Tenement flats

Heating system

Gas heating in individual flats is not condoned by many social housing landlords because of the potential consequences of a gas explosion, however where gas is already in place it would be the most economical form of heating. Centralised boiler plant is feasible, running from either gas or oil. Alternatively district heating or CHP can be used, either dedicated to the building or by connecting into a local scheme. Existing communal pipe runs to radiators etc. can often be re-used, and advantage can be taken of any insulation measures by fitting smaller and more efficient boilers. However if the pipe runs to individual flats are not already in place they can be difficult and / or disruptive to install. Consideration also needs to be given to the mechanism whereby tenants are charged for the energy they use.

Insulation measures

Walls

If the entire building is being treated then external insulation would be the best solution technically because cold bridges would be removed. This would be particularly beneficial in cases with solid concrete floors because of the difficulty associated with removing the thermal bridge. However, there would be a significant cost for scaffolding, and planning consent may be required, particularly if the building had period features.

For individual flats the most appropriate measure would be internal insulation, supplemented by flexible internal linings in areas where the additional thickness of internal insulation creates problems. Internal walls separating unheated communal spaces from flats could be dry lined to reduce individual household's fuel bills.

Glazing

If windows are not to be replaced consideration should be given to fitting secondary glazing. However, consideration also needs to be given to ventilation requirements. Metal frames can be more airtight than timber, but more difficult to provide background ventilation since trickle vents cannot easily be retrofitted. Specialist companies exist who are able to refurbish steel windows - contact the Steel Window Association for details.

Metal windows without thermal breaks are also more prone to condensation than other materials and the introduction of secondary glazing to combat condensation can lead to the structure becoming more airtight (particularly with solid concrete floors) leading to indoor air quality problems. The best solution in these circumstances would be to replace the windows with modern double glazed units with trickle vents thus allowing a sensible ventilation strategy to be implemented.

Floors

Any floor (or part of floor) that separates habitable rooms from unheated spaces should be insulated.

Suspended timber floors can be quite draughty, especially if square edged boards have been used. Effective draught sealing of the entire floor (for example by applying hardboard or similar and sealing around skirtings with mastic) would increase comfort levels markedly. If floorboards are replaced insulate between joists.

Solid concrete floors can lead to cold spots and condensation internally due to thermal bridging. This can be difficult to deal with if external insulation is not used. Insulation could be applied both above and below solid floors, but there will be problems with levels (a small step would be created between landings and finish floor level within each flat) and doors will need to be shortened. If the underside of an internal floor is insulated lighting circuits may need to be replaced or modified. However, in order to deal with the thermal bridge it would not be necessary to insulate all of the underside of an intermediate floor - only the perimeter adjacent to an external wall for a distance of roughly 0.5m would need to be insulated. This may mean that lighting circuits would not need modification, but there would be a visible step in the ceiling level.

Roof

Roofs on this type of structure can be quite variable and complex, ranging from flat to those with multiple pitches or combinations of flat and pitched portions.

Pitched roofs with accessible lofts should be insulated in the usual way. If the loft is not accessible then insulation can be applied to the ceilings internally, but that would be disruptive to tenants and may involve changes to lighting circuits.

Flat roofs can be insulated from the outside by creation of a warm deck construction, which would involve minimal disruption to tenants and the rest of the fabric of the building. Alternatively the building could have a pitched roof added in which case additional useable space can be created, particularly if the roof were insulated at rafter level.

Ventilation

Background ventilation should be provided in habitable rooms. Trickle vents can be fitted to existing windows, but this may not be practical for some types of frame. 'Through the wall' ventilators may need to be fitted, but tenants can easily seal these up.

Passive stack ventilation, particularly in kitchens and bathrooms, can be fitted during major refurbishment although routing ducting (which needs to be near vertical) may be difficult. Treatment of individual flats in upper floors may be more straightforward. Extract ventilation, preferably with heat recovery, should be fitted in situations where passive stack ventilation is not practical.

Fireplaces no longer in use should be closed off to reduce unwanted ventilation, but not completely sealed - it is important that chimneys no longer in use are ventilated by the fitting of small grills at the bottom (these can be fitted internally or externally), and of ventilated cowls externally.

Positive pressure ventilation could have a role to play in communal areas, but landlords should check that fire safety is not compromised, particularly with respect to smoke control systems that rely on pressurisation of common escape routes.