Post-war prefabricated houses can be very energy inefficient, increasing the risk of fuel poverty for occupants, however, as Tom Bradley outlines in the following guest article, there are several projects working to address this issue.
The UK has a major issue with poorly insulated buildings. Quite often these are the buildings in which the poorest live, pushing them into fuel poverty and with it all the associated physical and psychological health implications. Many buildings can be improved easily, others take far more work. One major group of properties which are particularly inefficient are the post-war prefabs. Many of these buildings have been inherited by housing associations, which means the tenants pay extremely high energy bills and are unable to afford to heat their homes to an adequate level. However, these buildings can be improved, and there are numerous projects currently underway demonstrating what can be done.
2 History of Buildings
Post-war prefabs were built to replace the high levels of dwellings destroyed or damaged during the Second World War. The legal basis for the build of these was outlined in the Temporary Accommodation Act 1944. The plan at the time from Winston Churchill was to build 500,000 prefabricated dwellings, with an expected lifespan of up to 10 years. Originally these buildings were to be built within five years after the end of World War II. The final plan legally drawn up by the Labour government reduced the number of dwellings to 300,000. The government set aside a budget of £150m for this construction. The idea was to use wartime production facilities and experience to roll out the construction of these homes quickly and effectively.
The prefabricated building project was coordinated by the Ministry of Works, who used the wartime manufacturing and organisation structure to roll out the building project in a military style. They opened a competition for designs of prefabricated buildings from commercial companies, and received 1,400 entries. After a review of the proposals, and testing and construction of the most promising, the following designs were put into production by the post-war government; Portal, Airey, Arcon, AIROH, BISF, Cornish Unit, Hawksley, Howard, Laing Easi-Form, Mowlem, Orlit, Phoenix, Reema, Swedish, Tarran, Uni-Seco, Unity structures, Wimpey No-Fines.
By the end of the program in 1951, a total of 156,623 prefabricated dwellings had been constructed. Now almost seventy years on from the beginning of the project, there are many prefabricated buildings left over which are still surviving and still in use as social housing. As would be expected, over fifty years after they were intended to have been replaced, dramatic improvements are needed to ensure these properties are suitable housing for residents; in order for them to have a good quality of life.
3 Energy Efficiency
It is worth noting that the prefabricated houses are often good family homes, of reasonable size. However, there are numerous energy efficiency issues with these types of properties. These are partly due to the design, and partly due to degradation over the years.
Taking the Tarran Newland as an example, the walls of these buildings are made up of precast concrete panels approximately 20mm thick. These are connected using fixing plates which have thermal bridging issues. There is then a gap before fibreglass insulation and fibreboard. These walls are remarkably thin, and so unable to hold in heat. Due to the shallow angles of the roofs, it is difficult (but not impossible) to fit insulation.
Additionally, these buildings are particularly ‘leaky’. A Tarran Newland property worked on had a level of air permeability of 19.26 m3 (h. m2) @ 50Pa. This compares with the part L regulations which specify a value of 10 m3 (h-1 m2), or the requirements of the code for sustainable homes which need a value of less than 3 m3 (h-1 m2).
The issues of thin walls, little insulation and draughts are endemic throughout prefabricated homes. This means residents we have worked with have been spending up to 25% of their income on energy over a year.
As mentioned before, there are various good points to these buildings. They are larger than social housing built today, and make good family homes. However, they do contribute to fuel poverty. Simple measures like cavity wall insulation cannot be implemented on these homes, but solid wall insulation can dramatically improve them (changing a Tarran Newland wall U-Value from 2.35 W/m2K to only 0.29 W/m2K). Loft insulation, although difficult on some due to shallow roofs, can be applied. Also, the obvious option of improved glazing and doors can make an impact. In recent years many companies have set up, or grown, applying external cladding to post war prefabs. The issue though is that cladding can be expensive, compare the cost of £12 000 to clad an end terrace detached Wimpey No Fines property against £500 to put cavity wall insulation into a modern semi-detached house
The improvement works can be invasive. Of the projects we have worked on, some properties have simply been cladded on the outside, whereas others have been completely gutted to allow for internal and external cladding, and replacement of internal walls.
With the reducing cost of PV installation, some housing associations are installing photovoltaics on properties, including prefabs. The cost of installing a 4kWp system in summer 2013 is about £5 500 (EUR 6 400), compared with about £12 000 in summer 2010. The tenant receives some free electricity in the daytime (around 900kWh a year) whilst the housing association can claim the Feed in Tariff.
There are many projects currently running, improving prefabricated homes in various ways. Some of these are also measuring data from selected properties. The projects include:
5.1 ERDF Social Housing Energy Management
This project is being carried out by Narec, Narec Distributed Energy, South Tyneside Homes and Homes for Northumberland. The project involves the improvements of around 350 homes, which are Tarran Newlands, Wimpey No Fines or flats. The properties are being monitored with a range of methods (tenant engagement, temperature loggers, thermal imaging, and air pressure tests) to show the exact improvements of the properties, to understand how much these homes can be improved and how this compares with costs. By the end of the project an improved prefab, with retrofit costs, can be compared to a typical new build, which will help inform future decisions on prefabs.
5.2 Council Retrofit Projects
Numerous councils and housing associations have carried out projects insulating numerous post war prefabs with solid wall insulation and other measures. Councils carrying out this work include: Powys County Council, North East Lincolnshire Homes, Barnsley Metropolitan Borough Council, One Vision Housing, North Tyneside Council, North Tyneside Council
6 Improvements Funding
As part of the UK Government’s Green Deal, there is a scheme called the Energy Company Obligation (ECO). The aim of this is to fund the improvements of hard to treat houses, such as post-war prefabs. This funding can be applied for by councils, housing associations, private landlords or individuals. The homes must either be owned by, or rented to, residents on certain benefits. More information can be found on https://www.gov.uk/energy-company-obligation.
The post-war prefabricated houses are extremely thermally inefficient, which pushes residents into fuel poverty. However, these homes can be improved with existing products and ultimately all of them in the UK need to be improved or replaced. It is very important to understand the comparison of a fully improved post-war prefab with a new build, and hopefully projects looking at this will soon be able to give definite answers for certain types of prefab.