Heat Pumps and Heat Waves: How overheating complicates ending gas in the UK

by Dr Aaron Gillich | Associate Professor and Director of the BSRIA LSBU Net Zero Building Centre

We have entered what many are calling the decisive decade on climate action. Among the most critical decisions that the UK faces this decade is how it will eliminate carbon emissions from heat. Heat accounts for over a third of our emissions, and over 80% of our buildings are linked to the gas grid. There is no pathway to Net Zero that doesn’t include ending the use of gas as we know it in the UK.

Given the size of the UK gas grid, no single technology or energy vector can replace it. We will need a combination of clean electricity and carbon‐free gas such hydrogen or biogas, delivered by a range of enabling technologies such as heat pumps and heat networks. And of course an extremely ambitious retrofit agenda that reduces the demand for heat in the first place.

The UK is investing widely in low carbon heating innovation. That innovation is essential, but is also unlikely to include any blue‐sky breakthroughs that aren’t currently on the table. In other words, the menu of low carbon heating technology options is set, and this decisive decade will be about deciding what goes best where, and how to ensure a just and equitable heat transition.

Low-carbon heating options

Of all the low‐carbon heating options available, low carbon heat pumps are the most efficient and scalable option that is market ready and can respond to the urgency of climate change this decade. The UK has set a laudable target of installing 600,000 heat pumps per year by 2028. Many have criticized this figure as unrealistic, but I believe that the target is highly achievable, and represents a pace that is in line with past transitions such as ‘the Big Switch’ that put us on the gas grid in the first place.

This race to replace gas in the UK has been widely discussed. As have the many barriers that face heat pump deployment in the UK. What I’ve heard discussed far less are the links between heating in the winter and overheating in the summer. Over the next decade, the end of gas will present both a threat and an opportunity to improve both the winter and summer performance of our building stock.

The threat of climate change is clear. The end of gas increases this threat because gas has allowed the UK to obscure poor building performance, and poor building knowledge for so long. Cheap gas has enabled a ‘set it and forget it’ approach to many building systems, and allowed us to maintain reasonable standards of comfort in most buildings despite very poor fabric performance. The irony is that this poor winter performance actually helps reduce the risk of overheating in the summer, as the leaky and poorly insulated buildings can more easily shed excess heat. It has been widely reported that many newer, better insulated buildings actually face an increased risk of summer overheating.

Replacing gas with heat pumps, or any other low carbon heat source, should be accompanied by ambitious retrofit to improve energy efficiency and reduce heat loss. There are many that argue heat pumps in fact require extensive fabric retrofit in order to function in most UK buildings. This is highly debatable and will be explored in detail in follow-up writings. Regardless, demand reduction and a fabric first approach is a good idea for its own sake.

Replacing gas with heat pumps, or any other low carbon heat source, should be accompanied by ambitious retrofit to improve energy efficiency and reduce heat loss.

But reducing the heat loss in winter will likely trap heat in the summer, presenting a conflict. The UK currently experiences over 20,000 excess winter cold deaths and around 2,000 heat related deaths in summer. It was previously thought that the increased temperatures from climate change would decrease winter cold deaths, but more recent work has shown that due to the increases in extreme weather events at both ends of the spectrum, it is far more likely that winter cold deaths will remain at similar levels, and summer heat deaths will increase dramatically under climate change.

We must use the transition from gas to low carbon heating as an opportunity to better understand our buildings. Many of 600,000 heat pumps we install by 2028 will be in new build, but up to half will need to be from existing homes.

Retrofitting a heat pump is also the time to think about not only how to improve energy efficiency for the winter but how to reduce summer overheating as well. Despite much effort towards a whole‐house approach to retrofit, most work remains quite siloed. Energy efficiency and heating installations are largely in separate supply chains, and the building physics knowledge to carry out an overheating risk assessment is even less likely to sit with the same project team. Overheating is also very poorly captured by the building regulations and planning process.

A holistic approach

The last few years has seen a growing awareness of overheating risk and an emergence of increasingly easy to use assessment tools. A very small fraction of UK homes have comfort cooling. Retrofitting a comfort cooling solution typically requires costly and complex changes to distribution systems. However, there are a range of low cost options, including using local extract fans to create interzonal air movement, or using night purges and thermal mass. Blinds are also incredibly useful, but often misused in summer, and can also help reduce heat loss in winter. There are also ways to use local microclimate features such as shaded areas or the North side of the building to bring in slightly cooler air from outside and reduce peak temperatures.

Improving the air tightness and fabric performance of our buildings to address heating in the winter will change how we implement these solutions for the summer. They require not only careful thought at the design stage, but also strong communication to help end users operate them properly. Simply opening a window is unlikely to help if the outside air is warmer than inside.

A significant problem is that there are insufficient drivers to force this type of holistic approach to design, performance, and communication. It is so often said that we need stronger policies in the area of heat and retrofit, and this is no doubt true. But while we await these policies it is incumbent upon each of us in this sector to share and collaborate as widely as possible, and use whatever influence we have over a given project to encourage a fair and forward looking solution.

