Written by our Senior Regional Surveyor, Hugh Riley.
The use of electricity produces electric and magnetic fields, together referred to as Electro Magnetic Fields (EMFs). In a residential context EMFs can be created by proximity to external sources such as power lines, substations, transformers, mobile phone masts and electrified rail tracks. Internal sources of EMFs include home wiring, household appliances and wifi signals. To reduce the effect of external sources within a house, electric fields can be screened by buildings, hedges, fences and trees. It should be noted, however, that magnetic fields pass readily through most buildings.
Despite many years of research, conflicting advice remains regarding the impact of EMFs and public health. The suggested link between EMF created by high voltage electricity supply apparatus and increased chances of childhood leukaemia or of breast cancer is still in dispute and there are continuing concerns about effects on health.
Public perception is therefore likely to lead to market resistance and, combined with the visual impact in many cases, may influence market value where properties are in EMF proximity. The publicity surrounding the issue may influence potential buyers of properties located near EMFs and any valuation undertaken for a lender on such a property must consider the public concern and how it affects marketability and saleability (even if the lender does not express a specific view over the conflicting scientific evidence in respect of the possible health risks associated with EMFs).
Electric fields are measured in volts per metre and magnetic fields in the UK are usually measured in microtesla. Exposure levels depend on proximity and duration to the EMF source. Background level EMFs around the home are in the range of 0.01–0.25 microtesla. For homes near powerlines, these levels may be as high as 0.5–1 microtesla but for homes immediately under a large powerline, magnetic field levels of 6–10 microtesla may be found. A small sub-station will produce about 2 microtesla near to the perimeter. Interestingly the magnetic field immediately next a microwave is 50 microtesla!
The level of external EMF exposure can change. The microtesla magnetic field levels do vary considerably with the power a line is carrying at the time which is measured in Mega Watts per hour (MWhr). EMFs will be higher at times of peak electricity demand which can vary with the time of day, school holidays, weekends and season. Pylon EMFs come from the cables and the highest level of emissions is to either side of the cables. As you move away from the line, the fields begin to drop away, depending on the voltage of the line (for the electric field) and the power it is supplying (the magnetic field). The higher the voltage or power, the further away, you must be for the field levels to be reduced significantly. Whilst professional equipment is required to measure this, rudimentary phone apps are now available to measure your snapshot (or daily) EMF “dose” but results tend to be significantly influenced but higher immediate proximity emitting sources such as or telephone masts or local wifi outlets.
Powerline cables going directly over a property will always give the sort of microtesla levels that have been associated with an increased risk of serious ill health, which cannot be screened against, especially in the bedrooms. Or, if residential electricity overhead supply is routed right outside houses, there are also likely to be quite high fields inside bedrooms as well.
Cables buried underground are significantly more expensive to install than overhead cables. Whilst the electric field will be absorbed by the earth above a buried cable, the magnetic fields will travel through the topsoil cover. A buried cable in a pavement close to the front of a house, brings homeowners into closer proximity to the cable (than an overhead cable) and will result in high magnetic fields in the front rooms.
It has been suggested that EMF fields are likely to drop away to below the “safe” 0.2 microtesla level at about 120 metres from 400kV and 275kV lines, 100 metres from 132kV lines, 50 metres from 66kV and 33kV lines, 25 metres from 11kV lines.
The UK has no planning restrictions on distances between homes and power lines, although appropriate legal wayleaves and easements may affect positioning. Historically there has been a call by several bodies, including the RICS, to stop construction of new homes and schools within at least 60 metres of existing overhead transmission lines and on the installation of new lines within 60 metres of existing homes and schools. As more powerlines are predicted to meet the need for the infrastructure to take power generated by wind farms, both on and offshore, to electricity consumers, current energy and housing policies may result in more people being exposed to EMFs from powerlines.
There is also a danger electricity distribution infrastructure risk could be ignored with respect to planning new housing, to meet the government’s housing targets and objectives, especially as land near power lines is affordable and often suitable for high density social housing. There are often no planning restrictions preventing development near to EMFs and if these new units are made available for rent by housing associations, occupying tenants may have little choice in whether they wish to live close to the EMF powerlines.
One of the other points to bear in mind when considering a property near to an EMF source is that the high electric fields around power cables attract airborne pollutant particles, including those associated with cancer. These are then “charged up” and become more likely to attach themselves to skin or lungs (Source Journal of Radiation Biology).
These particles can also be blown up to 5 kilometres away from the EMF source. It may be prudent not to consider living in a property near both a factory (or major road) and powerline!
As mentioned, pylons and powerlines can affect the value of properties. They can be heard to ‘hum’ and the publicity over the years in the media has now led buyers to be more concerned about possible health impacts than visual impact. This has raised concerns over the importance of future values to potential buyers.
Studies have stated that estate agents are finding it increasingly difficult to sell houses which lie close to, or under, EMF sources and some new home developers suggest that a discount of between 10% and 25% is needed to sell homes close to an EMF source. One study by Oxford Brookes University has shown that the visible presence of overhead powerline cables or pylons could reduce the number of potential buyers by as much as 80%, depending on the type of property concerned, and the distance from the pylon or cable. Also, any house within about 75 metres of a high-voltage powerline will tend to be discounted in price and this could vary from a few percent for a small terraced house to being almost unsellable for a very large upmarket house. It has also been found that valuers tend to underestimate the impact of powerlines on property value, the value of which was reduced by almost 40% at 100 metres away but averaged at just over 10% depending on property type, size and proximity to other features.
Lender policy on proximity of EMF sources is not consistent beyond a requirement to reflect adverse saleability and mortgageability. Generally, where power lines or other apparatus are located above or on the site and are for the normal domestic supply of electricity to the subject property, this is acceptable to most lenders. Properties where overhead/nearby power cables, sub stations, transformer houses and communication masts are noted within the general vicinity, are generally acceptable subject to a satisfactory valuation report. When reporting on properties close to high voltage electricity supply apparatus valuers should refer to this, in the report, and use balanced informative wording for applicants who receive a copy of the report to enable them to make further enquiries on the health risk, effect on marketability and future value.
Many lenders however will tend not lend on properties where high level power lines pass directly over the house or immediate garden site (except in exceptional circumstances) as this affects their core saleability and marketability requirement – due to public perception. Such property will be declined by valuers and a nil value returned. However often valuers will not be aware of any buried cables unless informed by legal advisers from environment searches post inspection.
Whilst a surveyor may point out the presence of an EMF source in a survey report and may even allude to possible health effects, the EMF source itself is, in all likelihood, going to comply with exposure limits. Whilst mortgage lenders always have the right to make individual assessments through their risk processes, there is no widespread general policy against mortgages on homes near EMF sources. Buyers however will have to make up their own minds, depending on the depth or research they undertake having been alerted to the EMF issue by their surveyor. And they then also need to consider possible exposure to EMFs from general household appliances within the home…