How is design outdoor temperature selected?

Use ASHRAE 99.6% design heating temperature (99.6th percentile of coldest hours = 0.4% of hours are colder). Conservative sizing avoids under-designed systems. Heating loads are less time-dependent than cooling loads.

What allowance should I make for infiltration?

Infiltration heat loss = ρ·c_p·Q_air·ΔT. Estimate ACH (air changes per hour): loose construction 0.5-1.5 ACH, average 0.25-0.5, tight 0.1-0.25. Use ASHRAE 62.1 minimum ventilation + measured infiltration.

Should solar and internal gains be credited in heating load?

For equipment sizing: conservatively ignore (worst case, coldest/darkest hours with no internal gains). For energy analysis: credit intermittent gains. ASHRAE Manual J uses tables for different building types.

Heating Load Calculator

Calculate building heating load: Q = Σ(U·A·ΔT) + Q_infiltration - Q_solar - Q_internal. Design outdoor temperature at 99% exceedance. Heat loss through envelope components. Boiler and heat pump sizing.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Calculate building heating load: Q = Σ(U·A·ΔT) + Q_infiltration - Q_solar - Q_internal. Design outdoor temperature at 99% exceedance. Heat loss through envelope components. Boiler and heat pump sizing. Use the heating load result to inform your clinical assessment.

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Frequently Asked Questions

How is design outdoor temperature selected?

What allowance should I make for infiltration?

Should solar and internal gains be credited in heating load?