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The Customer Advising Tool (CAT)

 

   

This tool can be downloaded as a zip file for use on a stand alone computer from here.

This tool provides guidance to the Building Owner, Inspector and/or Auditor on the potential for reducing the cooling demand of the building being Inspected or Audited. It achieves this by illustrating how the RELATIVE building heating and cooling DEMAND might be altered in percentage terms by changing certain elements of the building design or operation.

The tool is based on outputs from the Industry-standard ECOTECT and EnergyPlus Building Energy Modelling software tools. The data in the CAT has been produced using a simple building modelling approach that could be undertaken by anyone with a knowledge of building design, building energy use and these tools. The CAT has been produced on the assumption that the time available to undertake an Inspection or Audit will not allow this modelling to be done in the vast majority of cases.

The CAT does not cover all possible permutations of criteria and parameters, but should provide a good first guide towards the RELATIVE influence of various building aspects on the monthly and annual heating and cooling DEMANDS.

Use of the CAT:

To assess the relative influence of selected building criteria and parameters on the heating and cooling energy demands in a specific building, use the input areas below to describe as best you can the building you are inspecting or auditing. The more accurate the information you can provide for the building criteria in the CAT, the more useful the database search and resulting information will be.

Once the search has been undertaken on the data input to the CAT, the information presented in the graphs will allow the assessor to gauge the relative importance of each parameter to the cooling and heating demands. This information will provide an initial guide to the assessor on which aspects are important to reducing the cooling demand, and the effect of changing the parameter on the heating demand as well. The assessor can therefore state the potential % changes in cooling and heating demands to be achieved through various actions. Clearly it would be prudent to assess a variety of options and variations in parameters for the building being studied to check the sensitivity of each action to uncertainty in the input data.

Building Criteria
Building criteria refer to those aspects of your building that are fixed and not easily subject to change. The selections you make below will define the search criteria against which items in the database will be matched.

   
Location/Region:  
Choose the city location/region which is most likely to reflect the weather conditions to which the audit building will be subjected.
Display climate map...
Glazing Ratio - All Facades:  

Select the approximate percentage area of the entire external vertical facade of the building or zone that is composed of windows or transparent apertures.

Select glazing ratio... 90% Glazing 80% Glazing 60% Glazing 40% Glazing 20% Glazing
Thermal Mass :  
Estimate the relative amount of thermal mass exposed to the internal air within the building. A building with significant amounts of masonry or concrete visible would usually be classed as heavyweight, whilst a building which is predominantly suspended ceilings and lightweight partition walls would usually be classed as lightweight.
Select thermal mass... Heavy Weight Medium Weight Light Weight
Plan Depth:  
Choose the relative plan depth. This is defined as being the ratio of floor-ceiling height compared to the distance between opposing external walls, averaged over all zones within the building. A shallow plan will normally allow daylight and natural ventilation to be used over the entire floor area. A deep plan will usually be fully mechanically ventilated.
Select plan depth... Deep Plan Medium Plan Shallow Plan
Number of Storeys:

Enter the number of conditioned storeys in your building. This value will be used to both match case study buildings and moderate simulation results.

<< Not Yet Implemented >>

Select storeys... 40 Storey 25 Storey 15 Storey 10 Storey 5 Storey 3 Storey Single Storey
Building Form:  

Choose the plan layout morphology that best matches your building. Only the overall shape is important, scale is not to be considered.

<< Not Yet Implemented >>

Select building form... 'C' Shaped 'S' Shaped 'L' Shaped Cross Rectangular - Long Rectangular - Short Square
Internal Layout of Spaces:  

Choose whether the spaces in your building are predominantly individually enclose rooms or large open spaces.

<< Not Yet Implemented >>

Select internal layout... Cellular Open-Plan
   

Building Parameters
Building parameters refer to those aspects of the building which are generally under control of the occupants or can be varied in some way without major costs. Entering indicative values for each parameter for the building being assessed will enable this value to be used as a reference in the relevant graph shown on the results page. If no value is entered, the graphs default to a value the authors have taken to represent an average for that particular parameter.

