Floor-to-Ceiling Height Optimisation
Cat A to Cat B Flexibility
Building Performance
The Acre was originally built in the early 1980s. The Brutalist architecture, designed by noted architect Richard Seifert, made this a landmark building in Long Acre, Covent Garden.
The 240,000 sq ft office space was upgraded and extended in an impressive Cat A refurbishment that required the flexibility to easily transform different zones to Cat B as and when tenancy was agreed. The overall ambition was to revitalise the building, upgrading its performance and creating an optimal, wellbeing conscious workspace in the heart of London.
Artus units were a clear choice for the design specification. With The Acre’s existing structure largely retained, the project had tight floor-to-ceiling ratios while requiring optimal comfort cooling throughout.
Read this case study to find out how Artus helped The Acre:
Owner
Northwood Investors
Address
90 Long Acre, London, WC2E 9RA
Build Type
Retrofit Project
Development manager
Platform
Architect
Gensler
MEP consultant + Structural
ARUP
contractor
Lendlease
The requirement for occupier comfort and the ability to meet the increased demand for cooling within the refurbished office space were essential in the fit-out.
Another key priority was retaining as much floor-to-ceiling height as possible, which made selecting the right M&E solutions essential.
The project required a heating and cooling solution that maintained clean, uncluttered exposed ceilings while integrating seamlessly with varied ceiling tiles and baffles. Flexibility was just as critical. Heating and cooling that minimised ductwork was necessary to enable easily reconfigurable building services, allowing tenants to adapt layouts for collaboration, focused work, or evolving meeting spaces without compromising thermal comfort.
With restricted design parameters, the compact Artus Air AR60 units reduced required ceiling depth by 50% compared to traditional fan coil systems (250mm vs 590mm). This enabled smaller service zones and maximised floor-to-ceiling heights—delivering 2.6m clear space, extended to 3.1m in exposed ceiling areas.
Importantly, the minimal ductwork requirement of Artus units unlocks true flexibility—simplifying Cat A to Cat B transitions and allowing tenants to reconfigure layouts with ease as workplace needs evolve. By dividing floors into smaller, responsive cooling zones, the system integrates seamlessly with other services while supporting highly adaptable space planning.
How do we prove comfort cooling performance?
Comfort is subjective and notoriously difficult to measure; that’s why, at Artus Air, we can carry out site comfort testing in live buildings using Formula 1 technology that provides data to complement occupant feedback.
In The Acre in Central London, we assessed two aspects of performance: coverage and comfort. We tested both coverage (how air spreads across a zone) and comfort (how the indoor air will make people actually feel – are there draughts? Is there an even temperature?).
Using ultrasonic sensors combined with a 3D camera, we built a CFD-style plot from measured data. The results speak for themselves:
1. Formula 1 technology used to prove performance. Using the same technology as high-performance airflow testing in motorsport, Artus Air can measure comfort scientifically.
2. No high velocities in the occupied zone, meaning air is leaving the unit horizontally, mixing gently with air already in the space at a speed that can’t be noticed. Whilst discharge velocities (air leaving the unit) exceeded 1 m/s at the unit, they reduced significantly by the time air reaches occupants. The main point being that the risk of discomfort from draughts or cold spots is eliminated by the Artus units’ 360-degree airflow and efficient air mixing speeds.
3. Full zonal coverage. Air from the unit reaches all of the served area; combined with the noted point above about the Artus 360-degree airflow mixing gently, this means that the temperature across the whole zone is even.
Working with WELL and Predicted Mean Vote (PMV)
PMV measures thermal sensation on a scale of −3 to +3. The WELL Standard targets -0.5 to +0.5 with the ideal score being 0. Meeting the +0.5 or -0.5 PMV thermal comfort score is a prerequisite to achieving any grading in the WELL Standard.
At The Acre, three measurement locations returned tightly grouped scores of −0.2, −0.3 and −0.4 PMV. This sits comfortably within the WELL Standard target, with evidence of consistent conditions across the space, with the average being – 0.3 PMV.
Head-height temperatures of around 23 °C were measured. This temperature helps occupants to keep their focus, and the slightly cool average PMV of -0.3 value even leaves room for a higher set point and further energy saving.
Achieving WELL Standards
The Acre is delivering an indoor climate that sits perfectly within the WELL standard guidelines of high achievement.
Further energy saving possibilities
By testing comfort in their live environment, The Acre, already known for its sustainability credentials, could actually increase their temperature set points slightly to move upwards from -0.3 towards 0. This would save on cooling energy costs while maintaining a comfortable temperature for occupants.
A core part of the brief was to enhance the performance of the building. As Artus units operate using 87% less energy compared to the market average, this reduction makes a significant contribution towards The Acre’s NABERS ambitions.
Acoustic performance was also an important part of the specification, with the Artus Air solution required to achieve a maximum noise rating of NR38 at full speed.
In operation, the units can effectively temper a space at much lower fan speeds, supporting The Acre’s wider WELL ambitions.
The performance and design ambitions of owners Northwood Investors are already proving fruitful. The design specifications and solutions selected, including Artus Air, have provided a predicted reduction in operational energy use of over 70%. The Acre has achieved EPC A and a Fitwel 3-star rating and is on track to achieve BREEAM Outstanding, 5 NABERS UK Stars and WELL Core Platinum.
Explore our other projects where our air conditioning solutions have been used to lower carbon use and create comfort.
This product is protected by the following patents and other pending patent applications:
The Trademark ‘Artus’ is registered as GB 3220151.
The following designs are registered: GB 6350052 to GB 6350063 and EM 15052307-0001 to 0012
