kalamaja or Nõmme with sound original windows, we would start with sealing and, if the budget allows, secondary glazing on the coldest-facing rooms. It costs a fraction of replacement and keeps the original joinery, which is often part of what makes the house worth living in.

For a panel flat with tired plastic windows from an earlier renovation, or any window that is visibly failing, replacement is usually the better spend, since there is little original character to preserve and a new unit will need less attention for years.

Either way, we would look at the actual windows before recommending anything. Our window fitting and servicing starts from 90 € per job, and general sealing or draught-proofing work is billed as odd jobs from 39 € per hour, with a call-out of 25 € within Tallinn deducted from the bill if the work goes ahead.