   
Fabric U-Value:  
This element refers to the average thermal conductivity of the opaque elements in the external building envelope. The effects of this parameter have been modelled between 0.1 and 4.0 W/m2K. W/m2.K
Select fabric U-value... 0.10 W/m2.K 0.25 W/m2.K 0.50 W/m2.K 0.75 W/m2.K 1.00 W/m2.K 1.50 W/m2.K 2.00 W/m2.K 2.50 W/m2.K 3.00 W/m2.K 4.00 W/m2.K
Window U-Value:  
This element refers to the average thermal conductivity of the windows and transparent elements in the external building envelope. The effects of this parameter have been modelled between 0.5 and 6.0 W/m2K, where the most insulating transparent element available would have a U-value of around 0.5 and single glazing would have a U-value of around 6.0. W/m2.K
Select window U-value... 0.50 W/m2.K 1.00 W/m2.K 1.50 W/m2.K 2.00 W/m2.K 2.50 W/m2.K 3.00 W/m2.K 3.50 W/m2.K 4.00 W/m2.K 5.00 W/m2.K 6.00 W/m2.K
Solar Heat Gain Coefficient (SHGC):  
This is the fraction of incident beam (direct) solar radiation that enters the building through the transparent elements, such as windows. This includes the transmitted solar radiation and the inward flowing heat from the solar radiation that is absorbed by the glazing. The effects of this parameter have been modelled for SHGC’s ranging from 0.1 to 0.9, where 0.1 is highly shaded, i.e. little solar gain, and 0.9 means there is no effective shading – the reduction from 1.0 is simply due to the normal properties of glass.
Select solar heat gain coefficient value... 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Infiltration Rate:  
This refers to the uncontrolled exchange of air between internal spaces and outside air due to gaps in the building fabric linked to design details. This value is given as the number of complete air changes per hour. The effects of this parameter have been modelled between 0.1 and 4.0 ac/hr, where a well detailed, well-sealed building would be around 0.1 and a very leaky shallow plan building in an exposed and windy location would be around 4.0 ac/hr. ac/hr
Select infiltration rate value... 0.10 ac/hr 0.25 ac/hr 0.50 ac/hr 0.75 ac/hr 1.00 ac/hr 1.50 ac/hr 2.00 ac/hr 2.50 ac/hr 3.00 ac/hr 4.00 ac/hr
Internal Gains:  
This refers to the contribution of small power, lighting and people loads per metre squared floor area. The effects of this parameter have been modelled between 10 and 160 W/m2, where 10 W/m2 represents a very low density of occupation and equipment use, and 160 W/m2 would represent a very high density of equipment and occupancy, such as a call centre. W/m2
Select internal gains value... 10 W/m2 20 W/m2 30 W/m2 40 W/m2 60 W/m2 80 W/m2 100 W/m2 120 W/m2 140 W/m2 160 W/m2
   

System Parameters
In order to accurately compare heating and cooling energy, as well as calculating potential carbon emissions savings, you will need to estimate the relative efficiency of the plant and equipment used to supply the building's heating and cooling demand. These values are usually very difficult to obtain with any accuracy so you should ensure you test the likely range in the building being assessed to estimate the sensitivity of any recommendations to reasonable variations in these figures.

   
Heating System Efficiency (SCOP) :  
Enter the Seasonal Coefficient Of Performance for the equipment used to provide space heating within the building. This is given as the annual average ratio of total heat output compared to total energy input to the equipment. A good condensing boiler based system would expect to achieve a SCOP of around 0.9, whereas an old cast-iron boiler based system might struggle to reach 0.6. (Heating SCOP)
Select heating system efficiency... 0.10 0.25 0.50 0.75 1.00 1.50 2.00 2.50 3.00 4.00
Fuel Carbon Emission Factor - Heating:  

Enter the amount of carbon dioxide emitted through the consumption of 1 kiloWatt hour of fuel used. This is given as a value between 0.0 for renewable energy and 0.43 kgCO2/kWh for delivered grid electricity - although allowance is made for values up to 0.60.

For countries other than the UK the appropriate Grid delivered electricity factor should be used. Refer to the International Energy Agency for further information.

(kg CO2 / kWh)
Fuel Carbon Emission Factors 0.00 kgCO2/kWh 0.166 kgCO2/kWh 0.19 kgCO2/kWh 0.20 kgCO2/kWh 0.21 kgCO2/kWh 0.24 kgCO2/kWh 0.25 kgCO2/kWh 0.26 kgCO2/kWh 0.30 kgCO2/kWh 0.34 kgCO2/kWh 0.37 kgCO2/kWh 0.43 kgCO2/kWh
Cooling System Overall Efficiency:  

This is the Overall Annual Ratio of the Cooling Energy Demand met by the Cooling System, divided by the total energy input to the Cooling System. It includes Auxiliary Energy consumption as well as the Chiller energy consumption.

It is NOT the Energy Efficiency Ratio (EER) for the equipment used to provide comfort cooling within the building. A low rating (0.3 - 0.6) would apply to an inefficient system, and a high rating (>2.0) to an efficient system. An average performance is likely to be in the range 1.0 - 1.5.

Countries with high cooling demands are likely to see better Overall Efficiencies than countries with low cooling demands, as the chiller energy demand in hot countries will be a greater proportion of the overall cooling system energy consumption.

(Cooling System Overall Efficiency)
Select cooling system efficiency... 0.10 0.25 0.50 0.75 1.00 1.50 2.00 2.50 3.00 4.00
Fuel Carbon Emission Factor - Cooling:  

Enter the amount of carbon dioxide emitted though the consumption of 1 kiloWatt hour of fuel used. This is given as a value between 0.0 for renewable energy and 0.43 kgCO2/kWh for delivered grid electricity - although allowance is made for values up to 0.60.

For countries other than the UK the appropriate Grid delivered electricity factor should be used. Refer to the International Energy Agency for further information.

(kg CO2 / kWh)
Fuel Carbon Emission Factors 0.00 kgCO2/kWh 0.166 kgCO2/kWh 0.19 kgCO2/kWh 0.20 kgCO2/kWh 0.21 kgCO2/kWh 0.24 kgCO2/kWh 0.25 kgCO2/kWh 0.26 kgCO2/kWh 0.30 kgCO2/kWh 0.34 kgCO2/kWh 0.37 kgCO2/kWh 0.43 kgCO2/kWh
   

 

 

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