Proposals for additions and amendments
NEW APPROVED DOCUMENTS A AND C
These have now come into force and lo and behold a new set of queries and conflicts emerge. Two of these are discussed below, neither has reached the stage of having been finally and completely investigated and resolved. Comments from members would be greatly appreciated to help common policies into place.
Regulation A3 (General robustness and resistance to disproportionate collapse)
In most regards, and in housing in particular, this should only represent a continuation of what should have been done under existing code requirements and previous regulations. However its advent has prompted a closer scrutiny of these requirements and is leading many structural engineers to a more thorough approach to design and tying specifications. This is admirable but in some cases it is creating confusion of interpretation and producing conflicts with other requirements, such as sound insulation. The generally improved approach may on some occasions be delivering design in ways which are not easily compatible with some structural formats and party wall specifications and which might be held to be un-necessary.
The following commentary is offered in respect of housing.
Class 1: For low-rise traditional construction of masonry or timber frame the provisions of Sections 2 A to C of ADA or normal code standards for timber framing suffice.
However any MMC or innovative form of construction should be individually analysed for its needs, unless already proven.
Class 2A: It is this category that seemingly is producing the most questions, probably as it is seen as a new requirement whereas in fact it only requires the provision of the existing BS code recommendations for tying that should have already been specified even if they were not then a direct Building Regulation requirement.
The general BS requirement for masonry walling and concrete or timber floors is to provide effective horizontal ties or anchorage of suspended floors to walls around the entire periphery of horizontal elements, including internal walls, at 1.25m centres.
Some structural designers favour providing continuity of the ties from unit to unit across party walls.
Whilst this does improve the degree of robustness provided it is considered to be more than is called
for in this Class of building which could be considered as adequately designed by dealing with the periphery and internal walls of each unit (although there is some ambiguity as to what is meant by internal wall and the illustrations in Appendix C of BS 5628 shows ties running through internal walls which might be read as party walls).
Class 2B: This category falls within those buildings which were previously covered by old A3 and therefore should be subject to the same design regime. The requirement is either for horizontal ties as per 2A plus vertical ties as required in design codes, or to check and limit against the extent of collapse
occasioned by the notional removal of every individual column, beams supporting columns and load bearing wall elements.
Class 3: Over 15 storeys and subject to wide overall consideration and design.
Further debate can be expected on this subject, in the meantime NHBC have issued some guidance, which follows the above but somewhat glosses over the question of what is the periphery.
Regulation C2 (Weather resistance of window reveals)
ADC Section 5 contains some confusing and conflicting advice at section 5.32.
This basically recommends the use of 25mm checked rebates to all window and door openings in Driving Rain Exposure Zone 4, as illustrated in Diagram 13. However Diagram 13 then refers to such reveal details applying in areas of severe and very severe exposure, i.e. Zones 3 and 4. The latter combination embraces a considerable geographic portion of England and Wales and covers massive areas where the use of checked rebates is not and never has been traditional practice. Nor is it considered by many, whilst acknowledging the potential benefits offered by checked rebates, that it is entirely necessary to build in this manner.
An alternative is offered by the use of a “finned” insulated cavity closer. “Finned” is however not defined and there is according confusion as to what cavity closers are deemed to be suitable as an alternative under this term.
This does seem to have been a rather unplanned change as there is a very low awareness of the issue
and the window frame industry does not seem set to be able to accommodate the considerable impact it could have on their design and production.
Nor does the 5.32 advice follow consistently through from the old BRE document “Thermal Insulation:
avoiding risks”, neither does it correlate with the more recent Robust Details.
I am writing to ODPM to seek further clarification and advice.
PUBLICATION OF NEW ROBUST DETAILS FOR SOUND INSULATION
Four new options will come into effect on 24 January 2005
These are:
· E-WM – 7 Masonry separating wall – Aircrete thin jointed blockwork with render and gypsum based board finish
· E-WS – 3 Steel framed separating wall (modular steel framed housing)
· E-FC – 3 Precast plank separating floor with floating screed
· E-FC – 4 Precast plank separating floor with Thermal Economics Iso Rubber system and floating screed
Additionally amendment is made to E-WM – 3, E-WM – 4 and E-WM – 5 to allow
· British Gypsum Sound Coat to be used as an alternative to sand/cement parge coat
All existing owners of the RD Handbook will be receiving free updated pages and inserts.
