Chapter 5.1.4 - Radiant System Cost Analysis Factors

Electricity, oil, gas, propane, wood, and alternative energy sources have all been used
successfully as the source of energy for radiant heating. Deciding which energy
source to choose requires rigorous analysis. Factors to be determined include not
only the usual series of equipment and insulation iterations, but also the use,
lifestyle, and building-as-system control implications on operating cost. Initial, lifecycle,
and maintenance cost analysis add yet another dimension.

The simple first-order fuel cost per Btu analysis shows how the market currently
prices the various energy options, using Btus as the common indicator. Incorporation
of actual installation, use, and control factors leads to operating cost informa-
tion that reflects the actual system-specific Btu requirement under conditions of use.
The real-world, or miles-per-gallon, information may be expressed in a form that can
be used with Btu cost to determine which heating system using which fuel is the most
cost-effective in terms of annual operating cost.

A simple comparative indicator of overall Btu lifestyle efficiency is expressed as
Btus per heating degree day per square foot of total heated space. This index is an
excellent indicator of just how efficiently a heating system is able to address occupant
thermal comfort requirements in the routine use of occupied space and is
expressed in terms of known parameters as:

The performance parameter ζ is then given in units of Btu/ft² per heating degree-day
in a heating system. Typical numbers range from 2.5 to greater than 10. The lowest
number represents the lowest comparative conditioned space Btu usage. As an
example, consider a home where ζ is 4.0 for a 2000-ft² house in a region of the country
where there are 7000°F-days. Employing this equation shows that the annual
energy consumption to heat the home would be approximately 20,515 kWh, which,
at a rate of $0.06/kWh, would cost approximately $1231 per heating season.The simple
multiplication of ζ by the cost per Btu of the various fuels provides the actual
cost per degree-day per square foot of space as actually used for each system being
analyzed. The operating analysis provides perspective for the life-cycle cost analysis
and is worth looking at in detail.

Life-cycle analysis incorporates all original installed cost factors associated with
each heating system selection in relation to the building in which the system is to be
installed. To prevent surprises, review local code, building, or association regulations
to determine that all requirements for specific systems and equipment have
been included. Minimum energy standards adopted by most jurisdictions are those
from ASHRAE Standards 90.1 and 90.2 for commercial and residential buildings,
respectively.

Accurate maintenance, repair, and equipment life input is essential.An appropriate
cost of capital, or discount, rate is applied in order to reduce each alternative to
what is known as the net present value of the expenditure stream for each system.
The Federal Energy Management Program (FEMP) website provides extensive discount
rate information.

While there are life-cycle costing models in many texts, a universally accepted
model for energy analysis may be found on the Internet at the U.S. Department of
Energy website.The FEMP Building Life Cycle Cost (BLCC) program is designed
for use by both for-profit and nonprofit organizations with adjustment of tax
input. While the program is designed for the entire building, a similar approach
can be developed for heating- or cooling-system-only analysis. However, a true
appreciation of radiant system life-cycle cost performance stands out in a BLCC
analysis.

Finally, although out of the scope of engineering analysis, it is important to obtain
projections for long-term fuel cost and to incorporate an assessment of the impact of
market and technology changes. The array of projections may seem intimidating.
However, information developed by the U.S. Government Department of Commerce
contains long-term trend analysis, which provides perspective to other information
being reviewed.Analysis, which includes occupant comfort–based operating,
life-cycle, and present and projected fuel costs, provides meaningful information for
comparative radiant and convection heating system evaluation.

Electricity, oil, gas, propane, wood, and alternative energy sources have all been used
successfully as the source of energy for radiant heating. Deciding which energy
source to choose requires rigorous analysis. Factors to be determined include not
only the usual series of equipment and insulation iterations, but also the use,
lifestyle, and building-as-system control implications on operating cost. Initial, lifecycle,
and maintenance cost analysis add yet another dimension.

The simple first-order fuel cost per Btu analysis shows how the market currently
prices the various energy options, using Btus as the common indicator. Incorporation
of actual installation, use, and control factors leads to operating cost informa-
tion that reflects the actual system-specific Btu requirement under conditions of use.
The real-world, or miles-per-gallon, information may be expressed in a form that can
be used with Btu cost to determine which heating system using which fuel is the most
cost-effective in terms of annual operating cost.

A simple comparative indicator of overall Btu lifestyle efficiency is expressed as
Btus per heating degree day per square foot of...