Mechanical System Drawings

These drawings are typically part of the construction drawing set.
They are submitted with the construction drawings for a building permit application.
They are part of the package for pricing the project for the client.

They are used for construction. All ducting, venting, exhaust fans, heating and/ or cooling units, etc. must be supplied and installed as per the approved drawings.

A mechanical engineering consultant produces the mechanical drawings. Often the same company will produce the electrical and plumbing drawings.

These drawings must comply with the National Building Code of Canada, the National Fire Code and Model National Energy Code of Canada for Buildings.
The National Housing Code of Canada and the Model National Energy Code of Canada for Houses both apply to residential projects.
Drawing information must also comply with all Provincial and local codes.

The engineer prepares his/ her own drawings based on floor and reflected ceiling plans provided by the interior designer or architect. The plans indicate to the engineer the location of light fixtures, special ceiling features, toilet rooms and any equipment requiring special venting.

Generally, the engineer uses these plans and incorporates his/ her ducting layout. Diffusers, return air grilles and exhaust fans, etc. are drawn in as symbols. Heating and/or cooling systems are specified and the location indicated. Legends, schedules, details and notes specific to the project are added.
On small projects, all information required is covered on one or two drawing sheets.
For large of complex projects, many drawing pages are necessary to cover all areas of the project.

Typically, the engineer’s drawings must note the type, location and number of heating and/ or air conditioning units. HVAC and electrical connections are specified. As well, any connections to gas lines or water systems must be indicated. The thermostat type, location and number are also noted.



Many projects require that heat loss and heat gain calculations be provided.
Air balancing information or air distribution device schedules are usually included.
The information required all depends on the type of project.

Many cities/ towns have energy conservation regulations. The engineer’s drawings must abide by all codes and bylaws pertaining to the city, town or province where the project is located.

The following are typical to a set of drawings:
- Plans showing the size, type and layout of ducting
- Diffusers, heat registers, return air grilles, dampers
- Turning vanes, ductwork insulation
- HVAC unit, type, quantity, location
- Thermostats, type, quantity, location
- Electrical, water, or gas connections
- Ventilation, exhaust fans
- Symbol legend, general notes and specific key notes
- Heating and/ or cooling load summary

Other information, depending on the project:
- Connection to existing systems
- Demolition of part or all of existing systems
- Smoke detector and firestat re: ducting
- Thermostat programming
- Heat loss and heat gain calculations per area
- Details: Round duct, turning vane, lay-in diffuser
- Special conditions, i.e.: Seismic restraint codes


Engineer’s drawings are required for all commercial projects involving HVAC work. This applies to additions, renovations or new construction. A permit is required prior to commencing any on site work.

Drawings and permits are also needed for residential projects when any substantial work related to HVAC is to take place.
For small projects, a licensed mechanical contractor can provide the information required to obtain a permit.

Concept and designs are the first stage of any project.
When established, the next stage is construction drawings.
Once a floor plan and reflected ceiling plan are complete, they are passed to the engineer to produce the mechanical drawings. The engineer’s drawings become part of the construction drawing set.

To learn more about construction drawings, click on the heading below.

Mechanical Drawings to Construction Drawings

The following are examples of mechanical drawings.
The images shown below are for demonstration purposes only.
They are not intended to provide any specific information and therefore should not be copied.


Partial Plan