Modern medium rise 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, if gas is already available to individual flats then that would be the cheapest form of heating. Centralised boiler plant is feasible, running from either gas or oil, if there is a suitable location. Alternatively district heating or CHP can be used, either dedicated to the building or by connecting into a local scheme. 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. If centralised provision is not practical then a well-controlled off-peak storage system is probably best.

Insulation measures

Walls

Cavity fill would be the best option barring any technical barriers, but that would not deal well with thermal bridges associated with solid floors and balconies. Balconies would need to have external insulation applied to remove the thermal bridge, and this would be easiest to implement if the whole structure were to be insulated externally. If the rest of the building is insulated using other techniques then detailing of the balcony insulation is critical if thermal bridges are to be minimised - the balconies can be insulated with external insulation or they can be enclosed to create a buffer zone. The latter would have a number of benefits: more useable space for occupants, the thermal bridge would be reduced, and heat loss through doors and windows to the balcony would be reduced.

Internal insulation could be applied to individual flats, but thermal bridging issues would remain.

Glazing

If new windows are not to be installed then trickle vents should be added to timber windows if not already fitted, and the windows draught stripped. Secondary glazing could be considered, but ventilation and other issues such as egress in emergency should also be taken into account.

Floors

Suspended timber floor 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.

There may be an assumption that floor insulation/draught proofing is only an issue on the ground floor, but in many older properties air infiltration into the under-floor space at first floor level and above can occur from a number of sources. These include soffits of porches and passage ways, the junction between the floor and a bay, and via the eaves box in attic rooms. A proper survey of the building should be carried out if effective draught proofing of floors is to be achieved.

Solid floors can be insulated using an insulation / chipboard composite to create a floating floor above the existing, although the finish floor level will be raised and may necessitate other work such as shortening of doors and installing thresholds. An insulation/chipboard composite floor can be produced in a range of thicknesses, and this approach can be taken using only 5mm of latex foam beneath the chipboard 'floating floor'. Such a thin layer of insulation will not save large amounts of energy but may be sufficient to prevent condensation. If the floor is solid and bridges the cavity or extends to create a balcony there may be a significant thermal bridge depending on the type of insulation installed. The effects of the thermal bridge can be minimised by the creation of a 'floating floor' as described above, coupled with insulating the underside of the floor for ~0.5 meter adjacent to the external wall.

Roof

Flat roofs can be dealt with in two ways - either warm deck insulation can be applied or a pitched roof can be added. Flat roof technology may be quicker and cheaper, and may be the preferred solution if the building is not being fully scaffolded for other reasons. The drawback is the there is a long term maintenance commitment associated with it. Pitched roofs are longer lasting between maintenance cycles and have the advantage that they can make the building look more attractive and extra useable space can be created - they are, however, more expensive.

Existing lofts should be insulated (or topped up) to a depth of 250mm insulation. Care needs to be taken to ensure that the loft space is ventilated. If for any reason the loft is inaccessible (e.g. due to low pitch) insulating the underside of the top floor ceiling can be quite practical. If slates/tiles need to be replaced insulate roof at the same time, either by conventional loft insulation (breathable sarking can help with the ventilation issue) or by insulating at rafter level thus creating a warm roof construction. Insulation above rafters increases the height of the roof, which may be problematic if the building adjoins another.

Loft hatches and other points where services penetrate the roof space should be sealed to prevent draughts.

Ventilation

Rapid ventilation needs to be introduced to wet areas, and background ventilation to other areas. Passive stack would be an effective solution, but it may be difficult to retrofit unless major refurbishment of the whole block is being undertaken. It may be possible to fit in individual flats on the top floor. Background ventilation in the form of trickle vents would be preferable - if that is not practical then some draught stripping (2m per room) could be omitted from windows or 'through the wall' vents fitted (although these are prone to being sealed off by tenants).

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.