Online Seminar Questions - Materials
To help you understand the Code for Sustainable Homes, The Concrete Centre and our technical team have produced answers to the questions we have recieved from the online seminar.
This section will cover all questions relating to materials, the Green Guide and responsible sourcing.
1. "Can you describe the pollution produced by the manufacturer of concrete products?"
Response - Colin Marshall, Tarmac Topblock: "In common with most manufacturing processes concrete block production cannot claim to have no environmental impact, however, all of Topblock’s plants operate to ISO 14001 Environmental Management System, third party certified by the British Standards Institute. The certification number is EMS 507669. These schemes include detailed measures to control environmental impacts and limit the potential pollution from any accidental events.
The main environmental impacts of block production have been assessed by BRE using their validated life cycle analysis methodology to produce environmental profiles that are available on the BRE website at www.bre.co.uk . This methodology assesses a wide range of impacts right through from raw materials production, transport to our site, and the manufacturing process: so called 'cradle to gate'. Such issues addressed will include climate change, pollution to air, pollution to water, minerals extraction, waste disposal etc. This analysis is then taken further to assess the impact of the blocks when they are transported to site, used in construction and how they perform in a building over a 60 year life. Disposal methods will also be considered.
We believe this is the most complete method to assess all impacts and would encourage you to consult the BRE website for more details. The data on the BRE website will be updated during the summer of 2007 to take account of the latest environmental data available."
2. "The Zero Carbon option of brick slips or cladding is unlikely to be acceptable to a nation of traditional brick construction. How will full brick outer leaf construction be addressed with blockwork inner leaf. Are there prospects of improved insulation - better than the polyisocyanurates?"
Response - Colin Marshall, Tarmac Topblock: "The option of a solid wall using Durox or other Topblock products with external insulation was given as a practical solution to accommodate the increased thicknesses of insulation using technology and materials currently available. Cavities will, of course, be retained, but are likely to be increased widths. Whilst, at the moment, the use of external insulation lends itself more to rendered finishes, there a wide range of brick slip options available and there is no doubt that sales will grow over time, and reduce in cost as demand increases.
As concrete block manufacturers, we are not best placed to answer the question of improved performance of thermal insulation products, but it does appear that phenolic foam boards (conductivity = 0.021W/mK) are perhaps the best we can achieve at present."
3. "What alternatives are available to standard concrete blocks?"
Response - Colin Marshall, Tarmac Topblock: "As an alternative to the use of standard concrete blocks, why not consider the use of Durox System thin joint construction. Durox System comprises large format Durox units which are laid in a specially formulated thin layer mortar. Many advantages result including the rapid construction of walls as, unlike conventional masonry, there is no restriction on the height of walls that can be constructed in a day. The build speed is such that floor and roof elements can be readily programmed with predictability making the construction of a watertight shell very swift. This will allow service and finishing trades to commence their work sooner. Durox System is regarded as a 'Modern method of construction', and has been widely used in private and Government funded housing schemes as well as commercial developments. More information is available from www.topblock.co.uk or please contact us again if you would like a Brochure / DVD sent to you."
4. "I am concerned that if solid blocks with a rendered finish are used the homes will have a blandness due to the difficulty of including stone string courses, quoins and other features. What do you have to say about this?"
Response - Colin Marshall, Tarmac Topblock: "The use of external insulation on to solid block walls offers many advantages, not only on the energy front due to low U-values and high thermal mass offered, but also because it enables a variety finishes or claddings to be applied. These can range from timber or tiles on battens to proprietary renders or brick slip claddings to give a more traditional feel. It is also possible to introduce quoins or other contrasting features. There are a number of manufacturers in the UK who can supply these systems, many of whom are members of INCA "Insulated Render and Cladding Association" - see http://www.inca-ltd.org.uk/register-members.htm for a list of their members.
The website also gives case studies showing examples of the finishes which can be achieved via http://www.inca-ltd.org.uk/case-studies-1.htm.
5. "Where do you get the Materials Calculator? I've searched around trying to find the download."
Response - Colin Marshall, Tarmac Topblock: "The Code for Sustainable Homes' Materials Calculator is a Building Research Establishment (BRE) spreadsheet based tool designed to simplify assessment of the Materials Credits. Access is provided to BRE's licensed Code Assessors."
6. "Some builders do not always favour aircrete blocks due to the difficulty of fixing kitchen units, electrical wall sockets and staircase handrails etc. Can these difficulties be overcome?"
Response - Colin Marshall, Tarmac Topblock: "Aircrete is the most widely used of all masonry materials in housing. It is used by national housebuilders through to smaller builders for the construction of extensions and the like. It has become a very familiar material and through a combination of experience and the technical advice given by aircrete manufacturers such as Tarmac Topblock, fixings into aircrete have become quite straightforward. In many cases standard plugs and screws will be sufficient for most lightweight and medium weight fixtures. A useful tip is to avoid oversize drill holes - slightly under sized is better to give a more secure fixing. For heavyweight items - and kitchen units may fall into this category - specially designed plastic plugs are available from manufacturers such as Fisher Fixings, These have been designed to provide a greater weight bearing capacity. These types of plugs are readily available through builders merchants and DIQ stores. For securing lightweight items such as skirtings, timber battens etc, it is possible to directly fix these to aircrete using spiral nails or similar e.g. 'Helifix'.
