Decision-making for effective infrastructure integration is challenging because the performances of long-lasting objects
often depends on conditions which are either outside the control of the designer or difficult to foresee at the design
stage. In this paper we examine a new approach to estimating the range of cost-effective solutions for integrating
the construction/retrofit of two or more different types of infrastructure. Infrastructure integration has many perceived
benefits, but also faces serious new challenges and doubts from practitioners, particularly in sectors with complex
construction process, long asset lives, uncertain cost parameters, and slow and unwieldy decision-making, such as
is common with civil engineering works. We test all main options in integrating a ground source heat pump (GSHP)
system with the construction and retrofit of an archetypal, office building. A new simulation model is developed and
parameterized using actual data in the UK. We incorporate unavoidable uncertainties and randomness in how the
decisions are triggered, and test the effectiveness of proactive measures to embed future options. The model highlights
how sensitive the range of cost-effective solutions is to the setting of renewable energy incentives, discount rates,
technical performance and life-cycle asset management of interdependent infrastructure. This points to a clear need for
establishing appropriate regulatory standards. We expect this model to find increasing applications in the planning and
designing of integrated complexes of buildings, transport facilities, renewable energy supply, water supply and waste
management in dense urban areas, which are an increasingly key part of sustainable urban development