Publication - Research and analysis

Energy Efficiency Standard for Social Housing: peer review

Published: 22 Oct 2013
Energy and Climate Change Directorate
Part of:
Environment and climate change

Peer review scrutinising the example dwellings in the Energy Efficiency Standard for Social Housing consultation document.

Energy Efficiency Standard for Social Housing: peer review
6 Communal Improvements

6 Communal Improvements

This section provides commentary on how communal improvements can be adequately accounted for in the EESSH. It is important to recognise that many of the measures discussed can yield benefits in the form of reduced energy consumption, CO 2 emissions and fuel bills, however the RdSAP methodology does not take account of them, which means the effect of these will not be captured by the EPC ratings.

Some technology-specific issues are as follows:

6.1 Draught-proofing

The RdSAP methodology assumes all flats and maisonettes benefit from a draught lobby, and all houses and bungalows do not, without any consideration of the actual draught-proofing specification. This will impact on the infiltration calculated for the dwelling, consequently affecting the space heating requirements.

Any efforts to reduce heat loss from an unheated common area, such as draught-proofing, will yield benefits for the connected dwellings by reducing heat loss. However, the RdSAP methodology will not include these improvements in the calculated EPC ratings.

Aside from developing and researching a tool additional to RdSAP, it is difficult to see how this issue can be addressed. In this respect this review found very few and limited examples of projects where actual CO 2 savings were monitored and recorded. It is suggested that where some dwellings within multiple units marginally miss or are close to reaching the proposed ratings, landlords could be given credit for measures such as draught lobbies and draught proofing of communal areas. This would require assessment on an individual basis.

6.2 Communal corridors

The new version of RdSAP 2009 (v9.91) enables more detail treatment of internal corridor wall of properties ( i.e. 'sheltered corridor' wall), in comparison to the previous version (v9.90). This enables an assessor to specify alternative walls types for the sheltered wall which can be insulated thereby increasing the EE rating of the adjoining properties. Previous versions of RdSAP assumed that both the sheltered and outer wall would have similar characteristics.

6.3 Efficient Lighting

Replacement of communal lighting with energy efficient fittings can achieve significant savings in energy, CO 2 emissions and fuel bills, particularly for lights which are subject to extended periods of use ( e.g. stairwell lights which remain on all night). As with the draught-proofing of communal areas, this will not be taken into account by the RdSAP calculation for individual dwellings, and thus will not improve the EPC rating.

This issue is further complicated in terms of how these costs are accounted for and passed onto tenants, e.g. as part of rent or service charges. Costs may be spread between dwellings as part of a central contract, for example. In some cases ( e.g. older tenements), lighting costs might be borne by the local authority as part of the street lighting budget. It would therefore be difficult to account for these improvements in the standard, although it could reference and promote them.

6.4 Community heating

The introduction of a community space and water heating system can help achieve CO 2 emission reductions, but will require careful design and specification to ensure this aim is realised.

This approach is particularly relevant for harder-to-treat dwellings, where previous reports have shown community heating or CHP systems to assist tower block flats in meeting the SHQS criteria, without any additional insulation measures, however such insulation will of course increase energy efficiency. Retrofit examples also highlight the benefits with regards to lifting occupants out of fuel poverty [26] .

It is important that social landlords fully appreciate the differences between the calculated energy requirements (determined by RdSAP), and the actual operation of a community heating system. As an example, the following section considers a gas communal heating system and discusses a number of factors to be taken into consideration when assessing the operational performance.

6.4.1 Boiler efficiency of communal boilers

Reports have highlighted the importance of a high-efficiency boiler for communal systems [27] , however table 4a of the SAP methodology specifies an efficiency of 80% for all gas communal boilers serving existing dwellings (the figure is slightly lower for communal CHP systems). Whilst the benefits of a more efficient system may not be represented by the EPC ratings; in practice, greater energy, CO 2 and fuel bill savings will be realised for the occupants.

Communal boilers, addressing both space and water heating, provide more benefit over individual systems where the 'winter' boiler efficiency is applied all year round; normally a lower 'summer' efficiency is used for the domestic hot water ( DHW) calculation [28] . This will contribute to a better overall efficiency, lower energy requirements and consequently lower fuel bills and CO 2 emissions.

6.4.2 Additional Energy Requirements

An advantage of installing a new communal heating system is that optimal controls and specifications can be detailed, in an effort to mitigate any further increase in energy requirements. Factors to consider include:

  • Distribution losses associated with the network connecting the heat source to each dwelling. (Table 12c of the SAP methodology details the distribution loss factors which need to be applied, should the community system meet a number of criteria [29] . The factors range from 1.20 to 1.05, with the lower values describing modern systems.)
  • Electrical energy is needed to pump water through the distribution system. (This is accounted for by adding electrical energy equal to 1% of the energy required for space and water heating [30] , and will contribute to an increase in fuel costs and CO 2 emissions, affecting both the SAP and EI rating.)
  • Efficiency adjustments as specified in table 4c of the SAP methodology (these are applied by multiplying the energy use by a factor ranging from 1.0 to 1.1 in relation to the control strategy.)

6.4.3 Fuel Costs

The SAP methodology allocates a unit cost for gas supplying a communal gas heating system of 3.78 p/kWh, which is greater than the unit cost for an individual gas boiler of 3.10 p/kWh [31] . These higher costs for community heating take into account bulk rates for buying the fuel used in the plant, operating costs, and energy used in pumping the hot water [32] . The effect of this is an increase in fuel costs, which will contribute to a lower SAP rating. The CO 2 emission rate per kWh remains unchanged.

The costs to landlords of gas safety checks and maintenance of individual boilers are not included for standard gas systems but they will be indirectly passed onto tenants. Hence, RdSAP may not reflect the full costs to tenants of communal systems. However, this is a moot point if electric heating is being replaced and individual gas systems are not technically feasible.

Again, when enforcing the standard, the Scottish Government may want to look favourably on landlords installing district heating systems where some properties are close to reaching the proposed ratings. Limited research may also be possible in this area to compare actual running costs and those used in RdSAP.


Email: Agnes Meany