01
Loads and criteria
Establish design conditions and calculate loads before any geometry exists, because the plant size decides the plant room and the plant room decides the architecture.
HVAC design and ductwork BIM services
The discipline that usually decides how deep the ceiling void has to be — and therefore the one whose routing decisions everything else inherits.
HVAC
The engineering position
Duct depth is the constraint the rest of the project pays for
Rectangular ductwork is the largest single object in most ceiling voids, it cannot be rerouted as cheaply as cable tray, and it is usually drawn last. The result is a familiar sequence: the void is set architecturally, the mechanical route does not fit, and the resolution is either a bulkhead nobody wanted or an aspect-ratio change nobody calculated the pressure consequence of. We resolve the primary mechanical route first, and treat every subsequent change to it as an engineering change rather than a drafting one.
Aspect ratio is an engineering decision, not a coordination workaround
Flattening a duct to clear a beam changes its hydraulic diameter, its pressure drop and its fan duty. Done once it is invisible; done eleven times along a run it is a plant selection problem discovered at commissioning. Where our model carries the sizing parameters, that accumulation is measurable while the change is being made, which is the only point at which it is cheap to argue about.
Plant access is designed, not left over
Coil pull space, filter access, damper access and tube pull for a shell-and-tube heat exchanger are dimensioned requirements. They are also the requirements most often satisfied by whatever space happens to remain. We model them as clearance zones and test them as rules, so an access failure is a finding rather than an argument on site.
Deliverables
What is actually produced and issued
Any of these can be appointed on their own or combined. Nothing here depends on buying the intelligence layer, which is not for sale in any case.
DeliverableHeating and cooling load calculations
Room-by-room or zone loads against stated internal and external design conditions, with the assumptions listed rather than buried.
DeliverableDuct and pipe sizing
Sized against the modelled network with velocity and pressure criteria stated, and the sizing parameters written onto the elements.
DeliverableDuctwork and pipework models
Supply, extract, fresh air, chilled water, heating and condensate modelled with system assignment, insulation and connectivity intact.
DeliverablePlant room layouts
Arrangement with access, replacement routes and plinth and drainage requirements resolved, coordinated against structure and electrical.
DeliverableEquipment schedules
AHUs, FCUs, chillers, pumps, terminals and dampers scheduled from the model with duties attached.
DeliverableVentilation and fire damper strategy
Damper locations against compartment lines, with access provision modelled rather than assumed.
How it runs
The sequence, and why it is in this order
Sequence is not a formality on this kind of work. Most of the expensive rework we are asked to fix was produced by doing step four before step two.
02
Zoning
Allocate the mechanical zone in the ceiling void and the riser allocation, and agree it with the other disciplines in writing.
03
Primary distribution
Route the largest ducts and mains first, against structure. Everything that follows is fitted to this, not the other way round.
04
Sizing and terminals
Size the network, place terminals, and write the sizing parameters back onto the elements.
05
Access and clearance
Test coil pull, filter access, damper access and valve access as clearance rules across the whole model.
06
Documentation
Drawings, schedules and the duty data, issued with the QA rule set run and a named engineer's signature.
What we need to start
The inputs that decide whether a start is a real start
Missing any of these is survivable. Not knowing which of them are missing is not, so we establish it at enquiry stage rather than at forty per cent.
- Architectural model or plans with ceiling heights and compartment lines
- Structural model or beam layouts — the depth constraint comes from here
- Design conditions, occupancy and internal gains, or the standard to apply
- Selected plant, if already procured; otherwise we schedule to duty
- Acoustic and pressure criteria where they govern
Automation
Where automation applies to this work
Every line carries its real status. Three of the four states on this site mean "not yet", and we use them.
AutomationDuct and pipe parameter validationLive
Every run tested for size, system assignment, insulation and connectivity completeness before issue.
AutomationClearance rule sets for plant accessLive
Coil pull, filter and damper access tested as geometric rules across the federated model, not sampled by eye.
AutomationSizing reconciliationLive
Calculated size against modelled size, element by element, so a spreadsheet change that never reached the model is caught.
AutomationFan duty drift detectionIn development
Accumulated pressure consequence of geometry changes along a run, reported as the change is made. In development on our own delivery.
Scope boundary
What this appointment does not include
Published because a scope boundary discovered at month three is a dispute, and the same boundary stated at enquiry stage is just information.
- We do not perform detailed CFD analysis.
- We do not carry out on-site commissioning or balancing.
- We do not certify compliance with a jurisdiction's mechanical code; we design to the criteria you state or the standard you name, and your engineer of record certifies.
FAQ
Questions we are asked at enquiry stage
Do you calculate loads, or only model what we give you?
Either. Load calculation is a live capability and can be appointed on its own. If you already hold the loads, we size and model against them and will tell you if the modelled network disagrees with the sizing basis you supplied.
Which sizing method do you use?
Equal friction or static regain for air, with velocity and pressure criteria agreed at the start and stated on the output. The method is a project decision and we will recommend one, but we will not apply one silently.
Can you model to fabrication level of detail?
Yes — spool and fabrication drawings are a construction support deliverable. Say so at enquiry stage, because the authoring approach and the level of information need are different from a design model and cannot be retro-fitted cheaply.
How do you handle a ceiling void that is too shallow?
We report it as an engineering finding with the options and their consequences — aspect ratio change and its pressure cost, a bulkhead, a re-zoning, or a raised slab-to-slab. What we will not do is quietly flatten the duct until it fits and let the fan duty absorb it.
Related
Where this connects
Full MEP engineeringAll four disciplines coordinated as one set of interacting systems.
BIM coordinationWhere the mechanical route meets everyone else's.
BIM automationThe QA and quantity routines that make re-checking after a change affordable.
Data centre MEPWhere mechanical density and tolerance are at their most demanding.