Building your Sustainable Library

You wait a while for a good book and then two come along at once. 

I attended the UK launch of two different books relevant to you this week, the first was ‘Sustainable Cities – Assessing the Performance and Practice of Urban Envrionments’ edited by Pierre Laconte and Chris Glossop and published by I.B.Tauris ISBN 978-1-78453-232-1.

This is a portmanteau publication, containing a number of chapters written by other authors, some of which will have been published elsewhere in some form, but not all together as in this case, and not carefully considered for their relevant to this important topic. 

The question of sustainable cities, what defines them, what standards allies to them, how do we choose indicators to assess the, and when we build them how do we know we have succeeded, are all questions tackled by authors in this publication. Given that we have now passed the point at which 50% of the worlds population lives in cities, there is hardly a bigger question for sustainability specialists to work on. If we can crack this, we can avoid runaway climate change.

Authors include Dr. Kerry Mashford, the late Sir Peter Hall, Chris Glossop and Dr Ian Douglas.

I also attended a lecture given by architect Stefano Boeri on his recent project in Milan, Bosco Verticale. The event was hosted by the Engineering Club at the Congress Centre. (A few architects turned up)

Bosco Verticale translates to Vertical Forest, and his two buildings in Milan, evenly constructed for Hines, and then sold on to Qatari Diar, demonstrate what he means by this. Each apartment has a tree on the balcony, several metres tall, together wth a quantity of shrubs and smaller plants. The publication ‘un Bosco Verticale, a vertical Forest- instructions booklet for the prototype forest city’ published by Corraini,  ISBN 9-788875-705411 was available on the night and furnishes a lot of background information to the project including the following numbers. 

The project provides two hectares of forest and 8900 Sqm of balcony area.

This includes 711 trees, 5,000 shrubs, 15,000 perennials, absorbing 19,825kg of CO2 per annum.

There are approximately 1600 birds and insects (although how they could know this is not explained!) This includes a box of ladybirds imported from Germany to eat aphids and other pests. (I don’t know why they needed Germany ladybirds)

The design uses 94 species of plants, giving it a very high level of biodiversity.

The trees are planted in steel-lined planters to prevent the roots cracking the structure, and they are loosely tied back to the structure in case they could be blown off iin hurricane level winds. The steel-linings will also constrain the growth of the trees so that they cannot get too big for the space available or too heavy for the structure. They are a bit like enormous  bonsai trees. They are maintained partially from the balconies, but the outer sides are pruned by gardeners that abseil down the outside of the buildings twice a year. While this might sound outlandish, consider that many glass buildings are routinely maintained by abseilers. 

The result is extraordinary, a pair of buildings that look like no others, and a second project is underway in France. Stefano was quite straightforward in admitting that it took some time and a lot of effort to convince his clients that this could work. There are elements of what was built that he will change the second time, and he has plans to continue to develop  the idea on a larger scale.

He was asked many times by the audience about squirrels, which he was not in favour of, but which he expected to arrive anyway, and also about fruit trees, as none of the species used are fruiting trees. He cited concerns about the dangers of falling fruit as the reasons why they weren’t used. This sounds to me like a problem that could be solved, and would add a further beneficial dimension to what is already a beautiful and convincing idea. 

This is an inspiring idea and one that merits your attention.


Drones for Deliveries (Part 2)

Following from my first article on drones and how they might be used for making deliveries and how they could be organised I wanted to follow up with a closer look at how they would work when they reached their destination. Google and Amazon are both testing drones for this purpose, so it is a case of when, not if they will be used for this purpose, and I wanted to look at the potential impact on buildings for designers. I am interested in this in the first instance because I see that from their widespread use could lead to the removal of a large percentage of delivery vans off the streets of cities, a reduction in delivery cost, energy saving and lower pollution. This will bring attendant benefits to the attractiveness of urban life, with lower noise from traffic and more convenience for sending and receiving deliveries.

The diagram below shows the path a drone will take to its destination by ‘hopping’ from location signals from each address. While in the ‘circle’ of the signal it picks up delivery codes matching its package, these delivery codes will be time stamped, so to find the destination it has to follow the time stamped codes to their point of origin.


