Document 1254

Scottish Parliament: Research Briefings: RN 00-24 Energy Efficiency in Housing

Author(s): Scottish Parliamentary Corporate Body

Copyright holder(s): Scottish Parliamentary Corporate Body: © Scottish Parliamentary copyright material is reproduced with the permission of the Queen's Printer for Scotland on behalf of the Scottish Parliamentary Corporate Body.


Research Note 00/24
28 March 2000


The Green Paper on Housing (1) outlines a number of measures for improving energy efficiency in housing. The current housing stock is 2.3 million and 20,395 new dwellings were constructed in 1998. The Green Paper points out that the energy efficiency of Scottish housing is poor. According to the National Home Energy Rating (NHER) system for assessing the energy efficiency of houses the average NHER of the stock is 4.1, whilst new homes are required to achieve an NHER of around 7 under building regulations. 93% of dwellings examined in the 1996 Scottish House Condition Survey did not achieve this energy rating.

The Green Paper identifies a number of schemes to tackle energy efficiency in housing, and this research note provides an updated position on these schemes. These include the Warm Deal; the review of the building regulations; and the review of the tolerable standard.


Warm deal provides a grant of up to £500 to make a home more energy efficient. Qualification for a grant depends upon receipt of a qualifying benefit, although anyone aged 60 or over will receive a grant of up to £78.75. The grant can help with cavity wall insulation; loft insulation; draughtproofing; hot and cold tank and pipe insulation; and energy advice and up to four energy efficient lightbulbs.

The allocation of funding in the Warm Deal Programme for 1999 - 2000 is as follows:

Total budget: £12m of which:
£3m goes to local authorities
£9m goes to other of which 70% should go to private sector / housing associations, and 30% is not targeted.

Preparation of a consultation paper has been put on hold for the time being, given the launch of the Warm Deal scheme on 1 July and the commitment in the Executive's Partnership Agreement to developing a Healthy Homes Initiative.


A study reviewing Scottish Mandatory Energy Standards for Buildings was commissioned by the Scottish Office Construction and Building Control Group to assess a range of suggested improvements to Part J of the Building Standards. These improvements would contribute to the commitment by the Government to reduce emissions of greenhouse gases to 12.5% below 1990 levels by the period 2008 to 2012 . The final report by Environmental Resources Management was published on 30 April 1999, and examined a range of measures that could be taken that would assist in the reduction of CO2 emissions. It examined the practicality of implementation, the cost, and factors such as the availability of materials in the domestic market.

How energy efficiency in dwellings is measured

There are currently 2 ways in which the energy efficiency of dwellings are measured. There is the Standard Assessment Procedure (SAP) rating, and there is the ‘target U-value’. The SAP is a measure of the energy efficiency of the house as a whole and is measured on a scale of 1 to 100, with 100 being the most efficient.

The ‘U-value’ is a measure of how well a particular wall; roof, floor or window can retain heat. Highly insulated walls have low U-values whereas poorly insulated walls have high U-values. The various parts of a dwelling currently have assigned U-values. However, a dwelling also has a ‘target U-value’. This allows some flexibility so that if one element does not comply with the standard, it can be compensated for by increasing the standard of another element.

Under the current Technical Standards, higher efficiencies for heating systems can be offset by lower requirements for thermal efficiency. In other words, lower standards of thermal insulation are permitted in dwellings as long as an efficient heating system is put in.

The report proposes breaking the link between the overall energy efficiency of the house (the SAP) and the standards for thermal efficiency (target U-value), and the introduction of a separate standard for heating system efficiency. This would introduce a requirement for both efficient heating systems and a high level of thermal insulation, and thus reduce energy consumption and CO2 emissions.

