What does it take for a new house to pass Part L1A 2013?
To comply with Part L1A every new dwelling must pass a SAP calculation – which is the Standard Assessment Procedure. This is a methodology introduced by the Government to assess and compare the energy and environmental performance of dwellings to make sure all new developments not only meet Building Regulations, but also comply with all energy and environmental policy initiatives.
The principle aim is to assess how much energy a new house will consume when delivering a defined level of comfort and service provision using standard assumptions for occupancy and behaviour, with the calculated results expressed in terms of CO2 emissions.
What are the requirements to pass Part L1A 2013?
To comply with Part L1A all new houses must achieve a dwelling CO2 emission rate (DER) no greater than a target CO2 emission rate (TER). And to help designers and builders achieve this the government provides guidance within Approved Document L1A and supporting document, the Domestic Building Services Compliance Guide, setting out the minimum acceptable standards and specifications for all elements for the construction of a new house.
Although it is acceptable to work to the minimum standard for one or two of the elements within the design, it is important to note that a house built to the L1A minimum standards for all areas will result in a DER much higher than the TER, and so will fail a SAP calculation and not comply with L1A.
How do the London Plan energy requirements differ?
When building in a London borough you need to familiarise yourself with the London Plan, the overall strategic planning framework from the GLA for London, and note it’s set energy performance standards as they are more stringent than those set by other LPAs. Developments within the capital will need to achieve a DER that is at least 35% below the TER.
How can you improve the SAP calculations?
If the SAP calculations on your new development are currently not compliant with Part L1A then these are the areas that you can focus on to improve your ratings:
The main component of a Dwelling CO2 Emission Rate is primary heat demand. Reducing the heat demand within a house through effective insulation will have a significant impact on the DER.
Windows & Doors
Installing draught-sealed highly-efficient double-glazed (or tipple-glazed) windows will result in a significant reduction in heating demand within the dwelling, and consequently a significant reduction in the calculated Dwelling CO2 Emission Rate.
This is the heat loss that occurs where one element joins another i.e. where a wall meets a floor, or around windows and doors. For highly insulated houses the proportion of heat loss that occurs at these junctions can be significant.
To reduce the effect of thermal bridging attention needs to be given to how insulation is installed along these junctions. To help designers and builders address this, the Government has published a set of “Accredited Construction Details” that can be followed for most common construction methods, plus many manufacturers of related building components publish their own set of construction details that can be followed to mitigate against the effects of thermal bridging.
The amount of heat loss that occurs due to cold draughts is quantified as the air permeability rate for the dwelling and is an important element to tackle. It is measured via air leakage testing, which is carried out at the very end of the construction process. The lower the air permeability rate, the lower the level of heat loss via cold draughts.
With uncontrolled ventilation (cold draughts) kept to a minimum it is very important that adequate levels of controlled ventilation are provided. This usually occurs naturally through openable windows, window trickle vents and intermittent mechanical extractor fans. However, as the new clean air is taken from outside thus requiring heating again, this will have an impact on the calculated Dwelling CO2 Emission Rate.
For improved efficiency mechanical ventilation with heat recovery (MVHR) can be installed. MVHR systems will mechanically draw cool fresh air into a house at the same time as extracting warm stale air. The efficiency lies in the fact that heat from the warm air that is being extracted is passed to the cool air that is being drawn in, so reducing the requirement to reheat the supply air.
The efficiency of a heating system and the fuel it uses has a significant impact on the calculation of the Dwelling CO2 Emission Rate. Although electric heating does meet the minimum standards of Approved Document L1A, installing a modern gas central heating system will result in a significantly lower DER.
Houses with a floor area less than 150m2 only need to be controlled by a programmer, room thermostat and TRVs. However, installing zoned heating controls can result in a significant reduction in the DER. Zoned heating controls have a function that enables at least two separate parts of the dwelling to be heated at different times and to different temperatures.
Domestic Hot Water Heating
The second largest contributor to a Dwelling CO2 Emission Rate is domestic hot water demand. Again, like the space heating, although electric domestic hot water heating does meet the minimum standards of Approved Document L1A, switching to a modern gas DHW heating system will result in a significantly lower DER.
The minimum standard of Part L1A is for 75% of all lights within the house to be low energy. To be deemed low energy the light must have an efficiency greater than 45 lamp-lumens per circuit Watt. Most modern lighting will fall within this category. For improved energy efficiency all new houses should aim to have 100% low energy lighting.
Renewable technology systems can generate heat or electricity on site such as solar thermal systems that generate heat for domestic hot water from the sun, and a photovoltaic system that captures energy from the sun and transforms it into electricity.
It is not a requirement to include renewable technology to pass a SAP calculation, but these additions would give you greater flexibility elsewhere in the design.
Seeking Professional Guidance
To give you the greatest level of design-flexibility for your new development it is advisable to engage with an experienced energy consultancy from the outset.
At Energytest our fully qualified and knowledgeable consultants will give you confidence that your projects will achieve full compliance.