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Retrospective BIM Modelling of Buildings

Even with the challenges that are there in regards to retrospective modelling I feel the difficulties encountered in the process of actually attempting it emphasise the clear need for more efficient processes of data storage and access to building information, and isn’t that what BIM is all about? Having the information there, when you need it? Yes in this example I’m modelling a pretty old building with very outdated standards of data handover in the sixties, but the lack of available data has similarities to non-BIM’d buildings of today.

Over the past few months I’ve been extremely busy on some very innovative and intriguing projects which have been taking up a considerable amount of time, hence the lack of articles! I’ve finally had a few minutes to put aside to dedicate some time back into the site.

Over the past few 6 months I’ve been heavily involved in a European funded project Resseepe, which is focusing on the retrofit of large institutional buildings such as Universities, hospitals and schools. The project aims to establish informed and innovative solutions to optimise how we manage and develop refurbishment strategies for buildings.  Focusing not only on the innovative technologies that can be used and combined in refurbishment projects, but also on the processes and decision making procedures preceding retrofits.

The Building in Question

The Building in Question

Part of this project has led me to retrospectively ‘BIM’ modelling a large university building, around 5000m/2. Now having quite a bit of previous modelling experience I believed this would be a reasonably straight forward task. How wrong was I! Now modelling any building often takes a bit of technique refinement to get the software to do what you want, I’m talking a ‘new’ way to model a bespoke roof design, or massing a particular shape or form in a way that you haven’t done before. This kind of skills refinement is pretty normal as you progress through any existing or new software. I’ve always found that regardless of level of skill at any software with the commercial ‘new edition every year’ platform there is always something every year to brush up on. This process has been as usual invigorating, to keep pushing personal understanding and skills.

Now as I say, this level of skills evolution is normal, the real learning curve or hurdle has been the lack of available information on existing post war building stock. This is an issue that many Estates and asset management teams have to try to endeavour to overcome, in that much of the information on buildings is old, outdated and/or buried. For the building in question that I’ve been modelling there has been a close relationship with in house estates to try and muster up what information we can to give the best available current state and picture of the building. The challenge here is that this still leaves a lot of assumptions and estimations. For instance in a building designed in 1961, no one at the time considered the 3D modelling requirement of some BIM user when compiling the plans. The plans of the day were constructed with one criteria in mind; enough information to raise the building from the ground, in time and for the right money. Building handover or management was at best an afterthought, if that. In modern years the information being handed over to FM teams is greatly improving with initiatives like softlandings in the UK. Although, we don’t have to go too many years back’ looking at buildings where handover of data was an afterthought and still is in parts.  I’m thinking the rushed collection of building management and health and safety binder’s minutes before the impending deadline.

An early stage render showing BIPV refit option

Another key issue when retrospectively modelling existing stock is the accuracy of the details. In this case you can’t rely on existing original or CAD plans to hold accurate data because over
the years buildings evolve and often the records don’t show this in every detail. It may even be the case that when a plan reaches site, the detail was just not viable and the process or reality of the build altered slightly, this is where the need for ‘as built’ records derives, again this is key to BIM and softlandings. To counteract this there needs to be a process of model validation. Now this may differ slightly from the new build validation in that were not directly validating immediately against rule sets, such as in Solibri etc. The key here is to validate the accuracy of plans, CAD or assumptions so that the model is as close to ‘as-built’ as possible. Now what were encroaching into here is a level of detail aspect, much the same as any BIM new build, in that it needs to be established as to how accurate or refined does the model need to be. This all depends on what information will be required down the line, i.e. will the model be solely used for energy simulation or is there a desire to use the model for quantities asset management which will require far greater component and parametric data to be added. As with new builds, you can only draw off quality information when quality information goes into the model. There is a point where decisions have to be made on the practicalities of entering the detail and specification of every light fitting if that information is never going to be required.

Even with the challenges that are there in regards to retrospective modelling I feel the difficulties encountered in the process of actually attempting it emphasis the clear need for more efficient processes of data storage and access to building information, and isn’t that what BIM is all about? Having the information there, when you need it? Yes in this example I’m modelling a pretty old building with very outdated standards of data handover in the sixties, but the lack of available data has similarities to non-BIM’d buildings of today. The benefits that a BIM model can bring to new builds are very similar to those that are on offer in retrofit or building management. The challenge is to bridge that gap in retrospect. In years to come I envisage a FM process where it’s a lot more common for reasonably sized existing stock to be retrospectively modelled as the alternatives of traditional data management are far to cumbersome. In the case where a building retrofit is to take place I would go as far to say it’s crucial.   

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