Physics of Buildings

Sources and simplifications

Every reference cited on this site, and every place a figure idealizes the real system.

References

  1. Wilson, A. G. (1960). Condensation on Inside Window Surfaces, Canadian Building Digest CBD-4. National Research Council Canada, Division of Building Research. government research digest Condensation occurs whenever a surface falls below the room's dew point; windows are usually the coldest surface. Table I: inside glass temperature and maximum indoor RH without condensation at 70 °F indoors, single/double/triple glazing, natural convection inside, no sun (e.g. 0 °F outdoors, no wind: single 35 °F and 27 %, double 50 °F and 49 %, triple 56 °F and 61 %). (Dew point and condensation)
  2. Bucklin, R. A., Haman, D. Z., Bayabil, H. K. & Guzman, S. M. (2019). Using Psychrometric Chart for Frost Protection, ABE 372. University of Florida IFAS Extension (EDIS). university extension Definitions: wet bulb is the lowest temperature to which air can be cooled by evaporating water into it; dew point is where moisture starts to condense when air is cooled at constant pressure and humidity ratio; relative humidity is the ratio of the actual vapour pressure to the saturation vapour pressure at the same dry bulb. (Dew point and condensation)
  3. U.S. Environmental Protection Agency, Indoor Environments Division (2013). Moisture Control Guidance for Building Design, Construction and Maintenance, EPA 402-F-13053. U.S. EPA, Washington, DC. government guidance pp. 14–17: dew point vs relative humidity; 85 °F at 60 % RH has a dew point of 70 °F (read along the chart to the saturation curve); at 90 % RH a surface 3 °F colder than the air condenses, at 50 % about 20 °F; a 55 °F duct sweats in air with a 70 °F dew point; ventilation dries a building only when the outdoor dew point is below the indoor one; windows are usually the first cold-weather condensation sites; thermal bridges and air leaks chill indoor surfaces. (Dew point and condensation)
  4. Meyer, D. & Thevenard, D. (2019). PsychroLib source code, JavaScript implementation (src/js/psychrolib.js). GitHub, psychrometrics/psychrolib (MIT licence). source code Comments give the ASHRAE (2017) ch. 1 equation numbers: saturation pressure eqs 5 and 6 (Hyland–Wexler; ice at or below the 0.01 °C triple point; valid −100 to 200 °C); humidity ratio eq 20 (0.621945·pw/(p − pw)); specific volume eq 26 (R_da = 287.042 J/kg·K, factor 1.607858); enthalpy eq 30 (1.006·t + W·(2501 + 1.86·t) kJ/kg; IP 0.240·t + W·(1061 + 0.444·t) Btu/lb); wet bulb eqs 33 and 35; standard atmosphere eq 3 (101 325·(1 − 2.25577×10⁻⁵·Z)^5.2559 Pa). (Dew point and condensation)
  5. U.S. Environmental Protection Agency (2026). A Brief Guide to Mold, Moisture and Your Home. U.S. EPA (web page, updated 18 February 2026). government guidance “If possible, keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity.” Condensation on windows, walls or pipes can be a sign of high humidity. (Dew point and condensation)
  6. Meyer, D. & Thevenard, D. (2019). PsychroLib: a library of psychrometric functions to calculate thermodynamic properties of air. Journal of Open Source Software 4(33), 1137. doi:10.21105/joss.01137. peer-reviewed software paper Open-source implementation (C, Fortran, JavaScript, Python, VBA) of the moist-air equations of the ASHRAE Handbook—Fundamentals (2017), chapter 1. (Calculator)
  7. NOAA, NASA and U.S. Air Force (1976). U.S. Standard Atmosphere, 1976 (NOAA-S/T-76-1562, NASA-TM-X-74335). U.S. Government Printing Office, Washington, DC. government standard Sea-level pressure 101 325 Pa, temperature 288.15 K, tropospheric lapse rate 6.5 K/km; the pressure–altitude relation behind ASHRAE eq 3. (Calculator)
