The International Journal of Ventilation
Click Here for information and access details to all papers published in the IJV

PHPAIDA - The On-Line Natural Ventilation, Mixed Mode and Air Infiltration Rate Calculation Algorithm (Combined Stack, Wind and Mechanical Ventilation) Click Here for Tutorial Click here for ventilation rate calculations based on steady state CO2 concentration NEW! Click here for TRANSIENT AND STEADY STATE THERMAL MODEL FOR CALCULATING HOURLY INDOOR TEMPERATURE based on Indoor Heat Gain, Solar Gain, Ventilation and Thermal Mass Written by Martin Liddament PHPAIDA Input Form Location of Building:   City   Urban   Rural   Open Countryside Building Details: Building Height (m)        Top Ceiling Height (m)    Building Volume (m3)     Section 1: Natural Ventilation through User Defined Openings Flow Path 1:   height (m)   area (cm2) Flow Path 2:   height (m)   area (cm2) Flow Path 3:   height (m)   area (cm2) Flow Path 4:   height (m)   area (cm2) Flow Path 5:   height (m)   area (cm2) Flow Path 6:   height (m)   area (cm2) Flow Path 7:   height (m)   area (cm2) Flow Path 8:   height (m)   area (cm2) Flow Path 9:   height (m)   area (cm2) Section 2: Mechanical Ventilation Mechanical Extract Ventilation Rate (L/s) Mechanical Supply Ventilation Rate (L/s) Section 3: Air Infiltration Air Change Rate at 50 Pa (air change/hour)     Climate Data: Outdoor Temperature (Deg C) Indoor Temperature (Deg C)    Met Office (10m) Windspeed m/s

For full details order the Guide to Energy Efficient Ventilation Instructions: Enter data as indicated. Section 1 can be used in 'stand alone' mode (i.e. without data input to Sections 2 and 3). The maximum number of flow paths is nine and the minimum is two. Unused flow paths do not require data to be inserted. Section 2 must be used in conjuntion with either Section 1 and/or 3. Leave blank for natural ventilation (Section 1) or air infiltration only (Section 3) calculations. For balanced mechanical systems data are needed for both supply and extract ventilation. CAUTION: Always check that any installed fan can overcome the internal pressure generated by the fan as well as any pressure drop through ducting. The internal pressure is given in the output. Internal pressures of greater than 1000 Pa result in an error condition since it is unrealistic for intended applications. If high internal pressure occurs, the rate of mechanical ventilation is not compatible with the size of openings needed to relieve this pressure. Either reduce the mechanical ventilation rate or increase the size of openings. Section 3 can be used in 'stand alone' mode to calculate the natural infiltration rate for given airtightness (air changes at 50Pa) and weather conditions. It can be combined with Section 1 and/or Section 2 to determine how air leakage influences the overall ventilation rate of purpose provided openings and mechanical ventilation. When data entry completed click send. Edit and repeat process as required. Output: Flow rate and flow direction through each purpose provided path; whole building ventilation rate and air change rate; average internal pressure; air infiltration rate. Limitations: Purpose provided openings are based on orifice type openings (Cd=0.61); single zone well mixed; volumetric flow; uniform wind pressure coefficient on each face. The flow exponent is 0.5 for purpuse provided openings and 0.66 for infiltration openings. Opening area should never exceed the cross-sectional area of any connecting ducting. Exclusions: For approximate guidance only. The suitability of this algorithm for any particular application is neither implied or guaranteed. (Site operated by VEETECH Ltd. See main web site: www.veetech.co.uk for contact details and privacy statement.)