Innovations in wood fuels and boilers
Considerable strides are now occurring in the introduction and development of the use of sophisticated forms of wood fuels. In the main this is picking up on the technology that is quite common in central Europe and Scandinavia.
Fuel formats include wood chip, briquettes and wood pellet fuel. The latter is probably the most important in that its fine quality and sizing enables exact combustion technique, constant and uniform
fuel feed, and instantly responsive on/off ignition. It therefore allows for controlled burning like any other normal fuel and therefore ready usage in automatic domestic boiler situations.
Also a significant number of large boiler installations are converting to wood fuels and some are being set up to be of dual fuel usage.
Wood fuels have a number of attributes that are likely to find favour in today’s world of seeking energy efficiency and environmental benefits. This is a feature that could be readily recognised and captured by new Part L.
Wood pellet fuel can deliver:
· high combustion efficiency rates (80 – 90%)
· is a renewable energy source
· Carbon Neutral
· Even allowing for the carbon emissions generated by its production wood fuels reduce total carbon emissions of comparative fuel use by over 90%
The industry is developing and where established in other countries there does exist authoritative
sources of technical verification and national codes and guidance.
However as yet BS and Euro codes do not formally or fully cover all aspects of the technology. UK Building Regulations apply to these installations but similarly ADJ does not at present contain any specific guidance.
ADJ would classify wood burning boilers as Solid Fuel appliances and any installation should follow both the generic parts of ADJ plus the special provisions relating to solid fuel appliances. Some of the continental practices which may be flowing into the UK market, such as balanced flues, direct exhausts, and small diameter flue pipes do not meet with ADJ standards for solid fuel installations.
There is accordingly a need for the science and standards to be further investigated and formulated in a UK sense, and to become integrated into ADJ, together with fuel efficiency factors being established under draft Part L. In the meantime there may be scope for the creation of nationally
agreed interim standards and policies based on sound scientific or Euro empirical evidence.
Until such time that either of these steps has been concluded all installations should be checked for full compliance with existing ADJ recommendations for Solid Fuel Appliances.
Whilst domestic cases of the installation of wood fuel boilers do fall under the remit of the HETAS Competent Persons Scheme it should be noted that HETAS have not approved any such boiler
systems and that they would have to similarly require full ADJ compliance.
It should also be noted that wood fuels are not generally classified as Smokeless and therefore care is needed in respect of appliances in Smokeless Zones.
Part F (Ventilation)
The consultation on the draft proposals for new Part F closed a month or so ago. The responses are now under review and it transpires that there was only a very low level of response. This is a little worrying as it is an issue that could have some hidden consequences and it accordingly deserves
and perhaps need a wide scrutiny in order to ensure it achieves a balanced outcome.
LABC Services submitted a response and this can be sent to any member upon request.
I
t is expected that new ADK will come into effect on I January 2006 in conjunction with ADL with which it has been heavily influenced, perhaps overly so.
Main points of the proposals are:
· Moves from prescriptive one size fits all ventilation areas of opening to a performance based approach
· More reliance on background ventilation and balanced air transfer around the building
· Generally will require larger background vent sizing
· Allows for specific design of amount of window opening for rapid ventilation (now termed Purge ventilation) depending upon the opening nature and height of the window
· Gives more detailed guidance on different systems of ventilation
· Includes guidance on ventilation of basements and single aspect dwellings
· Ventilation of enclosed rooms remains the same principle
· Quotes far more guidance on ventilation performance standards for offices
· Includes comprehensive list of design guidance sources for other building categories
· Has a half baked requirement for background ventilation to be provided in refurbishment and replacement scenarios
· Roof ventilation (old F2) transferred to ADC
Comments/concerns expressed via consultation:
o Considered to follow the linked needs generated by new Part L too narrowly, does not develop or encourage the role windows and attendant features and controls can play in total energy efficiency and environmental comfort
o Does not consider the wider accommodation role and human purpose of opening windows
o Can result in very small opening window areas (as low as 2.6% floor area)
o Within the design approach is there not a case for a minimum size of window opening %?
o Fails to make sufficient cross reference to other regulatory, or necessary, requirements, e.g. fire egress, security, cleaning, car park risks, etc. Has become far too complicated in its application
o Disjointed document with linked design reference sections scattered all over the place
Team Talk 9 December 2004
o Guidance on little used systems gets in the way of mainstream usage
o Internal air transfer encourages conflicts with the integrity of fire doors
o Demands reference to an over large portfolio of other guidance documents
o There is probably a need for a sectoral AD on all aspects required of windows
PART L (CONSERVATION OF FUEL AND POWER)
A
consultation of massive impact and important consequence. A large number of responses were
received to this consultation and ODPM/Faber Maunsell are currently assessing these.
