Estimate heat load by room or whole house

BY WILLIAM AND PATTI FELDMAN COMPUTER AUTHORITIES THE FIRST STEP when specifying and recommending a residential heating system is to determine the heat load for the project. Here is software that can speed that process and guarantee accuracy. Suitable for additions, upgrades and new installations, Heat Load Pro (www.hydronicpros.com, $115 CD/$99 download) is a new design-assistance software solution

BY WILLIAM AND PATTI FELDMAN
COMPUTER AUTHORITIES

THE FIRST STEP when specifying and recommending a residential heating system is to determine the heat load for the project. Here is software that can speed that process and guarantee accuracy.

Suitable for additions, upgrades and new installations, Heat Load Pro (www.hydronicpros.com, $115 CD/$99 download) is a new design-assistance software solution for quickly and accurately estimating heat loads on a roomby-room and whole-house basis. It is graphics-rich, with many illustrations of building components, which help familiarize users with what they are doing right off the bat.

In determining heat loads, the program uses only a few screens — a big advantage both in learning how to use it and reaping fast results. The process is logical and straightforward.

The graphical interface allows selection of almost any type of residential construction and hundreds of building materials pretty much by sight as well as description. Pull-down menus feature preloaded R-values for traditional materials such as windows and exterior doors, and for contemporary materials such as structural insulated panels and insulated concrete forms.

The user selects the size, depth and composition of exterior surfaces of the space being built and the program automatically calculates the effective R-values of the materials.

The software offers detailed choices, such as whether a door has single-, double-or triple-pane windows and with what coating (if any), the composition of the door and whether there is a storm door. The program also handles skylights in exposed ceilings.

Ceiling selections include woodframed, unvented vaulted and flat roof. Exposed floor types include wood frame, basement (poured concrete), slab-on-grade and suspended slab. To accommodate new-to-market construction materials, the program allows overriding of the calculated R-value of any component.

The results — the amount of loss from each component — are immediately shown on screen three ways: as a percentage of loss from each component, in Btuh and as a bar graph. On the bottom of the screen are tallies both for total heat loss for the current room and total heat loss for the entire house. Any change to any room automatically generates recalculation of results.

After the user designs and calculates the heat load, the Heat Load Pro estimates the annual space heating cost of each room or the entire home depending upon type of fuel. The program enables comparison of costs using different local fuel options, taking into consideration their associated costs and efficiencies based on the inputted cost per unit and the efficiency at which each fuel is converted into heat by the heat source. The calculations can be based on either defaulted weather data for the state/province and city or user-entered project-specific data for annual degree-days at the home location.

Several user-friendly features speed the design process. For example, to speed data entry, the program can "copy" all the attributes of a defined room into another room, which eliminates repetitive data entry and is very handy if the home uses the same type of construction in multiple rooms. The Heat Load Pro program includes several pre-loaded room shapes, including some complex shapes, to facilitate quick calculation of any volume. A handy pop-up "calculator" tool enables easy determination of the area of complex surfaces and the volume of complex shape rooms once you put in the height and width of the shape (e.g., a trapezoidal wall).

The main screen is organized into different frames, including Room Data, where the user names the room and inputs the desired room air temperature. The Building Room List contains a listing of all currently defined rooms within the building. Conduction Losses contains data enabling calculation of the rate of heat loss by conduction through exposed surfaces such as walls, windows, doors, ceilings and floors. Air Leakage Losses uses the air change method. A Results frame sums everything up.

Results include the heat loss through each specified exposed surface of the room and the percentage of the room's total heat loss that surface represents. Heat loss due to air leakage is also shown. Both the total heat loss of the specified room and the total heat loss of the building (based on the sum of the room heat losses) are displayed. A horizontal bar graph indicates the relative percentage of heat loss through each component or due to air leakage, relative to the total heat loss of the room.

Heat Load Pro includes a pre-loaded "Air Change Table" for estimating air change rates in rooms of various sizes and types of construction with given values based on the Air Conditioning Contractors of America's Manual J. The values are guidelines to be used in conjunction with one of the three subjective descriptions of air sealing quality that best matches the building. This quality along with the floor area of the room will result in an estimate of air changes per hour.

The program aims to streamline to the minimal possible data entry to properly describe the room, eliminating assumptions that can negatively affect accuracy while gathering enough to yield an accurate result.

Bill and Patti Feldman are freelance writers for magazines, building product manufacturers and other companies on a broad range of topics. They can be reached at [email protected]

TAGS: PCs/Tablets