Design Performance Display
The Performance Tab within BGW2004 displays the yearly heating and cooling use by each major component in the building envelope and the solar performance, as well as several useful graphs for evaluating your design. The program includes a tutorial that guides you through the evaluation and improvement of your design's solar performance.
1. Building Total Load: conservation heating performance; is the total yearly predicted heating load on the building; which is derived from the building load coefficient times the location heating degree days times the heating degree day multiplier. Note: The Heat Loss calculations are yearly estimates and are not for sizing heating appliances. Heating equipment is sizing based on the heating design day or worst case heating condition.
2. Solar Savings: (SSF) solar savings fraction; the ratio of solar savings to the building load coefficient.
3. Mechanical Heating: auxiliary heating performance; is the predicted load on the building which must be offset by the building’s conventional heating system other than the solar system. It is the conservation performance minus the solar savings fraction.
4. Carbon Savings: is the reduction in CO2 emissions into the atmosphere due to the solar component of the total heating load. The two boxes show the pounds of CO2 that will be saved when the auxiliary heating system is using a gas fired appliance or resistance electric heating.
5. Total Heat Loss by Component: is the Building Total Load broken down by the individual envelope components. Component UA is the gross heat loss of the named envelope component, which is U-Value times surface area, expressed in kBTU/YR.
6. Mass Heat Capacity: The heat storage capacity of building mass expressed in BTU's per square foot of building floor area per degree Fahrenheit.
7. Temperature Swing: the number of degrees the temperature can be expected to vary in the course of a sunny winter day without the auxiliary heating system running.
8. Mass Area to Glazing Area Ratio: The ratio of building mass surface area to solar glazing area. It is desirable to have this ratio close to 6 and not less than 3.
9. Load Collector Ratio: (LCR) is the ratio of the building load coefficient to the projected solar collector area. The LCR ratio forms the basis for predicting heating performance, and for calculating the SSF.
10. Building Total Cooling Load: conservation cooling load; is the predicted cooling load on the building during the cooling season including any reductions in that load attributable to building mass.
11. Vent Savings: The contribution of the selected cooling strategy (night ventilation and or ceiling fan) to offset the conservation cooling load.
12. Mechanical Cooling: auxiliary cooling load; is the predicted auxiliary cooling load which must be offset by the building’s conventional cooling system. The building conservation cooling load minus the contribution of the vent savings.
13. Total Heat Gain by Component: is the Building Total Cooling Load broken down by the individual envelope components. Component UA is the gross heat gain of the named envelope component, which is (U-Value times surface area) times radiant barrier factor times absorptance times Heat Gain Factor, expressed in kBTU/YR.