Net zero is achievable but the profession has a vital role to play in teaching other stakeholders how it’s done, writes Satish Jassal.

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Source: Satish Jassal Architects

Satish Jassal

I believe that everyone (the scientists at least) agrees that human beings are causing the world to heat up. And to a point where life on earth may increasingly be at risk. The feeling that my generation will leave the world to our children in a worse state than we found it causes me some anxiety. I know that as architects we can do better, and I believe that a critical part of our job is helping others understand how we can make the journey to net zero carbon.  

The Mayor of London has produced a very useful guide to achieving net zero carbon. It states that a 100% reduction in CO2 emissions compared with Part L:2013 of the Building Regulations must be met to achieve net zero carbon emissions.

In simple terms, this can be achieved by:

  1. Thermal efficiency of building envelopes
  2. Selection of appropriate servicing strategies
  3. Onsite renewables

The guidance encourages design teams to achieve emissions reduction onsite as far as possible, using offset cash-in-lieu payments to local authorities only as a last resort. It sounds simple and great, but we realised that we still had a job to do in convincing our clients that it is possible.

A couple of years ago, at about the same time as the Mayor of London’s net zero carbon standard guide was published, we were working on a small social housing scheme as part of a new wave of council house building. The main focus was on delivering social homes to reduce council housing waiting lists.

We realised it was a great opportunity to achieve a net zero carbon housing scheme, the first in that borough. We had met a knowledgeable and passionate sustainability consultant who we approached to advise us. A good sustainability consultant is truly worth their weight in carbon.

Together we went through a number of strategies and options to get to net zero carbon emissions for our social housing proposal. We quickly realised how important incorporating onsite low and zero carbon technologies was, such as solar panels and air source heat pumps (ASHP). ASHPs have come a long way, particularly in terms of noise reduction and efficiency. But although solar panels have come down in price, they still require further leaps in efficiency.

A fabric-first approach produces thermally efficient building envelopes to keep the energy in the building. Constraints on cost mean that not all building envelopes can achieve the highest thermal efficiency, but bear in mind that it’s the combination of insulation, air tightness and thermal bridging that drives down heat loss. There is an arsenal of measures that can be used to improve fabric efficiency.

Based on the size of the project and the proposed number of people inhabiting the building, the sustainability consultant was able to tell us the number of solar panels and ASHPs required. We sharpened our pencils and started to plot the requirements onto our proposed housing scheme.

Once we were confident we could meet the net zero emission standard, we went back to the client’s project manager and presented our proposal. “This could be your council’s first net zero carbon housing scheme,” I told him. I could sense the apprehension of the unknown hitting him.

He called in the senior project manager, and we had a video meeting together. The senior project manager, as you would expect, was more experienced and a barrage of probing questions followed:

Is net zero achievable on this project?

The calculations and layouts demonstrate that it is achievable and meet the Mayor of London’s definition of net zero carbon.

Are the air source heat pumps noisy?

The market has some ultra-low noise air pumps that do not need acoustic mitigation.

Is triple glazing expensive?

Double glazing can be used, and the lower performance can be balanced against improved fabric performance in other areas, such as better air tightness or reduced thermal bridging.

Are solar panels expensive?

The price of solar panels has come down by 82% over the last decade, and efficiencies are improving. 

Will the green roofs grow under solar panels?

Yes green roofs are compatible with solar panels, if properly oriented and installed. And brown roofs or plug-planted sedum roofs also provide good biodiversity, help insulate the roofs and help with rain runoff.

Will it cost too much?

Together with the quantity surveyor, we have sourced some costings and provided comparisons, particularly for the renewables. Air source heat pumps cost about three times more than gas boilers, but an ASHP will save tenants approximately 15% on their energy bills compared to gas boilers per year. ASHPs will also reduce carbon by around 35% for flats, and 55% for houses, compared to a gas boiler per year.

Is this something we should be doing?

Your organisation has declared a climate emergency. Yes, we should be doing it.

All the questions thrown at me by the senior project manager were fair and diligent. Once satisfied, he finished the meeting with a resounding “Let’s go for it then!”

Excited at the thought of delivering a net zero carbon housing scheme, we hurried to complete the planning application and associated documents and proceeded to submit it to the planning department. Fast forward four months and the application was recommended for approval and was presented to the online planning committee. I was told that there were no objectors and that therefore I was not required to speak as agent for the application.

The planning committee recognised that they had their net zero carbon council-led housing scheme on the agenda. They seemed excited but at the same time they were required to hold the application to account.

In particular, they really were curious to find out more. Questions shot out from each committee member. Finally the planning officer suggested that “maybe the applicant team can assist?” More questions. 

Can the solar panels be stolen?

We can securely fix them on the roof to deter theft. 

How will the residents know how to use the new equipment?

A resident’s information pack will be produced, and the registered social landlord will provide training and support.

How do we know the actual energy performance will achieve the calculation provided?

A planning condition has been proposed to monitor the energy performance annually to see how it compares against the energy statement.

Why can’t we achieve net zero carbon emissions on all our projects?

There is a point when you physically run out of space for renewables and cannot provide enough for the number of homes you are proposing. This means there is a ratio of solar panels to homes that must be considered when achieving net zero carbon. It is much harder to achieve net zero carbon, for example, in taller apartment buildings, as the roof space is small compared to the number of homes. Eventually, the whole power network will become net zero carbon, and maximising onsite renewables is an integral part of that strategy.

We realised that clients have a lot of questions as net zero carbon is often new to them. Reassurance and a clear strategy that their buildings can meet the net zero carbon standard are what they are looking for. We worked a little harder to get here, but through our belief, we were able to bring our clients along with us.

The most rewarding outcome is that now that the client organisation understand the requirements and that it is achievable, their mindset has changed. They are now actively pushing net zero carbon emissions throughout their house-building programme.

The planning committee are now asking applicants, “why are you not achieving net zero carbon?” rather than “can you achieve net zero carbon?”