Town House HVAC Load Calculator

Calculator Form

Floor area sq ft

Average ceiling height ft

Exposed wall area sq ft

Roof or ceiling area sq ft

Window area sq ft

Door area sq ft

Wall U value

Roof U value

Window U value

Door U value

Cooling indoor design F

Cooling outdoor design F

Heating indoor design F

Heating outdoor design F

Infiltration ACH

Mechanical ventilation CFM

Occupants

Lighting watts

Appliance sensible gain BTU/hr

Solar heat gain factor

Window SHGC

Shade factor

Humidity grains difference

Safety margin percent

Example Data Table

Input	Example Value	Use
Floor area	1800 sq ft	Finds building volume with ceiling height
Exposed wall area	900 sq ft	Counts outside walls only
Window area	240 sq ft	Calculates conduction and solar gain
Infiltration	0.35 ACH	Estimates leakage airflow
Ventilation	80 CFM	Adds outdoor air load

Formula Used

The calculator uses simplified construction load equations for early planning.

Volume = floor area × ceiling height
Infiltration CFM = volume × ACH ÷ 60
UA total = area × U value for each envelope part
Conduction load = UA total × temperature difference
Sensible air load = 1.08 × CFM × temperature difference
Latent load = 0.68 × CFM × grains difference
Solar gain = window area × SHGF × SHGC × shade factor
Cooling tons = total cooling BTU/hr ÷ 12000
Lighting gain = watts × 3.412
Suggested load = calculated load × safety margin factor

How to Use This Calculator

Enter only exposed wall areas for the town house.
Exclude party walls shared with conditioned homes.
Enter roof area only where heat crosses the envelope.
Add window, door, and U value data.
Use local heating and cooling design temperatures.
Enter airflow, internal gains, and humidity data.
Press the calculate button.
Review the result above the form.
Download the CSV or PDF report when needed.

Town House HVAC Load Planning

A town house often shares one or two walls. That changes the load profile. Shared walls lose less heat than exposed walls. End units usually need more capacity. Middle units may need less capacity. This calculator helps you compare those conditions.

Why Load Matters

Oversized equipment can short cycle. It may cool rooms quickly, yet remove little moisture. Undersized equipment may run all day. It can still miss the target temperature. A balanced estimate gives better comfort. It also supports clearer talks with contractors.

Main Load Sources

The calculator separates envelope, air, solar, and internal gains. Envelope load comes from walls, roof, windows, and doors. It uses area, U value, and design temperature difference. Air load comes from infiltration and ventilation. Solar gain comes through glass. People, lights, and appliances add heat inside the home.

Town House Details

Town houses need careful surface entry. Do not count walls that touch a conditioned neighbor. Count party walls only when the other side is unconditioned. Use exposed roof area for the top floor. Use slab or crawl data outside this simplified tool. Corner units need more wall area. Basement units may need different assumptions.

Reading The Result

The cooling result shows sensible load, latent load, total load, tons, and suggested capacity. The heating result shows conduction and air load. The safety margin is optional. It is useful for uncertainty, but should stay modest. Too much margin can create comfort problems.

Practical Guidance

Use local outdoor design temperatures. Enter realistic indoor set points. Use tested U values when available. If you do not know them, use conservative estimates. Check window direction and shading. High west glass can raise afternoon cooling needs. Review air leakage carefully. Town houses can have vertical leakage through stairs, chases, and attic hatches.

Final Notes

This tool is a planning estimator. It is not a replacement for Manual J design. A licensed professional should verify final equipment size. They should also review ducts, zoning, ventilation, humidity, and code rules. Use the exported report as a starting record. Then update it when better site data becomes available.

Good records make later upgrades easier for owners. They also help compare bids on equal design assumptions carefully.

FAQs

1. Can this replace a Manual J report?

No. It is a planning estimator. Use it for early comparison, budgeting, and discussion. A certified professional should complete final Manual J sizing.

2. Should I count shared town house walls?

Do not count shared walls when the other side is conditioned. Count them only when they face garages, shafts, attics, or unconditioned spaces.

3. What is ACH?

ACH means air changes per hour. It estimates leakage through cracks, penetrations, attic access points, doors, and other envelope gaps.

4. Why is latent load included?

Latent load represents moisture removal. It matters in humid climates because comfort depends on both temperature control and indoor humidity control.

5. What does cooling tonnage mean?

One cooling ton equals 12,000 BTU per hour. The calculator divides total cooling load by 12,000 to estimate equipment tonnage.

6. What safety margin should I use?

A modest margin helps cover uncertain inputs. Very high margins can oversize equipment and reduce comfort, moisture removal, and cycle length.

7. Why are window inputs important?

Windows affect conduction and solar gain. Large west-facing glass can raise cooling load strongly during hot afternoon conditions.

8. Can I use this for row houses?

Yes, for planning. Enter only surfaces exposed to outdoor or unconditioned spaces. Adjust airflow, windows, and roof data carefully.