APPROVED DOCUMENT J
- YOUR QUESTIONS
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Part J - frequently asked questions   


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ODPM - Building Regulations

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questions

  • Is there special guidance for timber frame construction?   answer
  • What can be done to reduce the noise nuisance caused by wind blowing across a gas flue terminal?    answer
  • I want to reduce the depressurisation caused by an extract fan so that it will not cause flue gases to spill at a nearby open flued appliance. I would like to do this by improving the ventilation of the room where the fan is situated. Is there any way of calculating the extra ventilation that is needed?    answer
  • Can the outlet from a cooker hood discharge into a disused flue? Would the flue have to be lined?    answer
  • What is the difference between an integrally bunded oil tank and a twin walled oil tank?   answer
  • Is it true that heating and cooking appliances burning solid fuel or oil pose just as great a risk of carbon monoxide poisoning as gas appliances? I've had such an appliance installed fully in accordance with the Building Regulations. Will this eliminate the risks?   answer
  • The ODPM publishes a Building Regulations Explanatory Booklet that tells its readers that if they have a fuel burning appliance installed, replaced or relocated, the installer should "fix a notice plate in a place where it will be readily seen". Is this required for all such installations?   answer
  • Some of the British Standards referred to in ADJ will have to be withdrawn shortly, making way for the new BS EN's that are being published for flue and chimney products. Where can I find out how to follow the guidance in ADJ and meet the requirements of Part J when using products made to these new European standards?    answer

answers

**Q - Is there special guidance for timber frame construction?
A - The guidance in Approved Document J, if followed, will enable a gas fired installation to meet the requirements of the Building Regulations. However, "IGE/UP7 Gas installations in timber frame buildings" published by the Institution of Gas Engineers provides helpful advice on how this can be done in a way that addresses the particular design needs of timber frame. It may also be useful for some installations of modern oil fired appliances with flue gas temperatures less than 250ºC. There is, for example, detail on providing penetrations through vapour barriers when installing ventilators or balanced flues, advice on accommodating shrinkage movement when making penetrations and recommendations for supporting wall-mounted appliances.
Although the guide is a useful supplement to ADJ, the reader is nonetheless cautioned that it may not be up to date with the latest revisions of ADJ or of British Standards and that it is not endorsed by the ODPM as an Alternative Approach to meeting the requirements of the Building Regulations.
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**Q - What can be done to reduce the noise nuisance caused by wind blowing across a gas flue terminal?
A - Firstly, it should be pointed out that noise nuisance in flues has not been closely studied and there appears to be little in the way of general advice that can be offered on controlling noise down flues. In fact Approved Document J does not address this issue.
However, in the specific case of noise caused by wind blowing across metal terminals to gas flues, at least one manufacturer has reported that the problem can be reduced in some cases by changing to clay flue terminals, which they produce.
It should be stressed that any replacement terminal fitted to a gas flue should be of the appropriate type and size for the appliance connected to the flue: it is a contravention of the Gas Safety (Installation and Use) Regulations to make modifications to a flue that adversly affect the safe operation of a gas appliance. Persons looking to solve such a problem by changing to a clay terminal are therefore advised that they or their builder should consult a CORGI registered installer.
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**Q - I want to reduce the depressurisation caused by an extract fan so that it will not cause flue gases to spill at a nearby open flued appliance. I would like to do this by improving the ventilation of the room where the fan is situated. Is there any way of calculating the extra ventilation that is needed?
A - This answer presumes that you have first observed any limits on fan capacity as mentioned in Paragraph 1.20 of ADJ and that, despite these precautions, you are not satisfied of the safety of the installation.
Improving the ventilation of the room where the fan is situated is indeed a way of reducing its depressurising effect within the building. Unfortunately, variations in the size and leakiness of rooms and variations in chimney geometry and types of appliances mean that a predictive relationship between fan capacity and the ventilation required to avoid spillage cannot be given.
For instance, open flued appliances with fanned flues will, in general be much less susceptible to the depressurising effects of extract fans than will open flued appliances using natural draught. However, the move to higher efficiency boilers has resulted in natural draught models with low flue gas temperatures and consequent low flue buoyancy which might be expected to be particularly susceptible to spillage caused by extract fans.
It will be necessary to find the required extra ventilation by testing. BS 5440-2:2000 makes the following recommendation that may be a useful starting point in many situations:

As a general guide, an extra 50 cm2 of air vent free-area will be sufficient for most situtions, however, the spillage test should be repeated after extra vents have been fitted.

