| Airtightness NI E-Newsletter |
September 2007 - Issue 1 |
Welcome to Northern Ireland’s first e-newsletter on Airtightness! We promise to keep it short, informative
and, most of all, relevant to you, Northern Ireland’s construction professionals.
Most of you are probably aware by now that Anderson Mechanical Services (AMS) have linked up with the
Building Services and Research Company BSRIA to provide an airtightness testing service both here in Northern
Ireland and the Republic.
Since the introduction of the new Building Regulations in November, AMS have carried out 21 commercial and
13 domestic tests, and already a pattern is forming – namely, the lack of awareness to airtight details in
commercial applications (and the consequent initial test failure) and the relative ease to which houses are
meeting the criteria. Problems, problems…
Two retail units tested recently are good examples of what we are likely to encounter for a while until
airtightness is embraced as an integral facet of design, or at the very least given some consideration by
Designers - most reasons for failure have been attributable to situations easily avoided with a few simple
details.
 |
The responsibility for airtightness must start with the
Designer or Architect who should first specify his leakage
target based on normal or best practice tables according to
the building type and the Target Emission Rating (TER).
He should then denote the air seal line and mark it on the
drawings – the builder will then be in no doubt as to what is
required of him. This air barrier must be continuous, robust
and buildable and due consideration given where it changes
direction, trade or material (see picture left). |
Specific areas that often cause problems include junctions of wall and/or roof cladding, flashings and cills to
shopfronts/curtain walling, service riser shafts, excessive block leakage, expansion joints, dry-lining and
external doors and roller shutters. A more detailed path to achieving airtightness is outlined in BSRIA’s guide
to Part F2 of the Building Regulations, freely available to download by clicking here.
- Steel/block junction adequately sealed?
- Mastic seal beneath metal sole plate on wall?
- Leakage rate through rough unplastered block?
All issues that should have been addressed before now! |
 |
Consultancy
Russell Brothers are currently building a warehouse/office for Blair Neill Ltd in Newtownards and chose to take
advantage of a drawing review service during design stage.
Because of the relatively simple nature of the build, no low-scale details were shown on the drawings which
would have effectively left responsibility for airtightness in the hands of
the Site Supervisor and his Sub-contractors.
As Steel Structures NI had
been appointed as the specialist steel and cladding Sub-contractor by
this stage, liaising with them ensured details had been agreed prior to
commencement on site. |
Eaves detail, showing butyl strip
on roof sheet lap and double strip
on purlin.
|
AMS are also carrying out regular site inspections throughout the build
and will carry out a full airtightness test near completion in December
2007. Russell Bros meanwhile can concern themselves with other
matters, safe in the knowledge that everything is being done to ensure
the integrity of the air barrier and that a result well below the Building
Control requirement of 10m3/(hr.m2) should be achieved.
Domestic
Domestic tests carried out in recent months for the likes of Patton Homes, FT Ferguson & Co, MMM Design &
Build and Antrim Construction have shown that meeting the maximum air leakage criteria as set out in the
Building Regulations is not particularly onerous.
 |
All the houses tested to date had been built without any specific consideration given to
airtightness, yet none have come close to failing, the worst result being just under
7m3/(hr.m2) and the best, a ground floor apartment at 2.6m3/(hr.m2).
The traditional plastered block style of construction most common in Northern Ireland
is a factor in this, as studies have shown that dry-lined block walls (more common
across the channel) offer more potential paths for air leakage.
This is not true of
timber-frame construction however which is potentially capable of producing the best
results due to the use of prefabricated panels, vapour barriers etc. |
Anything else?
Plenty, but that’s probably enough to digest for now. Although I will mention that those of an Architectural
bent might be interested in reading a case study of the implications airtightness requirements had for an office
block in Newcastle-upon-Tyne, the first non-domestic building in the city to undergo a test back in 2002.
Written by members of the design team who had little experience or knowledge of airtightness at the time, it
may prove useful to construction professionals here in Northern Ireland where airtightness is a relatively new
concept. It can be downloaded from here and queries, enquiries or
general comment should be directed to
David Anderson, Anderson Mechanical
Services
Mobile: 07802 259 489
Email: david@andersonmechanical.net
|