  8. Thompson, A. & Taylor, B. N. (2008). Guide for the Use of the International System of Units (SI), NIST SP 811 (2008 edition), Appendix B. National Institute of Standards and Technology. standard 1 Btu_IT/lb = 2326 J/kg; 1 grain = 6.479891×10⁻⁵ kg (7000 grains per pound); 1 psi = 6894.757 Pa; standard atmosphere = 101 325 Pa; conventional inch of mercury = 3386.389 Pa. (Calculator)
  9. Lemmon, E. W., McLinden, M. O. & Friend, D. G. (NIST Thermophysical Properties of Fluid Systems) (2025). Saturation Properties for Water: Temperature Increments, NIST Chemistry WebBook, SRD 69 (IAPWS-95 formulation of Wagner & Pruss 2002). National Institute of Standards and Technology. reference data Saturation pressure of water: 0.611654 kPa at 0.01 °C, 1.22902 at 10.01, 2.34077 at 20.01, 4.24941 at 30.01, 7.38888 at 40.01, 12.3581 at 50.01, 101.454 kPa at 100.01 °C. (Calculator)
  10. Shelton, D. P. (2008). Air Properties: Temperature and Relative Humidity, NebGuide G1849. University of Nebraska–Lincoln Extension. university extension Dry-bulb lines vertical, wet-bulb lines sloping, dew-point lines horizontal, RH curves sweep from lower left to upper right; any two properties fix the rest. Example 1: 80 °F and 50 % RH → wet bulb 67 °F, dew point 59 °F (read from a simplified chart). (Calculator)
  11. World Meteorological Organization, Commission for Instruments and Methods of Observation (2018). Guide to Instruments and Methods of Observation (WMO-No. 8), Volume I, Chapter 4: Measurement of humidity (2018 edition). World Meteorological Organization, Geneva. standards body guide Annex 4.B eq 4.B.5: enhancement factor of moist air f(p) = 1.0016 + 3.15×10⁻⁶·p − 0.074/p (p in hPa), 1.0047 at 1013 hPa; its pressure dependence 0 to +0.6 %. Section 4.3: psychrometers need ventilation of 3 to 5 m/s past the wet bulb; insufficient ventilation can lead to overestimation of humidity (the wet bulb reads too high). (Calculator)
  12. Indian Institute of Technology Kharagpur (NPTEL) (2008). Refrigeration and Air Conditioning, Lesson 28: Psychrometric processes (Version 1 ME). National Programme on Technology Enhanced Learning, India. university course text §28.2(b): apparatus dew point is the effective coil surface temperature; by-pass factor BPF = (T_C − T_S)/(T_O − T_S), leaving state on the cooling and dehumidification line toward the ADP (Fig. 28.3). §28.2(g)(ii): when very cold air mixes with warm humid air the mixture may fall in the two-phase region; water condenses, the humidity ratio falls and the temperature rises from the released latent heat, the phenomenon that forms fog. Worked problems 8–10 give reference states. (Psychrometric chart)
  13. Tartarini, F., Schiavon, S., Cheung, T. & Hoyt, T. (2020). CBE Thermal Comfort Tool: online tool for thermal comfort calculations and visualizations. SoftwareX 12, 100563 (tool at comfort.cbe.berkeley.edu). doi:10.1016/j.softx.2020.100563. peer-reviewed software paper Implements ASHRAE Standard 55; inputs are air temperature, mean radiant temperature, air speed, relative humidity, metabolic rate and clothing insulation; the comfort zone drawn on its psychrometric chart depends on the mean radiant temperature chosen. (Psychrometric chart)
  14. International Association for the Properties of Water and Steam (2011). Revised Release on the Pressure along the Melting and Sublimation Curves of Ordinary Water Substance, IAPWS R14-08(2011). IAPWS. standards body release Sublimation pressure of ice Ih, eq (6): ln(p/pt) = (Tt/T)·Σ ai·θ^bi with pt = 611.657 Pa, Tt = 273.16 K; valid 50 K to 273.16 K. Used here only as an independent check of the ice branch. (Psychrometric chart)
  15. Gatley, D. P. (2004). Psychrometric chart celebrates 100th anniversary (ASHRAE Journal 46(11)); bibliographic record and summary. ASHRAE Journal, November 2004; record in the International Institute of Refrigeration FRIDOC database. journal article (record) Reviews psychrometrics before 1904, when Willis H. Carrier produced the first psychrometric chart, and the chart's development to 2004. (Psychrometric chart)

Simplifications