ServiceA-02.01
HVAC Design & Heat Load Calculations
Air-conditioning and ventilation systems sized from a calculated load rather than from a catalogue, through to equipment selection and duct design.
Engineering approach
How we work on this
The order matters more than any individual decision in it. Most of the failures we are called in to correct are sequencing failures rather than equipment failures.
- 01
Load before equipment
The heat load is calculated from the building fabric, occupancy, process equipment and fresh-air requirement before any plant is named. A system sized from a nameplate figure will usually commission and then underperform once the facility is fully occupied and running in season.
- 02
Air volume before duct
Supply, return, fresh-air and exhaust volumes are fixed from the load and the room’s air-change requirement. Duct sizing, filter staging and fan static all inherit from those numbers, in that order.
- 03
Selection against a duty, not a model number
AHUs, chillers and VRF systems are selected against the calculated duty with the part-load condition considered, because a plant that only meets design day is a plant that runs badly for most of the year.
Scope of workA-02.01
Everything carried under this discipline
Not a summary. If it is on this list we carry it ourselves rather than subcontracting it.
- 01.01Heat-load calculations
- 01.02HVAC system design
- 01.03AHU selection
- 01.04Chiller & VRF/VRV systems
- 01.05Duct design
- 01.06Piping design
- 01.07Ventilation systems
- 01.08Fresh-air systems
- 01.09Exhaust systems
Deliverables
What you are holding at the end
The documents that make the next stage of your project possible, and that an auditor will ask to see.
- Heat-load calculation sheet, room by room
- System schematic and zoning drawing
- Duct layout with sizes and air volumes
- Equipment schedule with selected duties
- Fresh-air and exhaust arrangement
Relevant standards
What the work is designed and tested to
- ASHRAE
- Design and installation practice for heating, ventilation and air conditioning.
- ISHRAE
- Design and installation practice for heating, ventilation and air conditioning.
Typical applications
Where this work goes
- Pharmaceutical production and packing halls
- Hospital wards, ICUs and diagnostic areas
- Precision manufacturing and electronics assembly
- Commercial and institutional buildings
Proof
Work of this kind
Most of our work is carried out under confidentiality agreements with pharmaceutical manufacturers and hospitals, so it is not published here. Reference contacts for comparable facilities are provided on request during a tender.
Questions
What people ask us first
- Can you work from an architectural plan alone?
- Yes, that is the usual starting point. A plan with room names and areas, plus a description of what happens in each room and what equipment it holds, is enough to produce a load calculation and a first system arrangement.
- Do you design only, or design and build?
- Both. The design can be issued as a standalone package for another contractor to build, or carried through execution, commissioning and qualification under one contract.
- What decides between a chiller plant and VRF?
- Load profile, the number and diversity of zones, whether close humidity control is needed, and the space available for plant. Regulated rooms that need controlled RH and filtration are normally on an AHU-based system; comfort zones alongside them may not be.