Working with Mechanical Engineers

*** by dzarro72, on FlickrAt a glance working with mechanical engineers can seem to present less visible coordination issues for interior designers than electrical engineering (previous blog post here).  However, the results of mechanical engineering (most commonly air conditioning ) are one of the most frequently complained elements of office fitout.   Whilst a lot of the reasons for the complaints about the air conditioning are not strictly due to coordination issues between the interior designer or architect and the mechanical engineer, there are ways that the design team can help to minimise any problems.  In my opinion there are three reasons for the majority of the occupant complaints:
  1. People’s different perceptions of temperature. 
  2. Under design of the mechanical systems compared to the intended use.
  3. The interactions between the base building systems and the fitout systems or modifications made due to the fitout.
Perception of temperature

Individuals perceive temperature and humidity differently depending on many factors.  This is always going to be an issue and if you are dealing with a large number of people in a single space it is difficult to design out.  There are some options now available for individual air flow controls at workstations, or you can allow user override in meeting rooms or offices – however these options generally have to be balanced against increased energy consumption and installation costs and are not necessarily going to be suited to every project or client.

Under design of mechanical systems
Under design of the mechanical systems is the area where the design team have the most influence and control over the functionality of the systems.  As an interior designer or architect you need to ensure that the mechanical engineer is fully briefed on the functions and occupancy of the room. Often mechanical engineers assume certain numbers of people and anticipated occupancy periods based upon the floor plan and the usual use of a room. For example if the floor plan shows a series of meeting rooms with operable walls, drawn with a certain number of meeting tables and chairs, frequently the mechanical design will be based upon the number of chairs on the floor plan. Whilst the mechanical design may take into account the operable walls and allow the space to operate as a single space – it may not take into account that when the operable walls are open the client intends to use the space for a lecture and the occupancy density will be higher. The mechanical engineer needs to understand if spaces are to be used in different ways with different occupancy densities.

I have also found that the mechanical engineer may under design the systems to save money, thinking that the client will not really use the space in this way very often and therefore not want to pay the additional costs – for example a training facility for 60 people which converts to a function room for 250 people. If the mechanical engineer believes that the cost of the briefed functional requirement is unusual or excessive then they need to discuss this with the interior designer/architect and the client.  The client would much rather understand and have the choice to pay the cost up front than to have to modify the system later after everyone has sweltered at the opening party. Particularly if they had asked for a space for 250 people.

Base building issues
One of the biggest issues with the mechanical systems for many interior fitouts is that you are working with, modifying and adding to an existing system. Often no accurate drawings or manuals exist for those systems. Whilst not frequently undertaken, a full site audit of the existing mechanical systems prior to design can be very worthwhile – if the client is willing to pay for this and if there is a way to arrange access (generally this will mean removing ceilings). If not, the involvement of the mechanical engineer during construction stage to work with the air conditioning subcontractor is essential.

The other issue with existing base building systems can be that there is an air conditioning subcontractor responsible for ongoing maintenance. It always makes sense to see if this subcontractor can undertake the fitout modification works as well. At least that way if there are any complaints there is only one responsible maintenance company. Some building owners and facilities managers require that modifications are undertaken by the maintenance contractor.

Other coordination tips
Many of the issues discussed above are not so much coordination issues as design management issues.  So I’ve listed below a few more of my tips on coordination between interior design / architecture and the mechanical engineer:

  1. Ensure the mechanical engineer understands the different partition or wall types in the project. In particular they need to be aware which walls are operable walls and which walls are full height to the underside of a slab or roof above, or which walls have baffling above.  Walls to the slab above or with baffling above impact on the path of return air above the ceiling and need to be taken into account in the design of the mechanical systems. Operable walls change the air flow within the space and again need to be taken into account in the mechanical system design.
  2. Coordinate different types of diffusers and grilles. Ensure that grilles are shown both on architectural and mechanical drawings. Ensure that you understand where the door grilles go and advise the mechanical engineer if there are any problems with proposed locations. For example grilles proposed in acoustic doors , glazed doors or other doors where the visual appearance is important. Similar issues apply to ceiling diffusers and grilles.  Ensure that the selection and style of grille and the colour are co-ordinated suits the interior design and are not specified differently in the architectural documents and the mechanical documents. Also ensure that linear grilles which crossover from room to room and could impact acoustics are considered and detailed appropriately.
  3. Check locations of thermostats and controls. Ensure they are not on operable walls, glazed walls, behind retractable screens or in other functionally or visually unappealing locations.
  4. Consider accessible outdoor space for condensor units and the need for either building owner or authority approvals for any outdoor units or grilles.

All of the above are my tips and suggestions – maybe the mechanical engineers reading this have their own suggestions?  What are your tips for working with mechanical engineers?  Does anyone have any more solutions to managing and coordinating with existing base building systems? Do you have any tips for hydraulic and fire engineering collaboration?

I thought my readers might also be interested in this blog post  on BIM collaboration – what it has to say about collaboration applies to every type of project, not just BIM projects. http://bimfix.blogspot.com.au/2013/02/collaborative-bim-planting-seed.html

Image Credits:
Creative Commons Attribution-Noncommercial 2.0 Generic License  by  dzarro72 

One Response to Working with Mechanical Engineers

  1. Disclosure up front: I am a mechanical engineer. A couple of comments:

    1. Meeting rooms 1: I think you are putting the onus the wrong way. If the only information I get on occupancy is the number of chairs shown in a room who is responsible. If the client and/or interior designer don’t tell me that the number of people will be 4 times what is shown on the drawings why should I doubt what I see? Indeed, the opposite can be the case: the engineer ignores the drawing and designs to code (m²/person and usually higher than chairs on the drawing) only to find that the person with the cheque book complains that the system is over designed. If you know there will be 250 people in the room and not 60, say so.

    2. Meeting rooms 2: In my experience the main reason for complaints about these is that there is a problem with zoning, often, because of limitations in the base building. A second source is problems with temperature sensor location (e.g. someone put a fridge in front of it).

    3. Thermal comfort: You are right that this is subjective. Carefully controlled research has shown that it is impossible to get a set of conditions that 100% of people will be satisfied with. This is commonly referred to as percent dissatisfied and is rarely below 10%.

    4. Return air path: A big coordination problem is the route conditioned air returns to the plant. What engineers think is efficient (like door grilles) architects often hate. There are also issues that need to be addressed like sound isolation.

    5. Ceiling coordination can also be a headache. There is a logical sequence to follow (usually lights first, then air conditioning then sprinklers then EWIS and all the other paraphernalia that goes on ceilings these days). In set plaster ceilings there will probably also be access panels and these are best laid out at the design stage and not left to the contractor – unless you want a Swiss Cheese effect.

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