Building Energy Modelling part 2 - First attempts and research
It was not long after reading the Whole House Book that Glyn and I went to a green hackathon in London (January 2012) and I spent my time creating a small web app that implemented a really basic model that produced estimates of 20 year savings of implementing various building fabric improvement measures, its still up here:
Try it out: http://vis.openenergymonitor.org/retrofit
Source code: https://github.com/openenergymonitor/retrofit.git
I had not quite realised the importance of solar and internal gains at that point or indeed utilisation factors and heating patterns so the green hackathon retrofit calculator will only be remotely close to actual heating demand in very leaky buildings, with few windows and consistently heated to an even set temperature all year. Paul Tanner pointed out the heating pattern flaw at the time in a tweet but it wasnt until more recently that I got how significant the difference is.
After the green hackathon retrofit calculator I tried to develop the idea of a calculator that would output a list of proposed measures, their energy savings and financial payback but had low confidence in the accuracy of its output so decided to shelve it for a while.
At around the same time I did a little work on dynamic simulation of heat conduction through a wall that can be found here: http://vis.openenergymonitor.org/dev/heatflow01/ but was also unsure of its accuracy, needing to brush up on my calculus to check precisely by computing an exact solution via the fourier method.
Searching for open source SAP implementations I found a useful open source version of the 2009 SAP worksheet implemented as a open office spreadsheet by Wookey here: http://wookware.org/files/SAPWorksheet9.80.ods which if you prefer spreadsheets to code is certainly worth looking at. There was also a thread on the greenbuildingforums calling for good open source building energy modelling software with a lively debate: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6574&page=1#Item_0
In my searching I also came across a fully dynamic open source building energy model called esp-r developed by the University of Strathclyde http://www.esru.strath.ac.uk/Programs/ESP-r.htm and created a page on how to install it on ubuntu on the openenergymonitor site which I never linked in here: http://openenergymonitor.org/emon/node/1715.
I'm also more recently aware that there is another open source dynamic building energy modelling project called OpenStudio which looks like it has a nice front end, OpenStudio is a National Renewable Energy Laboratories project https://openstudio.nrel.gov/ and has sketchup integrations, looks nice!
Next blog post: Carbon Coop and the open source SAP 2012
To engage in discussion regarding this post, please post on our Community Forum.
Next blog post: Carbon Coop and the open source SAP 2012