If you are in receipt of the birth certificate then I guess the question is what do you want to do next?
If you are looking at tracing your line then I would suggest continuing to use the government website to order certificates. They go back to 1837. I can't remember off the top of my head what the birth certificate info would give you, whether they would have an age of parents. If you are tracing your line then I would try and look for his parents marriage certificate. Most marriages happened in the bride's parish.
They may be able to find the marriage certificate just from the names and the parish if you give an approximate marriage year. Sacco is not a common surname in Malta, unlike something like Borg, Pace is more common but the name Loius is also less common although Rosa is more common, so hopefully they can find the marriage and get a certificate.
That certificate will give you both sets of parents, occupation and age of bride and groom and where they were born which leads you nicely into ordering their birth certificates.
I've also heard that someone has transcribed the Adami Collection which is the collection of marriages from the late 1500's to late 1800's and it is on the internet.
I also have a copy at home on cd so I could trawl through and look for a marriage if you would like me to.
I guess that would be cheaper then ordering another certificate. Or you can search for the website online, I believe it's still in Italian.
Oh, and for Birkikara their parish records are online - this is the website.http://archives.maltadiocese.org/
It's free to register and to use. Just create an account, sign in and look under 'Browse the Archives' then look for localities and Birkikara. Then the year, I'm not sure if it goes right up to the end of the 1800's but if it does you are in luck. You can find their marriage as well as any other siblings baptism and begin working back.
It is in Latin so if you need any pointers on how to read it or what words to look for let me know