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Why its important to insulate your roof

Hot air rises, which means that in your home, it heads towards the roof. In homes that are not insulated, around 25% of all heat loss occurs through the roof. 

If you want to keep your home warm in the most cost effective way then the roof is one of the most important areas to consider.

Fortunately, improving the energy efficiency of your roof/ loft space can be one of the cheapest and easiest ways to achieve significant energy savings.

The return on investment achieved from roof insulation is higher than all other energy efficiency improvements apart from LED lighting, so this is certainly an area worth addressing sooner rather than later.

roof insulation - brighton hove energy services coop - brighton hove energy - bhesco

Improving energy efficiency with loft insulation

If you are considering insulating your roof space, there are a variety of different materials and formats of insulation to choose from.

Traditionally insulation has been made from materials such as fibre glass, or rock or mineral wool, but there are now greener, more sustainable materials available such as recycled paper, sheep’s wool and hemp.

Insulation materials also come in different forms such as blanket, loose fill, sheet and sprayed (see below).

The recommended depth of roof insulation if using mineral wool is a minimum of 270mm, but recommendations for other materials may vary.

Blanket forms of insulation can be self-installed but we recommend that all types of loft insulation are carried out by an accredited professional. 

Forms of insulation

Blanket insulation is the most commonly used type of loft insulation. It comes in a roll and can be made of glass (sometimes recycled glass), mineral, rock, plastic (sometimes from recycled bottles), hemp or sheep’s wool.

Blanket insulation is used if you have easy access to your loft and the joists (the horizontal beams on the floor of the loft) are regular so that standard widths of the insulation fit neatly between them.

Made from light materials such as recycled newspapers, cork granules, vermiculite (a naturally occurring mineral), mineral rock wool or fibreglass, loose fill insulation works well in hard to reach or awkwardly shaped areas. It can be laid by hand or blown in through a pipe.

It can be spread evenly in the gaps between loft joists but if you are not boarding the loft floor, you will need to check the level of the material over winter as high winds can blow it around your roof space. 

Usually used to insulate the sloping side of the roof inside a loft, sheet and rigid foam insulation can also be used between floor joists. Rigid foam is particularly useful if your loft floor needs to support weight. It can also provide good noise insulation. 

Although more expensive than other forms of insulation and energy intensive to manufacture, sheet and rigid foam has a high insulation value. You only need 135 mm of insulating sheet to achieve the same capacity as 270 mm of mineral wool. 

Unfortunately, foam products cause a number of environmental concerns. They are created from oil-based raw materials. In Europe, HFCs (a greenhouse gas) are used as a blowing agent while foams manufactured outside the EU may have been made using HCFCs which deplete the ozone layer. The composite nature of sheet and rigid foam insulation makes it difficult to dispose of because of the potential presence of HCFCs.

Sheet and rigid foam is generally used when you are trying to create a warm loft, for example if you are using it as a room. 

As well as insulating the roof, you will need to insulate any gable walls, party walls and chimneys in the loft space as otherwise heat will leak out through these, making your new insulation ineffective.

If you are creating a warm loft to use as a room, you can insulate the roof by having foam sprayed between the rafters.

As well as insulating the roof, you will need to insulate any gable walls, party walls and chimneys in the loft space as otherwise heat will leak out through these, making your new insulation ineffective.

Spraying foam insulation directly onto the underside of your roof is not recommended as a way to fix a damaged or leaky roof. The whole of your loft should be in good condition and dry before adding any kind of insulation.

Environmental impact of insulation materials

All insulation materials have positive and negative aspects. The best method of insulating your roof depends on a combination of its environmental impacts, how you will use your roof space, the type of roof you have, and the budget you are willing to spend.

A brief summary of the environmental benefits and impacts of common insulating materials is given in the table below:

