Transforming commercial spaces to residences and the impacts on indoor air quality

The UK has seen around 89,500 homes created from former commercial buildings in less than ten years, following the relaxation of planning rules in an attempt to balance the excess of commercial space with the shortage of homes.

This imbalance is a global phenomena, no more so than in the United States where Federal, state and local governments are incentivising such conversions, not only to revitalise neighbourhoods, but also because such conversions can be environmentally beneficial.

Tony Abate, Vice President and Chief Technology Officer at AtmosAir Solutions explains how significant air quality is in these conversions.

The global pandemic wrote new rules for the modern workplace as many companies asked their employees to work from home, leaving their office spaces empty.

During this time, these companies and their employees learned about their capabilities to work remotely. As they learned they refined how we work, and even now when pandemic concerns have passed, remote and hybrid work is here to stay.

This has caused vast amounts of commercial office space to be unoccupied, as these companies need less or no office space. Currently the national office vacancy rate is 18.1% and some cities are over 20%.

Every problem presents an opportunity. Currently there is a shortage of housing in the US. The US housing market has a 4.5 million home deficit and this is a growing number. Many of these new remote workers are looking to buy homes or expand their living space to allow for a defined workspace within the home.

Policy makers, developers and commercial property owners are looking to convert former office space to residential space. This can help to revitalise some inner-city areas and turn unproductive empty space to revenue producing properties, but such conversions can help to combat climate change.

US commercial buildings account for 29% of greenhouse gas emissions and these conversions can improve this by 50 to 75% fewer greenhouse gas emissions. These new residential buildings can also be equipped with convenient amenities such as ground floors with restaurants, shops, grocery stores and other places all under the same roof. Less need for cars and other travel will also reduce greenhouse gas emissions.

These conversions can be a complex process. Many newer offices are designed on large open floor plates. These spaces need to be divided, bathrooms and kitchens added, windows to become operable and central HVAC to be converted to allow for unitary systems to give each owner or tenant individual HVAC control. For some of these reasons older pre-WWII buildings can be easier conversions as design tended to be more divided spaces then, with more operable windows, although HVAC systems were much less effective and efficient.

HVAC is often one of the largest considerations. As you can imagine, converting a space used for a very different purpose to now be individual dwellings can present challenges in mechanical redesign. First code compliance will change. In America, commercial buildings are typically designed to ASHRAE (American Society of Heating Refrigerating and Air Conditioning Engineers) Standard 62.1, while residential dwellings now need to comply with Standard 62.2.

A key aspect to each of these standards is ventilation. As the pandemic increased awareness, codes, designs and strategies are all looking hard at ways to provide optimal indoor air quality which today’s buyers are demanding. This can involve rethinking HVAC design to not just simply provide the right quantity of conditioned air, but to provide ventilation, pressurisation, filtration, air purification and also many are incorporating air monitoring, to provide clean and healthy indoor air.

The U.S. Environmental Protection Agency has defined the three key elements to improving indoor air quality:

• Source Control
• Ventilation
• Air Cleaning

Since source control can be challenging in a residential setting, as people conduct activities like cooking, etc. that won’t happen in a commercial building, this brings the other two aspects into a sharp focus. Taking a large commercial floor footprint where ventilation is more centrally distributed becomes more challenging when sub dividing the space into multiple dwellings, where each requires its own ventilation and control of pressurisation, so dwellings don’t impact each other or common spaces, like hallways or lobbies.

One example is that residential dwellings will each have kitchens and bathrooms and each of these require exhaust air. Each dwelling will require a higher air exchange rate to compensate for this to keep the space from becoming negatively pressurised.

Negative pressurisation can cause many bad environmental effects which can degrade indoor air quality. Unfiltered air will be impinging into the space which can increase particle and VOC (Volatile Organic Compounds) levels and worsen air quality and affect those who may have allergies or asthma or other respiratory concerns. Negative pressurisation will also make humidity control difficult. High relative humidity can cause microbial growth, molds and bacteria can grow and thrive in a high RH environment. Low relative humidity allows for an environment amenable to viruses and the spread of airborne illness. This can be a challenging task when a building was designed for commercial, and not residential purposes.

All of this also brings Air Cleaning into more importance than ever before. This has even been recognised in new standards for healthy spaces. In June 2023 ASHRAE at the urging of the US White House published Standard 241, Control of Infectious Aerosols. 

This standard provides guidance to design and operation for spaces to minimise the spread of airborne illness. A unique feature of this standard is a term called “Equivalent Clean Air” or ECA. Traditionally ASHRAE standards are based on outside air per person. Using outside air can be effective where outside air quality is good but is very costly and difficult to design, especially when converting a commercial space to residential. By designing effective air cleaning, you can provide clean, healthy air spaces that are also energy efficient, lessening the impact on our climate.

Air cleaning can come in many forms, media filters, electronic air cleaners, bi-polar ionisation technology and ultra-violet (UV) systems. These technologies can be used in combination to attain the required Equivalent Clean Air per person rates as outlined in Standard 241. States, municipalities and even the US congress are all proposing legislation that will require Standard 241 or other measures to be taken to ensure good indoor air quality.

To many of today’s homeowners, it’s more about knowing how your space is performing, especially if you intend to spend more time there than ever. This has fostered the growth of indoor air quality monitoring by means of sensors and other monitors that can measure crucial factors such as, Particles, TVOC (Total Volatile Organic Compounds) and Carbon Dioxide to name a few. These monitors can be placed in the occupied space and also in the air stream delivered into the space. More advanced systems can measure elements such as Formaldehyde, Ozone and PM 1 Particles. There are even devices that measure IEQ factors like light and sound levels.

Remote workplace technology continues to develop and the need for more residences is growing. What was once the workplace is now the home and also the workplace for many, with health and well being at the top of the list. Developers and property owners are well aware and are providing for these new healthy and efficient homes, by converting unused commercial spaces. Don’t be surprised if you hear someone say, “I used to go to work in that building, now I live there.”

Tony Abate is Vice President and Chief Technology Officer at AtmosAir Solutions in Fairfield, CT. a sustainable indoor air purification and monitoring technology company.