7. "As a social housebuilder needing to comply with NHBC all our cavities must be at least 50mm clear. None of your examples for Code Level 3 compliance show this-can you suggest a wall make up to achieve U 0.25W/m2K on a 100mm cavity with 50mm clear ventilation?"
Response - Colin Marshall, Tarmac Topblock: "It certainly becomes more challenging to meet lower u-values using current constraints on cavity width etc. However a typical solution using Durox (or Toplite equivalent) would be:
Facing brick, 50mm clear cavity, 50mm Kingspan Kooltherm K8 partial fill, 100mm Durox Supabloc 3.6N, plasterboard of lightweight plaster finish internally.
U-value = 0.25W/m²K
There may be other requirements, such as a need for a higher strength block, or perhaps a flanking sound insulation requirement, which may require the use of an alternative Topblock product. If you have any additional specification requirements please advise and we will confirm or otherwise compliance."
8. "Is the Green Guide 2007 now available?"
Response - Colin Marshall, Tarmac Topblock: "The Green Guide 2007 is expected to be published towards the end of 2007. However, revised ratings have been issued to registered Code Assessors by the Building Research Establishment as an interim measure. We will be including Green Guide Ratings that are applicable to concrete block construction on our Web Site shortly. www.topblock.co.uk."
9. " Are 'material miles' likely to become as hot a topic as 'food miles' have - will we be encouraged to source materials locally?"
Response - Colin Marshall, Tarmac Topblock. "In the UK, Environmental Profiles are increasingly being used to allow level playing-field comparisons of building materials. Environmental Profiles consider a number of environmental impacts including transport pollution and congestion. There is broad consensus that to make consistent holistic judgments about the environment, making decisions on single issues such as transport miles is not really practicable. The Code for Sustainable Homes does recognise the impact that materials have on the environment, and we support this approach through the use of element ratings (A, B, C etc.) based on the environmental profiling methodology."
10. "How will specifiers be able to find out and check the veracity of a given product's level of responsible sourcing?"
Response - Colin Marshall, Tarmac Topblock:" We envisage that initially specifiers and builders will have to rely heavily on the claims made by material manufacturers. This could be in the form of declarations in product literature and on manufacturers web sites. In many cases such claims will be required to be supported by evidence such as environmental management system (EMS) certificates. Indeed we are providing copies of our own EMS certificates in increasing numbers as the Code becomes more widely used. The Code assessment procedure relies on a lot of evidence being collected. It is inevitable that we will have to disseminate information on responsible sourcing and other elements of the Code in the most efficient ways possible. In addition to the efforts of manufacturers, certification bodies also have a role to play in allowing easy interrogation of manufacturer's certification details.You are probably aware that the concrete industry is in discussions with the Building Research Establishment about a sector scheme for responsible sourcing, which we hope will reflect much of the work already undertaken by manufacturers in the concrete sector in legally and responsibly sourcing their."
11. "The Materials Category also mentions Responsible Sourcing. What does this mean?"
Response - Colin Marshall, Tarmac Topblock: "This aspect is concerned with promoting the specification of responsibly sourced materials for the basic construction as well as finishing elements. In this context responsible sourcing means using materials that are produced and traded legally and ethically and with due regard to environmental, social and economic impacts throughout the supply chain. Although this aspect was originally developed to try to address concerns over the illegal logging of timber, the requirements apply to all materials. Compliance is based on a graded ('Tier levels') scale to reflect the rigour of the compliance scheme used to demonstrate responsible sourcing.The majority of our raw materials, about 95%, are sourced from within the UK from companies operating within the rigorous framework of UK legal and environmental requirement. Most of our suppliers operate an Environmental Management System (EMS) that provides a high level of assurance regarding the legality and responsible sourcing of the materials we use to manufacture our products. All Tarmac Topblock production sites operate a BSI Certified EMS, enabling the point available for Tier 4 to be utilised. Currently the concrete industry is working in consultation with the Building Research Establishment towards a concrete products sector compliance scheme which will eventually allow us to achieve maximum points available."
12. "Category 3 (materials) awards points based on the environmental impact of the construction. How do Tarmac Topblock products perform in this area?"
Response - Colin Marshall, Tarmac Topblock :"The minimum requirement at Code Level 1 is for at least three of the key elements (walls, floors etc.) to achieve a rating of at least D in accordance with the 2007 Green Guide to Housing. Beyond this points can be gained for constructions with a B rating and above. In fact many Topblock constructions used in beam and block ground floors, external and internal walls will achieve an 'A' rating so will help considerably towards meeting the required Code Level."
13. "What about external works on new housing developments are these materials covered by the Code?"
Response - Colin Marshall, Tarmac Topblock: "The materials used in external works are not covered by the Code for Sustainable Homes assessment. The development of the Code was based on the Building Research Establishment's (BRE) EcoHomes rating scheme for homes. Unlike EcoHomes, the Code does not take into account site related features and is very much focused on the environmental performance and operation of the dwelling itself."
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