Material Benefits Impacts
Paper
Made from post-consumer recycled newspaper, a renewable resource made from trees which lock in CO2 as they grow. Very low amounts of energy used in manufacture.
May give off gases from printing inks though can be controlled using vapour control membranes. Usually treated with a mixture of borax and boric acid to provide fire resistance and repel insects and fungi. Possible risks from inhalation of paper dust during installation.
Glass mineral wool
Usually contains 30% to 60% post-consumer waste glass. Some brands use formaldehyde-free binders. Non-combustable and resistant to rot.
Quarrying of raw materials can degrade the landscape. Emissions from manufacture (mainly from energy generation). Can include boron to improve moisture tolerance. High embodied energy.
Rock mineral wool
Can include around 23% of secondary industrial waste such as steel slag. Non-combustable and resistant to rot.
Quarrying of material can degrade the landscape. Production emissions include carbon monoxide, formaldehyde and phenol although emissions from UK manufacture are within legally defined limits. Bound with formaldehyde. Can cause temporary skin irritation during installation. High embodied energy.
Sheep's wool
A waste product from renewable resources. Stores CO2 as the sheep grows.
Usually contains a polyester binder which is a non-renewable material. Other binders can be used but may be made from materials of environmental concern. Uses boron-based flame retardants and biocides. If made from cheap imported wool, the conditions under which the sheep are reared are unknown and it may contain pesticides of concern. Importing wool adds to the embodied energy in the product. During their lifetime, sheep emit significant amounts of methane, a potent greenhouse gas.
Cork
A renewable resource if plantation is managed well. Stores CO2 during tree growth. Naturally resistant to insect and rodent attack (except wasps).
Cork dust may be a health concern if inhaled during installation.
Hemp
A renewable resource. Sometimes contains recycled cotton or wood fibres. The plant stores carbon as it grows. Pesticide use is rare.
Contains polyester binders made from non-renewable material. Production of crop fertilizers contributes to global warming. Contains an ammonium phosphate based fire retardant. Usually imported which adds to the embedded energy in the product.
Expanded polystyrene (EPS)
Resistant to rot and vermin.
Made from petrochemicals which are not renewable and present a pollution risk from oil and plastic production. Styrene and other hydrocarbons are produced in manufacture although emissions in the UK are within legally defined limits. HBCD (Hexabromocyclododecane) used as a fire retardant is regarded as hazardous. High embodied energy. Badly disposed of EPS has become a serious environmental problem.
Extruded polystyrene (XPS)
Slightly stronger than EPS. Resistant to rot and vermin.
Made from petrochemicals which are not renewable and present a pollution risk from oil and plastic production. Styrene and other hydrocarbons are produced in manufacture although emissions in the UK are within legally defined limits. HBCD (Hexabromocyclododecane) used as a fire retardant is regarded as hazardous. In Europe, most blowing agents used in the manufacture of XPS don't cause ozone depletion but this may not be true of XPS manufactured elsewhere. The finished product can have some unstable residues of monomers of styrene which may outgas. Relatively high embodied energy.
Rigid polyurethane (PUR/PIR)
Resistant to rot and vermin.
In Europe, most blowing agents used in the manufacture of rigid polyurethane don't cause ozone depletion but this may not be true of material manufactured elsewhere. Made from petrochemicals which are not renewable and present a pollution risk from oil and plastic production. The production process produces a number of emissions to air and water along with hazardous wastes. However, UK emissions are within legally defined limits. Rigid polyurethane panels can shrink over time, leading to gaps in the insulation layer. Installation techniques can overcome this. Insulation performance can reduce over the first three years due to gas exchange from the cells. This reduction is normally included in the manufacturer's declared performance values. Relatively high embodied energy.
Phenolic foam
Inherently flame resistant. High thermal performance.
In Europe, most blowing agents used in the manufacture of rigid polyurethane don't cause ozone depletion but this may not be true of material manufactured elsewhere. Phenolic foam is produced from phenol formaldehyde, a toxic petrochemical derivative. Phenolic foam can shrink over time, leading to gaps in the insulation layer. Installation techniques can overcome this.
Glass wool insulation

Insulating different types of roof space

If you are creating a ‘room in the roof’ it is advisable to insulate all walls as well as the ceiling to ensure that the space is adequately warm during the colder winter months.

Flat roofs are slightly more complicated but can be insulated using rigid foam insulation board. In addition to improving the thermal efficiency of your loft, this will also help to reduce noise levels from rooms below.

If you have an inaccessible roof space, you can get professionals to blow foam or torn up woollen insulation into the gaps.

An energy survey from BHESCo will help you to identify which type of loft insulation is most suitable for your property and what will deliver the best financial returns.

Points to note when considering roof insulation

When installing insulation it is important to be mindful of damp and to take steps to minimise the likelihood of this occurring. If you have a known problem with damp in your roof space you should make any necessary repairs before installing insulation.

Insulation stops heat from escaping your home and so will make the loft cooler which is a more likely to encourage damp and mould.

All pipes and water tanks in your loft space need to have their own  insulation as a cooler roof could cause them to freeze. You also need to ensure that all wiring is above the insulation.

You can increase the energy efficiency of your home even further by making sure that the loft hatch fits correctly, with no gaps. If it doesn’t you can consider applying draught excluder strips around the edge of the hatch.

The National Insulation Association website has a list of accredited installers who agree to follow a code of professional practice. They will know how to insulate without causing damp and condensation problems and how to deal with electrical wiring, pipework and water tanks.

What are the benefits of installing loft insulation in your home?

Insulation lasts for around 40 years and will repay itself several times over through the significant cost savings you can expect from making improvements to an un-insulated roof.

In addition to the obvious financial benefits, improving the insulation of your roof will result in a major reduction of your home’s carbon footprint. Improving the thermal efficiency of your loft will most likely also improve the Energy Performance Certificate rating (EPC) of the property which can increase the resale value.

The table below shows the average savings on energy bills, the cost, payback time and carbon dioxide savings per year for four different types of property if their loft insulation was increased from 0 mm of insulation to 270 mm of insulation.

Type of Residence Fuel Saving/ Year Averge cost of insulation Pay back time (yrs) CO2 savings per year (kg)
Detached House
£225
£395
1.76
920
Semi-detached house
£135
£300
2.22
550
Mid-terrace House
£120
£285
2.38
490
Detached Bungalow
£195
£375
1.92
790

Want to get loft insulation? Here's what to do next...

If you are interested in improving the insulation of your loft or any other part of your property then the first step is to conduct an energy survey.

In addition to evaluating the cost-effectiveness and expected benefits from loft insulation, a BHESCo energy survey will analyse your energy bills and identify ways that you can further reduce costs through other efficiency improvements and possibly even renewable energy micro-generation.

If you have any questions or would like to book an energy survey, you can call us on: 0800 999 6671 or use our Online Booking Form:


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