Date: July 1994

Author(s): E. D. Werling and G. K. Yuill

Many modular house manufacturers in the northeast do not install ducting for central heating and air-conditioning. Instead, they usually install electric baseboard heating systems and no cooling systems. They do this mostly because of the extra complication of connecting ducts when modular houses are assembled in the field. This creates a problem for the modular house manufacturers, because it reduced their competitiveness, and for the buyers, because they may not end up with the most cost-effective heating systems, and because they will have to pay the extra cost of the retrofit installation of a cooling system if they require one.

The objectives of this research were: 1) to develop a practical method for connecting ducts between modules of a modular house in the field; and 2) to find the most cost-effective heating and cooling systems for modular houses, considering local weather and fuel costs.

A simple method of connecting ducts between modules of a modular house was developed, using a full-scale mock-up of the relevant components of the modules. Also, an easy method was developed for determining the total cost (including the initial capital cost and the present value of the future fuel costs) of any HVAC system for a modular house of any size in any location in the northeast. This method includes a completed energy analysis for many locations in the region, and a method for interpolating it to any other location of interest. It allows the user to apply real installation and fuel costs for each place and time. In example analyses that were applied across the northeast, it was found that two systems were the most economical under the varying conditions across the region. These were: 1) a high efficiency gas furnace with a high efficiency air conditioner; and 2) a higher efficiency air source heat pump.

Modular house builders can now ensure that they provide the most cost-effective heating and cooling systems to their customers in the northeast. This will make modular houses more competitive and provide buyers with more cost-effective energy systems in their homes.

A follow-up project will apply some of the findings to the actual design, fabrication and installation of a Modular Home.