The Chance Of Later Addition Of EWI Is Higher For A Partially Filled Cavity Wall
Warm air always moves towards cold air, and in winter the heat from your home will escape through the walls into the surrounding air. Nearly 30% of heat is lost through an uninsulated external walls. By insulating your external walls, you'd save at least £150 per year in heating bills. Something you should consider seriously.
Most of the houses in the UK have either cavity walls or solid walls as the envelop of the building. A solid wall is build without a cavity, even if it consists of two or more walls. They are usually made of brick, blockwork, stone or concrete.
A cavity wall is made up of two walls with a gap in between, separated by an empty, hollow airspace in between. This cavity was supposed to keep the house warm, considering that the air is a poor conductor, and mainly to keep water and moisture away from the inner wall, keeping it dry and protected from decay and damp and allowing any deposited water to evaporate.
If your house was built after the 1920s, it is likely to have cavity walls. If the pattern of your house is regular the external wall is probably a cavity wall. Also, if the width of the brick wall is more than 260mm, it probably has a cavity. You can do that by measuring across the door or window. If the wall is made of stone, it can be thicker, but might not have a cavity. The older houses might not have cavity walls.
If your house is a steel-framed, timber-framed or is made from concrete, they are insulated the same way as a solid wall. They can be insulated from the inside or the outside. Insulating from the inside is cheaper, but would take out the living space and inconvenient to the inhabitants. External wall insulation is depends on the situation of the building, and the area regulations, but would be very effective in keeping the heat in and money in the pocket in the long run.
If your house is built after 1920s, and if you are having problems with heating, i.e, loss of warmth, you should consider insulating the external walls. It would be better to speak to an engineer or to a specialized insulation installer to determine, which system is better for you. If the masonry of your building is in good condition, not exposed to driving rain and has unfilled cavities, the external walls can be insulated by cavity wall insulation method. If you have any damp patches on your internal walls then that problem should be resolved beforehand. There had been complains of serious dampness, mould and condensation issues after insulating the cavity walls, but that was not because of the insulation, but because of the earlier damp issues were not solved beforehand and also the external leaf of the wall was not correctly repaired. Old house with correct cavity insulation would save heat and save money.
External walls of your house can be insulated internally or externally. There are advantages and disadvantages to both.
Internal wall insulation is cheaper to install than insulating the walls externally, but would reduce the floor area of the interior and be disruptive. Any problems with penetrating or rising damp must be fixed first. You'd also have to vacate your home for the time.
External wall insulation can be applied without disruption to the inhabitants, does not reduce the floor area of your home. It would fill cracks and gaps in the brickwork, reducing draughts and increase the life of your walls. EWI would improve weatherproofing and sound resistance and reduce condensation on internal walls and can help prevent damp. It would renew the appearance of outer walls. You may need permission from your local council. There should be good access to the external walls. If the walls are structurally unsound, they have to repaired first.
Before your walls can be insulated, any problems with penetrating or rising damp must be resolved, as this could lead to serious problems in the future. To prevent condensation, recessed areas around windows must be insulated as well as the walls. It may be necessary to extend window sills and the roof overhang to protrude beyond the insulation layer. All external pipework and other fittings will have to be removed and replaced or remounted on relevant fixings.
The external insulation would be covered with protective layers of render or cladding. The finish can be smooth, textured or painted, tiled, panelled, pebble-dashed or finished with brick slips to provide a real masonry brick finish.
Additionally,
Cost is the biggest barrier to uptake, but warmth is even more important than energy and bill savings for householders. When people start spending more time in their homes (retirement), warmth becomes more important, external wall insulation becomes more significant. Sometimes, even after installing the cavity wall insulation in an old house, you might still feel the lack of warmth. In such a situation, it would be better to decide on additional EWI installation. On the whole, EWI installation is more effective than cavity wall insulation, as it keeps the structural wall away from moisture ingestion, therefore damp and mould problems of the interior side of the wall.
Conclusion
If your home's external walls have a cavity, and they are still not insulated, you have choice of filling the walls with insulation, or add insulation to the external walls. Cavity-wall insulation is injected through the outer wall of your home into the space between the inner and outer leaves of brickwork that make up cavity walls. But, if your external walls are already had been insulated, but partially filled with insulation, it is practically impossible to fill the rest with insulation. There is also a problem of long term moisture ingression, and because of that damp problems of the interior part of the exterior wall. Most times, it would be impossible to get rid of the damp problems without removing or major repair to the outer leaf of the wall. The gap between the partial filled cavity wall is supposed to drip the water out and help it evaporate. But, water likes to hold on to surfaces that are not quite smooth, and the internal side of outer leaf and the insulation surface is not exactly smooth. So, in time, you may have damp problems. Their is a real chance of a need to add additional insulation to your partial filled external walls. The chance of later addition of EWI is higher for a partially filled cavity wall.