Historic Building Conservation

Wiley Blackwell has just published its latest volume in its series of books on the conservation of historic buildings. ‘Interior Finishes & Fittings for Historic Building Conservation’ contains a chapter on ‘Fire safety in Georgian houses’ by Peter Norris of Oculus Building Consultancy.


The series is particularly aimed at construction professionals – architects, decorative arts historians and specifiers, surveyors, engineers – as well as postgraduate building conservation students and undergraduate architects and surveyors as specialist or optional course reading.

Click here if you would like to purchase this book

Oculus Venture South-West

We are delighted to announce that we will be expanding our Bath based business by opening a satellite operation in the south-west from September 2011. 

This will be a natural expansion to effectively service the projects we have in the region.  Our Exeter based operation will be managed by David Warren, initially for just part of the week.  He will also continue his role in our Bath office for the remainder of the week and will be servicing our existing clients and projects. 

“Oculus already have a number of prestigious on-going projects in the south-west and opening an office will give us the opportunity of having closer contact with our clients in the region” says Peter Norris, Managing Director.

Building (Amendment) Regulations 2011

The Building (Amendment) Regulations 2011 come into force on the 15th July 2011.
Circular 02/2011 is available from the CLG website.

Repairs to flat roofs

Essentially the definition of 'renovation' has been changed such that the repair of a flat roof by the addition of a new layer to the existing layers to more than 25% of the roof area does not trigger a requirement to thermally upgrade in accordance with Approved documents L1B and L2B.  In effect this type of work is not notifiable building work.

Competent persons scheme

The changes extend the areas of work which some existing schemes and has introduced a new category that covers work involving the replacement of a window, roof window or door in existing buildings which are not dwellings. There are exceptions that include the replacement of load bearing glass, structural glass, display windows, glazed curtain walling and revolving glass doors.

Details will be available shortly by visiting the Communities and Local government website at http://www.communities.gov.uk/ where you will be able to view the amendments made in Schedule 3 to the 2010 Building Regulations by the Building (amendment) Regulations.

Nailsea Tithe Barn

The conservation of the 15th Century Nailsea Tithe Barn is now complete.
Specialist conservation Architects 'Architecton' of Bristol were the designers and the contractor was W. Coombes & Sons of Ilminster. The project manager was 'Prospect' of Banwell and Oculus Building Consultancy were the Approved Inspectors. The completed refurbishment of this Grade II listed building is now available for a range of community uses including meetings, concerts, wedding receptions, group meetings and community projects. Oculus wish the trustees, Nailsea Town Council all the very best for the future.

Considerate Constructors Awards 2011

As the Approved Inspector Oculus take some pride in being associated with the following contractors who received Considerate Constructors awards at recent ceremonies held in March and April 2011.

Most Considerate Site Runner Up
Laing O'Rourke Wales & West Ltd for their work on Minehead Community Hospital which was designed by DKA Architects, Bath
Gold Award
Laing O'Rourke Wales & West Ltd for their work on South Petherton Community Hospital which was designed by DKA Architects, Bath
Silver Award
Kier Western for their work on Bridgewater College Energy Skills Centre designed which was also designed by DKA Architects, Bath
Silver Award
Leadbitter for their work on a residential development at Cambrian Drive Yate in Bristol designed by Quattro Architects, Bristol.

Landlord fined for inadequate fire precautions

A landlord was sentenced to a fine of £135,000 and ordered to pay £23,000 costs for breaching fire safety regulations when he appeared at Exeter Crown Court on 29th March 2011.

The former owner of the property in Ilfracombe pleaded guilty to four offences under the Regulatory Reform (Fire Safety) Order 2005.
On 14th February 2008 a fire occurred at the premises which was sub divided into flats up to four stories high. The fire, which started on the ground floor, spread throughout the building, in total 13 persons escaped with difficulty to safety
Devon & Somerset Fire & Rescue Service subsequently carried out a fire safety audit and discovered that fire safety precautions were inadequate.
If you require formal or informal advice on fire safety then please call us.

