Air permeability 5 is the magic number

sinnerboy

From

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf

Air permeability of Q50/5 is a key datum .

When using natural ventilation ( holes in walls )

1.2.2.1 Where the air permeability is
5m3/(h.m2) or greater, the minimum total
equivalent area of background ventilators
providing general ventilation should be 30,000
mm2 with an additional 5,000 mm2 for each
additional 10 m2 floor area above the first 70m2
of floor area measured. For single storey
dwellings situated at ground level or on any
storey up to four storeys, an additional 5,000
mm2 per dwelling should be provided. Where
air permeability is less than 5m3/(h.m2) all
equivalent areas stated above should be
INCREASED by 40%.

(I have edited the word "increased" to read in caps )

When using MVHR

1.2.3.2 The minimum capacity of a
Mechanical Ventilation with Heat Recovery
system should be based on the calculated
general ventilation rate, adjusted to allow for
air infiltration due to permeability of the
building fabric. The calculated general
ventilation rate is determined as the greater of
a) 5 l/s plus 4 l/s per person, e.g. 25 l/s
for a five person dwelling. This is based on
two occupants in the main bedroom and a
single occupant in all other bedrooms.
This should be used as the default value if
a greater level of occupancy is expected,
then add 4 l/s per occupant.
Or
b) 0.3 l/s per m2 internal floor area, e.g.
30 l/s for a 100 m2 dwelling.
The adjustment to the calculated general
ventilation rate to allow for air infiltration is
0.04V (l/s), where V is the gross internal
volume of the dwelling in m3.

Where the air permeability is 5m3/(h.m2) or
greater, the ADJUSTMENT IS DEDUCTED from the
calculated general ventilation rate to give the
minimum capacity of the Mechanical
Ventilation with Heat Recovery system.
Where the air permeability is less than
5m3/(h.m2) NO DEDUCTION is made.

(I have edited the words "adjustment is deducted" and "no deduction"to read in caps )

sinnerboy

... if you plan an air permeability strategy to exceed Q50 /5 and you don't use HRV ..... your efforts will be rewarded by having enlarge your holes in walls . And you will be loose more heat .

No6

but take into account the transitional arrangements


Transitional Arrangements
In general, this document applies to works, or
buildings in which a material change of use
takes place, where the works or the change of
use commence or takes place, as the case may
be, on or after 1 October 2010. Technical
Guidance Document F Ventilation dated
2002, also ceases to have effect from that date.
However, the latter document may continue to
be used in the case of buildings
- where the works or the change of use
commences or takes place, as the case
may be, on or before 30 September
2010, or
- where planning approval or permission
has been applied for on or before 30
September 2010, and substantial work
has been completed by 30 September
2011,
- or a notice pursuant to Part 8 of the
Planning and Development Regulations
2001, has been published on or before
30 September 2010, and substantial
work has been completed by 30
September 2011.
“Substantial work has been completed” means
that the structure of the external walls has
been erected.

At the rate things are going there will be no houses built under these regs at all!!!:eek:

.

sydthebeat

these bloody transitional arrangements are ridiculous.

just put a single date implementation, say 1st jan 2011.

'substantial completion' before can be 2002 regs, anything after 2010. It never ceases to amaze me how convoluted DOE makes these things.