In summary, the availability of cheap gas has allowed us to escape having to understand our buildings in much detail. Climate change is the catalyst for an untold level of change in our lives that we are going to start to truly experience in the coming decade. Heating and overheating are coupled issues that must be solved together. We must use the end of gas as an opportunity to understand our buildings better, and implement solutions to climate change that work across seasons, or we risk trading one problem for another.

In summary, the availability of cheap gas has allowed us to escape having to understand our buildings in much detail.

Betting on the general election? Think again

This post was written by Julia Evans, BSRIA Chief Executive

This post was written by Julia Evans, BSRIA Chief Executive

There are number of ways of predicting the outcome of the general election and an equal number of ways of being wildly incorrect. Bookmakers across the land are considering the 7th May to be a field day equal only to the Grand National in terms of punter cash finding its way through the betting shop door and not finding its way out again.

The one thing that seems sure is that the outcome is likely to be uncertain with both a three way coalition and a rerun of the election in the Autumn both being seen as possibilities.  So, where does that leave construction and building services?

Just as education and the health service are perennials in political manifestos so construction has some constant themes. Although construction rarely makes front page news there are a number of issues that seem likely to make the political headlines. Maybe for reasons of one-upmanship, as in who is promising to build the most houses? It’s the Liberal Democrats, since you ask; who are promising 300,000 new houses a year and an assurance that they’ll all be energy efficient. Or the startling alignment and collaboration between the three main political parties who are promising to work together on climate change, which in itself is surely not a bad thing?

But what of the perennials that effect construction?

Representation at senior levels seemed threatened at one point by questions being asked about the continuation of the role of Chief Construction Advisor, this is now resolved at least for the next two years. However other things are less easy to solve – the impending skills shortage, the delivery of low carbon retrofit and the lurking influence of increasing devolution will all play their part. As will continuing pressure on late payment practices, poor treatment of supply chain and the weakening of centrally funded research programmes.

The uncertainty caused by the impending election has been felt in the slackening of demand for construction since the turn of the year, the recent results of our quarterly consultants survey suggested that there has been a halt in new work as we wait for a new government. This has also been seen in a reduction in the immediate pre-election period of house building starts just at a time when we need to be addressing the national shortfall.

So back to my punt at the bookies, I think I will put my money back in my pocket and find something more predictable to spend it on, maybe something in preparation for the barbeque summer?

Getting life cycle costing right

Stuart Thompson

Stuart Thompson,
Senior Design Manager,
Morgan Sindall

A guest post by Stuart Thompson of Morgan Sindall 

The NRP (Norwich Research Park) Enterprise Centre project is an Exemplar Low Carbon Building, which is targeting BREEAM Outstanding and Passivhaus Certification.

The project for the University of East Anglia (UEA) is being delivered using a collaborative single point of delivery system by main contractor Morgan Sindall and its team, which includes architects Architype, civil, structural and environmental engineers BDP and Churchman Landscape Architects.

The centre has been created to achieve a 100-year design life and aspects of the development will be constructed using traditional methods. Locally sourced materials including Thetford timber, Norfolk straw and heather, chalk, lime, hemp and flint will be used and the lecture theatre will be constructed of rammed chalk while various buildings will be thatched. The development is expected to be completed in early 2014.

A key aspect of delivering the Exemplar Low Carbon Building at UEA is ensuring that the project has the lowest life cycle cost possible. The life cycle cost of a project is often discussed in construction but not usually followed through therefore it’s been fantastic to work with a client team which is happy to dedicate time and resources to evaluating this aspect of the development in such detail.

As part of the life cycle costing process, the design team met with consultants from BSRIA to consider how the building’s Passivhaus specification might affect its life cycle output. It was reassuring to know that the early analysis proved that the Passivhaus specification has life cycle benefits. You can watch a film about our workshop below:

 

Following the initial life cycle study, we followed up with a workshop that included a mixed group of various representatives from the client team. We learnt more about which issues were of particular interest to the various client representatives, such as predicted energy costs, climate change considerations, maintenance, robustness of filters and the type of finishes used. The debate did not simply focus on the initial capital costs, but also about legacy issues, robustness and replacement. We covered a full range of topics, including energy source, landscape materials, PV and roofing, lighting and floor finishes. The client maintenance team fed back to the group about their current issues and concerns too.

BSRIA's Peter Tse at the workshop

BSRIA’s Peter Tse at the workshop

What was interesting following such detailed debate was we were able to address the long term issues and this changed our initial concepts within the life cycle analysis. Our changes have made our project report totally specific and the real use and maintenance scenarios follow the life of the building. For example, how often timber windows will be re-painted, how often timber floors will be sanded and sealed and whether the LED light fittings will be able to handle the lamp life and transformer life claims. The workshop allowed the group to ensure that the life cycle analysis is extremely relevant and targeted to this specific project and we will now be able to use the information garnered during the process to shape the scheme over the next few months when detailed design commences.

This landmark project is part-funded by the European Union through the European Regional Development Fund (the largest single ERDF project in the region in the 2007-2015 funding round) in addition to funding from UEA, the Biotechnology and Biological Sciences Research Council (BBSRC) and BRE.

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