South West Built Environment Awards

We are please to announce that the following projects have been shortlisted for this year’s South West Built Environment Awards.  Oculus Building Consultancy as Approved Inspectors have been involved in supporting the client, the design team and the contractor in achieving the high standards required.

1. Minehead Community Hospital designed by DK Architects and constructed by Laing O’Rourke.

2. Tyntesfield House a National Trust conservation project completed by CS Williams and Architects   
    Rodney Melville + Partners

3. Bridgewater College Energy Skills Centre designed by DK Architects and constructed by Kier Western.

The categories for the short listing included heritage, health & safety, integration and collaborative working and value.

Further details of the awards and other nominees can be found on the awards website at http://www.buildsw.org.uk/awards

BS 6180:2011 - Barriers in and about building

In our post dated 27th January 2011 we highlighted the issues concerning glass balustrades and the need for handrails. The new British Standard has now been completely revised and has addressed this issue.


The standard now provides the following guidance on free-standing glass protective barrier.

‘In this type of barrier, the glass should be designed to withstand the design loads. Each glass plate should be clamped to the structure along its bottom edge, the handrail attached to the top edge of the glass and there should be no balusters. In the event that a free-standing barrier is supplied without a handrail, each panel should be able to withstand the appropriate design load'.

CO2 comparison savings

When making energy efficiency decisions at the early stages of the design it is often difficult to realise the balance between installation and running costs. The following figures are rough comparisons of savings from base CO2 calculation emissions versus project costs when considering energy efficiency in new build non-domestic buildings. The figures are taken from British Constructional Steel Association Target Zero project, based on a retail building and are approximate.


High efficiency lighting:                 possible CO2 savings = 22%                 
                                                           project cost = 0.27%

Motion sensing controls:              possible CO2 savings = 4%                   
                                                           project cost = 0.08%

Efficient ventilation:                         possible CO2 savings = 2.37%              
                                                            project cost = 0.06%

Reverse cycle air source              
heat pumps:                                     possible CO2 savings = 5%                   
                                                            project cost = 0.25%

Photovoltaics:                                   possible CO2 savings = 14.41%            
                                                            project cost = 10.44%

Wind turbine (330kw):                     possible CO2 savings = 27%                 
                                                             project cost = 4.24%

Improved Chiller efficiency:            possible CO2 savings = 4.56%               
                                                             project cost = 0.3%

Radon protection - Recommendations by the Health Protection Agency

Recommendations made by the Health Protection Agency in respect of limiting human exposure to Radon for inclusion in future revisions of Building Regulations:

• The action levels are likely to apply to non-domestic buildings with a public occupancy of more than 2000 hours per year (including schools);
• The guidance to be extended to cover all new buildings, extensions, conversions and refurbished existing buildings in the UK such that they should have basic radon protective measures as standard;
• The guidance to be extended for buildings requiring full radon protection such that they will need a radon test within the first year of occupation.

Reference: Limitation of Human Exposure to Radon – Advice from the Health Protection Agency RCE-15

 

2010 Changes to Part J – Combustion appliances and fuel storage systems

Revisions to Part J includes new guidance on the following;

