Building Regulations Part L

We are specialists in the assessment of new and existing dwellings for Building Regulations Parts L1A and L1B.

For totally free advice or a quote call Tophouse Assessments on 01634 799115.

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About Part L

Part L of the Building Regulations deals with the Conservation of Fuel and Power. There are 4 approved documents

  • Part L1A is for new Dwellings ( flats and Houses)
  • Part L1B applies to work on existing dwellings or buildings converted to dwellings
  • L2A applies to new commercial buildings
  • L2B applies to existing commercial buildings

We do not at present assess commercial buildings (L2A and L2B). If you require a commercial EPC in Kent we are able to recommend someone.

Part L is changing again  – new much stricter regulations will be enforced for dwellings where the build commences after 1st April 2014 . Call us if you need to determine which set of regulations apply to your build. Buildings designed to the 2010 regulations will not pass the 2014 regulations. there are various differences between the two sets of regulations but the latest  regulations are designed to  further reduce the Carbon emmissions  and introduces new  Fabric Energy Efficiency targets  The targets are now set so low that new and innovative design and technologies are required to make dwellings pass . We at Tophouse are fully qualified to assess your design to the new regulations. To avoid disappointment we recommend that we work with architect from the onset.

). Not later than the day before the work starts, the person carrying out the work shall provide the local authority a notice which specifies:

  1. The target emission rate and fabric energy efficiency  for the building.
  2. The calculated CO2 emission rate and fabric energy efficiency  from the building as designed.
  3. A list of specifications to which the dwelling is to be constructed.
  4. An evaluation of e alternative high efficiency  systems.

In practice this means that before you commence work you must get your plans and construction details assessed by a qualified assessor so that a compliance checklist is prepared and submitted to Building Control along with the other construction details.

Qualified assessors

Only use qualified assessors who are members of an approved scheme.

It is a legal requirement that new dwellings require an Energy Performance Certificate on completion. For dwellings, this can only be issued by an Assessor who is an OCDEA (On Construction Domestic Energy Assessor) and who is a member of an approved scheme. Building contol should check that you have an EPC before signing off your dwelling. The same applies to dwellings that are created under L1B due to material change of use i.e conversion to flats or houses. Using an appoved assessor ensures that your L1A or B submission is acceptable to building control.

Martin Gill DEA, OCDEA, is a member of the NHER scheme member NHER001756 and is a BINDT registered air pressure tester.

New dwellings

If you are designing or building a new dwelling, before you start building we check that your designs conform to building regulations Part L1a. You send us plans and details and we perform the appropriate calculations and prepare the a report for building control. If we need information that is missing from the plans then we will contact you. We calculate the heating requirement from the details about the space heating and the water heating that you provide us with. We calculate heat losses – from openings and ventilation and through the insulation in the floors, walls roofs .We then perform various calculations to check the compliance with building regulations and which forecast the heating requirement as a SAP rating. We can also issue you with a PEA (Predicted energy Assessment) if this is required for marketing off plan.

Before you start building

It is important to do this before you start building – otherwise you risk failure.

Since October 2010 you must submit SAP calculations and supporting documentation with your notice to building control – before you start to build.

Some people think that it is sufficient to use certain U values or constructions – but this is not valid , The main criteria for limiting heat losses is that the DER is less than the TER (see below) and this can only be determined using a full SAP calculation. There are other criteria that you must meet (see below).

SAP calculations for new dwellings

SAP calculations for new dwellings are normally a a two stage process:

At design stage (before building commences) calculations are used to check that the dwelling meets the mimimum building regulation standards. A target air permeability value is set for the unplanned leakage of air from the structure. We provide all the reports and checklists required by building control.

This includes DER, TER, and predicted SAP ratings. If your designs require modification in order to pass, then we will advise you and discuss any changes required. We often find that some adjustments are required to achieve a pass – we are experienced in finding the best solution for you.

Single dwellings after construction will normally require an Air Leakage / Pressure Test. We can arrange this for you.

We are air leakage testing experts and our testers are members of the BINDT Approved scheme. We can advise you how to achieve this and how to avoid typical mistakes that lead to failure . Unless leakage is addressed during the construction it may be impossible to achieve the target by remedial action. So don’t stick your head in the sand – call us to get expert advice. Under the new 2010 Regulations much tighter construction is required to achieve lower leakage targets – penalties are applied to any dwelling not physically tested i.e.where a single test result is applied to more than one dwelling unit. therefore we anticipate that most dwellings will require testing. Our expert testers have a very high pass rate and will do their upmost to ensure that you pass. Once you book with us or register your interest we offer you free advice on how to comply and avoid common mistakes. We can even arrange site visits.

We take the pressure so you pass!

On completion

The design calculations are updated with any changes to the specifications during construction along with the actual air pressure test result. A second report and checklist are generated for building control – and an Energy Performance Certificate (EPC) is generated. If the address is new then the address has to be registered on the landmark register of addresses, the official address database cross referenced to EPCs. EPCs are also stored on the landmark datatabase and can be accessed on line for legitimate use if you have the correct report reference code from the EPC. Thus a new hard copy can be generated if the original is defaced or lost.

The completed checklist is used to demonstrate to building control that the building is compliant to Part L. Some parts of the checklist sometimes require additional certification or signoff from the builder or installers.

Accredited construction details – what these are and why they are important?

Accredited construction details are a set of approved construction standards and drawings for different types of construction. These were developed to ensure continity of air tightness and avoid thermal bridging (heat loss at junctions).