The following recommendations were made on changes to the Technical Standards in order to improve energy efficiency:

• To require an energy performance statement in environmental impact statements where one was required in the planning system.
• To introduce planning guidelines to promote the use of energy efficient glazing and windows designed to meet the requirements of historic buildings.
• Increase the required level of insulation for windows, doors and roof lights (for example, using low emissivity glass with 16mm air gaps which is currently used in other non-dwelling buildings) (the U-value would be changed from 3.3 W/m2K to 2.0 W/m2K).
• There is currently a variation in the requirement for glazing insulation according to the percentage area of glazing. It is recommended that this variation be removed, setting a fixed standard for glazing insulation equivalent to the highest standard.
• Increase the insulation requirement for walls (there are a variety of insulation processes that can be used for this depending on wall construction) (the standard would be changed from 0.45 W/m2K to 0.3 W/m2K).
• There are currently different insulation requirements for different types of roof. It is recommended that a common standard be applied, equivalent to the current highest standard (the U-value for all roofs would be brought into line at 0.25 W/m2K)
• Increase the insulation requirement for floors (for example, suspending mineral wool between joists) (the U-value would be changed from 0.45 W/m2K to 0.25 W/m2K).
• Builders are currently allowed to use inferior insulation standards if the window and door areas are reduced. Conversely, they are required to use higher standards if the percentage areas are increased. It is recommended that the lower standards be removed, and flexibility be accommodated by the target Uvalue method for dwellings instead.
• Separate standards be introduced for heating system efficiency.
• Some construction defects that lead to air infiltration can be difficult to identify. One method of testing this is through pressure testing. It is recommended that random pressure testing be introduced to promote improved construction practices, to reduce heat loss and CO2 emissions by infiltration of cold air.
• Reduction in building fabric insulation is currently permitted in return for high efficiency heating systems. It is recommended that this trade off be removed.

In terms of increase in construction costs, the report estimates that this would represent between 1% and 2% based on the recommendations made above. For example, for a semi-detached house of approximately 80m2, the construction costs may rise by anything between £500 and £900 depending upon the construction type used. It is suggested in the report that this would not create a significant market imbalance between new and previously used houses. It should also be noted that the increased costs would be partly offset by energy saving costs, which would benefit the occupiers of the house. Based on current construction rates, the proposed revisions to the Technical Standards would reduce CO2 emissions attributable to housing (as a whole – not just new housing) by 1.55% after 10 years.

The report contains a section on consultation that was carried out. The main element of this consultation appears to be with Building Control Officers themselves, which fed into the practicalities of the measures recommended by Environmental Resources Management. This report has been submitted to the Scottish Office for consideration, and does not represent proposals by them in any way. Draft regulations have not yet been published for consultation.

Tolerable Standard

The tolerable standard was introduced by the Housing (Scotland) Act 1969, and set out in s86 of the Housing (Scotland) Act 1987. It applies to all housing tenures and to all ages and types of house within them and has remained essentially unchanged since its introduction. It is complemented by a list of Standard Amenities that have been most recently set out in Schedule 18 of the Housing (Scotland) Act 1987. The tolerable standard was introduced at a time when demolition of slum housing was still common, and also acted as a standard to be reached if a house was to be saved by improvement. The Act places a general duty on local authorities to survey their areas from time to time to establish the number of houses which fall below the Tolerable Standard (BTS) and then take action to deal with them. There is no frequency of time limit for such surveys specified.

A consultation paper “Beyond the tolerable standard” was issued in May 1998. It states that the Tolerable Standard has remained unchanged for virtually 30 years, and that over that period the number of BTS houses has continued to steadily decline. There is therefore a clear need to review the position.

There doesn’t appear to have been any movement on this subject since the publication of the consultation paper. The Green Paper on promised an announcement on the future composition of the Tolerable Standard (or the introduction of an Index of Housing Quality) "shortly" (para 2.58). An announcement on the way forward was expected by the end of 1999, but nothing is forthcoming as yet.

Research Notes are compiled for the benefit of Members of Parliament and their personal staff. Authors are available to discuss the contents of these papers with Members and their staff but cannot advise members of the general public.

1 Investing in Modernisation – An Agenda for Scotland’s Housing

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The SCOTS Project and the University of Glasgow do not necessarily endorse, support or recommend the views expressed in this document.

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Scottish Parliament: Research Briefings: RN 00-24 Energy Efficiency in Housing


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