• The provision of adequate access for the visual inspection of concealed flues. This is to ensure that flues  can be inspected properly when being commissioned or serviced.
• The new requirement J2A, “warning of release of carbon monoxide” describes the need for carbon monoxide alarms where solid fuel appliances are installed.
• The position of flue outlet clearances relative to adjacent pitched roofs has been clarified.
• Guidance on the provision of hearths and wall clearances for solid fuel appliances has been revised to take into account the availability of modern appliances.
• The requirements for alternative approaches for appliances burning solid fuel have been revised. The guidance under BS 6461: Part 1:1984, (1998) and BS 7566: Parts 1-4: 1992, (1998) have been replaced with BS EN 15287-1:2007 Chimneys.  Design, installation and commissioning of chimneys for non-room sealed solid heating appliances.
• Guidance for permanent ventilation openings for flued appliances in very airtight houses (where the design air permeability is less than or equal to 5.0 m3/(h.m2) have been increased to counteract the decrease in
adventitious ventilation relative to older houses.  Appendix F gives advice on assessing the air permeability of older houses.
• There are additional provisions for oil burning appliances.  Section 4.7 includes guidance on the position of flues in proximity to roof windows.  An additional note concerning the discharge of wet flue products and the Environmental Protection Act as well as problems associated with materials susceptible to continuous damp conditions.  This section now explicitly includes liquid biofuel and blends on mineral oil and liquid biofuel within the scope of combustion installations designed to burn oil.
• In section 5.7 (Risk from oil pollution) advice includes guidance on the construction of above and below ground oil storage tanks.  The installation of underground oil storage tanks is not recommended.
• In section 5.8 ‘significant risks’ now includes reference to a location within Zone 1 (Inner protection zone) of an Environmental Agency Groundwater Source Protection Zone (SPZ) and refers the reader to the Environment Agency’s Groundwater Sources map.
• In section 5.11 additional guidance is provided on integrally bunded oil storage tanks.
• In section 5.21 & 5.22 further informative guidance is provided on the installation of LPG gas service pipework and refers to the problems associated with corrosion and ventilation.
• The new Appendix G provides a summary of the European chimney designation scheme.  The essence of the scheme is a series of code letters based on the general chimney designation scheme of BS EN 1443:2003.
• The reader is advised that many of the British Standards included in the guidance have been updated.

Glass barriers and balustrades

Guarding is required to safely protect the edges of a floor, gallery, roof, rooflight or any other area to where people have access such as car parks. Guarding should be designed in accordance with the requirements of Approved Document K, ‘Protection from falling, collision and impact’ and BS 6180:1999 (see note in footer) ‘Barriers in and about buildings. Code of practice’. The glazing must also comply with the requirements of Approved Document N, ‘Glazing – safety in relation to impact, opening and cleaning’

Guarding should be at an appropriate height and configuration and capable of resisting the expected horizontal design loads. Guidance on the design loads are contained in Table 4, BS 6399: Part 1, 1996 and are described as;

1. Horizontally uniformly distributed line load (Kn/m)

2. Uniformly distributed load applied to the infill (Kn/m2)

3. Point load applied to part of the infill (Kn)

The design loads to be applied depend on occupancy characteristics. Two examples of differing conditions are provided in the table below

There is a significant difference in the loading pattern for various types of occupancy. The use and future use of the building needs to be carefully considered at the design stage.


The guidance provided within BS 6180:1999 on the design of glass barriers and infill panels in and about buildings describes three types;

1. A full height barrier where the glass forms part or whole of a wall.

2. A barrier with a glass infill panel where the main frame of the barrier consists of a top rail and baluster. The frame is required to resist the horizontal loads described above. The glass infill panel does not provide any support to the main frame and has to resist the horizontal loads also described above.

3. A free standing glass protective barrier where the glass should be designed to withstand the horizontal design loads. Each glass plate is clamped to the structure along its bottom edge and a handrail is attached to the top edge of the glass. There are no balusters

The guidance is quite explicit in so far as a handrail must be attached to the top edge of the glass.
Many designers consider that this requirement is a constraint that is not acceptable and look for a solution that does not require a handrail at all or, a handrail that is not attached to the top edge of the glass. This approach creates a compliance issue.
In exceptional circumstances it may be acceptable to some building control bodies to accept a variation to the guidance. The variation will need to be justified and the justification may include the following:
A statement concerning the reason for the variation to the guidance and interpretation of Part K & BS 6180: 1999.