There are details provided for the main generic construction types: timber frame construction, cavity wall constuction, masonry and internal wall insulation, masonry and external wall insulation. There is also an introductory document with lots of guidance about air leakage.

In SAP 2010 you will normally have certify that you are using accredited construction details throughout the dwelling. If you do so then the assessor can use your dwawings to calculate heat losses from the various junctions and calculate a heat loss coefficient. If you are not using accredited construction details then a default value of 0.15 is added – The 0.15 value is is normally much worse than if the value was calculated by the former method and will push up the DER Thus it will be much harder to reach the Target TER. In effect – if you are not using accredited constuction details throughout – then a higher heat loss is assumed due to thermal bridging. The performance is impaired – making harder to pass building regulations.

Cavity Party walls – new requirements in the latest regulations

The 2006 regulations ignored heat loss from party walls between dwellings that were heated on both sides – but research has indicated that in practice there can be considerable heat loss up the wall by thermal bridging and air circulation in the cavity. Therefore the latest 2010 regulations have changed with U values that are now assumed, and assigned to cavity walls according to rules

Solid party walls U value = 0

Unfilled cavity party walls U value = 0.5 – a considerable penalty

Party cavity walls that are fully filled U value 0.2 – penalty

Party walls that are both fully sealed and have horizontal and vertical air movement barriers U = nil .

In the Target calculation (TER ) this value is set to zero. So assigning U values to party walls in the dwelling DER calculation is in effect, a penalty, that encourages certain construction types, or forces offsetting of these loss elsewhere in order to meet the target.

In practice party walls have to meet a number of criteria in addition – fire and sound resistance for example – product systems that claim to meet all of these equirements are still being developed by manufacturers. This is another area that is still evolving and new methods of compliance are being developed.

Summary of Criteria in the Checklist (2006 regulations)

(The 2010 regulations are similar but the targets are set higher! )

Criterion 1:

  • Predicted carbon dioxide emissions form the proposed dwelling should not exceed the target
  • We calculate the DER and the TER. The DER should not exceed the TER.

Criterion 2

  • The performance of the building fabric and the heating, hot water and fixed lighting systems syould be no worse than the design limits.
  • We check the u values of various elements to to make sure that they are not over the limits set out in L1A Table 2
  • We check the efficiency and configuration of the heating, heating controls and hot water storage against the set standards.
  • There are certain regulations concerning low energy and external lighting which need to be met.

Criterion 3

  • The dwelling has appropriate passive control measures to limit solar gains.
  • We predict if the dwelling has a tendancy to overheat in summer : If the risk is assessed as High then then this is a failure. This is a standard calculation.

Criterion 4

  • The performance of the dwelling as built is consistant with the DER
  • We provide a list of key features is produced as a standard output from SAP to facilitate sample checking by Building control. This consists of the compliance report and a list of the imputs used to generate it.
  • Builder states if accredited or non-accredited construction details been used. – refer to above
  • Builder states if there is satisfactory documentation of site inspection checks*
  • We provide the design air permeability (design stage)
  • Builder provides evidence that the air permeability has been achieved (Air pressure test results/certificate on completion)*
  • Builder provides evidence of comissioning of heating and hot water systems (certificate)*

Criteria 5

  • The necessary provisons for energy-efficient operation of the dwelling are put in place
  • Builder states that operation and maintenance instructions have been provided- so that the owner knows how to operate the equipment *

Items marked * require signing off by the builder or other qualified persons.

Existing Dwellings L1B

The 2010 regulations are very similar to the 2006 edition but:

  • There are higher standards for some U values / heating / glazing / other building services
  • The new regulations also clarify certain situations more clearly than before.

L1B typically applies if

  • You are renovating a dwelling
  • You are extending or making certain Alterations to a dwelling.
  • You are converting a building into a dwelling (material change of use)
  • If you are altering the number of dwellings in a building (house conversion into flats) – material change of use.
  • You require an extension or unseparated conservatory where there is lots of glazing

(This is not a full list – refer to L1b for a full list of requirements).

In the above cases building control will often ask for a SAP assessment and check that the building is compliant to Part L1B. This is not as clear cut as L1A for new dwellings as the code caters for many circumstances. We are experts in L1B. There are various scenarios and methods of compliance – different methods are appropriate according to individual circumstances. There are also various defences against having to attain standards :

  • The insulation should be cost effective
  • Measures might compomise the design ( make floor areas too small or floors uneven)
  • Preservation of listed buildings or buildings of historical interest.

We find that many Building Control offices are not fully conversant with L1B and often request additional and unnecessary measures. Because we are experts in L1B, we can save you time and money and effort. We prepare a fully documented report to present to building control – demonstrating compliance with the approprate sections. For over-glazed exensions we are able to offest heat losses from the glazing by additional savings that can be achieved elsewhere in the house. Sometimes we may require a site visit – if we require additional information to present your case fully.

Material change of use calculations will also require Energy Performance Certificates, the same as new dwellings. These can ouly be issued by qualified persons .We are fully qualified under the regulations.

Code for Sustainable Homes Levels 2 3 or higher requires a more energy efficient constuction and possibly the use of Renewables such as Photovoltaics

Free service

We hope that this information is useful. If you are not sure you could always ask us and we will do our best to help you along – there is a complimentary service giving you free advice – based upon our considerable experience of testng and assessing dwellings.