The typical UK home uses 60% of its energy for heating. Eventually all that heat finds its way to the outside of the property either through leaks or conduction through the walls, floor and ceilings. With good insulation that heat loss can be dramatically reduced , almost to zero for a newly built ‘eco-home’.
For the conscientious homeowner taking a medium-term view of energy use it is vital to understand the costs associated with leaks and poor insulation, and the savings that can be made by installing measures from the very simple to the very complex.
Starting with the very simple.
Loft insulation is well known to be the ‘lowest hanging fruit’ in the insulation hierarchy. The recommended thickness of insulation is at least 270mm of mineral wool. The government estimates that 33% of English homes do not have even half of that thickness installed. Depending on your circumstances installing loft insulation can save hundreds of pounds a years in heating costs, the impartial energy saving trust suggest an astonishing £340 a year saving for a typical detached house that goes from no insulation to the recommended 270mm click here to read. The material cost to go from zero to 270mm will be in the region of £500 for an average sized loft space (50 square meters), labour costs need to be added. Considerations: Installing loft insulation is a relatively risk-free job in terms of unwanted effects, but there are still some things installers need to be aware of such as:
: The need to maintain ventilation within the loft space.
· Need for consistent insulation to prevent cold spots on the downstairs ceiling that may attract mould.
· Awareness of air leakage from the living space entering the loft through penetrations such as downlights, those penetrations should be treated using downlight covers. · Care should be taken to ensure the loft hatch is well sealed and insulated.
Floor insulation is a more rarely applied measure, but for some homes it can make a tremendous difference. Typically, floors will have one of two types of construction, either a solid floor or a suspended floor.
Solid floors can then be divided into two types, either concrete slabs or traditional solid earth. Concrete floors can be very cold, and they transmit cold in from the outside of the home. Solid earth much less so and thus would not usually be a candidate for insulating.
Concrete floor insulation: There are two ways to approach this measure, either by laying insulation over the existing floor, or by digging up the floor and laying insulation down before re-covering. Either way there are drawbacks, laying over the existing floor may cause problems with door and step heights, and digging out the floor is extremely disruptive.
Suspended floors are those with timber or concrete beam construction over a void separating the living area from the ground. Concrete type suspended floors are modern and uncommon so we will not deal with them here. Timber suspended floors are the most common type of flooring in the UK, the void beneath the floor is ventilated by air bricks that ventilate to prevent moisture building up and damaging the floor timbers, it also means that air flows freely causing uncomfortable and wasteful draughts to permeate the living area. As well as allowing draughts into the living areas these floors if left uninsulated will wastefully transmit heat into the void below.
Options for improvement: There are two approaches that can be taken, either installing replacement airbricks that open and close according to the weather conditions, thereby maintain the benefits of ventilation but minimising draughts in cold weather. Or, insulating the floor itself, that maybe achieved by either removing the floorboards and installing insulation between the floor joists, or by gaining access to the underfloor void and insulating from underneath. Doing so will prevent draughts and general heat loss.
Cavity Wall Insulation ‘CWI’ is possibly the most controversial upgrade that a home can have. However, the data about CWI problems show that its bad reputation is for the most part unwarranted. The many millions of homes that do not suffer issues quietly benefit from the work. It is known that around 30% of the heat generated in older homes can be lost through walls. Adding cavity wall insulation can dramatically reduce those losses. Houses built before 1990 did not need to have cavity wall insulation installed whilst being built. Many have been upgraded in the last 20 years with insulation injected into their walls, but around 30% of suitable homes have still not taken advantage of this straightforward method of improving efficiency and comfort.
Cavity wall insulation garnered a bad reputation due to a lack of understanding and unscrupulous contractors cutting corners when schemes were first rolled out. However, less than 0.5% of properties have needed remedial works according to CIGA the industry monitor. What pitfalls there were are now very well-known and the local authority – who administer many of these jobs – only works with reputable contractors who will give proper impartial advice as to whether or not a property is suitable for these works. So, if your property does not have CWI fitted then it is worth speaking to a reputable installer – likely via the council or a grant funding body – to see if its suitable for you.
Internal Wall Insulation 'IWI' This is an uncommon measure but that’s not a reflection on its effectiveness. ‘IWI’ is installed by adding a layer of insulation to the interior surface of a building’s exterior walls, this can be greatly advantageous if you want a dramatic improvement in the thermal qualities if a building without changing the exterior look, which may be desired due to taste or required due to planning considerations.
IWI can provide a huge benefit to the thermal qualities of a property and is suitable for installation onto otherwise inefficient solid walls. Fitting IWI is disruptive for the occupiers with builders needing to empty rooms to carry out the works. The installation can take different forms but typically it would involve installing wooden batons then filling in with insulation before installing a finishing layer of plasterboard ready for a skim and decoration. Drawbacks include difficulties related to installed bathrooms and kitchens that either need to be omitted from the IWI upgrade or stripped out for the works, IWI requires careful design and material choices to maintain a walls breathability. Also, because IWI does not provide a continuous envelope around a property careful design is needed to mitigate against moisture transfer through cold spots. However, don’t let the above be off-putting, IWI is a significant upgrade to comfort and efficiency.
External Wall Insulation. 'EWI' is considered the ultimate insulation upgrade, it gives an occupier the opportunity to make a huge leap in thermal efficiency and simultaneously change the appearance of the property which may be welcomed. The most common method of installing EWI is to attach a foam insulation to the exterior wall, followed by a series of layers to ensure weather protection and attractiveness. There are also renders available which can contain naturally insulating materials, these may be suitable to improve both modern cavity wall and traditionally built solid wall properties. Advantages of an EWI scheme include the ability to fit sufficient thickness of insulation without limiting living space (as IWI would) and thermal consistency avoiding any cold spots that can lead to structural and moisture problems down the line. The disadvantages include the cost and the complexity of the works that might require moving drains, repositioning windows and extending the roofline.
Conclusion. It is vital that each property is assessed on its own merits to determine which insulation measures should be incorporated. Given the complexity of floor insulation, IWI and EWI those measures especially need careful consideration to ensure that the outcomes are modelled to meet the homeowners aspirations, be that for a financial return in terms of lower energy bills or lower carbon footprint thanks to lower energy use.
You may wish to take advantage of our thermal camera loan scheme to help detect weaknesses in their properties, click here to find out more.
Lastly, for an overview of how o approach your home as a whole check out our 'where to start' blog by clicking here.
