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.

“Clean Energy Revolution” puts building and product standards back on the Federal agenda

by Krystyna Dawson

The inauguration of the new President-elect, Joe Biden, marks the start of a period that could bring a substantial shift in US building-related markets. Air conditioning, heating, ventilation and controls are likely to face requirements from policy and market demand that will change dynamics in several segments.

Net Zero Emissions

With the President-elect’s Clean Energy Revolution announced during the campaign, the federal green agenda is set to make a strong comeback. President Biden signalled his intention to re-join the Paris Agreement, notably on the first day of his presidency, and outlined a national goal of net-zero emissions across the economy by 2050. Although less ambitious than the progressive Green New Deal target (net-zero emissions by 2030), with Congress now on his side he can venture putting his intention into law.

The President has promised a nearly USD 2 trillion investment plan, much of which is due to support green initiatives. He also promised to work towards achieving decarbonised electricity by 2035. Although during the campaign he was careful not to promote the ban of gas and oil fracking, his Clean Energy Revolution includes plans to improve energy efficiency in buildings and houses, and promises high investment in R&D related to zero carbon technologies to produce cutting-edge equipment for internal markets and export.

Even if not all of it might come to fruition, there is certainly a significant change of direction ahead in all industry sectors, including energy and HVAC in buildings.

HVAC Industry

During the Trump presidency, the federal government kept progress in energy efficiency standards for appliances and equipment at a low level. This has been countered by initiatives in several states, like California, Vermont, Washington, Colorado Texas and Hawaii, which have been setting their own efficiency standards for a variety of products. Federal standards nevertheless cover a wide range of HVAC products. Hence, the re-activation of ambitious federal efficiency programs will be important for industry and consumers.

California will likely increase its influence on federal decision making, not only as Kamala Harris’ home state, but because of its leading set of environmental regulations and standards. Its Title 24 Building Standards Code that sets requirements for “energy conservation, green design, construction and maintenance, fire and life safety, and accessibility” that apply to the “structural, mechanical, electrical, and plumbing systems” in buildings might provide a template for wider adoption. The experience the state is gathering on the application of a variety of solar and heat pump combinations can support the uptake of these technologies on a larger scale.

Green Agenda

With the push towards energy efficiency in buildings, technologies that support their smart operation are likely to see dynamic uptake. Currently, smart buildings represent a niche market across the US, with just some cities in the North-East, Texas or California seeing their increased emergence. They usually belong to corporations who are keen to emphasise their green credentials, aspiring to achieve high sustainability certificates through building sustainability assessments like LEED or WELL.

The impact of the federal policy change on the building HVAC and controls market will not be instant, but waiting for it to become obvious might have serious consequences for market players.  The unfolding of the green agenda by the federal government will strengthen ongoing efforts of market stakeholders and demand from consumers as environmental awareness creates favourable conditions for the shift towards efficient, environmentally friendly products.

What makes a good PICV?

by Andrew Pender, National Sales Manager at FloControl Ltd.

Over the last 5 years, PICVs have been widely accepted as the best method of terminal control in variable flow systems due to their energy saving potential.  The surge in popularity has led to an influx of products with varying designs, features and functionality.  This article reviews some of the mechanical PICV design elements and how they can impact on the PICV’s performance in an applicational context.

Where do we start?

To help specifiers and project engineers assess which PICV is best suited for an application, the BSRIA BTS1/2019 standard has been developed to provide a consistent test method for PICV manufacturer’s products to be benchmarked against.

Manufacturers should be able to provide test results in line with this technical standard which covers:

  • measured flow vs nominal flow
  • pressure independency or flow limitation
  • control characteristics, both linear and equal percentage
  • seat leakage test

Repeatability & Accuracy are central to the tests and they are key to good temperature control and realising the full energy saving potential of a PICV installation.

An accurate PICV means the measured results will be equal or very close to the manufacturer’s published nominal flow rate each time it is measured, known as low hysteresis.

