double glazing frames/units build quality

garysletters

I'm about to get my entire house some new double glazing. I've had loads of salesmen round and need the opinion of someone who knows.
1) which is best reinforcement metal? Galvanised steel or aluminium??
My mind says steel (its stronger and shouldnt rust) but a couple of people have told me aluminium is now used as it doesnt bend as much, which would cause unit seal breakdown. Sounds like rubbish to me but was from a good source.
2) whats best for sound insulation a) 2x4mm panes with 20mm gap, b)1x4mm and 1x6mm (or more) pane with 18mm gap.
3) anyone in Leeds area got any personal recommendations of who to use. I've previously had bad experience with Anglian so won't use again + Everest cost too much.

Thanks for your opinions.

alanobrien

Assuming the steel is a standard 316 base its almost 3 times stronger in bend strength than the aluminium. Steel has a typical Youngs Mudulas of 200 GPa compared to 70 Gpa for Aluminium. The bigger the number the better.

The *real* reason that aluminium is used is that it is lighter and cheaper than galvanised steel. The reason it is cheaper is that it is sold be weight from the foundry and because aluminium is lighter you get a lot more (bigger volume) of material for your money.

Aluminium may be slightly better than the steel at resisting corrosion but that will depend on how well the steel is galvanised.

Oh and of course aluminium being lighter than steel means the windows will be lighter and therefore less costly to ship.

Can't answer the other questions though

Gilster_2

The material used to reinforce doesn't matter too much as it is non load bearing, the weight of brickwork being taken by the lintel. We used to use aluminium as it was lighter and easier to cut but now use steel which makes each window much heavier.

garysletters

Thanks to both of you. Thats exactly what I suspected. The only point I didnt expect was the steel galvanisation. I presumed even badly galvanised steel would be safe from corrossion as no water should get to it through the plastic frame....however I guess condensation would account for this.

I think I'm best going for a galv. steel construction.!