Using debt to fund projects and lower costs?

Hi guys,

I am wondering if debt can be used for a private company to finance a construction project in such a way that the overall costs is reduced? This question is also related to the previous thread I started in a way

Current situation is as such: -Small private construction company -100% equity financed by shareholders with zero debts at all -Financing and funding for construction projects currently sourced from retained earnings only - Projects usually short term 3 years

However in recent years, the company has been starting to lose to competitors due to competitors submitting lower and more competitive quotations to win tenders.

I am wondering if using 100% retained earnings to fund construction projects is a good idea and whether or not debt such as bank loans can be mixed in with retained earnings to fund projects and somehow lower the overall costs of the project and allowing us to submit lower quotations for tenders.