Accuracy has a positive impact on a building’s energy consumption.  “Measured over time, a 1% increase in the accuracy of a PICV can result in a reduction of around 0.5% in the building’s overall hydronic energy consumption” (FlowCon International).

Valve accuracy is driven by the design, manufacturing process and material used for the internals of the valve.

  • The design of the PICV should allow for Full Stroke Modulating Control at all flow settings without any stroke limitation.  The flow setting and temperature control components should operate independently.  Some PICV designs use the stroke of the actuator stem to set the flow rate resulting in limited stroke and control.  This can cause issues at low flow rates whereby the PICV effectively becomes on/off irrespective of actuator selection.  
  • The manufacturing process and the component materials also contribute to accuracy. For example, injection-moulded, glass-reinforced composite materials cope better with water conditions that valves can be exposed to.  They also have less material shrinkage than other materials, delivering higher accuracy than valves that use alloy components.

What else should be considered?

The importance of accuracy and repeatability are paramount when selecting a PICV however there are other factors that should be considered:

  • Wide flow rate range – including low flow rates for heating applications, ideally covered by a small number of valves.
  • Setting the flow rate – setting the PICV can influence the accuracy. There are various scales used including set points related to flow rates and percentages. PICVs with very detailed scales with small increments between set points are more difficult to set accurately, leading to higher tolerances than the BSRIA standard recommended + 10%.
  • Wide ΔP Range – low start up pressure. To operate satisfactorily, the PICV requires a minimum pressure differential to overcome the initial spring resistance within the PICV, enabling the spring to move and take control. Care should be taken to ensure the minimum pressure differential is as low as possible to maximise the energy saving potential of the system.  The maximum DP should also be considered to ensure the PICV operates effectively under part load conditions.
  • Dirt tolerance – the Valve Control Opening Area [A] on all PICVs, irrespective of the manufacturer, is identical for each flow rate. The shape of the Control Area can be different depending on the valve design. A Rectangular flow aperture is more tolerant than an Annular flow aperture. Debris will pass through the rectangular aperture more easily.
  • Removable inserts – deliver the greatest flexibility and serviceability.  Products can be easily serviced in line without disruption. This is especially of value when water quality is poor or when flow requirements change due to changes in space usage.  Inserts can also be removed during flushing.  Valve bodies can be installed with blank caps eliminating the risk of damaging or contaminating the PICV element, whilst having a full-bore flushing capacity.
  • Installation – PICVs in general have no installation restrictions however in line with BSRIA BG29/20, it is recommended that PICVs should be installed in the return branch as small bore PICVs will have a high resistance which will hinder the flushing velocity during the forward flushing of terminal units.

Making the right choice

There are many aspects for specifiers and project engineers to consider when selecting the right PICV for an application.  The BTS1/2019 standard provides an excellent benchmark, but the individual designs also need to be carefully considered.  A correctly selected PICV will ultimately lead to a more comfortable indoor climate with better control of the space heating and cooling as well as potentially reducing the pump energy consumption in a building by up to 35%.

This post was authored by Andrew Pender, National Sales Manager at FloControl Ltd. All views expressed are those of the author. If you belong to a BSRIA Member company and wish to contribute to the BSRIA Blog, please contact marketing@bsria.co.uk

Shift in Construction Technology for a ‘post-Covid, pre-vaccine’ era

by Amy Butler, JB Associates

In 2017, McKinsey Global Institute slated construction for evolving at a ‘glacial pace’ due to its ranking as the least-digitised industry in Europe. While plenty of technological advances were pitted as ‘on the horizon’, many companies were reluctant to take the necessary steps to push forward with digitisation. Critics warned that a lack of innovation would lead to companies folding, although it took a global pandemic before this prophecy materialised and those without suitable digital infrastructure in place were shaken.

The pandemic is now considered a catalyst for industry improvement, propelling construction out of its ‘glacial’ evolution and deep into the digitised era. A recent study undertaken by Procore found that two thirds of the surveyed construction companies had rolled out new technology during the lockdown, with 94% of these seeing an improvement to productivity and teamwork. However, what exactly are these technologies and where do we go from here?

