HVAC Professional Design Review
Review your documented design loads, manufacturer performance and duct pressure budget.
Review worksheet — enter values from a complete load report. Capacity differences are arithmetic checks, not Manual S approval. Final equipment selection needs verified loads, manufacturer performance and duct evaluation.
What to do first: project checklist
Check items as you complete them. Save on this device or export your project to retain your progress.
1. Start here: understand the problem
Note which rooms are hot, cold or damp, the time of day, outdoor weather, thermostat setting and indoor humidity. A room problem can be an airflow problem rather than insufficient whole-house capacity.
Check the filter according to its instructions and keep supply/return grilles clear. Schedule a professional maintenance visit before assuming the unit is too small.
Replacement, addition, window replacement, air sealing or a new heat pump? Size for the planned finished home. Decide whether one system or several systems serve it.
Keep plans, equipment model numbers, previous load reports, window labels, insulation records and twelve months of energy bills. Bills help describe the problem; they do not directly determine AC tons.
2. Measure the home and collect design inputs
Measure each room length, width and height. Leave out an unconditioned garage. For multiple floors, enter only surfaces exposed to outdoors or an unconditioned space; do not count interior partitions twice.
Record net opaque exterior wall area, exposed ceiling/roof area, windows and exterior doors. Deduct openings from gross wall area. Ground-contact floors need a separate method rather than a simple outdoor-air U×A×ΔT assumption.
Measure each window group, note its compass direction and copy whole-window U-factor and SHGC from the label or manufacturer. Record overhangs, trees and skylights.
Ask the designer for a consistent local weather source, cooling and heating outdoor design temperatures, indoor targets, and moisture difference. Do not substitute the hottest recorded day.
Ask for assembly U-factors and an air-leakage assessment. Nominal insulation R-value alone does not describe a framed wall. ACH50 from a blower-door test is not natural ACH.
Note outdoor-air ventilation, exhaust fans, duct location, insulation, leakage and return paths. Have a professional establish effective infiltration/ventilation airflow for the load method. Do not blindly add fan nameplates to infiltration.
3. Before approving a size or buying equipment
Request Manual J inputs and output showing heating, sensible cooling and latent cooling loads, plus the block load used for equipment selection. Ask which software and version produced it.
Check floor area, weather, occupants, insulation, windows, shading and duct location against the home. Ask for corrections to guessed inputs. Avoid adding an arbitrary extra safety percentage.
Request exact outdoor/indoor/coil model combinations, AHRI match and manufacturer expanded performance at the actual design temperatures and selected airflow. A nominal ton label is not the delivered capacity.
For a heat pump, request output at winter design temperature, defrost effects, backup heat and minimum modulation. For a humid home, review latent capacity and ventilation/dehumidification strategy.
Ask how room airflow, returns, filters, fittings and blower pressure were checked. A larger air conditioner cannot fix a restricted return duct.
Compare design reports, installation work, permits, warranty, commissioning and total scope. Do not compare price and tons alone.
4. Professional design review
Record software/version, report date, system or zone, designer, site and whether room values are coincident with the equipment block load. Check that totals and duct loads are not duplicated.
Review assemblies, infiltration interaction, ventilation recovery, solar orientation, shading, time effects and adequate exposure diversity in the full method. This worksheet does not perform that validation.
Use expanded manufacturer data at matching outdoor dry bulb, indoor dry/wet bulb, airflow and altitude as applicable. Check sensible, latent and total capacity for each relevant stage.
Apply the governing Manual S edition, equipment type and local jurisdiction requirements. Do not use a universal 15% oversize pass/fail rule, especially for variable-capacity heat pumps.
Use blower tables at design CFM, applicable component drops and supply-plus-return critical path effective length. Use pressure drops at the same airflow and avoid subtracting an internal coil already included in the blower rating.
Record airflow settings, zoning/minimum flow, ventilation, humidity controls and backup heat settings. Confirm OEM installation requirements and applicable permits/code.
5. Installation day and handover
Request measured system airflow, room balancing, supply/return static pressure, refrigerant charging verification and duct leakage results where applicable. These are professional tests.
Have the installer verify condensate drainage, controls, accessible filtration and that rooms work with doors in normal positions.
Save the load report, equipment selection, AHRI match, duct/balance report, permits, startup readings, warranty and maintenance instructions.
Record temperature/humidity and room comfort after installation. Ask for a follow-up when actual seasonal conditions expose an unresolved problem.
Detailed explanations & instructions
Start with the load, then choose the machine
The house sets the required load; a manufacturer’s performance tables show what a particular matched system can deliver. Keep the room distribution requirements separate from the equipment block load.
ACCA Manual S: equipment selectionHomeowner worksheet: measure and understand
Add rooms or one whole-house block. Enter exterior surfaces and windows, outdoor-air load inputs and internal gains. Every numerical input must be supplied; the worked example is fictional. Use the breakdown to identify what needs measuring or checking.
