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Volume 4
Chapter 7 Thermal Insulation

7.1. A house meets the tolerable standard if it has satisfactory thermal insulation.

Introduction

7.2. To comply with the tolerable standard a house must have satisfactory thermal insulation. This new requirement reflects a recommendation from the Housing Improvement Task Force.

7.3. The Task Force noted the existence of a consensus that some basic thermal insulation is essential to the functioning of a building as a home. It also highlighted a major change in expectations in respect of the thermal performance of a house over the past thirty years.

Legislation

7.4. The 2006 Act added this new element to the tolerable standard.

Definitions

7.5. Thermal insulation: the concept of thermal insulation relates to the capacity of a house to retain heat. It can refer to both the performance of building elements and the impact of any insulation measures added after construction.

7.6. In the context of the tolerable standard, it is worth highlighting the distinction between thermal insulation and energy efficiency. Thermal insulation relates to the qualities of the fabric or structure of the house. Energy efficiency, on the other hand, is a broader concept. When applied to a house, it takes account not only of the thermal qualities of the structure but also the type and performance of the heating system. The two most widely-known tools for measuring energy efficiency in houses are NHER¹⁶ and SAP¹⁷.

7.7. So, thermal insulation relates only to the capacity of the house to retain heat. It does not extend to the performance of the heating system or the interaction between the heating and the building fabric. We deal with the heating requirements of the tolerable standard in the chapter on lighting, ventilation and heating.

7.8. Satisfactory: for the purpose of this guidance, we recommend that assessors use the presence of roof ¹⁸ insulation in a house as the indicator of satisfactory thermal insulation. We describe below how assessors should make this assessment.

7.9. We considered a number of alternative measures, covering both an elemental and whole house approach, as we developed this guidance. Annex B describes the options we considered and the reasons for our conclusion. We concluded that a house should have some form of roof insulation to meet the tolerable standard. This approach allows assessors to make a judgement using a straightforward indicator. It also enables local authorities to target easily-identifiable action which can achieve a significant improvement in thermal insulation performance.

Making the assessment

7.10. In the remainder of this chapter we offer practical guidance to help assessors:

• identify the types of house that are capable of having roof insulation;
• check for roof insulation in individual houses; and
• focus on those houses in their area most likely to have no roof insulation.

7.11. The flowchart below summarises the main issues an assessor should consider. We explain each stage in detail in the following paragraphs.

Roof insulation: exclusions

7.12. Roof insulation is not an option for all houses ¹⁹. It is not possible to fit roof insulation in flats which are not on the top floor. Any flat which is directly below another flat does not have a roof space and is therefore unable to have roof insulation.

7.13. It would be unreasonable to declare a non top-floor flat as BTS because of a lack of roof insulation. Assessors should not consider this house type when looking at the thermal insulation element of the tolerable standard.

7.14. Assessors should therefore concentrate on houses where roof insulation is a practical option for the owners. Broadly, these are:

• top floor flats; and
• non-flats ( i.e. terraced, semi-detached and detached houses).

Level of roof insulation required

7.15. Roof insulation comes in a variety of materials - fibre rolls are most common; a range of loose-fill insulation options are also available. Assessors are likely to find variations in the thickness of roof insulation in houses they check.

7.16. For the purpose of the tolerable standard, assessors should look simply for the presence of insulation across the roof space of a house. The thickness of the roof insulation is not a consideration. As a guide:

• A house which has insulation across all its roof space meets this element of the tolerable standard.
• A house that is a top floor flat or a non flat and which has no roof insulation in its roof space will normally be BTS.
• Assessors may find a house that has partial roof insulation. An example might be where a house has insulation in the roof space of an extension or conversion but not in the original roof space of the house. In houses with partial roof insulation, assessors should use their judgement, and in particular take account of the balance between the insulated and non-insulated areas. As a guide, assessors should normally look for insulation to cover at least the roof space in the main original part of the house.

7.17. The tolerable standard represents the minimum requirements a house should meet in the 21st century. Our recommended approach to assessing thermal insulation focuses on the houses that perform most poorly in terms of roof insulation. A large number of houses have roof insulation which does not comply with current industry good practice standards (for example a depth of 270mm for loft insulation) ²⁰. These houses meet the tolerable standard. But we would encourage assessors, where possible, to highlight to owners the advantages of improving existing roof insulation in terms of improved thermal insulation performance and to signpost householders to additional sources of information and financial assistance. We provide details of sources of information and assistance later in this chapter.

Checking individual houses

Houses with pitched roofs and loft spaces

7.18. Checking whether an individual house has roof insulation will be straightforward in many cases. For houses with a pitched roof and an accessible loft, assessors should check in the loft space to confirm whether it is insulated. Assessors might need to consider access issues and make specific arrangements, for example where the loft is in a common close and is locked.

7.19. Assessors should be aware of health and safety issues and work in line with their organisation's procedures when carrying out this task. Occupiers who access the loft space in their homes should take sensible safety precautions when doing so.

More complex house types

7.20. Checking for roof insulation is potentially more complex for some house types. Examples include houses with a flat or mono-pitched roof, attic rooms or where the owner has converted a pitched loft space into a room. In these cases the insulation will possibly be between the plasterboard and the roof construction. On flat-roofed properties, if the roof has been re-covered within the last 20 years or so, it is possible that this work has incorporated insulation in the roof build up between the roof deck and waterproof covering.

7.21. When considering these house types, assessors should bear in mind the points in paragraph 7.28. below about the requirements of Building Regulations for houses built or converted since the mid 1960s. The effect of the Regulations is that most houses built since this date are likely to have roof insulation, as well as extensions and conversions to existing houses. This will help assessors make a judgement in many cases without the need to inspect the roof space.

