How changes to sustainability criteria affect how we cost plan

As a cost consultant in a volatile and uncertain market, cost planning and feasibility estimates are already bringing new challenges in how we deal with supply chain issues, the increasing cost of materials and services and soaring energy and fuel prices.

Alongside these cost challenges in delivery of schemes, we also are looking at a different strategy of how we design and cost sustainability measures within new developments. So what do we need to do to keep up with the changes and separate these considerations?

Back in circa 2010, a new-found excitement and exuberance was felt industry-wide for renewable technologies and the newly introduced feed in tariffs, zero carbon technologies and housing initiatives such as the Code for Sustainable Homes. Original feed-in tariffs were significant and made for comfortable pay-back periods, sites were being developed with district heating solutions and all manner of renewable technology bolted on to dwellings to increase their efficiency.

Then things started to change, feed-in tariffs started to diminish and the pay-back periods and offset against initial investments didn’t look so financially viable. Renewables were still there, bubbling away in the background, but without their initial vigour.

Now we are in the new realms of the updated Part L Regulations, a change to the overall strategy with emphasis on a ‘fabric first’ approach and a change to utility strategy with many schemes moving to all electric supply due to the recalculation of the SAP calculations. That alongside the continued push towards renewables technologies such as air source heat pumps and PV on our dwellings and combined with the increased requirements of EV charging, both public and in the home, gives us a new set of challenges in how we cost future schemes.

Our cost profiling changes in a number of ways:

Building cost – Fabric first approach

With this approach the construction methods and materials are upgraded to provide a more thermally efficient building with improved air tightness and insulation, before relying on a services or renewable strategy. The new Part L does not weight the offsetting of renewables as highly as previously, therefore a poor thermal performance of a dwelling cannot be offset as easily with a few more PVs. I surmise that with the increasing cost of living, this change can only be a good thing for the future tenants and owners of these dwellings.

From a costing point of view this means changes to wall thicknesses, increased insulation thickness and upgrading of windows and doors to meet new U-values. So back to the benchmarks we go to re-test these new construction methods, but how do we know what is an upgrade and what is a victim of the current market conditions? Herein lies the challenge…

Changes to infrastructure

As noted above, electric-only schemes are now more likely to comply with Part L, therefore many schemes are opting out of the gas utilities altogether, which feels like a good thing for cost and potentially lead-ins and delivery on site. However, in the light of the EV car era, dwellings and public charging are on the rise for both active and future proofed capacity which increases the electric loadings and, frequently, requires more infrastructure such as substations. How long before developments are needing to contribute towards wider electricity infrastructure? We aren’t sure yet, but initial signs point towards ‘load management’ being the key in the design of buildings going forward.

Top 3 takeaways

• Harnessing a cost effective ‘fabric first’ approach and updating benchmark data for costing schemes
• Understanding the affect on infrastructure of a different utility strategy and the affect of car charging requirements is key
• Reviewing the above separate to the market volatility where possible to ensure we are assessing cost data accurately for future schemes