Frame material is the second decision after shape, and the three real options behave differently enough that comparing quotes across them tells you very little. Aluminium, uPVC and timber differ on how thin the frames can be, how well they insulate, how much maintenance they need and how long they last, and each of those matters more or less depending on the house.
Aluminium: thin frames, and a thermal break that has to be there
Aluminium is strong, so the frames can be slim and carry large panes, which is why contemporary designs use it. Aluminium is also an excellent conductor, so the profile has to be thermally broken, with an insulating barrier between the inner and outer faces. A cheap aluminium system without a proper break will be cold and will attract condensation, so this is the specification to ask about rather than the colour.
The uPVC conservatory: the volume product, and why it is cheaper
uPVC frames are wider than aluminium for the same strength because the material is not as stiff, so more of the elevation is frame and less is glass. It insulates well without needing a thermal break, it needs no painting, and it is the cheapest of the three by a clear margin. The trade off is the sightline and, on some systems, how the white ages.
Timber: the one that suits period houses and needs looking after
A timber conservatory on a Victorian or listed house looks right in a way the other two do not, and modern engineered timber with a factory finish is far more stable than the softwood of forty years ago. It still needs recoating on a cycle, and that cost over twenty years is real. It is also the most expensive of the three to buy.
Do not compare totals across materials
A cheaper aluminium quote and a dearer uPVC quote are not the same job made cheaper. Fix the material and the profile first, then compare, or you are comparing two different buildings and choosing on a number that means nothing.
Questions people ask about aluminium conservatories
Which material lasts longest?
Well specified aluminium and well maintained timber both outlast uPVC on current evidence, and the failure modes differ: aluminium fails at the seals and the thermal break, timber fails where water sits, and uPVC discolours and its hardware wears. Maintenance decides more than the material does.
Is aluminium cold?
A thermally broken aluminium system is not, and an aluminium system without a proper break is. That single feature is the difference, and it is worth asking for the system name and looking up its performance rather than taking a general assurance.
Can I mix materials?
Yes, and it is common: an aluminium roof over uPVC side frames is a normal combination because the roof benefits most from the strength. Ask what each element is, because a quote that says aluminium may mean only the roof bars.