Path of Delivery Drone to Destination

Another benefit arising from my ideas about how their distribution system would work is that a recipient of a package could have it delivered to wherever they were, in the office, at home, or in the park. That is covered in more detail in the first article.
I wanted to look at what happens when the drone arrives to your home or building. If you aren’t there, what happens to the delivery? How is it stored, and protected until you arrive to collect it.
I am assuming that there will be a horizontal separation of drone traffic above an urban zone. See Fig 1. Drones would be allowed to circulate freely in this area, with helicopters restricted to fly above them. Landing zones for helicopters would be created by geofenced openings in this layer.


Fig 1. Stratification of Drone Traffic

To begin with the drone has to be guided down to its destination. Fig 2 shows a diagram of a geofenced area which a drone could follow when it leaves the circulation zone above buildings.


Fig 2. Location Beacon cones used to ‘geofence’ drone arrival

Once the drone has followed this guidance down to its landing area and has safely landed, it can deliver the parcel. The parcel needs to be stored until it is collected, and this could be a delivery box that could sit in a garden, or on a balcony if one is available, or on your roof if it is flat and accessible. This is shown in Fig 3.


Fig 3. Delivery Box for a single address, plan section and elevations

The delivery box has a lid which opens when a drone arrives with a delivery, and the package is dropped by the drone into the box, which then closes up awaiting the owners to collect the package, or for another delivery. The box would be equipped with a system that recognises the delivery code of the package that the drone uses to match owner and package. The same code is used to open the delivery box by the package owner.


Fig 4. Delivery Box for multiple addresses.   I Drone arrives.   II Package is accepted.   III Package shunted to store.   IV Ready for new delivery

For people living in apartment buildings the problem is a bit more complex. If deliveries could be accepted on a balcony, the solution is similar to that for a garden or flat roof. A delivery box with a hatch and a door would work. If this can’t work and deliveries have to be made to the roof, the storage box has to be big enough to anticipate a lot of deliveries and needs an arrival box and a storage box, the sequence of how it could work is shown is Fig4.
This arrangement assumes that a concierge would come and collect the deliveries and take them to their relevant destinations. This is a weak point in the security of the system, and assumes that the concierge is trustworthy. In all cases the delivery is electronically tagged with a unique identifier, enabling the recipient to track its movement from when it leaves the shop to when it arrives at the delivery box.

Ask not what Drones can do for you, but what can you do for a Drone.

Musing over the idea that drones (and by this I mean the little ones, usually small quadcopters, not multi-million pound aerial weapons flown by remote) will have a major role to play in modern urban societies, I concluded that it would be both fun and instructive to work through just what their role might be. 

Both Google and Amazon are experimenting with drone delivery systems and I can see the appeal of this immediately. Instead of having to wait a whole day for gratification, the lengthy gap between ordering online and when our newly purchased parcel arrives, we can have our gratification almost immediately if we can organise a drone to deliver the purchase instead. We see that thing online that will make our lives either complete or a bit less incomplete, we buy the thing, and a drone delivers it to our door a mere hour later. 

Lets just take it as read that this will happen in any case, because if for no other reason, there are a lot of pizzas that need delivering every day, and this would take a lot of maniacs on scooters off our roads, and thats the thin end of the wedge. With the growth of online shopping I have heard a TFL* representative say that 30% of Londons traffic is delivery vehicles. Even if we took 50% of the vans off the road, we would reduce congestion a lot, reduce emissions a lot as most vans are diesel powered, and the streets would be quieter and safer. Apart from the hum of drones that is. Perhaps the pigeons would disappear too, perhaps there would be too much aerial traffic for them to feel comfortable, one can hope.

But there are a lot of problems to be solved and barriers to that future. 


They’re illegal, and cannot be flown near to people, which is a bit of a problem when you want them to get close to people to deliver goods to them. I think this will go away presently as the software systems running on the drones enables them to be more or less autonomous and able to avoid crashing into things or people. If cars can be considered safe as driverless objects, then drones shouldn’t present much of a challenge, being much smaller and lighter, and posing much less risk to human life. Lets assume that that challenge is surmountable.


Drones don’t currently have much of a range from the signal that controls them, which means that if you are a kilometer away from their controller they aren’t much use. I think that this can be dealt with by allowing the drone to control itself and by having a distributed network of guidance, like cellular telephone masts, that provide locations to the drone as it comes close to the mast. We use these masts to locate ourselves with smartphones, so why not drones too? To get it to deliver to our houses we just need a way to broadcast a signal to it that it can recognise, perhaps like the one created by our WiFi routers?