Any additional ventilation should be shown to be sufficient to prevent spillage when the maximum achievable depressurisation conditions have been established in the building as described in Paragraph 1.21 of ADJ and the ventilation would need to be non-adjustable, i.e. set permanently open at the required area.   back to questions

**Q -  Can the outlet from a cooker hood discharge into a disused flue? Would the flue have to be lined?
A -  Part J of the Building Regulations and Approved Document J are concerned with the safe installation of combustion appliances. A cooker hood, even when carrying fumes away from a hob, would not be regarded as a combustion appliance and, in principle, the outlet from a cooker hood could discharge into a disused flue. There would be no obligation for the flue to be lined.
However, the flue in question should indeed be disused and not one which is also serving a combustion appliance. Furthermore, it is important that the pressures created by the cooker hood installation do not adversely affect the operation of other open flued appliances in the kitchen or nearby rooms. A powered cooker hood discharging to the outside is a mechanical extract system which can lower the pressure in a building and reduce the efficiency of flues working elsewhere. The adverse impact of the cooker hood could be enhanced by the stack effect of warm effluent in the disused flue. Where mechanical extract systems are installed in a building, their effects on any open flued appliances should be checked in worst case conditions as described in Section 1 of ADJ.
A further potential for problems might arise if the disused flue runs in a chimney that also contains a "live" flue. The walls between old flues are commonly in poor condition and the operation of the cooker hood fan might adversely affect the conditions in the live flue.
Care should also be taken to ensure that the installation does not contravene other parts of the Building Regulations. For example, using a flue in this way could in some cases involve the penetration of fire compartments (eg in flat conversions) and in such cases the guidance in Section 11 of Approved Document B should be considered.
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**Q - What is the difference between an integrally bunded oil tank and a twin walled oil tank?
A - These two terms do not have the same meaning. An integrally bunded tank comprises a main tank - which holds the oil in the normal course of events - standing within another vessel, called the secondary containment, or bund. This latter is large enough and strong enough to contain all of the oil in the event of a leak in the main tank. In an integrally bunded tank, both the main and the secondary vessels are self-supporting. Integrally bunded tanks, suitable for meeting the requirements of the Building Regulations are available in both polythene and steel construction.
However, tanks placed on the market might also be described as being "twin walled", or "twin skin". These may comprise an inner liner that receives support from an outer container. Tanks matching this description are not regarded as being integrally bunded and cannot be used alone to comply with the guidance in Paragraph 5.10 of ADJ
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**Q - Is it true that heating and cooking appliances burning solid fuel or oil pose just as great a risk of carbon monoxide poisoning as gas appliances? I've had such an appliance installed fully in accordance with the Building Regulations. Will this eliminate the risks?
A - Carbon monoxide poisoning can be caused by appliances burning any fossil fuel, which includes not only gas but oil or solid fuel (including coal, smokeless fuels, wood and paper).
It is a contravention of the Building Regulations to install such appliances so that they are unsafe to operate and Approved Document J has been written to guide builders and installers on how to provide for a safe installation. If work is done in accordance with the relevant regulations and in compliance with the Building Regulations, your newly installed appliance should normally be safe to operate.
However, the Building Regulations do not cover the subequent use of an appliance or maintaining the state of its installation, such as looking after its flues and keeping ventilation routes clear. These matters are for whoever takes responsibility for an installation when it is complete, usually householders or some landlords. Even if it has been properly installed, a solid fuel or oil burning appliance can still cause carbon monoxide poisoning through improper used or if the installation deteriorates. Indeed, statistics show that deterioration is involved in a high proportion of fatalities from heating appliance installations.
A leaflet available from the Office of the Deputy Prime Minister highlights the dangers of carbon monoxide poisoning from solid fuel or oil fired appliances and lists key precautions to minimise the risks during their service life.
You can read the text of the leaflet or download a copy to keep handy via this link: http://www.safety.odpm.gov.uk/bregs/br19.htm
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**Q - The ODPM publishes a Building Regulations Explanatory Booklet that tells its readers that if they have a fuel burning appliance installed, replaced or relocated, the installer should "fix a notice plate in a place where it will be readily seen". Is this required for all such installations?
A - No. The Explanatory Booklet is alluding to the notice plate to comply with Requirement J4. However, the booklet is intended to be brief and its text on notice plates is not detailed.
To comply with J4, information should be displayed on the performance of hearths, fireplaces or flues that are permanent features of a building. This is so that someone who comes to re-use these features in the future knows their performance limits, for example if they are changing the appliance.
However, a notice plate is unnecessary for a flue that is part of the appliance and would have to be changed whenever the appliance were changed for a different one. Therefore, notice plates would not normally be required for installations of room sealed balanced flue appliances whose composite flue outlets / air intakes are dedicated only to specific appliance ranges.
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**Q - Some of the British Standards referred to in ADJ will have to be withdrawn shortly, making way for the new BS EN's that are being published for flue and chimney products. Where can I find out how to follow the guidance in ADJ and meet the requirements of Part J when using products made to these new European standards?
A - There is a companion document of supplementary guidance for ADJ that deals with this relationship between the new BS EN's and the British Standards they replace. It is produced by the British Flue and Chimney Manufacturer's Association with support from the Office of the Deputy Prime Minister. It is available in hard copy from the Stationery Office and also in downloadable form on the BFCMA website by following the link below. It is intended that the BFCMA will periodically place updates of the supplementary guidance on their website to reflect developments in standards as they occur.
Approved Document J - 2002 Edition: Guidance and Supplementary Information on UK Implementation of European Standards for Chimneys and Flues
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