Old houses often have very cold floors. Most homes built before 1914 have uninsulated floorboards and under these boards is usually a void into which cold air flows through ‘airbricks’ in the walls of the building. Suspended floorboards help keep old houses free of damp but they leak large amounts of heat.
The slow flow of colder air into the ground floor rooms from the void under the house not only cools the downstairs rooms but adds to the sensation of cold discomfort in winter. The gentle internal breeze carries heat away from the unlucky occupants. Since the temperature of the feet is lower than that of the head, people have a sensation of particular cold. Better floor insulation and reduced drafts would make a big difference to the perceived warmth of the older homes.
What we can we do to achieve this? Applying a clear sealant to the gaps between the boards can assist in reducing in the air flow and it slightly improves the insulation. But a significant change requires that the homeowner takes up the floor boards and applies an insulating backing, then replacing them all. This is difficult and disruptive and few people do it.
Things may get bettter. A new London company has developed Q-Bot, a robotic machine that can get into the void through the airbricks, carry out a thorough survey and then apply a coating to the underside of the boards. Results from the first trial of Q-Bot have been impressive with occupants recording a very much improved level of comfort in their homes.
Described as a ‘miniature JCB’, Q-Bot is said to be ‘highly manoeuvrable, capable of pulling heavy loads and .. designed to operate in tight spaces and harsh environments. The robot can be folded to fit through restricted openings, such as a core hole, air vent or access hatch, and then remotely deployed to carry out the mission’. Q-Bot is a lovely piece of engineering, robust and intelligent. The inventors even claim that in most cases, the skills of the robot mean that insulating the floorboards of a home can be done when the occupants are out. Q-Bot gets into the void through an airbrick, does all its surveying and then applies the insulation without noise or damage.
The developers of Q-Bot have their eyes on the 6 million or so homes in the UK build before the First World War. Most of these - about 4m – are in the hands of owner occupiers, some of whom will pay well to improve the sense of warmth of their homes in winter. Social housing providers– with perhaps 1m homes of this age – will see the Q-Bot as a useful means of reducing the fuel bills of tenants and upgrading the properties. Government schemes imposed on the energy companies, such as ECO, have produced vociferous complaints from the utilities that they are running out of houses to improve. Q-Bot is the least disruptive technology to employ and the target houses are easy to identify and to treat. I suspect that industry enthusiasm for this rugged robot will grow.
What do the economics look like? These machines are expensive to make and will be leased to companies that deploy them for insulation purposes. Q-Bot’s makers gave me a quote of approximately £1,500 to £2,500 for each property that their robot treats. These numbers seem high and I suspect the cost will have to come down. But let’s consider whether today’s quote makes sense financially.
How much is the average pre-1914 home likely to save? A UK home typically loses about ten per cent of its heat through the floor. This is the green slice in the chart below. Much of this loss – perhaps 80% - will be saved by really good insulation. A more significant heat loss is from what the Domestic Energy Fact File calls ‘ventilation’ and we usually term draughts. The brown slice shows that about a quarter of all heat is lost through draughts.
(The chart measures the loss of the average house in watts of energy for each degree of temperature difference between the outside and interior of the house. The figure is a total of 290 watts per degree, meaning that a house that is ten degrees warmer than the exterior loses 2900 watts or almost 3 kilowatts of energy to the outside world. That’s 3 kilowatt hours an hour).
Heat losses from the average house in watts per degree of temperature difference
Older houses shed more energy than newer buildings. The average heat loss for each square metre of space in a pre-1914 house is about 35% above the UK average, meaning that the boiler has to work that much harder to keep the temperature up. Some of this extra heat requirement comes from the poor floor insulation compared to modern homes.
It’s only a guess, but I suspect that really good floor treatment might save 20% of the total heating bill, including both the insulation and draughtproofing elements. For a detached Victorian house this might mean 5,000 kilowatt hours a year, or about £200 in saved gas costs. For a smaller terrace, the figure is probably half this, or around £100. These figures aren’t overwhelming compared to the costs of installation, but occupiers will also get the improved sense of comfort.
And, second, compared to the costs and benefits of other expensive measures, such as double glazing or external wall insulation, better floor insulation is cheap, non-intrusive and visually acceptable. For example, the UK’s truly remarkable refusal to allow visible double glazing in the ‘conservation areas’ of many towns and cities means that Q-Bot is especially valuable.
Q-Bot’s owners are currently raising £400,000 in new shares to fund the further commercial development of the company.