• Occupancy characteristics (including numbers, activity, age and profile etc)
• Building usage or purpose group.
• Prevailing conditions such as occupancy, layout, barrier configuration, glazing area.
• Risks associated with sudden impact, fracture and fire.
• Additional safety measures.
• Height of fall.
• Manifestation and degree of transparency.
• Provision of secondary barriers such as fixed seating.
• Traffic factors such as traffic dynamics and traffic flow.
• Safety factors.
• Structural design including calculations and drawings.
• Manufacturer’s details and supporting design.
• Agrément or other acceptable certification.
• Glazing material properties and characteristics.
• Psychological factors.
• Access.
• Maintenance regime and longevity of fixings.
• Vandalism.
• The safe design of the top edge

The above design criteria is not exhaustive but should be included in a risk assessment and submitted to the building control body as a justification statement for the variation to the design guidance provided by the Approved Documents.
I would welcome any further comments especially from structural engineers or manufacturers.

note; BS 6180: 1995 Code of Practice for protective barriers in an about building, cited in the Building Regulations have been superseded by BS 6399: Part 1, 1999. Barriers in and about buildings. Code of practice

Consequential Improvements – Part L2B Building Regulations 2010

Where an existing building has a total useful floor area over 1000m² and it is intended to;

1. Build an extension.
2. Install the initial provision of any fixed building service (other than a renewable energy generator).
3. Increase the installed capacity of any fixed building services (other than a renewable energy generator).

Then it may be necessary to undertake additional works to the existing building as well as the new work. These works are referred to as Consequential Improvements.
When applying the requirements it is important to review the exemptions contained in paragraph 3.5 to 3.22.
The requirements can also apply to large dwellings over 1000m² (see Approved Document L1B).
The requirements are that in addition to the principal works, consequential improvements will also be required in order to comply with the requirements of Part L 2010, unless it can be demonstrated that such works to the existing building are not technically, functionally or economically feasible. Such supporting evidence must be prepared by a suitably qualified person.
Measures that would be considered economically feasible are generally based on a simple 15 year payback on the cost of the thermal improvement works through energy savings – unless there are other unusual circumstances, such as the building has a life span of less than 15 years.  In this case a reasonable provision would be to achieve a simple payback on the life of the building.

Consequential Improvements on extending a building

To demonstrate compliance it would be acceptable that the consequential improvements provisions can be restricted to a value of not less than 10% of the value of principle works or the cost of the extension.
The value of principal works and consequential improvements should be calculated by a suitably qualified person and submitted as a report to the Building Control Body.

Examples of technically, functionally or economically feasible consequential improvements include;

1. Upgrading heating systems, cooling systems, air conditioning or air handling systems more than 15 years old by provision of new plant or improved controls.
2. Upgrading general lighting systems that have an average lamp efficacy of less than 40 lamp - lumens per circuit watt – and that serve areas greater than 100m² by the provision of new luminaries or improved controls.
3. Installing energy metering.
4. Upgrading thermal elements having a ‘U’ value worse than table 5a.
5. With provisos and exclusion by replacing existing windows, roof lights and doors (see guidance).
6. Subject to conditions by increasing on-site low and zero carbon energy generating systems.
7. Other measures recommended as a consequence of the EPC.

Consequential Improvements on installing building services

Consequential improvements will apply where it is intended to install a fixed building service as the first installation, or as an installation which increases the installed capacity per unit area to an existing service.

Examples of technically, functionally and economically feasible consequential improvements include;

1. Where economically feasible improve the buildings thermal performance to those parts of the building served by the services installed, and in addition.
2. Make consequential improvements to bring the existing as well as the new building into compliance with Part L unless it can be demonstrated that such works to the existing building are not technically, functionally or economically feasible.

The cost of the improvements required in (1) cannot be considered as contributing to the value of such consequential improvements in (2).  This is to avoid higher CO2 emissions due to a higher level of servicing from the new building services conditioning the environment.
The ‘installed capacity per unit area’ to an existing service is defined as the ‘design output of distribution system output devices [thermal units] serving the space in question divided by the total useful floor area of the space’.
This means for instance that if the boiler size to serve an extension is increased, rather than to increase the existing buildings heating provision, consequential improvements must be carried out in accordance with the requirements for an extension but not to comply with the requirements for increasing the installed capacity as described below.

