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Design Master HVAC 5.0 Load Calculation Changes

The load calculations in Design Master HVAC 5.0 underwent a major revision. This page describes the changes we made to help you model more complex buildings.

We added a brand-new feature that we call load maps. It is an experimental concept to help you visualize the load defined in your project. You can read about load maps and how they can help you with your design in the Load Maps article.

You can read about the other non-load changes in the Design Master HVAC 5.0 article.

Toolbars and Pulldowns

The first change you will notice is that the DM Building pulldown menu has been removed. All of the load calculation commands can be found under DM HVAC->Building Definition and DM HVAC->Load Calculations.

HVAC load calculations   building load calculations 

There are a number of new toolbars that you can use instead of the pulldown menu.

The Building Definition toolbar has commands for modifying the project, zone, and floor settings.

building definition

The HVAC Rooms & Walls toolbar has commands for editing room definitionsin the database and outlines on the drawing.

HVAC rooms and walls

The Load Calculations toolbar has command for viewing and printing the loads, including the new load maps.

load calculations   Load maps
 A load map

Modeling Changes

The changes in this section relate to the information you provide to define the building model.


Room Schedule

All rooms in a project are linked to a specific room type in the schedule. When first created, all room settings are inherited from the room type. If the room type is redefined, the rooms linked to it are redefined also. Settings can be overriden in specific rooms if necessary.

Rename Room

Rooms can be renamed (and it's about time!).

Exclude from Calculation

Rooms can be excluded from either the heating or cooling calculation.

Multiple Ventilation Criteria

Two ventilation criteria can be set for a room. This allows room to meet ASHRAE 62, which specifies both ventilation based upon both the area and occupancy of a room.

Infiltraction Criteria

The infiltration into a room can be based upon CFM / sf of wall.

Heating and Cooling Outside Air Settings

The ventilation and infiltration values can be set differently in the heating and cooling calculations.

Minimum Supply Air

A minimum supply air value can be set in a room.


A room schedule that has ventilation numbers set to match ASHRAE 62.1-2004 can be downloaded. These room definitions will allow you to satisfy the ventilation requirements for specific rooms.

The ventilation required in zones can be calculated using ASHRAE 62. These values end up being higher than what Design Master would normally calculate. The calculation requires that you specify Ep, Er, and Ez in the Zone dialog. The definition of these values can be found in Appendix A of ASHRAE 62.1-2004.



Pyschrometric can be calculated for each zone. The AHU and Coil Settings and Duct Settings in the Zone dialog were added for this calculation.

psychrometric settings

In the pyschrometric output, the humidifcation or reheat required for the system is displayed.

Project Settings

Indoor Air Defaults

The indoor air default values have been moved out of the project setting and into the zones.  This includes the heating temperature, cooling temperature, and relative humidity values.

Custom Cities

The design conditions for cities can be customized. Temperatures for existing cities can be modified. Cities can be renamed or removed. New cities can be added.

Safety Factors

A separate ventilation safety factor has been added.


zones and roomsZones are much improved in this release. Previously, you were limited to a Project->Zone->Room hierarchy. Now, you can have zones underneath other zones, giving you a Project->Zone->...->Zone->Room hierarchy.

There is a new Zones and Rooms dialog that has a tree view of the zones and rooms in the project. You can drag-and-drop zones and rooms around like you do folders in Windows Explorer.

Tempered Air

The outside air wet bulb temperature can be tempered.

Plenum Return

A zone can be defined as having a plenum return. In this configuration, the roof, and part of the lighting and wall loads are all removed from the room load and seen only in the system load.

People Diversity

The number of people in a zone can be diversified.

zones and rooms

In the project shown above, there is a single zone with three rooms in it. The load in each of the offices is based upon one person. The load in the conference room is based upon two people.

However, we know that there will never be more than two people in the space, either in their office or the conference room. The people diversity in the zone is set to two to model this situation.

People diversity.

As a result, the total people load in the zone is lower than the sum of the people loads in the three rooms that are in it.


Lower Wall Type

A second wall type on the lower portion of a wall can be defined.

Glass Shading

Glass shading based upon overhangs and fins can be properly calculated. This calculation requires that the dimensions be provided for the window, overhang, and fins.

Multiple Glass Types

Walls can have multiple types of glass defined.

Output Changes

Load Detail Dialog

There is a new Load Detail dialog. It replaces the old Load Calculation Dialog that docked on the side of your screen. The new dialog is used to display the load of specific rooms and zone. You can view the dialog by using the View Room Load command and by pressing the View Load button on the Zone Tree dialog.

The dialog lists all of the heating and cooling load details from before. It also includes the area and number of people in the room or zone.

At the bottom-right, there is a Print button that can be used to print the current load exactly as it appears in the dialog.

Load detail.

General Printing Changes

Page Break Option

There is an option to turn the page break after each section of the load print-out on or off.

Calculation Date

In the Project Information section of the print-out, the time and date of the last calculation is display.


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