How To Achieve Part L Without Renewables – Graham Suttill, Sustainable Buildings Assessor, Darren Evans Assessments

Greame Suttill

Increasingly stringent efficiency requirements within Part L of the Building Regulations mean that many projects struggle to achieve compliance without bolting on renewable technologies. However, despite renewables being an easy option this is not always appropriate. In these instances, creative thinking can instead be used to enhance the building fabric and services in ways that are cost-effective, easy to implement, and above all, low energy.   

With the 2013 Part L revision having had a chance to bed down, developers, architects and housebuilders now have a good understanding of what is needed to comply with the regulations. However, it would appear that the majority of initial SAP calculations do not meet the emissions or fabric energy targets with the specification provided. The simplest approach in this situation might be to just add on a few PV panels, but this is rarely the route to compliance many clients want to take due to the additional cost added to a project and the resulting change in its appearance.

So what can we do? The first step should be to look at the fabric of the building, which would either mean increasing the insulation thickness or specifying a higher performing insulation product which provides a better U-value with the same thickness. This might increase the capital cost but would balance against savings on additional systems such as heat recovery which might be required to enable a building to pass.

Within the latest SAP software the thermal bridging calculation (heat loss across junctions such as where the wall meets the floor, known as the Psi value) has a large impact on whether the dwelling will pass or fail, as improvements here will positively impact emissions and the fabric energy efficiency targets. As a starting point we will always use accredited construction details (ACDs) but ideally you need to be offering a further improvement.

The most widely used set of calculated values which offer improvements over the ACDs are the Aircrete Product Association (APA) details; these can be used when a lightweight block is specified as the inner leaf of the external wall. The junction which has the largest impact on the heat loss figure is the lintel, so using an independent or high performance lintel such as the IG Hi-Therm in conjunction with the APA detail will offer a significant improvement to your SAP calculation.

There are other straightforward design approaches that can be modelled to offer enhancements to an SAP score in addition to improvements to the building fabric. The two most commonly specified are flue gas heat recovery systems (FGHRS) and waste water heat recovery systems (WWHRS) which are both used with combi boilers, however, WWHRS can also be used with a hot water cylinder. A FGHRS works by taking the combustion heat from a boiler which would normally be lost through the flue and using it to preheat cold water entering the boiler; this lowers the amount of energy needed to heat the water to the required temperature. WWHRS works by recycling the heat from waste water from a bath or shower to preheat cold water via a heat exchanger before it enters the boiler.

Both of these systems can make significant improvements to your SAP calculation which can be the difference between a pass or fail. They are also much cheaper to install than solar PV or solar hot water systems making them a preferred route to compliance for clients in many cases.

So the lesson is that by thinking outside the box and exploring alternative ways of ensuring a building meets the tougher demands of Part L on CO2, it is possible to arrive at a simple and effective solution which avoids the need for bolt-on renewables.


One Way To Sustainably Solve The Uk’s Housing Crisis Is Right Under Our Noses


The Housing Minister Brandon Lewis last week said that the Government wants to build 1 million homes by 2020 to solve our housing crisis of skyrocketing demand matched with a lack of supply. The need to address this is now acute, and there will be a concerted effort in the industry over the next few years. However with many reasons why building on greenfield sites is not the most advisable option, a far more sustainable alternative is presented by the hundreds of thousands of existing buildings lying empty across the UK.

Following re-election in May this year the Government published its house building policy saying it would make public sector land available to build a further 150,000 houses, which is laudable. It also announced the creation of 30 Housing Zones on brownfield sites which would provide a vital stimulus for building in urban areas. However there seems to be precious little in terms of national policy when it comes to unlocking the potential of reusing and refurbishing our unused buildings to create energy-efficient, good quality housing and kill two birds with one stone. This plentiful opportunity is being left to ad hoc initiatives by enlightened housing associations and developers when it could be a much more powerful source of progress.

Across our public sector there are swathes of empty buildings which are being maintained but are standing empty, and which could provide the raw materials for a sustainable refurbishment revolution. Even the City of London recorded vacant property rates around the 16% mark in 2005 (the DCLG has not been able to publish figures since then due to budget cuts), and if a case is not being made for releasing such assets even in an area of such premium real estate then clearly something is wrong. The NHS revealed in 2014 that is it is spending up to £60m annually on maintaining empty buildings which is a fairly shocking figure. Additionally, the bar doesn’t seem to be being raised for refurbishments when it comes to building performance in the Building Regulations in the same way as it is for new builds currently, which might force some of these buildings to be addressed.

The fact is, upgrading empty buildings into modern fit for purpose housing would be a sustainability double whammy. We would firstly be reusing existing resources in terms of land, building materials and their embodied energy. And while many of these buildings might provide a useful base in terms of building fabric to work from, whether they are Victorian or 1990s construction (in fact the latter might prove less energy efficient in some cases), upgrading them would produce sustainable assets from wasteful empty shells.

Clearly incentives such as tax breaks for companies investing in refurbishing empty buildings need to be looked at in order to encourage innovation and bravery, however the opportunity is clear. In many cases such schemes would answer

urgent housing needs in one fell swoop, creating sustainable, quality environments where people want to live. This could be the low hanging fruit that we urgently need to pick as a nation, and it’s crucial that the Government looks at a thorough review of our public assets to see where the opportunities are.