Why air quality is the next net-zero challenge

As we move towards mak­ing homes ener­gy-effi­cient, look­ing back may not be intu­itive. But Graeme Fox, who is head of tech­ni­cal at the Build­ing Engi­neer­ing Ser­vices Asso­ci­a­tion, sug­gests that is exact­ly what we should do. 

Fox points to homes that were built decades ago as hav­ing res­o­nance in the design of today’s heat­ing sys­tems. The house he grew up in, for instance, had a cen­tral cup­board con­tain­ing a warm air fur­nace, with ducts shoot­ing off to dif­fer­ent rooms: a cen­tral sys­tem that pro­vid­ed warm air from the building’s core.

After boil­ers and elec­tric heat­ing sys­tems, tech­nol­o­gy has repli­cat­ed some­thing sim­i­lar to that old­er design in mechan­i­cal ven­ti­la­tion heat recov­ery (MVHR). This more effi­cient sys­tem can pro­vide around 3–3.5 kilo­watts of heat for every kilo­watt of elec­tric­i­ty con­sumed. At the same time, it brings in new air from the out­side and extracts stale, moist and pol­lut­ed air, which improves indoor air qual­i­ty. It sig­nif­i­cant­ly reduces ener­gy used for heat­ing as up to 91% of the heat from the extract­ed air can be retained and trans­ferred to the incom­ing fresh air.

This is fun­da­men­tal because build­ings have ramped up ener­gy-sav­ing insu­la­tion, becom­ing more air­tight and a lack of ven­ti­la­tion can have seri­ous health impli­ca­tions. That’s why, on 15 June 2022, an update to Approved Doc­u­ment F of the Build­ing Reg­u­la­tions came into effect, over­haul­ing the UK’s rules on air qual­i­ty and ven­ti­la­tion. Also updat­ed was Approved Doc­u­ment L, which relates to the “con­ser­va­tion of fuel and pow­er”. 

The two updates go hand in hand, as bet­ter insu­la­tion will be essen­tial to reach net zero. To address its chal­lenges, some busi­ness­es are invest­ing in their infra­struc­ture, whether that means MVHR, heat pumps or water recov­ery sys­tems. And while the sig­nif­i­cant cost of such sys­tems can’t be dis­re­gard­ed, adopt­ing the long-term approach is a spur to boost efforts to achieve net zero.

The refresh may help the UK deliv­er net zero by 2050 but the Covid-19 pan­dem­ic has had more than a minor role in push­ing for bet­ter indoor air qual­i­ty. 

It is also a step toward the Future Homes and Build­ings Stan­dard 2025. This new set of stan­dards will ensure that homes built from 2025 will pro­duce 75% to 80% less car­bon emis­sions than under cur­rent reg­u­la­tions: the require­ment is 30% this year. But some non-prof­its, such as the New Eco­nom­ics Foun­da­tion, say the bench­mark has come too late after the scrap­ping of the zero-car­bon homes stan­dard in 2016, which would have forced net-zero car­bon homes to be built by 2020.

Oth­ers believe the 2025 reg­u­la­tions should be set at or close to the Pas­sive House stan­dard (which aims to make heat­ing and air con­di­tion­ing sys­tems obso­lete) for fab­ric per­for­mance. A renew­able heat require­ment for new builds with a bal­anced retro­fit tar­get involv­ing fab­ric improve­ments for exist­ing build­ings would also be wel­come.

“Such a tar­get, plus finan­cial dri­vers such as an ener­gy-sav­ing stamp duty allowance, should also be announced now and imple­ment­ed by 2025 so that the enor­mous task of improv­ing all of the UK’s exist­ing build­ings can pro­ceed in time to meet our 2050 net-zero tar­gets,” says Jon Boot­land, chief exec­u­tive of the Pas­sivhaus Trust.

With­in indus­try, the new reg­u­la­tions are gen­er­al­ly wel­come, says Fox, as they pro­vide need­ed clar­i­ty for the var­i­ous appli­ca­tions of ven­ti­la­tion sys­tems.

As well as MVHR, heat pumps are cur­rent­ly advo­cat­ed with the gov­ern­ment intro­duc­ing a zero-rat­ed fee. Fox says heat pumps have had a bad rep for high upfront costs but could be imple­ment­ed more cheap­ly with split-lev­el pumps.

“Out­side of the sec­tor, split-lev­el pumps went under the radar. But they could be impor­tant in future home build­ing,” he says.

Projects such as the Man­ches­ter Engi­neer­ing Cam­pus Devel­op­ment and the Devizes NHS Med­ical Cen­tre are build­ing smart, sus­tain­able build­ings that include ener­gy effi­cien­cy and ven­ti­la­tion in their designs.

The Man­ches­ter devel­op­ment has tech­nol­o­gy-assist­ed win­dow con­trol to pro­vide nat­ur­al ven­ti­la­tion. It uses machine learn­ing for automa­tion and adapts accord­ing to occu­pant and ener­gy needs. The Devizes med­ical cen­tre is one of the UK’s first net-zero health facil­i­ties and uses heat pumps and solar pan­els for heat and elec­tric­i­ty, sav­ing around 25 tonnes of car­bon a year. Its antic­i­pat­ed pay­back was 15 to 20 years, but the cur­rent ener­gy cri­sis makes this like­ly to be soon­er, accord­ing to a spokesper­son for the project.

Retro­fitting, how­ev­er, is a dif­fi­cult ask, explains Richard O’Brien, design direc­tor of house­builder North­stone. This is because addi­tion­al work is need­ed to adapt an old­er build­ing, such as poten­tial­ly adding more radi­a­tors. That’s why North­stone explored how every mate­r­i­al used in a home could be made to work in its most sus­tain­able way.

“Any­body inter­est­ed in how build­ings work, how you design them – should be look­ing at ways to make our build­ings more effi­cient,” he says. “And it’s a con­tin­u­al process. Bench­marks are there as a guid­ance – nev­er use them as the min­i­mum.”

In a world where peo­ple are increas­ing­ly at risk of hav­ing to choose between warmth or food, work­ing towards pas­sive house prin­ci­ples could be pow­er­ful, says O’Brien. 

“Busi­ness­es are com­pet­i­tive by nature, so step changes need to be incre­men­tal to avoid a mas­sive impact on your busi­ness finan­cial­ly,” he rea­sons.

For now, much advo­ca­cy is need­ed to get all the dif­fer­ent par­ties involved in the con­struc­tion chain – con­trac­tors, spec­i­fiers, man­u­fac­tur­ers – on the same design page, so that these rel­a­tive­ly new stan­dards and fea­tures work togeth­er holis­ti­cal­ly.

While the tech­nol­o­gy evolves, flex­i­bil­i­ty can be use­ful. That way, when the next set of tar­gets makes sus­tain­able design even more urgent, hav­ing some built-in adapt­abil­i­ty could pre­vent retro­fitting from becom­ing the conun­drum it is today.