Consequential improvements on increasing the installed capacity per unit area of a heating system

Unless it is demonstrated that such works are not technically, functionally or economically feasible, consequential improvements will apply where the installed capacity per unit area of a heating system is increased.  The 10% rule threshold as described for other consequential improvements does not apply. Examples of technically, functionally and economically feasible consequential improvements include;

1. Thermal elements within the area serviced by the systems and having a ‘U’-value worse than those in Table 5 (a) must be thermally upgraded.
2. Existing windows, roof light etc (with provisos and exceptions) within the area served and that have a ‘U’-value less than 3.3W/m2.K are replaced in accordance with table 3.

Consequential improvements on increasing the installed capacity per unit area of a cooling system

Unless it is demonstrated that such works are not technically, functionally or economically feasible, consequential improvements will apply where the installed capacity per unit area of a heating system is increased.  The 10% rule threshold as described for other consequential improvements does not apply. Examples of practical and economically feasible consequential improvements include;

1. Thermal elements within the area serviced by the systems and having a ‘U’-value worse than those in Table 5 (a) must be thermally upgraded, and
2. If the areas of existing windows and roof windows (not display windows) within the area served exceeds 40% of the façade area or the rooflights area exceeds 20% of the roof area and the design solar load exceeds 25W/m2, then the solar control provisions should be upgraded to meet at least one of the following criteria's to reducing solar gain and thereby the cooling requirements which in turn reduces energy consumption:

• the design solar load is no greater than 25W/m2
• the design solar load is reduced by at least 20%
• the effective g-value is no worse than 0.3 (See CIBSE TM37 calculation), and

3. Any lighting system within the area served by the relevant fixed building service, which has an average lamp efficacy of less than 45 lamp-lumens per circuit watt, should be upgraded with new luminaries and/or controls in accordance with the Non-Domestic Building Services Compliance Guide.

Part G - Building Regulations 2010

I expect most of you are aware of the changes to Part G that took place in April 2010.  Most of the changes are only to be expected but the more radical changes are highlighted in this short description of the changes.

Legal Requirements


Requirement G1
• There is new requirement for the supply wholesome water for the purposes of food preparation or drinking.
• G1 also requires a supply of wholesome water or softened wholesome water for washing purposes.
• The requirements allow the provision of water of a suitable quality to sanitary conveniences fitted with a flushing device.


Requirement G2
• G2 and Regulation 17K require new provisions for water efficiency for dwellings.


Requirement G3
• New requirements for hot water supply and safety and applies safety provisions for all types of hot water systems.
• There is a new requirement on the prevention of scalding.


Requirement G4
• Sets out the requirements for sanitary conveniences and hand washing facilities.


Requirement G5
• Sets out the requirement for dwellings and buildings used for residential purposes to incorporate a bathroom containing a wash hand basin and a fixed shower or bath.


Requirement G6
• New requirements for sinks to be provided in areas where food is prepared.


Other changes
• Where there is a change of use of a building there is a requirement that the water efficiency requirements in G2 and Regulation 17K and the hot water safety requirements in G3 (4) will apply.
• The requirements for cold water supply (G1) and hot water supply and systems (G3) now applies to domestic greenhouses, small detached buildings and extensions to buildings, including conservatories.
• The requirement that a building notice which includes work on an unvented hot water system be accompanied by a statement giving details to the system and the installer has been revoked.
• Regulation 17 has been amended to state that the local authority is unlikely to issue a completion certificate for a new dwelling unless a certificate stating the potential consumption of wholesome water per person per day has been received.  Likewise an approved Inspector will not issue a final certificate for the same reason.


