The tiles fitted in this part of the world generally last at least 30 years. The steel waterproofing kit and panels will last about the same. The initial “plastic” waterproofing kit failed and was replaced with steel under guarantee – the German plastic failed to cope with the temperature range and expansion/contraction in France. The new kit uses the same steel parts used to cover industrial buildings and has a proven track record. I’m confident.
The fact the tiled roof needed maintenance was part of the investment decision. The panels only cost 30% more than having the south-facing roof retiled. I sorted the tiles I recovered from the south face and used them to replace the weathered ones on the rest of the house. Win, win, win.
An economically efficient building isn’t necessarily a thermally efficient one.
Given that every investment I’ve made to make the building thermally efficient pays for itself in heating costs I disagree.
Approximate return periods.
Wood burner – immediate as the combi packed up and the stove was cheaper than a replacement, wood being cheaper than gas per kWh it would have paid for itself on fuel saving alone in around 10 years.
Roof insulation – first layer: 3 years, second layer; 6 years. third layer and gable ends; 12 years
PV panels 6.5 years
More energy efficient oven 10 years
LED bulbs – variable depending on use
Wall insulation – around 10 years
Solar thermal – 11 years
Floor insulation – harder to calculate (because values for heat loss through floor vary so much) but my lifetime.
Triple glazing – less than 30 years