Professional worksheet: review documented values
Enter sensible cooling, latent cooling and heating figures from a documented design report. Compare a proposed model at the same design conditions. Record the source, equipment match, indoor wet bulb, stage and airflow. The app checks arithmetic, not report authenticity or compliance.
How this screening math works
Opaque conduction uses U×area×temperature difference. Windows add that conduction plus area×SHGC×entered incident solar intensity×remaining-sun fraction. Outdoor-air sensible gain uses Cs×CFM×ΔT; latent gain uses Cl×CFM×moisture difference in grains/lb. Internal watts multiply by 3.412142 to become BTU/h. These are simplified gains; a full cooling-load method treats time effects and diversity.
ASHRAE residential heating and cooling loadsNo automatic weather or hidden sizing factor
The tools do not infer weather from a ZIP code, auto-convert ACH50, choose assembly U-values or add a blanket safety percentage. Enter a source beside the project and mark assumed data as unverified. Zero means a term is intentionally omitted, not that it is known to be zero.
Duct pressure budget
Use external pressure available from the blower table at selected CFM. Subtract only component drops outside that rating boundary. The remaining pressure divided by the complete critical supply-and-return effective length, times 100, is the design friction rate in inches of water per 100 ft. The result is a budget, not a finished duct layout.
ACCA design friction rateWhat the result does and does not tell you
BTU/h is a rate of heat transfer. Cooling kW here is thermal output, not electrical consumption. Tons equivalent is a conversion, not a shopping recommendation. A positive capacity gap does not establish correct equipment selection. The screening model does not include latent removal control or a seasonal energy simulation.
Your next step
Use the completed checklist and report in a contractor conversation. Resolve missing inputs, obtain the full load report, equipment selection and duct review, then collect commissioning measurements after installation.
ENERGY STAR contractor hiring guideWorked example: one fictional room
A 20 × 15 ft room has 300 ft² of floor area and an 8 ft ceiling. For this example only, 250 ft² net exterior walls have U = 0.06, 300 ft² exposed ceiling has U = 0.03, and 40 ft² windows have U = 0.30 and SHGC = 0.25. Outdoor cooling temperature is 95°F and indoor temperature 75°F. Solar intensity is assumed 200 BTU/h·ft² with half remaining after shading. These are invented teaching inputs, not defaults for your home.
Conduction: (250 × 0.06 + 300 × 0.03 + 40 × 0.30) × 20 = 720 BTU/h. Window solar: 40 × 0.25 × 200 × 0.5 = 1,000 BTU/h. Effective outdoor airflow 15 CFM adds 1.08 × 15 × 20 = 324 sensible BTU/h; with moisture difference 40 grains/lb, it adds 0.68 × 15 × 40 = 408 latent BTU/h. Entered internal gains are 500 sensible and 400 latent BTU/h, plus 100 W = 341.2142 sensible BTU/h.
Sensible subtotal = 2,885.2142; latent subtotal = 808; total = 3,693.2142 BTU/h, or 0.308 tons equivalent. At 70°F indoor and 30°F outdoor, the same entered U×area and 15 CFM yield 2,088 BTU/h heating loss. The example omits opaque solar/time effects, ground contact and duct loads. It demonstrates the worksheet; it does not size an AC for a real room.
HVAC questions & answers
Can this give the same report an AC company uses?
It can organize measurements and review a contractor’s figures. The homeowner component worksheet is a transparent screening calculation; the professional worksheet works with entered report values. A complete Manual J report still needs the full method, appropriate software and verified inputs.
ACCA Manual J: residential loadsWhat should I do first?
Record the comfort problem, check routine maintenance, measure the conditioned rooms and gather window/insulation records. Then request a load calculation before selecting equipment.
ENERGY STAR maintenance checklistWhy is square footage not enough?
A shaded, tight house and a leaky house with large west-facing windows can have different loads at the same size. Heating and cooling loads must reflect the actual enclosure and local conditions.
DOE proper HVAC sizingWhat are Manual J, Manual S and Manual D?
Manual J calculates heating and cooling loads. Manual S uses those loads and manufacturer data to select equipment. Manual D addresses residential duct design. They are connected steps, not interchangeable calculations.
ACCA Manual J: residential loadsWhat do sensible and latent mean?
Sensible cooling reduces air temperature. Latent cooling removes water vapor. Both contribute to total cooling load, so a system needs to address temperature and moisture.
ASHRAE residential heating and cooling loadsIs bigger AC better?
A larger system can cycle off quickly and fail to control humidity well. Ask for the load report and equipment performance instead of choosing the next larger label.
PNNL air-conditioning design guidanceWhat is one ton?
A refrigeration ton represents 12,000 BTU per hour of cooling. Dividing a load by 12,000 shows its equivalent in tons; it does not select an equipment model.
ASHRAE residential heating and cooling loadsWhat are U-factor and SHGC?
U-factor describes heat transfer through an assembly; lower generally means less transfer. SHGC describes how much solar energy passes through a window. Use the whole-window rating, not center-of-glass data alone.
PNNL window ratings and performanceDo new windows change the AC size?
