June 2010 - NHBC Home

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Sustainability Extra NEWS The Code for Sustainable Homes: Case studies Three years on from the introduction of the Code for Sustainable Homes, the Department for Communities and Local Government (CLG) has published its second volume of case studies showing examples of five developments designed and built to comply with the Code. The examples cover a range of development types built in both the private and affordable sectors to achieve between Code Levels 3 and 6, using various construction methods. The case studies summarise builders’ experience of working with the Code. Amongst the comments included is that “unsurprisingly, those projects that planned to build Code homes from the outset found it easier to meet the requirements rather than adapt homes that had been designed to a different standard, as there are significant differences between the Code and previous standards” – a useful tip for builders who have yet to confront the challenges of the Code. The document is available for free download from: http://www.communities.gov.uk/publications/ planningandbuilding/codecasestudiesvol2 Code for Sustainable Homes: A cost review This review published by CLG in March updates the Impact Assessment produced in November 2007 that analysed the costs and benefits of introducing Code ratings on a mandatory basis. This study considers the extra-over cost of building to the Code above constructing homes to comply with building regulations. Four dwelling types were modelled, combined in a variety of ways (in terms of number of dwellings, dwelling mix and dwelling density) to create development scenarios and cost data were obtained through a direct consultation with the house-building industry. The overall finding is that there is significant variation in the extra-over costs at each Level of the Code between the dwelling types and across the development scenarios. Typically, however, the extra-over costs expressed as a percentage of base build cost are: Code Level Extra-over cost 1 Less than 1% 2 1-2% 3 3-4% 4 6-8% 5 25-30% 6 30-40% The report is available from the CLG website at: http://www.communities.gov.uk/publications/ planningandbuilding/codecostreview HB2503 06/10
Issue 47 June 2010 Regulations changes A new requirement to Part F means that where possible, fixed mechanical ventilation systems require testing and commissioning. In addition, for both intermittent and continuous mechanical ventilation installations, air flow should be measured. This would include cooker hoods for kitchens and extract fans to bathrooms. Details of this data must then be sent to the Building Control Body within five days of completion, adding another procedure to follow at the completion stage. It is also a requirement to hand over sufficient information to the building owner in relation to the systems installed in a new dwelling. Main changes As mentioned above the most significant change is to dwellings with air permeability of less than 5.0m 3 /(h.m 2 ). By choosing a continuous mechanical extract system, Part F 2010 now removes the need for background ventilation in dwellings designed with air permeability rates above 5.0m 3 / (h.m 2 ). There are also benefits in SAP 2009 for continuous systems, which may lead designers to adopt whole house mechanical extract ventilation systems, possibly including heat recovery as well, which would maximise the SAP benefits. If using passive stack ventilation, internal pipes should now be sized at 125mm diameter serving all spaces, an increase from the Part F 2006 requirements. Published alongside the new regulations is the Domestic Building Services Compliance Guide, in which a new requirement for specific fan power of less than 0.5 watt/sec applies for intermittent extract fans. ACTION Part J 2010 – Combustion appliances and fuel storage systems Introduction There are a number of changes in the new Part J 2010 beyond those relevant to the new requirements of Part L 2010, the most significant change is the requirement for carbon monoxide alarms in dwellings with fixed combustion appliances. There is new guidance on protection to oil tanks, external vertical flues, access to concealed flues and additional ventilation requirements for open flued appliances in dwellings with air permeability of less than 5.0m 3 /(h.m 2 ). Main Changes There is now a requirement to provide a carbon monoxide alarm to dwellings with a fixed combustion appliance, although the Approved Document guidance applies only to solid fuel and biofuel appliances. An alarm should be sited between 1m and 3m of an appliance, and be provided with a suitable long term power supply. There is guidance on the provision of access to concealed flues/chimneys. Inspection hatches should be at least 300mm x 300mm, the number and location must be sufficient to allow visual inspection of the flue/chimney system, and check that: • The flue/chimney is continuous throughout its length • Joints are correctly assembled and sealed • The flue/chimney is adequately supported throughout its length, and • Any required gradient or drain points for condensate are provided. Flues should be designed not to pass through other dwellings, and access If you would like to find out more about the changes or would like to talk about a new project please contact 0844 6331000 and ask for ‘Building Control’ / ‘Colin Blatchford-Brown’, or visit our website www.nhbc.co.uk/bc should not adversely affect fire, thermal or acoustic provisions. To link in with the requirements in Part L 2010, for dwellings with air permeability of less than 5.0m 3 / (h.m 2 ), there are additional ventilation requirements for open flued appliances. For example an appliance with a rated output up to 50kW should have 850mm 2 /kW of permanent ventilation for this level of air permeability as opposed to 550mm 2 /kW for more leaky dwellings. Another consideration within Part J 2010, is the potential requirement to provide additional containment protection to oil tanks up to 3500 litres for new dwelling. If a new dwelling is located within Zone 1 of the Environment Agency Groundwater Source Protection Zone (SPZ), then secondary containment is required to the oil tank. Further information on the mapping can be found at www.environment-agency.gov.uk/ research/library/maps. And finally there is now clarification on the recommended flue outlet position for external vertical flues fixed to an outside wall, essentially to comply as if it were a normal chimney or flue above a pitched roof. …and building regulation changes in Scotland In April the Scottish Government published the 2010 edition of the Technical Handbooks. The amendments to the Scottish building regulations come into force on 1 October 2010. The handbooks can be downloaded from the Scottish Government website (http://www.scotland.gov. uk/Topics/Built-Environment/ Building/Building-standards/ publications/pubtech). Alternatively hard copies can be purchased from The Stationery Office (TSO). 7
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