Putting extension on house: which eco-measures to install?

And then I will install it. If in 3 years time the anual cost of solar v conventional is fairly equal I can install it (probably relatively more cheaply because of more demand and economies of scale in production of the systems) and have it for 10 years (the lifetime of current panels) from then. Why install it now for it to cost you money for 3 years and then just when it is starting to payback have to replace the panels.

Of course from an environmental point of view I should install it but at the end of the day it's all about what is possible within the budget.

some solar systems will not last as long as the pay-back period

BLOB said:

also, a friend has suggested a condensed boiler - we do not have underfloor heating, will it still be good for us.

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It will certainly be better than a standard gas boiler, event for standard house with hot water/rads.

davidoco said:

Think about this.

Construction

Outer concrete block
40 mm gap
60 mm polyiso type insulation
inner concrete block
25 mm polyiso type insulation
plasterboard

Any dampness, water that gets into or around your inner block will not be able to escape because of the polyiso on either side which is impenetrable to moisture. Moisture can rise up from poor workmanship on damp proof course at foundation level, leak around windows or items bridging cavity. Wind driven rain can penetrate plaster and outer block, move across cavity on ties etc etc. It just might make your inner block nice and warm and wet.

This is just my opinion. Would be much better to go for the larger cavity.

Also your internal leaf, concrete only, acts as a heat store during the day and releases it at night, if you insulate your wall internally you loose that.

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Re : Double Insulation ...

Would you recommend internal insulation if the cavity was 150mm and filled with bonded ecobeads ?

Teabag said:

Re : Double Insulation ...

Would you recommend internal insulation if the cavity was 150mm and filled with bonded ecobeads ?

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Firstly I wouldn't really be qualified to recommend. Each to his own.

The only thing I look out for is the uvalue. If you have attained the desired uvalue with the 150mm bead leave it at that. You will have the obvious heat store from the internal walls. On the other hand if you wanted faster heat up the insulated plaster board is the way to go.

This is anecdotal but my friends house is timber frame seems to hold the heat well when the heat is on, but when it’s off for more than an hour you notice whereas in my concrete built it could be over 2 hours or more before you notice the heating has gone off. In my mind that’s the heat store in the block. I’m comparing timber frame because the insulation is on the inside.