What are the most cost-effective thermal improvements that could be undertaken?
By answering this Plain Langauge Question, I am beginning to realize the true potential of Tŷ Crempog‘s information model by answering real questions that will impact on how I undertake any retrofit works. To answer this question, I have turned to Standard Assessment Procedure (SAP).
SAP is Building Research Establishment (BRE)‘s procedure to calculate the energy rating of dwellings. SAP is referenced in Approved Document L of the Welsh and English building regulations, adopted by the UK Government and is used to assess dwellings to produce their Energy Performance Certificate (EPC). New dwellings use SAP in its entirety while, as of November 2017, existing dwellings like Tŷ Crempog (or Joe’s Garage) use the Reduced Data Standard Assessment Procedure (RdSAP) to support completing the SAP calculations.
The advantage of RdSAP is that it provides several permitted assumptions that can be used within the SAP calculations. I plan on using Tŷ Crempog‘s information model to complete the hundreds of values required. Now there are too many to do at once, so instead of having a Freak out! I am addressing each section at a time; using RdSAP to fill in the gaps.
Once my SAP calculations are complete, I will be able to manipulate the information to see what improvements will provide the greatest impact. For example, would it be more cost effective to improve Tŷ Crempog‘s thermal performance, reduce the infiltration rate or improve the efficiency of my heating system? Once complete, I will be able to test these scenario’s and inform future home improvements.
1 Overall Dimension
- Total Floor Area (4). To determine the total floor area, SAP asks for the areas of each floor, which is calculated using the internal dimensions and storey heights. While my Architectural COBie has internal space areas, I didn’t have a value for the Gross Internal Area (GIA) or the average height of each storey (many of you will know my battle with Storey, Floor, Level).
To resolve this, I did area calculations within my model, and placed those values onto two new properties:
Once I had exported these properties to COBie, I could populate my calculations automatically (WhooHoo!). This is because I have used Google Sheets which allows me to reference other external Google Sheets using formulas like:
Which also means that any updated I do to my information model will be reflected in my SAP Calculations. Note: my EPC was calculated within a total floor area of 81m², this difference will likely affect other values as I proceed with my calculations.
- Dwelling Volume (5). Once I had imported GrossPlannedArea and MeanStorey, calculating Tŷ Crempog‘s volume was straightforward.
My SAP calculations for overall dimensions can be seen below:
And there we have it. While I have only just started, it seems possible to automate the population of SAP using Tŷ Crempog‘s information model, using COBie. This fills me with a lot of confidence that I can use my information model to complete the other SAP sections. Fantastic, PLQ 3.4 is underway!
Operation and Maintenance
3.1 What are the sizes and condition of the windows & doors?
3.2 What assets are in a poor condition?
3.3 What costs can be attributed to my assets?
- 3.4 What are the most cost effective thermal improvements that could be undertaken?
Now that my overall dimensions have been calculated, it is time to look at Ty Crempog‘s ventilation rate and heat loss…
Note: If you have any comments regarding my use of SAP, then please let me know either on Twitter, or by commenting below.