There have been a few questions with RDSAP from clients in the UK.
Hopefully it will help you with your epc 's in Northern Ireland.
Flat roofs - Why do you not record the thickness of theinsulation? RDSAP currently does not enable the DEA to record theinsulation level actually installed. The RDSAP application uses thebuild date to obtain a U-value from the Table S10 Sap 2005 appendixS document.Solid/Suspended Floors – the EPC does not reflect theconstruction of my property. RDSAP obtains the floor constructiondetails from the prevalent building method relating to the age band ofthe property. This U-value and floor type is from Table S11 Sap 2005appendix S document. This may not match the actual instance of theproperties floor.Belfast Solar Water Heating – Is my solar water heating included in theEPC? RDSAP currently only enables the DEA to acknowledge thepresence of SWH. The values used by RDASP are obtained fromSAP2005 appendix S document, and use a default value for panelsize, inclination and overshading.The DEA should be aware of these limitations within RDSAP to betterhelp the homeowner understand the details produced on their EPC. Acopy of SAP2005 appendix S document is located on the NorthgateDEA website.Northgate are currently engaging with CLG and other Accreditationbodies to investigate what changes are possible within RDSAP toaddress these and other issues. As these changes are finalised wewill produce further guidance.