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Volume 4
Chapter 6 Lighting, Ventilation & Heating
6.1. A house meets the tolerable standard if it has satisfactory provision for natural and artificial lighting, for ventilation and for heating.
Introduction
6.2. This element of the tolerable standard aims to ensure that a house provides the occupants with a basic level of comfort and safety.
6.3. This chapter provides advice for assessors to help them judge whether the provision of lighting, ventilation and heating is satisfactory. This element of the tolerable standard ties in closely with a number of others. Assessors should consider the advice here alongside other chapters of this guidance, in particular thermal insulation, electrical installations, bath/shower and wash-hand basin, and water closets.
Legislation
6.4. The tolerable standard was first defined in the Housing (Scotland) Act 1969 and has always included the requirement for a house to have satisfactory light, ventilation and heating. The Housing (Scotland) Act 2006 does not change this.
Definitions
6.5. Natural & artificial lighting: Natural lighting is daylight that enters the house, normally through the windows. The amount of light that enters the house is dependent on the size and number of windows. It can also be affected by shading caused by other buildings or objects outside the window. Artificial lighting generates light inside the house and is normally, but not always, powered by the electric supply.
6.6. Ventilation: Ventilation is the exchange of air inside the house with fresh air outside. Ventilation is an essential factor in controlling the moisture content of the air inside the home and helps prevent the occurrence of condensation. The most obvious method of ventilation is opening a window. Others include mechanical extractor fans, air vents and ventilation via fireplaces.
6.7. Heating: To be habitable, a house needs to be able to provide heating for the occupants. A house that has no means of heating is likely to present a risk to the health of the occupants. The majority of houses in Scotland have central heating systems, most of which use gas or electricity. Other forms of heating include oil fired range cookers, solid fuel fires and electrical heaters.
Making the assessment
6.8. The flow-chart below will help guide an assessor through the process of determining whether the house meets the tolerable standard for this element. Further information on each step is given below.
6.9. The flow-chart refers to both apartments and rooms. Assessors should take these terms to have the meaning given to them in the Scottish Building Standards Agency's Domestic Handbook. These are:
6.10. apartment: any room in the house not used solely as a kitchen, store or utility;
6.11. room: any enclosed part of the house not used solely as a bathroom, shower room, washroom, toilet, stair or circulation area.
6.12. An assessor should consider the following questions when making the assessment:
Is there satisfactory provision for natural light in all apartments?
6.13. An assessor should ensure that all apartments in a house have a satisfactory level of natural lighting. A simple way to judge whether there is satisfactory provision for natural lighting is to consider the ratio of the combined surface area of the windows against the floor area of the apartment.
6.14. As a guide, each apartment should normally achieve a ratio of at least 1:20. In other words, the surface area of the window should be at least one twentieth of the floor area. We present this ratio as a guide to assist assessors alongside their professional judgement. We do not expect assessors to routinely take precise measurements of window and floor areas.
6.15. Other factors might also influence the amount of natural light entering an apartment. For example, an apartment might achieve a ratio of 1:20 or greater, but receive little natural light during daytime because an adjacent building or structure outside the house obstructs the amount of light entering the apartment. In other cases, the position of the window(s) in relation to the overall dimensions of the apartment may mean it is unsatisfactory.
6.16. Sometimes the occupants of the house will use a normally habitable apartment for an alternative purpose, such as a photographic dark-room, and it may not have satisfactory natural lighting. In these cases, a house will not normally be below tolerable standard.
6.17. Assessors may occasionally find that a very small room with no natural light or ventilation, often referred to as a "box-room", is being used as a bedroom by the occupants of the house. This type of situation is not normally within the scope of the tolerable standard because it relates to the way the occupants are using the house as opposed to a specific deficiency in the house itself.
Is there satisfactory provision for artificial lighting?
6.18. Every apartment in a house, plus a bathroom, toilet, kitchen, utility, and all circulation areas, should have provision for permanently-fixed artificial lighting to allow the occupants to carry out normal domestic activities in safety and comfort. This will usually take the form of a wall light switch which controls an electric light on the ceiling or wall. A very small number of houses are not connected to the mains electric supply, or have a private generator, and may have alternative fittings, such as gas mantle type artificial lighting (where light is produced by heating an oxide-based compound with a flame).
6.19. An assessor does not need to measure the amount of light that the system is capable of delivering, rather that the occupants are able to use this to light their home should they choose. Occupants may opt to use alternative light sources, such as table lamps or candles, but the house should nonetheless have provision for fixed and permanent artificial lighting. An assessor should use his/her judgement to decide on each case if the provision for artificial lighting is satisfactory.
Is there satisfactory provision for ventilation?
6.20. It is essential that all houses have provision for ventilation so that the occupants are able to properly manage the environment within their home. Unsatisfactory ventilation is a major contributing factor to the occurrence of condensation in houses, and can also lead to hygiene problems.
6.21. All apartments, plus the kitchen, should have provision for ventilation. An assessor should use his/her judgement to decide if the provision for ventilation is satisfactory for each individual apartment. The most obvious method of ventilating a room is to open a window. For an apartment with a window, an assessor should consider the ratio of the window opening against the floor area. As a guide, the ratio should normally be at least 1:40 opening to floor area. As with natural light, assessors should use the ratio as a guide alongside their professional judgement. Where the ratio does not meet 1:40, assessors should also take account of the presence of other forms of ventilation such as air vents, open fireplaces and doors which might provide additional air changes in the apartment. A window that provides ventilation should open directly to the outside and not into an adjacent apartment, circulation space or common access route, such as a tenement close.
6.22. For bathrooms, and other apartments, plus the kitchen, where there is no satisfactory openable window, they must have an alternative ventilation system. Normally this will be a mechanical device, such as an extractor fan, but in some cases an assessor will find other systems such as a passive stack type (where warm, moist air passes through a vent into an almost vertical duct and is expelled at an outlet on the roof). The device or system must vent directly to the outside and not into an adjacent apartment, circulation space or common access route, such as a tenement close.
6.23. It is not essential for an assessor to test if a device is working if this is not practical at the time of the visit. But he/she should be satisfied that it is fit for purpose and not broken or damaged to such a degree that it cannot be used and is beyond economic repair. If the assessor considers the cost of repairing the device is disproportionate to the cost of replacement, the house is below tolerable standard.
Is there satisfactory provision for heating in all apartments?
6.24. To meet the tolerable standard a house must be able to support a heating appliance in each apartment. Most houses have a central heating system that delivers heat to all parts of the house, either from a gas powered boiler, electrical storage heaters, or from an oil fired boiler or range cooker. Where a house has a functional central heating system, it will meet the tolerable standard.
6.25. A house does not need to have a central heating system to meet this element of the tolerable standard. For houses without central heating, the minimum requirement where the house has a mains electric supply is that the house should be able to support the use of portable electrical heaters. This means that each apartment should have a fixed electrical installation capable of servicing a plug-in electrical heater.
6.26. In some cases, there will be no electrical socket in a room, and in some rural situations there may be no mains or private generator supply of electricity to the house. An assessor should consider what provision exists for heating the house and decide whether it is satisfactory. A fixed fireplace that can be used for burning solid fuel is normally satisfactory, but portable bottled gas heaters alone are not sufficient.
6.27. A house that does not have satisfactory provision for heating is below tolerable standard.
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