The U-value drops sharply
An old double-glazed window typically sits around 2.6–2.8 W/m²K, while modern windows are below 1.0. The exact figure is on the product data sheet.
All energy measures
Building envelope
Windows and external doors
Windows lose more heat per square metre than any other part of the building envelope. The gain depends as much on what you replace as on what you replace it with.
See what this means for your homeThis measure is relevant if
- The windows are double glazed from before the 1990s, or single glazed with a storm window
- Condensation forms on the inside of the glass in winter
- You feel cold downdraught when sitting near the window
- The facade is being renovated anyway
What it does to energy use
The cold downdraught disappears
A cold pane cools the air, which sinks along the window. It feels like a draught even when the window is airtight.
Solar heat works both ways
New glass coatings admit less solar heat. That helps in summer and hurts in rooms that rely on free solar gain in winter.
Installation counts just as much
A large share of the loss goes around the frame, not through the glass. Sealing and fixing decide how much you actually get back.
Sequence matters
Replace windows at the same time as, or after, insulating the walls — but before the heat source. Both measures cut the heat demand, and sizing the heat pump between them makes it too large. If the facade is opening anyway, do both in one round.
Enova funding
Replacing windows and external doors is among the measures Enova funds. The terms have been tied to the U-value the new windows achieve and to how many square metres are replaced.
Rates and terms change. What you can receive depends on the building, how the work is carried out and which schemes apply at the time. Always check Enova's own pages before relying on a figure.
The rates tell you what you can receive. The calculation tells you what the measure actually does to your home — how much it saves, what it costs, and whether it should come before or after the others.
Which measures pay off in your home?
Enter the address. Gadder collects what is known about the building, calculates the energy demand and ranks the measures by what they actually deliver.