Achieving good energy efficiency in buildings

This post is largely based on the article Advances Toward a Net-Zero Global Building Sector in Annual Review of Environment and Resources 2020 [1] The article is open access so anyone can access it for free. It explores why energy efficiency is important for net zero emissions, what sort of target to aim for and policies for achieving them. The focus is on the UK although much of the evidence comes from elsewhere, primarily Europe.


Energy efficiency is critical but health must be protected.
Energy efficiency is critical on the path to net zero emissions because our current needs are considerable and replacing current building energy use with new renewable generating capacity (not using gas), energy storage and transmission capacity would be even more expensive. Efficiency is also beneficial in other ways including improving health and reduction of energy poverty. For example, in the past efficiency measures have contributed to sick building syndrome – to avoid this air tightness must be accompanied by adequate ventilation. Also temperatures below 18°C can trigger health problems in vulnerable adults directly; there is evidence that 18°C is warm enough for most people [2].


Stringent energy efficiency standards make homes cheap to heat.
The PassivHaus energy standards are widely used for social housing as they reduce the energy bills for tenants. Lower bills and healthier tenants reduce costs for landlords too as tenants are less likely to fall into arrears with the rent [3]


Passivhaus standards for new build are achievable in all regions of the world. 

There are many examples of Passivhaus certified buildings in the northern hemisphere where winters are cold but relatively few in the south where the main requirement is cooling[1]. The requirement for Passivhaus certification is that total heating and cooling energy demand should be no more than 15 kWh/year. This is a huge reduction on typical UK homes where energy demand is typically 11,500 kWh/year for gas alone, ignoring electricity (according to British Gas). 

Air conditioning will be more widespread by 2050.

Very few homes are cooleded with  air conditioning, at the moment. However, climate change will make cooling more essential by 2050 [4]. Passivhaus standards are a challenge in hot humid regions. In regions where the main requirement is for cooling, even very efficient buildings can use 90-180 kWh/m2/year for cooling compared to 15 kWh/m2/year for heating. The heating requirement can be reduced by super insulation and ventilation with heat recovery to avoid wasting heat. Cooling that does not increase energy demand is best achieved by shading (such as deep eaves over windows) and stack effect natural ventilation. Sadly these are hard to retrofit. Also dehumidification may be needed as cooling humid air can lead to condensation which allows mould to grow. 

Energy Efficiency in buildings has improved substantially since 2000 as shown by Figure 2 from [1]

Figure 2 from [1] showing decreasing energy use intensity for home energy since 2000.

However, much of this improvement has been offset by increasing building size, especially outside Europe. 

The best time to install energy efficiency is at build time or when maintenance is required. 

Retrofitting energy efficiency measures into existing buildings is often very expensive as well as a major hassle for residents. In comparison, the marginal cost for efficient components such as windows are often quite small in comparison to the anyway cost of replacement. 

Energy efficiency retrofits can easily take 10-20 years for payback in lower bills and this is too long for most home owners or landlords. Hence financing packages are needed. Also these retrofits are a major hassle, requiring planning permission and contractors to be hired and managed. During the retrofit, parts of the building may be unusable or at least need to be emptied of furniture. Temporary accommodation may be needed. (We conducted our retrofit in phases, with each phase requiring some furniture moved into storage but we never moved out. This was possible because we live in a large home that is arguably under-utilised.) 

One stop shops such as Action on Energy Cambridgeshire  can reduce the hassle and facilitate access to funding schemes.

One stop shops can reduce the hassle, providing planning advice, project management and often access to finance. We used an architect for project management but there are also specialist firms such as Ecofurb. Some local councils offer a one-stop-shop service through a partner. Cambridgeshire uses Action on Energy 

[1] ( Diana Ürge-Vorsatz, Radhika Khosla, Rob Bernhardt, Yi Chieh Chan, David Vérez, Shan Hu, and Luisa F. Cabeza, 2020 (2020) Advances toward a Net-Zero Global Building Sector, Annual Review of Environment and Resources (https://doi.org/10.1146/annurev-environ-012420-045843) 