Smart Buildings

While we are all now experts in the world of Zoom and Microsoft Teams, the challenge lies in returning safely to offices and various other workspaces. With many UK companies pushing for their teams to be back in work physically, how do we ensure that commercial buildings remain safe? Smart Building technology is reshaping the workplace and ensuring safety as well as energy optimisation. Buildings with integrated BMS systems and IoT sensors were already an option before the pandemic. Now, they are a wise choice for business owners.

Essential for a post-Pandemic and pre-Vaccine era, IoT systems can control air quality and ventilation. High-performance air filters and moisture controls will now be key due to Covid-19’s airborne nature. OKTO Technologies (Smart Buildings specialists) have even launched an Artificial Intelligence-led air filtration solution that is reportedly so advanced it can eliminate 99.98% of SARS-CoV-2 (the virus that causes Covid-19) from the air in 10 minutes.

Similarly, density control counters and heat detection cameras can be incorporated into BMS systems to ensure that viruses are less likely to spread or enter into a facility. Airports have been trialling infrared cameras to measure body temperatures for a fever and several companies offer leases or installations for these cameras. While they are not a definitive medical diagnosis, they add a level of reassurance. This may be the aim of much of this technology; a form of due diligence in protecting staff.

BIM & VR

Technological advances are also prominent on site. Construction News reported that contractors employed for the Nightingale Hospital projects found huge value in Autodesk programs. A vital tool for tracking constant streams of updates in rapid working conditions, construction management software proved its worth in recognisably challenging projects across the UK.

As social distancing measures remain in place, it is imperative that technology is prioritised; virtual communication is still far safer than face-to-face. Software like BIM is also providing insights and tools to manage projects during a more challenging time. Even more impressively, companies are merging BIM models with the cloud, GPS and Virtual Reality software. This development means a ‘digital twin’ of a facility can be created and it opens a world of opportunities for Project Management and Design efficiency.

Remote working could even be a trend that stays long past pandemic precautions. Drones have been used previously to reduce safety hazards for technicians and now may be utilised in future remote inspections. Similarly, researchers at the University of Strathclyde have been given £35,000 in funding to create a remote inspection system. The 3D immersive building environment program aims to reduce risks by eradicating the need for Quantity Surveyors or Health and Safety Inspectors to be physically present on site.

Whether enabling remote working, improving the health and safety of commercial buildings or aiding on-site processes, technology has become a necessary tool for construction in the last 6 months. The companies that had embraced digitisation long before 2020 were undoubtedly the ones able to continue thriving in the tough lockdown period. The next step is for many companies is to streamline their management processes or workplace systems to ensure technology works for them as efficiently as possible. Breaking out of its inertia, construction’s ‘glacial evolution’ is firmly in the past and technological advances are here to stay.

This post was authored by Amy Butler of JB Associates – building consultancy specialists. The views expressed are those of the author.

BSRIA Members wishing to make a guest contribution to the BSRIA Blog should please contact marketing@bsria.co.uk

The selection criteria of refrigerants

Salim Deramchi, Senior Building Services Engineer at BSRIA

Salim Deramchi, Senior Building Services Engineer at BSRIA

This is part two of a three part series from Salim. You can read part 1 here

There is no general rule governing the selection of refrigerants, however there are of course the five classic criteria and those are:

  • thermophysical properties
  • technological
  • economic aspects
  • safety
  • environmental factors

However, in addition to these criteria, others have to be considered such as local regulations and standards as well as maintainability and ‘cultural’ criteria associated with skills to support the units, application, and user training requirements.

