Hugh Franklin from Aeroseal UK explains how the airtightness of a building can be improved using a water-based, low VOC atomised polymer which is delivered when the building is pressurised. This simpler approach speeds up the process of air sealing and gives real-time feedback on the airtightness score.
Interview with Hugh Franklin
Hugh Franklin is the Head of Operations at Aeroseal UK, where he leads the development and deployment of the AeroBarrier airtightness system. His career began in archaeology, spending years de‑constructing historic buildings and extracting lessons about passive cooling, solar shading and other age-old strategies. Those insights sparked a shift toward eco‑construction, where he focused on scaling sustainable building practices before narrowing his expertise to airtightness over the past eight years. Today, Hugh combines his deep appreciation for traditional building wisdom with the latest technology to help builders achieve high performance homes.
The ‘mist’ sealant automatically hones in on the leaks
Airtightness is a key characteristic of a high performance home, but airtightness strategies can be labour‑intensive using boards, membranes, tapes, liquid paints and so on. Hugh describes how a mist of low‑VOC polymer sealant, delivered under pressure, automatically seeks out leaks and creates a uniform seal. This reduces material waste, shortens installation time, and delivers measurable improvements in the building’s air‑leakage score.
“We create a fog, a mist of a water-based low-VOC sealant… the sealant is drawn towards those leaks by the escaping air.”
It is possible to dial‑in the airtightness you want
AeroBarrier is introduced into a building during a standard blower‑door test. When the building is pressurised the mist travels through any gap or crack, collides with itself and solidifies around the leak. Because the product is an acrylic polymer that is 60–80 % water, only a few litres are needed for a typical 200 m² home. The sealant does not expand; it accumulates only where airflow exists, allowing the airtightness score to be dialled down to the exact target.
The building is carefully controlled during misting
Everyone steps outside while the mist is applied and it doesn’t take long. Workers inside wear appropriate respiratory protection, but the low‑VOC formulation produces minimal fumes. After sealing, the space can be re‑entered within 30–60 minutes once the mist has dried, making the process practical for busy construction sites.
“We control the space during the install, much like if you’re doing an airtightness test.”
Long‑term durability is proven in the lab and the field
AeroBarrier has undergone lab testing up to 5 000 Pascals (hurricane‑level pressure) and shows no degradation after 50 years of simulated ageing. Field studies report only a 1–2 % loss of airtightness over 25 years, confirming that the polymer remains flexible and effective long after installation.
Automation works best when paired with manual detailing
The system can seal gaps up to 10 mm. Larger openings generate a visible “white halo” during misting, signalling that manual patching is required. This hybrid approach lets builders concentrate on the biggest defects while AeroBarrier handles the multitude of smaller, hard‑to‑detect leaks.
“AeroBarrier will try and seal that, but it will start to form a white halo around a hole that’s quite large… you can walk around the building… and find those gaps and then fill them manually.”
Real‑time feedback turns airtightness into a visible metric
A key obstacle in airtightness is the lack of instant performance data. AeroBarrier integrates with the blower‑door test, displaying the current ACH (air changes per hour) score on a screen as the mist seals each leak. This immediate feedback lets site teams see which details are performing well and which need attention, fostering ongoing learning and improvement.
There is an optimal moment to apply the sealant
For new builds, the best time to apply the mist is post‑first‑fix, after windows, glazing and major services are installed but before interior finishes. In retrofits, the building must be sufficiently sealed to become a “pressurisable box”; otherwise, the mist will escape and the process loses efficiency. Coordinating with the contractor to schedule the test at the right stage is essential for success.
“We want the building to look as much like a porcupine as possible. Post first fix is really when we want to come in.”
A draught-free home will deliver savings
AeroBarrier is priced at roughly £12.50 per square metre of floor area. For a 200 m² home, material costs are about £2 500, plus labour. Hugh notes that the return on investment typically appears within three to five years through reduced heating and cooling demand, especially when moving from a standard Building Regulations home to the Passivhaus standard.
Achieving airtightness this way requires a slightly different plan
Hugh says that their best clients keep an open mind about the approach to airtightness. It’s much better to have a talk upfront about how to get the most out of the system. For example, setting clear tolerances early on will avoid unnecessary work (e.g., keep penetrations ≤ 5 mm for high‑performance builds). Builders, plumbers, electricians and ventilation suppliers need to understand these limits and coordinate their work to avoid unintentionally creating new leaks. Brief on‑site training and visual guides help keep everyone aligned.
Once achieved, airtightness must be preserved
If a great airtightness result is achieved at first fix this is not a cue to rest on your laurels. Throughout the project it’s important that everyone who is working on site understands the airtightness line. Typical mistakes might include cutting through an airtight membrane without making good afterwards. Hugh shares a couple of examples. When electricians are installing recessed lighting they might not quite have enough room so they cut through the membrane. Also when it comes to adding services, like cables, pipes and ducting, a similar problem can occur. Because the airtight layer is often invisible, any breach can dramatically reduce the airtightness of a property. Scheduling blower‑door tests at key points and encouraging a culture that reports issues without blame can help maintain a good airtightness score.
Scaling airtightness for mass‑market housing
Hugh believes that making airtightness cheap, fast and easy to verify is the key to bringing low‑energy homes to the broader market. By combining automated sealing with clear performance metrics, builders can deliver consistent results without needing specialist airtightness gurus on every site. The goal is to demystify airtightness, turning it from “black magic” into a routine part of construction.
Find out more
Transcript
Download a transcript of this episode.
Please connect with us
Subscribe, rate and review us on Apple Podcasts
