u values, insulation.

[legin]

Having read many an interesting discussion within the group, thought that I would tap the resources. Assuming that wall is principly constructed using the same materials, i.e. the u value would be the same. Would it make amy difference where the insulation was. Surpose outer brick, cavity, inner block then insulated, boarded and skimmed as against outer brick, insulated cavity, inner block, boarded and skimmed. The u values would be the same but I would have thought that the initial warm up time would be less as the blockwork mass would have to be heated to get to the insulation in one of the examples.

Nigel

[Peter Taylor]

Hi Nigel - basically, the position of the insulation doesn't make any difference to the U Value of a wall. The U value is calculated by inverting the sum of the thermal resistances of all the materials, surfaces and cavities, so you can get minor differences if you create any extra cavities.

You're right - insulation on the inside face means the structure has a lower thermal capacity and a room will reach target temperature more quickly, but then it will also cool down more quickly too. There are advantages and disadvantages - personally, from the point of view of comfort, I prefer a higher thermal capacity but it can work out more expensive if you leave the house cooling while you're out. You can partly get over this by adjusting the on/off times on the programmer.

Peter

[The Natural Philosopher]

I think you have it in one.

The better the insulation, and the bigger the thermal mass inside the insulation, the less it makes sense to have a timed heating system.

I keep imagining those mediaeavel castles with 9ft thick stone walls, and how long it must have taken to get them up to working temperatures,....

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