Differences

This shows you the differences between two versions of the page.

--- planning:building_services:ventilation:differentiation_between_vv_and_vn50_values [2023/01/30 11:28] – [V<sub>n50</sub> – Net air volume for pressurisation test] zbastian
+++ planning:building_services:ventilation:differentiation_between_vv_and_vn50_values [2023/01/30 11:52] (current) – [Vn50 – Net air volume for pressurisation test] zbastian
@@ Line 25: / Line 25: @@
 ===== Vn50 – Net air volume for pressurisation test =====
-The air volume V<sub>n50</sub> within the heated building envelope is the volume that will be used for calculating [[planning:airtight_construction:general_principles:blower_door_test|the n50 air leakage value]]. It is supposed to indicate the //actual// volume of air that will be heated or cooled within the building and should be calculated separately for each room. The calculation should be carried out in accordance with detailed rules given in the Criteria for Buildings, section 3.2.10 Airtightness of the building envelope.
+The air volume V<sub>n50</sub> within the heated building envelope is the volume that will be used for calculating [[planning:airtight_construction:general_principles:blower_door_test|the n50 air leakage value]]. It is supposed to indicate the //actual// volume of air that will be heated or cooled within the building and should be calculated separately for each room. The calculation must be carried out in accordance with detailed rules given in the [[https://passivehouse.com/downloads/03_building_criteria_en.pdf| Criteria for Buildings]], section 3.2.10 Airtightness of the building envelope.
-==== Calculation methodology ====
-The base area of each room should be multiplied by the average clear height of the room. Overall assumptions for determining the internal volume of the enclosed space (gross volume) by means of a reduction factor are not permissible. \\
-The base area to be used for this calculation differs from the treated floor area (TFA) which is normally used.  The TFA follows certain rules and applies certain percentages for considering areas from the energy use point of view. The base area for consideration the V<sub>n50</sub> value considers all net areas within the building, as can be seen in the example below (Figure). Irrespective of the degree of completion of the building during the airtightness test, the dimensions used should always be those of the finished building (e.g. where there is no screed).
-As mentioned before, the V<sub>n50</sub> value is supposed to depict the actual volume of air that will be heated or cooled. According to the norm, air volumes above suspended ceilings do NOT count towards the total air volume. This is a means of simplification of the calculation and it is so regardless of whether the ceiling already exists, is tightly connected with the wall, or has different types of holes (“acoustic ceiling”). The reduction of the volume by layers of plaster does not have to be taken into account. From a practical perspective, this approach makes it possible to determine the air volume in existing buildings even without plans.
-A full and comprehensible room-by-room calculation of the volume must be provided for each airtightness measurement. Auxiliary calculations may also be necessary; these must also be provided. For example, in the case of inclined roofs, the air volume is determined by means of triangular or prism calculations.
-Visible rafters, beams, plasterboard encasings, wall-mounted installations (if these do not have the same height as the room) and the like are not taken into account; in the calculation they are not deducted for simplification. They are thus treated as if they did not exist (= air space).
-The volume of window reveals is not taken into account either (measured only up to the inner wall surface). The same applies in the case of doors and openings. Please note that these stipulations are for the purpose of simplification. Any deviations occurring as a result are usually small.
-Moreover, the volume of a stairwell is part of the air volume and is fully taken into account.
-Therefore, the base floor area of the stairwell is simply multiplied by the clear height of the storey. The volume for flights of stairs and intermediate landings does not have to be subtracted.
-The air volume of elevator shafts and of any other kind of shafts inside the thermal envelope is part of the Vn50 and is fully taken into account. The volume of the elevator cabin as well as of pipes, ducts etc. themselves counts as part of the Vn50 in a simplified way and is not deducted. The base area of the shaft can thus be multiplied with the clear height of the storey.
-----
 ===== Example =====