LABC Services submitted a response and this can be sent to any member on request.
The proposals include many hard targets and challenges, much debate is being generated and the
whole process is a learning curve for all involved that will go on long past the consultation period.
It is expected that new ADL will come into force on 1 January 2006, and EU law is requiring that most of the core measures be in place by 2006.
Much has to be done in the intervening year, including bringing into place some of the large-scale fundamental features of the proposal.
Everybody stands to be effected including Building Control in no small measure. We are seen as being vital to the successful implementation of ADL. There is a high expectation on Building Control to deliver, particularly as there exists some perceptions that current ADL has faltered in part due to difficulties in our domain.
This is a misplaced viewpoint as many other non Building Control, but far more critical factors, have been the cause of the uncertainties and patchy implementation surrounding the 2002 edition.
Pleasingly the current initiative is being shaped in a way that looks to succeed and to learn from any previous mistakes across the board. It is recognised that much planning and training is necessary and that full-scale support is needed to facilitate this into place. Time is however very tight.
General
· Looks to initially reduce carbon emissions from buildings by 25-30%
· In longer term will aim for 60% reduction
· Implements the Energy Performance of Buildings Directive
· Requires Energy Certification of Buildings when new, at points of sale and tenancy changes
· Will impose ongoing controls over certification, maintenance and monitoring of energy use
ADL1A (new dwellings)
· Requires all dwellings to follow whole building compliance approach via the singular allowed
use of SAP2005 as the design tool
· SAP and Energy Certificates can only be produced by accredited and independent energy assessors
· Hence the Elemental, Target U value, and Carbon Index methods of design and checking are deleted
· SAP 2005 allows for flexible gathering and deployment of all construction and energy
features and benefits
· Some minimum U-value fabric requirements are retained as long stop against any temporary failure of energy features and to prevent fabric degradation
· Checks against solar overheating
· DCER as calculated by SAP2005 should not be worse than TCER derived from core features of proposed dwelling as set out in AD (18+lighting factor) x floor area, shape and fuel factors)
· 7 step compliance verification process
· Compliance check list to be completed, monitored and verified
· Control of thermal bridging
· Air tightness testing required (reasonable but fairly extensive sampling), TM23 and only by ATTMA certified testers
· Services to be commissioned
· Certificates to be submitted in support of compliance check list
· Allows for development of “Model Designs” (via LABC Services Type Approval) as an
alternative to some requirements
· Possible role for Robust Details
ADL1B (work on existing dwellings)
· Widens the definition of building work to include the thermal envelope of buildings as a controlled element
· Keeps simple rules for elemental u-values and % limits on openings as the design medium
· Brings in new requirement for energy improvements to existing buildings to be undertaken when works are conducted costing £8k or more
· Energy improvements linked to 7 year pay back period and 10% marginal cost limits
· Energy improvements to be subject of survey, analysis, preparation of schedule, submission
with Building Regulations application and implementation and enforcement
· Energy Certificates, HIP information to be updated when works carried out to existing buildings
ADL2A (new buildings other than dwellings)
· Requires carbon emissions of proposed building to be no more than a similar notional building
performance based on ADL2 2002 edition elemental standards plus stipulated improvement
factors (as much as 30%)
· Calculations must be carried via stipulated design tool by accredited and independent energy
assessors
· 7 steps compliance verification process
· Compliance check list to be completed, monitored and verified by Building Control
· Thermal bridging and continuity of insulation controls are to be exercised
· Worst acceptable elemental U-values are included
· Pressure testing required to all buildings, with the exception that buildings <500m² need not
test if they assume for calculation purposes a poor air tightness figure
· Ductwork to be tested for air leakage
· Services to be inspected and commissioned
· Building Log Books are required
· Energy Performance Certificates should be provided
· Energy meters must be installed
ADL2B (work in existing buildings other than dwellings)
· Very much as ADL1B in general principle and coverage, including energy improvements
· But extensions over 100m² are to be treated as new build
· More detailed controls over services and air conditioning
Comments/Concerns
· There is a relatively short space of time for everything to be formulated, understood and to be
put into place
Information supplied from LABC Teamtalk December 2004 |