Being battery powered the current quadcopter drone designs are limited in terms of the distance they can travel and the loads they can carry. Battery technology is getting better, so distance will grow over time. The location masts or beacons used above to tell them their location could also provide charging points, so a tired worn-out drone could stop off for a quick gulp of electrons on the way home after delivering your pizza, book, fresh coffee,..whatever. To take on heavier loads drones could cooperate. This video by ETH shows a group of drones constructing a rope bridge, and this one shows another team creating a structure using bricks. The relatively straightforward task of delivering a parcel looks rather easy in comparison.


One of the major problems with drones is privacy. People don’t like the idea of a machine equipped with a powerful camera flying over their heads on a daily basis. This seems a bit Luddish to me, after all, in our cities we are surrounded by cameras in the hands of everyone we pass as well as those on the streets and buildings. But lets address the problem anyway. Imagine a scenario where the drone is autonomous, and not under control by any external agent, as it winds its way from depot to you. It doesn’t even need to go to your house, if you are in the park having a coffee, it could deliver the pizza directly to you. What the drone needs is autonomy, and a way of getting an anonymous set of directions to you. It need never know who you are, or where you live, and even better, it need not know what it has delivered to you. This will help to avoid the problem of Amazon and Google knowing everything you ever bought so that they can try and sell you a duplicate of everything you own. (why don’t they try and sell you something you haven’t bought?)


Lets take a scenario where you order a pizza and its awaiting delivery at the ‘restaurant’. A signal is sent out that a delivery needs to be made, and the nearest drone accepts the job in the same way that a Uber car would. The shortest distance to pick up the pizza would offer the cheapest transaction cost. The drone collects the pizza, and is given an electronic token at the same time. This was created by you when you ordered the pizza. Half the token goes to you, and half to the drone. You broadcast the token from your location and the token is passed from one point on the network to the next, every time the token is passed on it gets a bit added by every node on the network. The network propagates the token from one node to the next indiscriminately. This enables the drone to follow the trail back to you by seeking a broadcast token that is shorter than the one it has picked up from the network and which matches the other half of the token it already has. It will find its way to you without knowing who you are, or where you are. 

Esch bubble represents a location beacon, such as a wi-fi router., the routers broadcast the destination to the drone, and the drone follows this to you, wherever you are. The box at the top left is the warehouse sending in the message, the box on the right is you waiting for the delivery. Drones already in the network pick up the message signal, follow it to the warehouse, pick up the package and deliver it to you.



In the same way that BitCoin has developed a security system that is distributed, and every bitcoin node knows how many bitcoins there are, and who owns them, without being controlled by a central source, drones could carry out the physical transactions managed by a similar system to the electronic transaction. In a nice parallel where BitCoins enable Payer A to use currency B to pay C, the drone can carry the package from C back to A using the network B. Read this article on blockchains and BitCoins and you will see what I mean. This method would prevent anyone knowing which drone was carrying which package, and who it was intended for. The only way someone could steal your pizza would be to follow you home and steal it from the drone as it delivered it to you. Of course there will always be people who will snare a drone for whatever it happens to be carrying, but at least they won’t be able to steal on demand. 

Physical Implications

A drone needs somewhere to land a drop off its parcel. It needs a flat surface to land, and if the person for whom the delivery is intended isn’t there, it needs an electronically linked drop box where it can leave your parcel. It could lock the box with its half of the electronic delivery token, and you can unlock it with your matching half when you get home from work. But the box needs to be big enough to accept your pizza, post, packages and needs to be somewhere that the drone can get at but where other people cannot. For apartment buildings this would ideally be the roof, where a landing platform and a set of drop boxes could be located without too much difficulty in many flat-roofed apartment buildings. 

Perhaps one day drones will be able to post letters through your letterbox, if you still get any, any that you actually want to read that is.
*Transport for London

Is London going to go Zero Carbon?

Business Green reported an interchange last week between the Mayor and Green Assembly Member Darren Johnson  in response to his question about the Mayors position on Zero Carbon homes. Boris’s reported response was

“What we are looking at is making sure that we can continue, through the London Plan, to ensure that Zero Carbon Homes are delivered in London and we will be issuing further guidance in due course to provide industry with the certainty it needs about how to do that.” 

Boris reported that London aims to achieve a 60% reduction in CO2 by 2025 and has achieved 14% to date. This represents a per capita reduction of 20% as London’s population has grown by 600k during the reporting period.

