Envelope conduction
Exterior wall, roof, floor, window and door heat transfer is calculated from exposed area, construction value and the applicable indoor-to-outdoor or indoor-to-ground temperature difference.
HVAC load calculation software
Online HVAC load calculation software for peak heating and cooling loads
Estimate room-by-room peak heating and cooling loads from a scaled PDF floor plan, envelope, design weather, occupancy, ventilation and internal gains.
Free to start. Built for mechanical design workflows in Canada and the United States.
Current scope: a simplified hourly design-day estimator for preliminary room and block loads. Final equipment selection, permit submissions and code compliance require the accepted calculation method and professional engineering review.
What the peak heating and cooling load estimate includes
A useful HVAC load calculation must respond to more than floor area. MEPFlow combines plan geometry with the major room-level heat-loss and heat-gain inputs, while keeping the assumptions visible for engineering review.
Interior partitions
When traced rooms share a boundary, the module detects the adjacent space. Transfer across that wall uses the difference between the two room setpoints rather than outdoor design temperature.
Solar and orientation
North rotation, design day and glazing properties are used to estimate orientation-dependent window solar gain and the effect of solar exposure on exterior surfaces.
People and equipment
Occupant sensible and latent gains, lighting power and equipment power can be assigned room by room instead of applying one whole-building allowance.
Outdoor air and infiltration
Manual ventilation and infiltration inputs contribute sensible and latent cooling load and heating load. They are explicit inputs and are not automatically presented as an ASHRAE 62.1 compliance result.
Peak and airflow results
The module reports room heating, sensible and latent cooling, total cooling, peak hour, estimated supply airflow and component breakdowns, plus block heating and coincident cooling.
Move from isolated calculations to a connected workflow
MEPFlow's Loads module turns a floor plan into a reviewable preliminary load model. Upload and calibrate a PDF, trace the conditioned spaces, partition rooms and assign the envelope and space inputs that drive peak heating and cooling. Results remain connected to the plan, so the designer can see how exposure, adjacent rooms, glazing and internal gains affect each space.
Upload a PDF floor plan, calibrate its scale and trace room geometry directly in the browser.
Partition a larger outline into spaces and automatically identify exterior walls and shared interior boundaries.
Place windows and exterior doors on exposed walls and assign thermal and solar properties.
Define wall, roof and floor construction values, including outdoor, ground and conditioned boundary conditions.
Set design temperatures, orientation, occupancy, lighting, equipment, ventilation and infiltration by space.
Review room heating, sensible cooling, latent cooling, total cooling, airflow and coincident block results in IP or SI units.
From PDF floor plan to room-by-room peak loads
Trace and partition spaces
Upload the plan, calibrate a known distance, trace the conditioned area and split it into individual rooms. Shared boundaries are treated as interior partitions; exposed boundaries remain exterior walls.
Assign load inputs
Set indoor and outdoor design conditions, north orientation, wall and roof values, floor condition, glazing, people, lights, equipment, outdoor air and infiltration.
Calculate and review
Run the simplified design-day calculation and review each room's heating and cooling peak, estimated airflow, component breakdown and the coincident block cooling result.
Who can use MEPFlow's online HVAC load calculator
Mechanical engineers and HVAC designers who need fast preliminary room-by-room loads during early design.
Canadian consulting firms that want a browser-based workflow with a Winnipeg design-condition preset and editable weather inputs.
Teams that want heating and cooling results tied to the same scaled PDF geometry used for duct and hydronic layouts.
Designers comparing envelope, glazing, occupancy or setpoint options before completing a final code-compliant load model.
Related MEP tools and workflows
HVAC duct design software
Carry estimated room airflow into duct sizing, layouts and pressure-aware system design.
ExploreHydronic design software
Convert heating or cooling duty into hydronic flow and pipe sizing decisions.
ExploreMEP design software
Connect load calculations with ventilation, duct, plumbing and hydronic workflows.
ExploreFrequently asked questions
What does HVAC load calculation software calculate?
HVAC load calculation software estimates the heating capacity needed at winter design conditions and the sensible and latent cooling capacity needed at summer design conditions. MEPFlow calculates preliminary results by room and also reports block-level heating and coincident cooling.
Can MEPFlow calculate heating and cooling loads room by room?
Yes. Trace or partition each room on the calibrated floor plan, then assign its setpoints, height, occupancy, internal gains, outdoor air, infiltration and construction inputs. The result panel reports each room separately.
How does MEPFlow distinguish exterior and interior walls?
The geometry engine compares room boundaries. A wall shared by adjacent traced spaces is identified as an interior partition; a wall on the outside of the traced model is identified as exterior. Designers can review and override the classification when needed.
Does the calculation include windows, doors and solar heat gain?
Yes. Windows and exterior doors are placed on exposed wall segments. Window area, U-value, solar heat-gain coefficient, orientation and design-day solar exposure contribute to the cooling estimate.
Does MEPFlow use Canadian weather data?
The current release includes a documented Winnipeg design-condition preset and lets the designer edit winter dry-bulb, summer dry-bulb and wet-bulb, ground temperature, daily range and solar design date. A full Canadian city and weather-file library is not yet included.
Is this a Manual J, HAP, IES VE or TRACE replacement?
No. The current Loads module is a simplified hourly design-day estimator for preliminary engineering decisions. It is not certified Manual J software and does not replace a complete HAP, IES VE, TRACE or code-compliance model. Final equipment selection and permit calculations require qualified engineering review and the method accepted by the authority having jurisdiction.
Can I use imperial and metric units?
Yes. MEPFlow supports IP and SI display and input workflows. The default interface uses imperial units, and the top toolbar can switch the Loads module to metric.
Is the online HVAC load calculator free?
MEPFlow is currently free to start. Create an account, open a project and select Peak Loads to test the workflow on a floor plan.
Put your next MEP calculation into a repeatable workflow
Start free, test the available modules on a real project, and decide whether MEPFlow fits your engineering process.
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