Technical requirements


Requirement G3
• There is a new requirement to provide hot water to baths, showers, wash hand basins and sinks.
• There are new measures to ensure the safe operation of all types of hot water systems, including controls and safety features to ensure the system is robust and the water temperature does not exceed 100°C.
• Safety features associated with hot water storage vessels now applies to all hot water storage systems.  It has been extended to include primary thermal stores.
• There is a new requirement to the prevention of scalding through the provision of protection devices that limit the temperature of water supplied to baths.


Requirement G4
• Additional guidance is provided on the separation of sanitary accommodation from areas where food is prepared.

The ventilation of buildings

Generally the ventilation requirements of Approved Document F 2010 apply to the:

• The erection of new buildings
• The material alteration of an existing building
• The material change of use of a building

There are some exemptions including the erection or extension of buildings that are exempt under Regulation 9, Schedule 2.  This usually includes buildings unfrequented by people, small detached buildings, greenhouses, agricultural buildings, temporary and ancillary buildings.  Historic buildings are a special case and application of the requirements needs to be applied in a sympathetic manner having due regard to the sensitive nature of the fabric and its contents.
The purpose of ventilation is to replace ‘stale’ indoor air with ‘fresh’ outdoor air.  The process is essential to ensure a healthy internal environment by;

• Providing fresh air for breathing
• Removing air borne pollutants
• Controlling humidity
• Providing combustion air for fuel burning appliances

‘Purpose-provided’ ventilation is achieved by incorporating some or all of the following:

• Extract ventilation which may be natural, mechanical, continuous or intermittent and usually at a high rate
• Whole building ventilation which is continuous and usually at a low rate
• Purge ventilation which may be intermittent, manual, natural or mechanical usually at a high rate

Ventilation can be described as:

• Natural
• Mechanical
• Mixed-mode, or
• Hybrid

The strategy to be adopted in any particular building needs to be carefully considered and cannot be determined as a stand-alone solution.  In complex buildings ventilation strategies are normally designed by Building Services Engineers.  However, whatever the strategy it is important to consider the following:

• Conservation of fuel & power
• Condensation
• Temperature and humidity
• Controls
• The provision of combustion appliances
• Airborne substances
• Height, width, length, layout and design of the building
• Building fabric
• Fire safety
• Occupancy characteristics
• The spread of infection
• Uncontrolled infiltration of air or air leakage
• Air tightness of the building
• Testing and commissioning
• Installation and maintenance

Approved Document F 2010 provides detailed guidance on the various strategies that can be adopted for the ventilation of new dwellings including information on extract ventilation rates, whole building ventilation and purge ventilation.  There are generally four specific ventilation strategies described and they are;

1. Background ventilation - the provision of background ventilation, (such as ‘trickle vents) intermittent extract fans and purge ventilation.

2. Passive stack ventilation - the provision of free flowing ductwork to naturally vent the building, background ventilation and purge ventilation.

3. Continuous mechanical extraction - the provision of continuous extract ventilation, background ventilation and purge ventilation.

4. Continuous mechanical supply and extract with heat recovery - the provision of continuous whole building supply and extract ventilation with heat recovery and purge ventilation.

The use of natural or mechanical ventilation can be severely compromised when buildings incorporate basements, deep plan layouts, addition of extensions or the lack of through ventilation.  Additional guidance for dwellings is included in the Approved Document.
Guidance on the requirements for new buildings other than dwellings is also included in the Approved Document and includes specific guidance for offices.  However, more complex buildings will need to comply with other Approved Documents including CIBSE Guide B:2005.  The full list is provided in Table 6.3.
Additional guidance is provided in Appendix A on performance based ventilation.  This section should not be dismissed as it provides useful guidance on the background to the requirements and should be referred to when a variation to the guidelines is being considered.
The most important consideration is to provide an holistic and simple approach that enables the users of the building to control the ventilation of the building in a manner that is not only healthy but is also sustainable. The control of unwanted air leakage on new buildings is part of a planned control.  The same techniques associated with historic buildings may cause future problems especially with respect to surface and interstitial condensation.