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Frequently Asked Questions

  • What is the difference between SAP and SBEM?

    Every new building with a heating system will need to be assessed to check energy efficiency against current Government emission targets.

    If you are building houses or apartments blocks, each dwelling will need it’s own SAP calculation completed – this should ideally happen before work starts on site.

    Any building that isn’t a dwelling will require an SBEM calculation. The fundamentals of both SAP and SBEM are the same, but SAP is designed to more accurately reflect the carbon emissions of our homes.

    SBEM is geared up to reflect CO2 from any other type of building, from offices to hotels, warehouses to sports halls.

    There is a grey area when it comes to student accommodations and care homes. Generally, if individual apartments are self-contained (in other words, they each have their own bedroom, kitchen and bathroom facilities), they will need individual SAP calculations.

    Any shared areas (corridors, shared lounges, staff rooms) will need to be covered in an SBEM calculation.

    Guest houses and holiday homes could fall into either category, as they could be defined as both a commercial property, but the building is being used as a dwelling. In these cases, we would refer to the local building control body to see if they have a preference.



  • Why is my EPC (Energy Performance Certificate) rating different to my predicted result?

    When you receive your Part L design reports from your SAP assessor, you should receive a Predicted Energy Assessment. This tells you what the expected Energy Performance Certificate rating of your new home will be.

    The EPC is a report which gives your home an A-G rating, where A is the most efficient and G is the least efficient. Most new homes score a B or C rating.

    Sometimes this rating will change by the time your building is constructed. There are a number of reasons for this to happen.

    The most common reason for a different figure is if you have made alterations to the building fabric or heating systems since your PEA was produced. Any change which ultimately affects the amount of fuel needed to heat and power your home will have a knock on effect on the EPC.

    Another key reason is a change in methodology. Every few years the SAP calculator is updated to reflect latest trends and fuel prices. If this update occurs between the publication of your PEA and your EPC, you may notice a change.

    If you score a better-than-expected air test on your home, this information will be fed back into the SAP and you could receive a better EPC score because of it. Similarly though, achieving a worse than expected air test result could lead to a worse rating, so make sure you know from your SAP assessor what is expected from your air leakage test.



  • What is the difference between solar PV, Solar Thermal and PVT?

    Solar PV

    Solar PV is the most common of the three seen in the UK today. These are the types of solar panels that you are likely to see in every town and city in the country, attached to the slopes of roofs. In a nutshell, they use the natural light found during the day to generate electricity, which is then available for a household to use – essentially, they mean that households are able to create free electricity.

    One extra advantage to Solar PV panels is that they can actually make a home money. This is because it is often the case that solar PV panels generate more electricity than a home actually needs, therefore meaning that this excess can be fed back into the National Grid. The homeowner will then receive a nice sum of money thanks to the feed-in tariff overseen by the Department for Energy and Climate Change.

    Solar Thermal

    Solar thermal is not as common around the UK as solar PV, although it is seen occasionally around the country. These types of panels use the sunlight to heat water, unlike the solar PV panels, which create electricity instead. This means that, instead of making savings on electricity, a household with solar thermal panels will make savings on their heating bill instead. This means that, in the right circumstances, a homeowner can choose between the two and still make substantial savings on their outgoings.

    “In the right circumstances” is an important phrase though, as many houses in the UK simply don’t have the ability to use solar thermal panels. This is because they require direct sunlight (unlike PV which can work on a cloudy day) – meaning that north facing roofs are not suitable for them. This explains why they are so popular around the Mediterranean region; a region that gets a huge amount of sunshine every year.


    The final one to look at is PVT, and these are a combination of solar PV panels and solar thermal panels. They work by having the PV panel at the top, but then underneath they also incorporate a solar thermal panel as well. This means that they get the best of both worlds and, providing they are positioned correctly, they will generate both hot water and electricity for the home. They are slightly more expensive, but this is made up for by the fact that they can save more money in the long run.



  • I’ve been told we need to use PV (Photovoltaics) to pass the SAP, is this true?

    The short answer is “No, there are other techniques”.

    The long answer is “No, but it might be the simplest, cheapest and most sensible option to take.”

    It depends where you are building, what you are building and what your local planning conditions stipulate.

    In England and Wales

    If you have no additional planning conditions concerning the emission rates, you can usually show full compliance providing you install plenty of insulation into the building fabric, minimise heat loss through thermal bridging (low air leakage levels), install high quality glazing, and also use high efficiency heating, hot water, ventilation and lighting systems.

    However, if the above specification would cost you ten thousand pounds more than usual, and you could offset the same level of energy use by installing five thousand pounds worth of PV panels to the roof, which would you choose?

    Our Technical Team will never second guess you, and will work with you to strike the perfect balance between complying with the regulations and meeting your own needs.

    In Scotland

    The current Target Emission Rate is more stringent in Scotland than anywhere else in the UK. This means it is more likely that you will need to install PV panels to meet compliance.

    When the TER is calculated, it is based on one kilowatt peak of PV for every 100sqm of floor area. This means that, if you don’t install PV panels, you need to offset this by improving the specification elsewhere in the build.

    Again the use of renewable technology isn’t mandatory, but will probably be an easier and cheaper option than the alternatives. Our Technical Team will be happy to look through the available options and advice accordingly.

    Planning Conditions

    You may have planning conditions which clearly stipulate that your site needs to offset a certain percentage through the use of low carbon or renewable technologies.

    Local authorities cannot insist you use PV panels specifically, but you will need to consider their feasibility at the very least.

    In these cases, you’ll be expected to consider the use of all kinds of low carbon technologies, including biomass, turbines and heat pumps. It’s usual for PV or solar thermal to be one of the most feasible technologies.

    The council will expect you to install the most feasible low carbon technology as part of this planning condition.

    For more information on this, see our Energy Statement service.