It is heartening to hear these words from the Mayor, and I hope that the candidates for the Mayoralty are listening. If devolution is to mean anything it should promote the ability of cities in the UK to sidestep the damaging and short-sighted environmental policies of central government.

Having recently completed a large zero carbon scheme at Hanham Hall with low-rise construction and learned what it means for most of the UK’s housing development, I thought that it would be useful to share below some analysis that we have done to assess how tall buildings can achieve the zero carbon standard. Given that many of the buildings that are proposed for the capital in future are going to be tall it is interesting to assess how the regulations might affect those building types.

The analysis has been done for a twenty five and a forty storey tower with six units per floor to demonstrate how different systems meet the targets. We tested gas boilers, CHP with gas backup, all-electric heating and hot water and finally Air Source Heat Pumps. Three of the four rely on a communal hot water distribution system, the all electric system being the exception.

Energy Options to meet the London Plan and Zero Carbon

Energy Options for a 25 Storey Tower to meet the London Plan and Zero Carbon



Energy Options fora 40 Storey Tower to meet the London Plan and Zero Carbon

What the research shows is that for taller towers there is no difficulty in meeting the current definition of zero carbon. In fact it shows that achieving it is technically easier than achieving the London Plan, as the London Plan has a lower emissions target than the Zero Carbon definition. This is assuming that there is no special treatment for electric heating or hot water, unlike the current version of SAP which is based on comparative performance rather than on a definite figure as set out in the Zero Carbon Hub’s definition.

Based on these figures I would say that towers should be forced to meet the lower emissions target of 10kg/CO2/sqm since in both gas-based options this target can be met. Perhaps an all-electric version could be left as it is at the higher 14kg/CO2/sqm.

It also shows that a very efficient 25-storey building can meet the targets irrespective of the energy system used, the top graphs shows that it can achieve the target in all four options, even an all-electric option. The 40-storey is not so easy. My assumption is that only the roof can be used to house renewable energy,  but for the 40-storey version it would be necessary in the electric options to put some pv panels on the facade to reach the target.

But of course the technical success is not the full picture. In addition to the Fabric Energy Efficiency target of 39kwh/sqm/yr that apartments have to hit, and towers have no difficulty doing so, there is the Carbon Compliance which is shown in the graphs above, and again there doesn’t appear to be much of a problem for towers, but finally there is the Allowable Solutions element which says that whatever CO2 emissions remain must be offset. This offset is achieved by multiplying the tonnes of CO2 emitted, by the figure of 30 years, and by an agreed sum for each tonne. Currently the GLA uses £60/tonne. This produces a figure of approximately £1,000 per apartment to offset the emissions elsewhere.

Sadly the all electric system is unwelcome in London as it it not seen as ‘futureproof’ according to the gas-led ideology preferred by the GLA. This is understandable as an all-electric system does not emit the lowest CO2 emissions possible, at current levels of grid CO2 intensity. What will be interesting to see is how long before the grid CO2 intensity drops to a low enough level to change that thinking. The Committee for Climate Change has suggested that we need to stop burning gas by 2035 to meet our carbon budgets. What is the point in investing in gas burning equipment and networks now if they have to be decommissioned in less than twenty years time?

Certainly an all-electric system is the cheapest to install, avoiding the central distribution system, and it could be argued that an all electric system is just as futureproof as a hot water led system as the Grid is inherently flexible. Interestingly our research also suggests that in the majority of cases an all-electric system is cheaper than a communal system for residents as the standing charges are lower, even if the energy bills are higher than gas. The standing charge is used to create a sinking fund to replace the communal system. If there is no communal system the sinking fund is either not needed or is much smaller, thus lowering residents total bill. The cheapest system of all to run is an individual gas boiler, but no-one would consider installing that into a tower, and it has a higher maintenance and replacement cost than an all-electric system.

A major hole in this analysis is that it is carried out using SAP, which is pretty poor at dealing with apartment buildings. The energy for pumping heat around the building is ignored, as is the energy for ventilating corridors, pumping hot water, lifts, communal lighting etc, etc. Since the communal spaces in these buildings are not heated, SBEM isn’t particularly useful either. As buildings get taller these additional energy uses and losses will become more a more significant part of their energy use, we need better tools to assess them, and more regulations to deal with their particular demands.


MMC: Evolution or Revolution?