They may change conductive and solar gains. Recalculate for the new rated U-factor/SHGC, shading and installation conditions before ordering equipment for a renovation.
PNNL window shadingCan I use insulation R-value to find U?
For a single ideal layer U is the reciprocal of R, but whole assemblies also include framing, surface films and other materials. Obtain a whole-assembly value for a design calculation.
ACCA Manual J: residential loadsCan I enter my blower-door ACH50 as natural ACH?
No. ACH50 describes airflow at an imposed test pressure, not natural outdoor-air exchange. A designer must convert and account for weather, height and ventilation interaction using the applicable method.
ACCA Manual J: residential loadsDo I add every exhaust fan’s CFM to infiltration?
No. Balanced and unbalanced ventilation interact with infiltration, and heat/energy recovery can change effective loads. Enter method-derived effective outdoor airflow or use the full load report.
ASHRAE residential heating and cooling loadsWhat weather should be entered?
Use the local design conditions required by the chosen method and project. Record the weather source and station/county. Design temperature is a sizing condition rather than a forecast or record extreme.
ENERGY STAR design temperature guidanceCan I use humidity percent as grains difference?
No. Relative humidity depends on temperature. Moisture difference in grains per pound must come from a psychrometric calculation or a load report using both indoor and outdoor conditions.
ASHRAE residential heating and cooling loadsWhy separate each room?
Room loads help establish distribution needs. Equipment uses a block load at an appropriate common design condition; summing room peaks from different times can overstate it.
ACCA Manual J: residential loadsWhy is the screening load different from Manual J?
The screening worksheet sums entered steady-state heat gains. It does not reproduce time-delayed cooling loads, exposure diversity, slab/ground methods or detailed duct/infiltration procedures. Use differences to ask about assumptions.
ACCA Manual J: residential loadsCan this tell me a duct diameter?
The pressure worksheet gives an available-pressure budget and friction rate. Complete duct selection also needs branch CFM, material/fitting data, velocity/noise limits and return design. A velocity-only diameter is not a complete duct design.
ACCA Manual D: residential duct designWhy are returns and filters important?
They affect the air path and pressure the blower must overcome. Use component performance and pressure drops at the design flow; have airflow checked after installation.
ENERGY STAR quality installationCan I assume 400 CFM per ton?
Treat that as a familiar rough figure, not a universal requirement. Use the equipment manufacturer’s allowable/design airflow and humidity performance for the actual model and operating stage.
ENERGY STAR quality installationCan the AHRI certificate replace expanded performance data?
The certificate confirms a rated matched combination. Equipment selection should use manufacturer expanded performance at your design conditions rather than only the certificate’s rating conditions.
PNNL air-conditioning design guidanceDoes a positive capacity margin mean the system is approved?
No. The worksheet displays arithmetic differences and ratios. A designer must check selection limits, moisture removal, airflow, control behavior and the governing requirements.
ACCA Manual S: equipment selectionWhat if cooling is fine but the house feels damp?
Record indoor humidity and ask the contractor to check airflow, runtime, ventilation and moisture sources. EPA recommends keeping humidity below 60%, ideally 30–50% when possible. A moisture-control plan may need more than an AC change.
EPA moisture and humidity guideWhat extra work does a heat pump need?
Check heating output at winter design conditions, modulation, defrost and backup heating, alongside cooling and dehumidification. Do not size it from cooling tons alone.
ACCA Manual S: equipment selectionWhat should I ask an installer to measure?
Ask for system airflow, refrigerant charge verification, duct evaluation and a room balance/pressure record appropriate to the installation. Save the startup report with your warranty.
ENERGY STAR quality installationCan I do all of this myself?
You can collect measurements, labels, notes and questions. Have trained professionals perform electrical, refrigerant, pressure/leakage and combustion work, and obtain the required design and installation documents.
ENERGY STAR contractor hiring guideDo these tools need a paid API key?
No. These HVAC worksheets calculate locally in your browser. An API key is not needed for loads, checklists, explanations, copy or print.
Where are saved projects kept?
Save on this device stores the inputs and checklist in the current browser. Export a project file for a separate backup. Shared links include project entries; omit private addresses and contact details before sharing.
Research sources & professional resources
Reviewed 2026-10-10. This guide summarizes the workflow; follow the governing edition and local requirements for your project.
- ACCA Manual J: residential loads
- ACCA Manual S: equipment selection
- ACCA Manual D: residential duct design
- ACCA approved load-calculation software
- ENERGY STAR quality installation
- ENERGY STAR design temperature guidance
- PNNL window ratings and performance
- PNNL window shading
- PNNL air-conditioning design guidance
- ACCA design friction rate
- ASHRAE residential heating and cooling loads
- ENERGY STAR contractor hiring guide
- ENERGY STAR maintenance checklist
- EPA moisture and humidity guide
- DOE proper HVAC sizing
For a formal load report, review ACCA’s current approved-software directory with your designer. CalculatorWiser is not listed here as ACCA-approved software.
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