System built flats

Heating

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 installed then it will be cheapest fuel. Centralised boiler plant is feasible, running from either gas or oil, if there is a suitable location within the block. 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. Where distribution pipes are already in place smaller communal boilers with effective controls can be connected to it, taking advantage of lower heat loads resulting from insulation upgrades. 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.

Walls

External insulation is a robust solution for flats, particularly when the external wall is in poor condition. This copes well with thermal bridges associated with intermediate floors, balconies and access walkways. Balconies and walkways can be fully enclosed to create buffer zones. If external wall insulation is not considered then enclosing the balconies etc. will also reduce the effect of the thermal bridges associated with them.

If external walls are in good condition cavity wall insulation can be used at heights up to 25 meters in some circumstances, but may leave problems with thermal bridging at intermediate floors.

Individual flats could be treated with cavity insulation or internal insulation, but that would present problems dealing with thermal bridges.

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.

Spandrel panels below windows are frequently very poorly insulated and should be treated separately if necessary.

Floors

Thermal bridging at the edges of intermediate floors is the most common issue with this sort of construction. If external insulation is not used then dealing with the thermal bridge is very difficult. External insulation could be used locally (i.e. only on the edge of the floor slabs), but that would be highly visible externally.

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 may 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 in blocks of flats 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 that 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 and would need scaffolding.

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).

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.