 I spoke last week at the Residential Construction Network hosted by the RICS in Westminster.
The three speakers were myself, Paul Inch from Innovare and Jean-Marc Bouvier from Nudura Insulated Concrete Formwork.
I introduced the topic by pointing out the continuing and rising gap between housing production in the UK and housing need. See image below. At current levels of construction and demand we will see two million people short of a home by 2030.
 The Housing Gap
My view is that offsite construction is needed to fill the gap because the gap is mainly made up of people who cannot afford to buy their own homes at current prices, and are unlikely to ever do so. Affordable housing including shared ownership models needs to be provided for them by Registered Housing Providers(RHP’s) and by the Private Rental Sector(PRS).
There is little or no motivation for the private sector to build more housing than their current capacity to deliver. The hostorical figures show that speculative housing rarely delivers over 150,000 homes per year. They are making good profits with current numbers, so why would they change a formula that is working?
The current housing industry based on speculative housing for sale tends to use traditional construction methods as the average rate of sales on sites is slow and building faster doesn’t actually make much difference to them. What does make a difference is changing labour rates, particularly in a boom which makes their land and construction pricing difficult to predict. The regular boom and bust cycle in UK housing means that they are unlikely to either dramatically change their levels of housing supply or change the way that they build.
A possible solution to the problem is to marry up the large balance sheets of local authorities and RHP’s and use additional borrowing to construct homes offsite. This would require decisions on the part of these large clients to support a new industrial sector, housing manufacturing. A medium sized factory could supply 2,000 homes per year, but investors will only commit to constructing such facilities with a confirmed pipeline of demand. There can be competitive tendering, but between similar factories, and not between factories and site operations. This is not to promote more expensive housing, but to give factories the support they need to get going. Clients need to decide that this is the route to deliver affordable housing and government needs to support them in any way it can.
Ten new factories every year for five years will deliver 50,000 new dwellings that we are currently not building, from finance we are not using. That will go a long way to closing the gap in the housing supply. Once the market in offsite manufacturing is more mature, it can expand to take up the remaining gap and supply products to the sale market. The factories can be distributed across the country to places where there is greatest housing need and staffed by locally trained people. These plants can be set up and be running within a year, particularly if they use timber frame manufacturing. The jobs will be stable long term ones, possibly as many as 100 per factory. Thats 5,000 jobs within five years without counting the site works and the finishing trades on site. Its not wise to construct entire dwellings in factories, some work needs to be done on site to prepare foundations, and to finish the facade and roof on site.
Paul Inch, Business Development Director, Innovare
Innovare are one such factory, constructing homes and schools from their factory in Coventry using Structural Insulated Panels. They have a strong history of building high performing homes and buildings that provide very well-insulated building fabric. This is achieved by constructing using large format panels containing the building structure and insulation. Speed of construction is much faster than traditional methods and the quality of the final building is higher, particularly delivering low levels of air leakage and reducing the heating demand from the finished building.
In Paul’s opinion, RHP’s should use the market to deliver their buildings and not try and go it alone. There is a lot of manufacturing skills in the market and it is best left to the market to provide it rather than try and bring it in-house as some RHP’s have done.
Jean Marc Bouvier Director of International Sales and Business Development
Jean Marc Bouvier from Nudura Corporation, a supplier of Insulated Concrete Formwork products described their system. It provides large insulation panels that fit together much like Lego and are then filled in with poured concrete to form the walls of the design. It is a very rapid form of construction and delivers very high performance buildings. By using large lightweight elements the construciton process is safer and quicker, and because of the pured concrete there are no air gaps in the construction. Another benefit is that it is very resilient to wind effects and is being used to construct storm shelters in the southern regions of the US. Like SiPs it enables a highly productive delivery, with far fewer man-hours required to deliver the finished building compared to traditional building methods.

The Electric City

WSP Engineering group have carried out some interesting research into the potential of the Electric City. The basic principle is that we should move away from combustion within cities for heating homes, buildings, generating power, cooling or transport, and rely on electrons instead.

The potential benefits are staggering. The future city powered by electricity has a much better environment for its inhabitants with lower emissions and fewer particulates in the air, the air is cleaner because much of our air quality problems stem from combustion in boilers and engines. The city is quieter because electric motors are quieter than combustion engines. The city produces less CO2 emissions because heat pumps are more efficient than boilers and electric cars are more efficient than combustion engines.

