Roof surveying: decarbonising badly insulated buildings

An innovative flat roof surveying technique combines moisture mapping with carbon calculation to help property managers identify the buildings most in need of attention


  • Stephen Cousins

27 January 2022

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The built environment is directly responsible for 25% of all greenhouse gas emissions in the UK. Which is why efforts to renovate the nation’s existing stock of approximately 30m assets will be critical to achieving the government’s pledge to reach net zero carbon by 2050.

The scale of the challenge is informing changes to regulation, including recent updates to Part L and Part F of the Building Regulations for new dwellings and forthcoming Future Homes and Future Buildings Standards, due out in 2025.

It has also galvanised a growing contingent of building owners, landlords, property and facilities managers to implement stringent sustainability goals. These are intended to accelerate carbon reductions, while reaping the associated rewards of lower energy bills and improved thermal comfort for occupants.

Those that don’t act may soon be forced to. Under proposed UK Treasury rules, announced by chancellor Rishi Sunak at COP26, most big firms would be required to set out detailed public plans for how they will adapt in line with the net-zero target by 2023.

John Llewellyn, divisional director for flat roof systems specialist Bauder, says: “We're hearing more and more clients talk about reducing carbon in response to net zero goals and wanting to prioritise the portfolio of properties they manage. Whereas up until the start of 2021 they were mostly interested in the energy savings alone.”

In a bid to help its clients maximise the carbon saving potential of existing real estate, Bauder offers an innovative surveying / carbon dashboarding service for flat roofs.

The moisture mapping and carbon dashboard solution combines flat roof surveys, carried out by a specialist team. Numbers are crunched in energy saving software to accurately identify the flat roofs most in need of insulation improvements, as well as the estimated cost and carbon savings if insulation and solar PV upgrades are carried out.

Prioritising refurbishments

Building portfolio management organisations can use this information to prioritise the assets most in need of refurbishment and clearly demonstrate where the biggest gains can be had to meet in-house energy saving and decarbonisation targets. 

The specialist survey technique has already been applied to over 80 projects nationally, including schools and universities, hospitals, police stations, ambulance stations and commercial buildings. Clients have ranged from building consultants to local authorities and facility managers.

According to Llewellyn, the worst affected roofs were able to achieve up to a 25% reduction in energy consumption following upgrades to insulation.

Faulty or damaged flat roofs are a particular concern when it comes to energy performance. Factors such as insufficient insulation, inadequate seals, unprotected penetrations, and non-optimised skylights and curbs can degrade thermal performance and cause leaks that saturate insulation, increasing heat loss.

“The amount of saturation normally depends on the size and the age of the roof, but we have found that even relatively new roofs, installed within the last 10 years, can experience significant levels of saturation,” says Llewellyn.

The initial moisture mapping condition survey is critical to understand the level of saturation, as an indication of thermal performance, and how much insulation needs replacement.

The survey is carried out using a nuclear device that directs neutrons into the waterproofing and insulation of the roof. Some of the neutrons emitted bounce back from hydrogen molecules in water to give a precise reading on the amount of moisture present.

According to Llewellyn, the integrity of modern air and vapour control layers means it’s not uncommon to see saturated insulation even when there are no visual signs of damage to the internal fabric of the building. Furthermore, a significant number of flat roofs in the UK and Ireland have had warm roofs retrofitted, trapping water ingress within the insulation zone of the original flat roofing system.

“We have found that even relatively new roofs, installed within the last 10 years, can experience significant levels of saturation” John Llewellyn, divisional director at Bauder

Delving into the data

Data from Bauder’s moisture mapping survey provides a figure on overall roof saturation in the carbon dashboard, while data on the existing roof build-up is used to generate a baseline statistic on the current U value (the measurement used to see how effective building materials are as insulators).

Depending on the type of building being assessed, the program exploits data either from the Simplified Building Energy Model (SBEM), the government-approved energy modelling software for non-domestic energy assessments, or the Standard Assessment Procedure (SAP), used for homes.

When a virtual slider on the dashboard is moved to increase the flat roof’s U value, to reflect possible upgrades to insulation, clients can instantly see the associated energy savings (as a percentage), CO2 savings (in tonnes) and financial savings per annum.

“A typical roof with 50mm of PIR insulation might have U value of around 0.45 W/m2K, but to meet current building regulations it would require a U value of 0.18 W/m2K. So we would move the slider to 0.18 and the client will immediately see the impact on performance,” says Llewellyn.

To show deeper levels of decarbonisation, the dashboard can be configured to calculate the benefit of installing solar photovoltaics on a flat roof. Moving the associated slider adjusts the peak output of installed PV and updates the readings on overall energy, CO2 and financial savings per annum.

According to Llewellyn, payback periods of five to six years are now possible for solar panels thanks to increased panel efficiencies and reduced capital costs.

Outputs from the carbon dashboard can inform property managers’ decisions on whether to, for example, remove and replace defective insulation or leave the insulation intact and install a new waterproofing system across the roof area.

By taking the guesswork out of the process, the tool can sometimes prevent unnecessary remediation work, says Llewellyn: “We've seen situations where people were renewing good roofing. This technique can prove where the insulation is good,” therefore avoiding material and labour costs associated with stripping out materials. This means less material sent to landfill and the related implications for the climate.

That’s good news for property managers keen to minimise their carbon footprint and experience a welcome boost to their bottom line.


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“We've seen situations where people were renewing good roofing. This technique can prove where the insulation is good” John Llewellyn, divisional director at Bauder

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