The thermal mass, vapor barrier, and envelope leakage will affect the capacity, configuration, and performance of HVAC systems. Simply using R-values without defining the construction materials when performing the energy model will not account for the floor, roof, columns, and envelope material characteristics. The energy code has evolved and become more stringent so thatīrick-and-mortar and HVAC systems have become more interdependent. The HVAC systems that meet the energy code are considered the base option. The engineer will need to understand this balance and help the owner make decisions that align with the OPR.Īt a minimum, the design professional must comply with the adopted localĮnergy code. Owners often have a threshold for spending CAPX to gain OPEX. There is a balance between CAPX and OPEX for each project. Figure 5 is a summary sheet for the lifecycle cost analysis (LCCA) of a replacement central utility plant for a health care campus. Figure 4 shows the operating costs of the different energy-consuming systems for an office, hospital, and data center. Figure 3 shows the capital construction costs of a new office, hospital, and data center. It is safe to say all owners care about CAPX however, not all owners understand the impact of CAPX on the OPEX. Building owners have varying expectations regarding the overall economic impact of HVAC systems. The economics of HVAC systems can be broken into two distinct buckets: capital expenditures (CAPX) and operating expenditures (OPEX). In the event the owner does not provide an OPR, the engineer will need to survey the stakeholders to gather the project requirements. Included within the OPR may be the minimum LCC payback and/or adjusted IROR. An owner that has experience with the construction process will provide the owner’s project requirements (OPR) document. It is the design professional’s responsibility to understand what is important to the building owner. ** Accounts for time cost of money and maintenance/repair, replacement, and salvage value * Does not factor in the time cost of money or maintenance/repair, replacement, or salvage value SIR = (option 1 net savings) ÷ (option 1 first cost increase)Īdjusted IROR = (average annual operating cost savings)** ÷ (initial investment) Net savings ($) = HVAC base option LCC – HVAC option 1 LCC Lifecycle payback (years) = (first cost difference) ÷ (annual operating savings cost difference)** Simple payback (years) = (first cost difference) ÷ (annual operating savings cost difference)* Simple payback, net savings, savings-to-investment ratio (SIR), adjusted internal rate of return (IROR), and discounted payback are all methods to measure an HVAC option’s economic performance over time. There are several ways to represent the results when comparing the lifecycle costs of two or more options. Often, engineers are asked to determine the best option between one or more HVAC system options. Lifecycle cost (LCC) = first cost + maintenance and repair + energy + water + replacement – salvage value Before we dig into the indirect cost impacts, we must review some of the basic concepts of the engineering economic process. Numerous articles and books have been written to guide engineers through the mathematical representation of HVAC economic analysis.
0 Comments
Leave a Reply. |