High rise

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 present it would be the most economical choice. 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 pipes running 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

Overcladding using some form of external insulation with either a rendered finish or rain screen cladding is a popular solution for tower blocks, particularly when the external cladding is in poor condition. This copes well with thermal bridges at 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 internal insulation, but that would present problems dealing with thermal bridges.

Glazing

Window areas are often very generous in high rise, leading to high heat loss and discomfort in colder months and overheating in summer. Consideration could be given to reducing window sizes in such cases. 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 (ie 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 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 in high rise 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.

Ventilation

Precast concrete buildings with solid floors can be inherently very airtight unless they are fitted with poorly fitting windows. Existing single glazed units should be draught stripped, and any replacement double glazed units should incorporate effective draught strips and trickle ventilation. Humidistat controlled extract fans, preferably with heat recovery, should be fitted to kitchens and bathrooms.