How to improve energy efficiency with insulation

In the UK, households are just behind transport as the second biggest contributors of greenhouse gases. The average household emits 2.7 tonnes of CO2 every year and approximately two thirds of all homes in the UK are poorly insulated. In terms of energy efficiency, a good heating system needs to be paired with high-quality insulation – there is no point in having a top-of-the-range heating system installed if you are losing heat through poor insulation.

Around 10 to 15% of heat in the home escapes through glazed surfaces. If you're in the process of renovating, you have the option to change your glazing but keep the window frame which will lower costs but may reduce window size and therefore the amount of light allowed in. Alternatively, you can replace the whole window which will improve thermal and acoustic performance even further.

Choose between standard double glazing, low-emissivity glass (which features an invisible microscopic coating for improved thermal efficiency) and triple glazing. It's worth noting that the lower the heat transfer coefficient (in Uw), the better the insulation.

When it comes to choosing an efficient front door, you need to first think about material: PVC is cost-effective and efficient; aluminium is known for its energy efficiency; and wood is naturally insulating but does require maintenance. If your front door is glazed or partially glazed, it should be fitted with double or triple glazing.

Pay close attention to the U value of a front door – the lower the value, the more insulating the door. Look out for air permeability ratings (classed 0 for no test up to 4 for the highest performance), water tightness ratings (ranges from Class 0 to Class 7A) and wind resistance (VA1; VA2; VA3; VA4; VA5).

Your roof can be responsible for up to 30% of overall heat loss in the home. Three main methods can be used to insulate a roof terrace as part of renovation work:

• Classic roof insulation which involves laying a vapour barrier and thermal insulation over the roof before covering it all up with a waterproofing membrane.
• Inverted roof insulation where the insulation is installed over a waterproofing membrane before being covered with gravel or concrete slabs.
• Adding a green roof: a more expensive but attractive option, this method involves laying a layer of thermal insulation followed by a drainage layer and filter membrane. These layers are then covered with moss through which plants can grow.

If you're looking to insulate a warm loft – meaning a habitable attic space – you have two solutions:

• Insulate on the inside just beneath the rafters. Panels or rolls of insulation are placed between the roof rafters to prevent heat from escaping. It is also possible to use blown-in insulation. In this case, the insulation is either blown behind a waterproofing membrane or OSB panels.
• Insulate from the outside: this option is more expensive but proves efficient and makes for an attractive result as it allows the roof trusses to be visible from the inside. Roof sarking involves installing rigid insulation boards between the roof truss and the outer roof covering and topping it off with a vapour barrier.

A cold loft is an uninhabited, unheated loft which must be insulated from the rest of the house to prevent heat loss. Insulating your roof space is the most effective way to improve the energy efficiency of your home and you may be eligible for free loft insulation if you have no existing insulation.

You can choose between:

• Loft rolls: designed to fit between joists on on the floor. This option is ideal for cold lofts that are easy to access and where insulation is straightforward to lay.
• Blown-in insulation. In this case, the insulating material is blown directly onto the floor of the loft and settles into every gap.

Walls represent about 20 to 25% of overall heat loss in the home. Insulating your walls will improve the efficiency of your home as well as limiting the cold wall effect. In turn, this helps to reduce moisture, enhance comfort and reduce bills. Several options are available:

• Screw-in or glue-on insulating panels secured directly to the walls. This technique can only be carried out on perfectly flat and dry walls.
• Stud wall insulation boards.
• Blown-in insulation between wall studs.

Floors lose a considerable amount of heat and are thought to account for about 7 to 10% of overall heat loss. Two different insulation methods can be used for flooring:

• Insulation from above. In this case, insulation is placed directly over the floor before covered by flooring. While an ideal solution if your house is all on one level, you won't usually be able to live in the house while the work is being carried out.
• Insulation from below. Insulation can also be fitted to the underside of a floor meaning directly on the ceiling of a basement or crawl space. Easier to carry out, this method means you won't have to redo all your floors.

Insulation can be divided into three broad categories.

Mineral insulation

Glass wool, made of a mix of sand and recycled glass, comes in all forms and is a highly insulating material. Rockwool is made using basalt fibres and has a really long lifespan. Another option is perlite, the strength of which means it works well for insulating ceilings and roofs. Vermiculite is perfect for lofts and floors. Cellular glass is a recycled material used for walls and roof terraces.

Natural and bio-based insulation

Natural insulation is made, as the name suggests, using natural materials while bio-based insulation is made from materials derived from plant or animal biomass. This type of insulation helps to reduce greenhouse gases. The main types of natural insulating materials include wood and wood-based products, straw, hemp, flax, cotton, cork, coconut fibre, sheep wool and duck feathers.

Synthetic insulation

While not too expensive and highly efficient, synthetic insulation is derived from petrochemicals. Polyurethane is water- and compression-resistant and highly insulating. Extruded polystyrene boasts excellent thermal performance and is relatively thin. Expanded polystyrene is cost-effective and versatile. Phenolic foam is thin and fire-resistant.

• What is the energy transition?
• Home energy efficiency grants
• Home energy efficiency standards and certifications
• Energy-efficient heating systems: what are the options?
• Energy-efficient ventilation systems: what are the options?
• Energy-efficient water heaters: what are the options?
• Energy-efficient windows and doors: what are the options?