Hi C. Santini:
I wonder if these sample sentences might be of use:

Dear Client:
May I take the liberty of presenting to you an outline of the business proposal which I have prepared for you in response to your request dated  . . .

Dear Client:
Thank you for giving our firm the opportunity to present to you a business proposal outlining _________________ for your company. . . .

Dear Client:
I have studied the needs of your company in accordance with the material you have submitted and am taking the liberty herein to submit a business proposal which outlines what ABC Company would be able to do in an effort to help you meet your _______ goals for 2006 and beyond . . . . etc., etc., etc.

área instalada = industrial plant ???
enclosed area/space  ??
restricted area ??
solarium ??
construction site ???

Can you be a little more specific, put in context "área instalada" -- a little more than that it has to do with industry? I could not figure this out. Maybe Tom knows what you mean . . . Where are you, Tom?

Hope the above sentences are of help, anyway :)
Abraços,
Ana