2.4 Ventilation flow rates
Table 1.
ADF 2010 – Extract ventilation rates
Room
Min high rate
Min low rate
Kitchen
13 l/s
Utility room
8 l/s
Bathroom
8 l/s
Sanitary
accommodation
6 l/s
Table 2.
Whole dwelling ventilation rates
Number of bedrooms in dwelling
1
2
3
4
5
Whole
13
17
21
25
29
dwelling
ventilation
rate l/s
1, 2
Notes:
1, In addition, the minimum ventilation rate should be not less than 0.3 l/s
per m2 of internal floor area.
(This includes all floors, e.g. for a two-story building add the ground and
first floor areas).
2, This is based on two occupants in the main bedroom and a single occu-
pant in all other bedrooms. This should be used as the default value. If a
greater level of occupancy is expected add 4 l/s per occupant.
2.5 ADF 2010 Ventilation calculations
Design of MVHR systems
The MVHR system has been sized for the winter period.
Additional ventilation may be required during the warmer
months and it has been assumed that the provisions for purge
ventilation (e.g. openable windows) could be used.
Step 1:
For any design air permeability, determine the whole
dwelling ventilation supply rate
from Table 2.
As an alternative where the design air permeability is intended
to be leakier than (>) 5m
3
/(h.m
2
) 50 Pa, allow for infiltration
for all dwelling types by subtracting from the whole dwelling
ventilation supply rate
from Table 2
; 0.04 x gross internal
volume of the dwelling heated space (m
3
).
Step 2:
Calculate the whole dwelling extract ventilation rate by
summing the individual room rates for ‘minimum high rate’
from
Table 1.
(For sanitary accommmodation only, as an alternative, the
purge ventilation provisions given in ADF 2010 can be used
where security is not an issue. In this case ‘minimum high
extract rate’ for the sanitary accommodation should be omitted
from the step 2 calculation).
Step 3:
The required airflow rates are as follows:
n
the maximum whole dwelling extract ventilation rate
(e.g. boost) should be at least the greater of step 1 and
step 2.
Note that the maximum individual room extract rate should
be at least those given
in table 1.
for minimum high rate.
n
the minimum air supply rate should be at least the whole
building ventilation rate found in step 1.
For Scotland refer to BRE Digest 398.
For further information refer to “Domestic Ventilation Compliance
Guide” www.planningportal.gov.uk/buildingregulations/approved
documents/partl/compliance
3
27. 11. 17. Leaflet Number 671582
Installation and Maintenance
MRXBOX95B-LP1 Mechanical Ventilation with Heat Recovery & Summer Bypass
Any air intake terminal MUST be installed in accordance with the
appropriate regulation.
As a guide, the BS5440 series of British Standards deals with this
issue and currently states that an air intake must be at a minimum
distance of 300mm from a gas boiler balanced flue.
Installers are advised to be aware of the requirements of this
standard when installing ‘through the wall’ supply air ducting.
Pre Commissioning MRXBOX95
MVHR Units
MRXBOX95 units are designed to ventilate the whole
dwelling and must not be used during site construction
or the clean-up period. Cement and plaster dust can be
abrasive and can affect fan performance and reliability.
Please ensure that the filters are checked prior to
commissioning to ensure there is no build-up of dust or
debris.
While the property is drying out, very high moisture levels
are likely to occur. Therefore it is advisable that if the
installation and building works are complete the unit is
left running. If the building works are not complete please
close the air valves or cover up the air valves to prevent
condensation forming in the ductwork and the
MRXBOX95 unit due to natural migration of warm air.
Total extract rate should
be at least the whole
dwelling ventilation rate
given in table 2.
