diminishing returns
figures are made up but reasonable
let's suppose you have a renovation house with no loft insulation.
Let's suppose your bedroom ceiling is 10 m2 and loses 2kW of energy when 20C inside and 0C outside.
Let's suppose you add a meagre 50mm of glassfibre to the loft. The heat loss from that room halves to 1kW (hooray) and maybe saves you a pound a day on cold winter nights.
You then add another 50mm glassfibre. The loss halves again, to 500W
You then add another 50mm and it halves to 250W.
So the greatest benefit, and the best financial return, was on your first 50mm
If you carry on adding more thickness, the incremental value becomes trivial.
This is especially important if you are insulating walls internally, and reducing the room size.
In Switzerland I have seen some kind of shiny white foam board added externally to old stone buildings, then a cement board added and a render-look paint added. They just do 100mm. Some of their winters can be long and cold, but they have calculated that this gives a worthwhile economic return.
figures are made up but reasonable
let's suppose you have a renovation house with no loft insulation.
Let's suppose your bedroom ceiling is 10 m2 and loses 2kW of energy when 20C inside and 0C outside.
Let's suppose you add a meagre 50mm of glassfibre to the loft. The heat loss from that room halves to 1kW (hooray) and maybe saves you a pound a day on cold winter nights.
You then add another 50mm glassfibre. The loss halves again, to 500W
You then add another 50mm and it halves to 250W.
So the greatest benefit, and the best financial return, was on your first 50mm
If you carry on adding more thickness, the incremental value becomes trivial.
This is especially important if you are insulating walls internally, and reducing the room size.
In Switzerland I have seen some kind of shiny white foam board added externally to old stone buildings, then a cement board added and a render-look paint added. They just do 100mm. Some of their winters can be long and cold, but they have calculated that this gives a worthwhile economic return.