WSP calculate that if we aimed to create an all-electric London by 2030 we could have
– reduced NOx levels by 37%
– vehicle noise levels will be reduced by 25-50%
– electricity usage in the capital would double from 40k GWh to 80k GWh per year
– CO2 emissions would drop from 88 MtCO2 to around 8 MTCO2 per year, a drop of around 90%.

SAP, the tool used to assess the compliance of UK housing for Building Regulations, uses a CO2 factor for UK Grid electricity based on a three year average prediction of the Grid emissions. What WSP’s work makes clear is that this is the wrong period to use for predictions. The long term predicted emissions for the UK Grid is for it to be lower than gas, and to reach this point before 2020. Using a ‘dirty’ Grid emissions factor now, means that we are installing gas CHP and gas boilers in the anticipation that they will drive down CO2 emissions. But during the lifetime of these systems the Electricity Grid emission will drop below gas and continue to drop until it is much lower. So installing systems now that have a twenty or thirty year life of predicted emissions is actually likely to raise emissions rather than reduce them.

A major issue for housing in all of this is that currently it is much cheaper to heat a home using gas than electricity, because electricity is three times more expensive. The problem we need to solve is how to reduce heating demand to a point where new homes can be heated by electricity for the same amount of money as other homes on the market can be heated by gas. There are well documented problems where newish homes were heated by heat pumps resulting in higher than average bills because the homes simply weren’t efficient enough. Perhaps we need to look again at dual tariff electricity supplies to new homes using off peak electricity to drive heat pumps?

With cars the picture is different because petrol is so much more expensive than gas, electric driving is a much cheaper option, so it is entirely likely that electric transport will lead the electric revolution faster than the construction industry. Cars have a shorter life than building services, so the replacement rate for cars will mean that technological changes will be introduced more quickly in any case.

Whatever the outcome this is an excellent piece of work, and highlights the benefits of taking a long term view of energy policy and market intervention.

Zero Carbon(2016) Exemption Proposals

The plan to exempt small sites from zero-carbon legislation strikes me as being a total waste of time, energy and money and I cannot fathom why DCLG are wasting their precious time (and mine if it comes to that) with it.

The consultation document can be read here. The main elements are
– The proposal is to exempt small sites from the Allowable Solutions element of the Zero Carbon(2016) proposals. That is, the CO2 offset payment for that CO2 not mitigated on site by the development multiplied by 30 years multiplied by the agreed cost of CO2 per tonne.
– The consultation seeks views on the proposals including
The definition of small sites
Whether the exemption should relate to developers who are small or to any developer developing small sites
Whether the exemption should relate to Allowable Solutions only or whether the exemption should relate to Carbon Compliance as well
How long a time-frame the exemption should last for.

The problem I have with this is: where is the evidence that this is going to promote development? I haven’t seen any. Figures from the consultation document point out that 10% of planning applications in the UK measured by unit number were for single dwellings. That amounted to 24,000 units. So that tells me that there is a lot of activity in this sector and we can expect that to continue.
The Allowable Solutions impact of about £2-3k per plot will act as a small disincentive to development, but since many of those applications (my conjecture) are for the people who will actually live in those homes, the additional costs can be weighed against a lower cost of living for the occupants. The savings in fuel bills over the lifetime of the dwelling will pay for the relatively small additional cost. This is a calculation that many people will be able to do, and probably will realise that if they increase the build specification slightly they will reduce the Allowable Solutions costs and save themselves even more money. This seems to me to be a virtuous circle. People build more efficient homes for themselves, and they save money over and lifetime and there is less CO2 produced. This sounds like a market actually working. So why does the Government think that this is a market they need to interfere in before they actually have it in place?
The likely time frame would be from 2016 until the next issue of the Building Regulations, around 2020. This would allow the costs of the Zero Carbon (2016) to drop and the costs of Allowable Solutions to be absorbed. Again this seems to me to be counter productive. The way to reduce the costs of the Zero Carbon (2016) standard is to have everyone use it as soon as possible. This will bring down the cost of the insulation and window products that are needed to reach the standard, and then they will be available to all and not just the large housebuilders with very cost-effective supply chains. This proposal risks creating a two tier industry with higher costs of smaller builders and lower costs to larger builders.
The problem lies with the speculative nature of so much of our housebuilding. The builder of some of these small plots doesn’t know who the buyer has, and therefore has no interest in how that buyer lives in the home. There is no way for the lower costs of living in a more efficient home to be passed on to the developer in a beneficial way. A developer cannot build a more efficient home and offer it on the market for a small premium, this benefit is simply not recognised in the valuation of a property.
So, can I suggest that a more effective way for the Department to spend its time and mine, would be to investigate ways of making the speculative housing market function as a better market instead of trying to undermine those elements of future legislation that are likely to help it to function as a better market. But in an election year, perhaps that is too much to hope for.

