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What is Energy Efficiency Retrofit?

Energy retrofit is installing energy efficiency measures into an existing building. There are many options available depending upon the construction of your property.

Loft insulation is one of the most cost effective ways of improving energy efficiency in your home and also one of the easiest to install.  The most common form of roof space (loft) insulation is mineral wool matt, simply rolled out over the ceiling between and over ceiling joists.  Current building standards require a depth of around 270mm.  The term mineral wool includes both rock or glass wool and matting.  It is available in a range of thicknesses and forms including a sealed format where the material is wrapped in polythene or linen for occupants with allergies.

You can bring in a professional to install it for you. Alternatively, you can speak to your local Builders Merchant or DIY specialist for advice on how to install it, and what protective clothing you should wear.  You will need to empty your loft before insulation is installed.

It is recommended that you draught strip and insulate your loft hatch.  You should also insulate any water tanks and pipes in the loft at the same time. You should never insulate directly under the water tank. Follow instruction for leaving a breathable gap around the perimeter of the loft space. Attention should also be paid not to cover down lights or electrical cables. In cases where the loft space is poorly ventilated it may be advisable to install roof vents. This is a job that should be carried out by roofers.

A flat roof should preferably be insulated from above.  A layer of rigid insulation boards can be added either on top of the roofs weatherproof layer or directly on top of the timber roof surface with a new weatherproof layer on top of the insulation.  This is best done when replacement of the roof covering is required. If your flat roof needs to be replaced, you must insulate it to comply with building regulations.

It is possible to insulate a flat roof from underneath, but this can be an intrusive and disruptive process and can lead to condensation problems if not completed correctly.

Properties built after 1920 are mostly constructed with cavity walls; two layers of brick with a gap, cavity, between the layers. This type of wall can be insulated by filling the gap between the two skins of masonry forming the external wall with an impervious or self-draining insulation material. Small holes are made (driller) in a pattern on the external wall and the insulation material is then injected through these holes into the cavity. Once the cavity has been filled with insulation these small holes are then sealed. These works should only be carried out by approved installers.

Properties build before 1920 are mostly constructed with solid external walls. Solid walls can be insulated either internally or externally. During the 1960’s and 70’s many non traditional build type construction methods were developed. These vary throughout the country, but similar techniques can be used to insulated as with solid wall construction.

a) External wall insulation

External wall insulation involves fixing a layer of insulation material to the external wall, then covering it with a special type of render (plasterwork) or cladding.  The finish can be smooth, textured, painted, tiled, panelled, pebble dashed or finished with brick slips.

In addition to making a property more energy efficient it will renew the appearance of outer walls and improve weatherproofing and sound resistance, reducing draughts by filling any cracks or gaps in the brickwork.  It also increases the lifespan of your walls by protecting the brickwork. 

b) Internal wall insulation

Internal wall insulation involves fitting rigid insulation boards to the internal wall or by building a stud wall filled in with insulation material such as mineral wool fibre. It is generally cheaper to install than external wall insulation but it will slightly reduce the floor area of any rooms in which it is installed (the thickness of the insulation board is around 100mm).  The process is quite disruptive but can be done room by room to minimise disruption in the home.  Skirting boards, door frames and external fittings need to be removed and then reattached once the insulation board has been installed. It can make it hard to fix heavy items to inside walls, although special fixings are available.

Underfloor insulation is normally only required for ground floors.  However, you should consider insulating any floors that are above unheated spaces such as garages as you could be losing a lot of heat through those.

a) Timber floors

Timber floors can be insulated by laying mineral wool insulation, supported by netting, between the joists underneath the timber floor.  If there is an adequate crawl space, normally around 1meter under the floor. Then the insulation can be fitted from below, this is the preferred option as the floor boards can remain in place.  Alternatively, the insulation can be fitted from above but this is disruptive as it involves lifting the floorboards.  A recent innovation for timber floors with a crawl space which is too small to allow traditional insulation to be installed from underneath is to use a robot.  The robot applies spray foam insulation to the underside of the floorboards.

You can also fill gaps between floorboards and skirting boards to prevent heat loss and draughts. When underfloor insulation works are being carried out, attention should be paid to ensure that all air bricks and vents are free of obstructions and that the underfloor space has adequate ventilation.

b) Solid floor insulation

Solid floors are insulated using rigid insulation foam which can be fitted either above or below the concrete. If the concrete is above the insulation it can sometimes store heat during the day which helps keep the room warm at night.  If the insulation is above the concrete the room will heat up more quickly in the morning.

Rigid insulation can be laid on top of the original floor then chipboard flooring can be placed over it.  This will raise the level of the floor so you will need to make sure doors are trimmed shorter to make room for the insulation.  Skirting boards and some electrical sockets may need to be moved.

a) Secondary glazing

Involves installing supplementary glazing on the inside of an existing single glazed window.  It can be permanent although often secondary glazing panels are added as a temporary measure. Secondary glazing can be a useful addition when properties are within conservation areas where double glazed units may not be permitted by local planning authorities.

b) Double glazing

Double glazed windows use two sheets of glass with a gap between them that creates an insulating barrier.  In order for double glazed windows to be effective thermal barriers the gap between the panes of glass needs to be airtight and filled with an inert gas (or a vacuum).  Double glazing is more expensive than secondary glazing but does provide a higher level of energy efficiency as well as reducing noise and enhancing the look of your property.  You are advised to check that the installer complies with all planning and regulatory requirements.