The best approach when presenting evolution and trends is certainly the per-application approach. The desirable characteristics of “ideal” refrigerants are considered to be:

  1. Normal boiling point below 0°C
  2. Non-flammable
  3. Non-toxic
  4. Easily detectable in case of leakage
  5. Stable under operating conditions
  6. Easy to recycle after use
  7. Relatively large area for heat evaporation
  8. Relatively inexpensive to produce
  9. Low environmental impacts in case of accidental venting
  10. Low gas flow rate per unit of cooling at compressor

The choice of alternative refrigerants should involve a review of recycling or disposal of refrigerants. You must decide which criteria for the ideal refrigerant is of most importance to your organisation. It must be considered that the operation phase is the key factor when determining the environmental impact of the various refrigerants as there is less impact to the environment in the production and disposal stages. As an example, supermarket retailers are steadily moving away from long-established HFC refrigeration systems.

Decision making for new refrigeration plant using refrigerant alternatives such as ammonia, CO2 or hydrocarbons, which have comparatively little or no impact on global warming and zero impact on ozone layer, should consider not only the impact on the environment but the additional required skills to maintain (Ko Matsunaga).

You can  find out more information in BSRIA’s library

Refrigeration Part 1 – Choosing the right refrigerant

Salim Deramchi, Senior Building Services Engineer at BSRIA

Salim Deramchi, Senior Building Services Engineer at BSRIA

Refrigerants are a key component for air conditioning and refrigeration. Since the 19th century there have been many refrigerants developed and used but none of them has as yet become the industry standard.

As an industry we should not consider reducing F-Gas emissions as just complying with legislation to meet government set targets, but reducing them will also have a positive effect on operating costs.  We can make cost savings through efficient operation and we can also help enhance market reputation by being more environmentally friendly.

To have a good understanding of this we need to look at:

  • Available refrigerant types
  • Our selection criteria
  • How we evaluate the available refrigerants

Traditionally commercial businesses have been using R12, a CFC, and R502a CFC/HCFC. In addressing the ozone depletion problem, most manufacturers have adopted either R404A a HFC blend or R134a. However, both are potent greenhouse gases (Nicholas Cox).

So the industry needs to look at future solutions which might be natural refrigerants, although some design change might be required on the equipment used. The following refrigerant replacements all require system and operational changes to current practice:

20140213_132647_resizedIsobutane (R600A) is a hydrocarbon , and hence is flammable. The thermodynamic properties that are very similar to those of R134a. Isobutane presents other advantages, such as its compatibility with mineral oil and better energy efficiency and cheaper than that of R134a. The use of isobutane requires minimal design changes, such as the relocation of potential ignition sources outside of the refrigerated compartment. Operational changes will also be required.

Propoane (R290). With a boiling point of -42C, propane is an excellent alternative to R22 as it requires similar working pressures. An added advantage is that except for added safety measures because of its flammability, virtually no design change is required in systems when switching from R22 to propane. The combination of its good thermodynamic and thermophysical properties yields systems that are at least as energy efficient as those working with R22. The use of propane is increasing in countries where regulations allow it.

Ammonia (R171). Ammonia has been continuously used throughout modern refrigeration history. Despite its numerous drawbacks, it is toxic and flammable in concentrations between 15.5% and 28% in air. It is not compatible with copper, thus requiring other materials of construction. Its thermodynamic and thermophysical properties also yield very efficient refrigeration systems. Because of its acute toxicity, stringent regulations apply for ammonia systems, which require close monitoring and highly skilled engineers and technicians.

20140213_132339_resizedCarbon dioxide (CO2) is not a new refrigerant. Rather, it was ‘rediscovered’ in the early 90’s. The use of carbon dioxide as a refrigerant has gone back well over a century. Its application was abandoned in the mid-50s, with the widespread use of the CFC refrigerants, which were more efficient, more stable and safer. Due to its low environmental impact, low toxicity and non-flammability, CO2 is now regaining popularity from refrigeration system designers when an alternative to fluorocarbons is being sought. (Ahmed Bensafi and Bernard Thonon)

So there are alternatives on the market and technology development is tackling this issue it is now up to the designers and operators to specify something new to move the industry forward. With F-Gas regulation 2 coming we need to get ahead of the game.

We have tried to cover some of the available refrigerants seen in the market and we will be evaluating and discussing the selection criteria in our future blogs.

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