Cold bridge to the garage?

Ahoy,

our garage (the smaller rectangle in the drawing) has an iron door (steel door?) as a passage to the utility room. The utility room contains the gas boiler and otherwise only the refrigerator and is heated little to not at all.

The iron door (approx. 25 years old) might be a thermal bridge? The garage itself is not insulated, the rest of the house has approx. 14 cm insulation and brick cladding. Does it make sense to consider replacing the door here or is that not so relevant because the utility room serves as a "buffer"?

Let's put it this way: an unheated room is included less poorly in an energy loss calculation than outside air :D Whether the exchange is economically worthwhile is unclear. What do you spend annually on heating costs?

Thanks for the quick reply! Now I’m quick for once ;) We use about 12kWh of gas per year in a 25-year-old house – so it’s relatively okay. But a new door might only cost a few hundred... so the question is what it would save me... :cool:

very simply: old door has a U-value of ... let's assume 6 W/m²K (that's about single glazing) and an area of 2 m². New door has a U-value of 1.2 W/m²K ... in a super severe winter lasting 20 weeks at -10°, the old door would therefore have 604 kWh heat loss - the new one only 100 kWh -> savings would be about 35 € per year. Even with this completely absurd example, it is rather less worthwhile. (it will never be -10° for 20 weeks straight - especially not in your garage ;-))

Please contradict me if I have made a mistake in my thinking.

One might think I had been drinking -.- but well, I hope the idea came across clearly. Certainly an energetically lousy component, but with its 2 m² still not so dramatic at first.

Since we are talking about NRW, we can rather halve the €35/year in your calculation due to the temperatures – even that would still be the worst case.... Therefore, it will pay off in about 20-30 years, so not so great... I'd rather save the money for a gas boiler in a few years ;)