The Government’s July 2020 announcement of Green Home Grants (GHG) for homeowners of upto £5,000 to make energy improvements has increased the interest in underfloor insulation for suspended floors. Reducing energy bills whilst also delivering warm feet has huge appeal!
However, insulating underneath suspended floors has always been a challenge, especially if the homeowner is keen to avoid the disruption of ripping up their floors. Until now, installers insulating floors from below have had to brush up their potholing skills and be prepared to work in a dusty and cramped restricted crawlspace often no more than 30 centimetres high (12 inches). Anyone who has any experience of this type of work will know it is not something you want to do every day.
Making Life Easy: Use a Robot!
Fortunately, there is now another way to install underfloor insulation in the form of Q-Bot, a robot dedicated to crawling in sub-floor spaces and spraying insulation onto timber floors and joists. The robot can work in tight spaces and is able to deliver a polyurethane foam insulation which expands and moulds itself to the shape of the floorboards. The insulation is built up in layers, typically to a depth of 125 mm (around 5″) and can deliver a U-value of around 0.19 W/m2K, which is better than the figure required by Building Regulations for new thermal elements in an existing dwelling (0.22 W/m2K). It is also significantly better than the average U-value for uninsulated suspended timber floors of around 1.0 W/m2K.
As well as reducing thermal heat loss through the floor, the insulation will also significantly reduce ventilation heat loss from cold draughts coming from under the floor. An analysis of air permeability in 100 properties treated by Q-Bot showed that average air permeability (measured in m3/m2.h @50Pa) fell from 16.8 to 11.5. Just by addressing losses through the floor, this is a good step along the way to meeting the limiting fabric standard for a new home of 10.
What types of home are most suitable?
An initial survey is carried out to check the home’s suitability for insulation using Q-Bot. Either floorboards are lifted, or an existing access hatch is required in the floor to allow the survey to be carried out. There may well be an existing underfloor access hatch in the property if the heating system has been upgraded or the property rewired at some stage. The survey checks that:
- The underfloor crawlspace has a minimum height of 30 cm (12 inches)
- The underfloor space is well ventilated with cross ventilation
- Piping and wiring will allow installation using Q-Bot
- Timber joists are below a 20% moisture content
- Outside walls are not suffering from damp.
If damp was discovered or the ventilation was inadequate, then remedial measures would have to be undertaken before insulation could be installed. If there is upgrade work to do on electrics, plumbing or gas then this is best done before the insulation is installed.
What is the installation process?
A four-wheel drive robot, Q-Bot, is inserted into the floor space attached to the hose which feeds the insulation material to the robot.
If no access hatch exists, then:
- Either a floor access hatch is created with a minimum size 44 cm x 30 cm (17 x 12 inches) to allow Q-Bot to be placed in the crawl space,
- Or in some circumstances access via an external wall may be possible.
The Q-Bot explores the crawl space and constructs a detailed 3-D map of the area to be insulated and checks that the floor is suitable for the planned insulation. Some homes may require more than one access hatch, as a sleeper wall may prevent movement through the whole underfloor area. Great Home’s experience is that a previous heating or electrical installer will often have already cut an access through the sleeper wall to run cables or pipes.
Once the 3-D map is complete then the robot starts to build up the insulation in layers. The insulation expands to fill gaps and will end up about 12cm thick (just under 5 inches). Q-Bot will apply a flash layer of coating on water pipes to avoid any issues, as the void becomes colder after installation and there is less heat loss through the ground floor. In accordance with the Building Regulations Q-Bot does not encase gas pipes or electrical wiring.
Q-Bot clears out the air vents that service the void to help maintain adequate ventilation and will ensure that the insulation does not block air vents. On the outside walls, if a wall was slightly damper than ideal then the insulation can be sprayed to a tapered finish at the wall.
How long does it take and what is the cost?
Installation in a typical 3-bedroom semi-detached house with a floor area of around 40m2 would take around 2 days and would cost around £2,400. Cost is mainly dependent on floor area, ease of access and location. The price includes creating access to the under-floor void, including any openings within the property and making good any access points after installation.
The benefit of insulating the floor from below is that disruption in the home is minimised.
Warranty, Health & Safety
The insulation has a 10-year material warranty and an expected life of 40 years. Q-Bot advise that the insulation is approved by the BBA for use in this application and meets all the relevant Building Regulations requirements. The insulation will not add to any existing fire hazard until the floor is destroyed, and therefore, the insulation will not contribute to the development stages of fire. It will not present a smoke or toxic hazard either.
Q-Bot is mentioned in a recent Guide to Best Practice on Retrofit Floor Insulation – Suspended Timber Floors published by BEIS and has BBA certification.
As part of any floor insulation project it is worth examining the existing air bricks which ventilate the underfloor area. Over the years they may have become blocked by debris, deliberately covered over to stop cold draughts, or simply buried under an extension. Signs that the underfloor ventilation is inadequate is timber with a moisture content in excess of 20% or a musty smell when floorboards are lifted for inspection.
It is important that all the airbricks are functioning and in good condition or joist timbers and the outside walls may be damper than desirable. On some occasions it may be necessary to add an airbrick to ensure there is good cross ventilation; so that air can flow freely with no still spots in the underfloor area. This is true whether using Q-Bot or installing insulation manually.
A good source of information on underfloor ventilation is the BRE Good Repair Guide on Improving Underfloor Ventilation which is available at the ukradon.org website. Whilst this is primarily focused on reducing Radon build-up it is equally good for tackling reducing moisture issues.
It is important that ventilation is sufficient as when the suspended timber floor is insulated, the ventilation levels in the sub floor area could well change, as freezing cold air can no longer find its way into heated rooms!
Great Home Conclusion
Whilst we have not yet seen Q-Bot in action ourselves, it has been operating for some time, particularly in the area of social housing, so the technology has had some time to prove itself. Speaking as someone with personal experience of installing underfloor insulation, this is a big step forward on manual installation methods. There may be cheaper manual ways of doing this, but this is a great alternative to older methods; you will be hard pressed to find many people willing to work in a 30cm high crawlspace installing insulation. The end result is consistent application of insulation. This will reduce heat loss and eliminate those cold draughts, improving thermal comfort to occupants whilst also reducing heating bills. Typical case studies show financial payback in circa 16 years although those with leakier homes may well see payback quicker than that and will immediately begin to appreciate the added level of thermal comfort.
BEIS (2020). Guide to Best Practice: Retrofit Floor Insulation – Suspended Timber Floors. Available at: BEIS (2020). [Accessed 20 Aug 2020]
BRE Good Repair Guide on Improving Underfloor Ventilation (2012). Available at: ukradon.org. [Accessed 20 Aug 2020]
Q-Bot website (2020). Available at: https://q-bot.co/ [Accessed 20 Aug 2020]