[2] (R. Wookey, Dr. A. Bone, C. Carmichael, A. Crossley, 2014) Minimum home temperature thresholds for health in winter – A systematic literature review (Public Health England) online. (https://assets.publishing.service.gov.uk/media/5c5986f8ed915d045f3778a9/Min_temp_threshold_for_homes_in_winter.pdf) 

[3] Sustainable Homes (2016) Touching The Voids: The impact of energy efficiency on social landlord income and business plans (2016, online) (https://www.passivhaustrust.org.uk/UserFiles/File/PH%20Social/touching-the-voids---Sustainable%20Homes.pdf) 

[4] J. Crawley, S. Ogunrin, S. Taneja, I. Vorushlyo and X. Wang (UKERC, 2020) https://ukerc.ac.uk/publications/domestic-air-conditioning-in-2050/

Paludiculture for the Fens

The Fens are wetlands but when drained for agriculture the peat becomes a major source of GHG emissions. Waterlogged soil supports microbes that produce methane which has intensive GHG effects. Even worse, drained peat can harbour underground fires which release GHG emissions as well as being a huge danger to wildlife [1]. Farming in wetland is called paludiculture [2].

Paludiculture can produce a wide variety of useful crops including food (not just fish, though in medieval times the fenlands were renowned for producing a large quantity of fish [3]), fibre and growing media to replace peat.

In the UK, the Centre for Ecology and Hydrology has trialled growing rice and the Wildlife Trusts are exploring a range of wet farming techniques [5].

Here is a range of useful products [4] including many listed by a project in Germany called Greifswald that aims to promote peatland as a vital ecosystem.  In the UK the fens are mainly used to grow food but there is potential for many other products.

Comparing plant based yogurts

Vegetarian versions of high protein foods are often much less nutritious than the 'normal' versions. I have compared a number of plant based yogurts, all from Sainsbury's, mainly in terms of protein per calorie and find a huge range - a factor of 9. Since protein rich foods are generally more 'satisfying' this could help you reduce your calorie consumption, at least a little.

This is not the 'Christmas' blog post for this year - the only relationship to Christmas that I can think of is that it is about food. Having said that, if you have an intention to try a more climate friendly diet in the new year this could be relevant to implementing your resolution. The Christmas one is the one about good news in 2025 (https://energy-surprises.blogspot.com/2025/12/good-news-in-2025.html). It was published earlier this month.

Good news in 2025

It's nice to end the year on a positive note. Despite my ongoing brain function issues my main concern remains climate change and the clean energy transition. Every little helps but the big changes help more. So I have collated some news which shows progress we have made this year. 

A short holiday in Margate

Travelling by train is energy efficient. 

My beloved and I recently came back from a few days holiday in Margate. I was yearning for a few days by the sea – this is a good way to have a reasonably sustainable holiday without air travel. On this occasion we travelled by train. It is easy for us: Cambridge to Kings Cross then St. Pancras to Margate. We carry our minimal luggage in back-packs. 

We stayed at the Premier Inn which is just next door to the railway station so easily walkable even with luggage. I cannot find anything on the Premier Inn website about sustainability other than pledging to reduce water consumption by 20% per guest by 2030. Reducing water use is good, and often saves water heating energy too, though the flow restrictors on taps can be annoying – it took rather longer to fill the kettle than at home. The same applied to the bath which turned out to be a very good thing as I had trouble with the plumbing and had to ring for help to get the bath taps to turn off! If not for the low flow taps we might have had a flood. The shower was fine. I don’t need a monsoon to get washed properly. A/C can be a major energy hog too but in this place there was none. The weather was not very warm anyway. 

Low flow taps rarely save water. 

The annoying thing about the low flow taps solution for water saving is that quite a lot of time it makes no difference to the amount of water you use, only the time it takes to get it out of the tap. Filling the bath takes an amount of water depending on the shape and size of the bath and how deep you want it. A bigger bath or low flow taps means it takes longer to fill. The amount of water you need to put in the kettle depends on the number of cups of tea/coffee you are making. Again, low flow taps means you take longer to get the required amount of water.