7.22. For more complex house types where the Building Regulation requirements are not relevant, assessors should take reasonable steps to find out whether the roof space has insulation. Possible methods of doing this - depending on individual circumstances - could include:

• looking for an accessible space in the roof - such as a wall hatch - that allows access to check for the presence of insulation;
• asking the occupier if they know whether installation has been installed;
• checking whether the local authority has records of historic insulation schemes;
• checking with an architect or other professional who has knowledge of the construction methods of the house type, or with a local archive;
• inspecting the inaccessible area with a borescope (where not disruptive); or
• using thermal imaging equipment, which may be able to provide an indication of the rate of heat loss.

Fitting roof insulation

7.23. This guidance document does not extend to offering detailed advice on how to deal with houses that do not meet each element of the tolerable standard. We provide links at the end of this chapter to other sources of practical information and financial support relating to roof insulation. The Scottish Government's Warm Deal and Central Heating programmes provide financial help for certain households to insulate their homes. The package of available measures includes loft insulation ²¹. You can follow the weblink at the end of this chapter for more information about the Warm Deal.

7.24. Installing roof insulation will be a straightforward solution for many of the houses that fail this element of the tolerable standard. But for some houses, such as those with flat, mono-pitched, mansard ²² roofs or attic rooms, adding roof insulation could be challenging.

7.25. Installing additional insulation in the roof space in these types of house after construction can be disruptive, difficult or not technically feasible. So, requiring an owner to install insulation may not be a practical solution in all cases. Assessors should take a pragmatic approach, on a case by case basis, and use their judgement when deciding whether to take action on individual 'hard to treat' BTS houses. One option in some circumstances may be to consider whether an appropriate response is to link insulation work with future improvement work to the house. For example, it may be possible to install insulation externally at the time of recovering the roof.

Profiling houses with no roof insulation

7.26. We would expect that local authorities will want to develop a strategic understanding of houses most likely to have no roof insulation, particularly given that this is a new element of the tolerable standard. Authorities may want to develop a profile of the types of houses that are at most risk of not meeting this element of the tolerable standard. This could help to help shape an authority's local housing strategy and allow it to target and prioritise action on an area basis.

7.27. In the following paragraphs we set out a summary national profile of roof insulation by house type and age, drawing on data from the 2004/05 Scottish House Condition Survey ²³. Authorities might also be able to use findings from local house condition surveys and other local knowledge to help build a profile of their area.

Age

7.28. The most significant factor influencing whether a house has roof insulation is its age. Before the mid-1960s there was no national requirement for new houses to have roof insulation. Since the mid-1960s, Building Regulations have required that new houses (including houses with flat roofs) and extensions / conversions to existing houses have a specified level of roof insulation. The required level of insulation has increased in stages over the years from an initial 25mm in the mid-1960s. The current requirement is based on the U-value (a measure of heat loss) rather than a specific thickness of insulation.

7.29. The effect of this requirement is that the vast majority of houses built or extended since the mid-1960s have roof insulation to all or part of the property. Assessors should be aware that there will be exceptions, such as situations where owners have removed roof insulation as part of improvement work. Conversely, many owners have added roof insulation to houses built before the 1960s. But generally, newer houses are much more likely to have roof insulation than those built before the mid-1960s. Therefore, assessors may want to give greater attention to older houses.

7.30. Focusing on houses built before 1965:

• pre-1919 houses are more likely than newer houses to have no roof insulation:
• around half of all houses without roof insulation (and capable of having it) are pre-1919; and
• almost 1 in 5 pre-1919 houses (and capable of having roof insulation) do not have any.
• the next biggest category - in terms of numbers - is houses built between 1945 and 1964. This period saw the construction of many non-traditional houses which are hard to treat:
• almost a quarter of all houses without roof insulation were built in this period;
• this represents a much smaller proportion of all the houses built between 1945 and 1964 - around 5 per cent - compared with the earlier period.

House type

7.31. At a national level there is no significant difference in the percentage of houses with roof insulation between flats and non-flats ( i.e. terraced, semi-detached and detached houses), once we remove flats without roofs from the calculation.

7.32. Overall, the vast majority of houses without roof insulation are non-flats. This reflects the fact that many more non-flats than flats have the capacity for roof insulation, as discussed above.

Further Information

Energy Action Scotland

7.33. Energy Action Scotland's website provides information about improving thermal insulation as well as broader information on fuel poverty and energy efficiency: http://www.eas.org.uk/

Energy Saving Trust

7.34. The Energy Saving Trust ( EST) Advice Centres provide expert and independent advice about the full range of financial support available to households to insulate their homes. The EST website also provides information on loft insulation: http://www.energysavingtrust.org.uk/home_improvements/home_insulation_glazing/loft_insulation/

Scottish Building Standards Agency

7.35. The SBSA Technical Handbook provides guidance on achieving the standards set in the Building (Scotland) Regulations 2004: http://www.sbsa.gov.uk/tech_handbooks/tbooks2007.htm#1

Scottish Government Warm Deal programme

7.36. The Warm Deal and Central Heating programmes provide financial help for certain households to insulate their homes. The package of available measures includes loft insulation: http://www.communitiesscotland.gov.uk/stellent/groups/public/documents/webpages/cs_017267.hcsp#TopOfPage

Energy Efficiency Commitment

7.37. The Energy Efficiency Commitment provides grants and subsidies for all householders to improve the energy efficiency of their homes. Under the EEC, electricity and gas suppliers are required to achieve targets for the promotion of improvements in domestic energy efficiency. From 01 April 2008 the EEC programme will be renamed the Carbon Emissions Reduction Target ( CERT) programme. The suppliers under this scheme will continue to promote energy efficiency measures to consumers. http://www.defra.gov.uk/environment/climatechange/uk/household/eec/

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