When trying to reduce operational energy for RIBA 2030 or otherwise, we suggest using good old common sense and the Mesh Energy Hierarchy. As you work from the top down you give your project the best chance of becoming low energy for the least hassle and capital invested. That’s because all parts of a building’s design and function are not created equal.

By far and away the largest contributors to the overall operational energy usage of a building is the space heating/cooling, ventilation and hot water loads. In most buildings these combined key regulated loads make up 70-80% of the annual operational energy usage.

This blog assumes you are fairly restricted with building size, shape and form due to the site, location and work done so far. If you haven’t got that far and you are in the very early stages of conceptual building design then you can use a more compact building shape, use natural positioning and orientation to reduce unnecessary seasonal heating, cooling and ventilation for the building.

Fabric Element Design

The next logical step to reduce operational energy demand and heating is improving the building fabric as far as is practically possible. To help you, we have, based on extensive design experience, suggested some target U-values in the table below for key thermal elements to get you close. Fundamentally the walls, floors and roof need to be 25-45% than they are today to get even close to the RIBA 2030 target. The more time and effort you spend on this element of the design will pay dividends for the life of the building and long-term running cost reductions.

Airtightness & Ventilation

The ‘leakiness’ and controlled ventilation of a building also plays a big part in energy efficiency. Increasingly you will have to build to a tighter and smaller infiltration rate to meet stringent RIBA 2030 targets and provide mechanical ventilation and heat recovery systems. It is estimated that compared to a standard naturally ventilated building that MVHR systems on average reduce heating related energy usage by approximately 20%.

To achieve the RIBA 2030 target we estimate that a building airtightness design level has to be below 1 m3/m2h.

Renewable Technology

Once you have building form, external fabric design and airtightness sorted you have likely made some serious progress to making long-lasting passive energy improvements to the building that should outlast the occupants. Beyond these design elements you can turn your attention to the technologies that will power, provide heating and hot water in a sustainable way. Realistically, you will not get anywhere considering fossil fuel technologies and will have to look at renewable heat pump technologies as well as solar photovoltaic (PV) panels in some instances. Installing solar PV in large quantities will just about allow some to put in a high efficiency gas boiler.

It is likely that in order to meet the RIBA 2030 targets, air or ground source heat pump technology and a small contribution from solar PV will be required.

Low-Energy Appliances & Lighting

As a cherry on the cake when you get to considering appliances and lighting (particularly for a commercial project) there is still a significant operational energy saving contribution that can be made by using LED lights and smart technology to monitor and manage usage at appropriate times. Commercially, it is suggested that lighting power density of 4.5W/m2 during office hours is where you need to be to meet the RIBA 2030 targets.

If you have any questions about the RIBA 2030 Climate Challenge, please don't hesitate to contact the Mesh team today.