In many hotels the kitchens are a major hot-spot for GHG emissions. I have no idea about this particular hotel but I do know from other research I have done that boiling water can be a major hot spot for energy use. For example, steaming eggs is usually more energy efficient than boiling because you only need to heat a small amount of water – enough to generate steam for the required amount of cooking time. (This reminds me I now have an egg steamer at home and I should measure how much energy it uses.) Also, I gather many hotels and restaurants keep a pot of water boiling all the time for things like coddled eggs. This saves time for the staff and customers because you don’t have to heat the water from ambient temperature for each order but it wastes energy because you lose steam constantly. 

The beaches were remarkably clean.

There was very little litter on the beach, possibly because the weather did not encourage al fresco eating but maybe not. There were plenty of tidying opportunities by putting recyclable things into bins and there was plenty of messaging advising us to do so. Sometimes the messaging looked like graffiti. I liked this busy bee, set into a cliff face (presumably blocking up the entrance to a cave or tunnel.)

 

This thing that looks like a bathing machine is actually a sauna, possibly recycled from a horse box. Out of picture on the right there is a sign that says ‘Welcome to your community sauna. Volunteer powered, Wood Fuelled and Free to Use.’ Next time we go there I think I will take my swimming costume – whatever the weather. 

Bathing machine = sauna.

There was also a tidal pool nearby which you could use for cooling off. There were several of these along the coast. We even saw people swimming in them although the air temperature was only 11-15°C. I dread to think what the sea temperature was like.

One more energy-related thing – wherever we walked on the coast path we could see wind turbines on the horizon. My pictures were not good enough to show you but the turbines were definitely there and turning.. Turbines are easy to see on the coast because there are no buildings floating in the water cutting off the view. (Next time I buy binoculars I will see if I can find an adapter for taking a photo. Or possibly a tripod so I can hold the binoculars steady and take the photo by hand. The turbine blades were always turning. The North Sea is a very good source of clean power. Thank goodness the current government is including them in their growth plans. 

Finally, I was very taken with this hat (or whatever it is). This was exhibited in the Turner Contemporary museum and I think it was part of a competition for young people, possibly making use of found objects. There is a sign that suggests the age category was 11-15 years. Perhaps a budding fashion designer?

If ever you are in the area I also recommend a visit to the Shell Grotto and to the Margate Caves. 

Shell grotto

Margate Caves.

What does flushable mean?

Most of us know (I hope) that we should only put the 3 'P's down the loo (pee, paper and poo). However, sewer blockages prove that we often ignore this advice [1]. So what does it mean when an item is labelled as flushable? I found a protocol for testing this [2] which is a bit long in the tooth (2008) but I doubt it has changed hugely since then.

This post is not really about energy at all, rather plastic and how to avoid it blocking up our sewers. I have experienced a sewer system clogged with wet wipes and believe me it was smelly. I did not actually have to get into the pipe to clear it; I just viewed it from the ground level but the sewage worker did get in, wearing rubber waders. I did not envy him. This particular blockage mainly consisted of wet wipes which are a common cause of blockages as they contain plastic and are not fully biodegradable. These did not come from us but from a neighbour; we have a shared drain.

lnspiration from Ocean and the Regen Festival on Parker’s Piece

Inspiration from Ocean (2025), and the Regen Festival on Parker’s Piece.

I recently went to the see the film Ocean (Not Oceans, part of Blue Planet, though both feature David Attenborough.) This is the second time I have seen it and it was definitely worth watching again. The film is horrific in places but also beautiful. The horrific bits include the trawling for fish and shellfish and consequent devastation of the sea floor vegetation and (separately) the turtle tangled up in ghost fishing gear. Did you know that trawling is still allowed in most marine protection areas? Hopefully not for much longer, however.  Also in this blog post I describe my reaction to snorkelling over a coral reef, some advice on avoiding microplastics and the book: ‘A Dairy Story’ about adapting a dairy farm to avoid separating calves from their mothers. 

The most beautiful bits of the film were undoubtedly the kelp forests, and I also loved the footage of huge orcas (or something like - we could only see part of the head) delicately picking up and eating sea urchins. This is akin to watching donkeys eat stinging nettles.