Assessing Microclimate in Urban Environments

“People, life and vitality are the biggest attractions in a city. We see it in the choice of peoples seating, where the most populated benches are located, how people choose to sit on sidewalk cafes facing the people walking by rather than the buildings behind them.
The biggest quality of a sidewalk café is simply the interaction with other people. Do you have a choice between walking through a deserted, empty street and a street with other people walking, people will choose the liveliest street that provides them with more experiences, visual variety and a feeling of safety.” Jan Gehl 2002

This quotation from Jan Gehl, and many others like it, have brought home to the design professions how much we had moved away from a human-centric design philosophy to a building-centric and car-centric design philosophy for much of the 20th Century. Even now we are still living with many of the mistakes made in those decades, a car dominated lifestyle, buildings that don’t address the street, housing with high level access walkways, large highways that unsympathetically cut through historic urban fabric, the list is a long one.

Considering the human impact of buildings and the quality of spaces between them means that we should spend much more time considering, drawing and analysing these spaces than we previously did. The tools are now more available to analyse these spaces than ever before, now we just need to use them more often. Here are some examples of the tools available and where to use them.

1. One can use tools like IES to assess the Wind Microclimate between buildings. The tool uses historic weather data to predict the wind conditions between buildings by calculating how the shape of the buildings that are there already and that are in our proposals will affect the wind speeds throughout the year. This calculation is usually carried out at pedestrian level because that is where the pedestrians are, as well as at higher levels where people might sit on balconies or on roof terraces. The results are compared against the Lawson criteria for pedestrian comfort, a scale that compares the type of activity with the prevailing wind speed. Activities such as sitting outside cafes and window shopping are suggested to be best places where the Beaufort Level 3 ‘Gentle Breeze’ is not exceeded for more than 1% of the time in a simulation. It is a notable failing in the Lawson Criteria that it doesn’t adequately deal with cycling and ‘windiness’. Cycling and wind are are particular problem as this combination presents a risk to life where cyclists can be blown into traffic by sudden gusts of wind, a problem not normally faced by pedestrians. Any suggestions by readers as to what an appropriate criterion would be are welcome.

2. IES can also be used to assess the solar irradiation on roofs to highlight locations for renewable energy systems, helpful in determining whether some buildings overshade others or whether some roofs will get ehough solar insolaton to make it worthwhile putting renewable systems there art all.

3. One can use ENVI-met to carry out a similar assessment, but with the additional sophistication of assessing the impact of planting and street trees on the local environment.

4. We can use ECOTECT to evaluate the solar incidence on the facades of buildings to tell us whether the cafe will be in sunshine for long periods of the year and whether people will get too hot sitting there and whether we should provide an awning. Ecotect is useful for many other type of analysis as well, but its imagery for this type of use is particularly helpful.

5. We can use simple tools like SketchUp to look at shadows cast by our designs at a early stage to assess the impact of one design versus another by comparing the impact at the equinoxes and solstices. This is paricularly helpful as it can be done easily and quickly by the designer in the tool that they are woring on (assuming that they are using SketchUp for early stage designs) and gives them immedate feedback. The other tools used here are for more specialist use and are typically used by consultants who specialise in this type of analysis.

6. There is a substantial piece of work being carried out at MIT to develop a suite of tools for urban design analysis based on the Rhino modelling software. This suite is intended to include tools for early daylight, energy and embodied energy analysis. It is still a work in progress but highlights the level of ambition made possible by readily available computing power. An example of the progress to date is the DAYSIM engine used for modelling daylight in and around buildings.

These are just some examples of the tools available to investigate whether the spaces we are creating between and around our buildings are going to be fit for purpose and enjoyable to use. Here is an example from the Kings Cross masterplan of a very successful intervention, a set of sout-facing steps connecting to the canal. It was popular before the astroturf was added, being a sheltered and sunny place to sit and chat, drink a coffee or eat lunch, now it is both sunny, and more comfortable to sit on.


Sitting in the Sun

Sitting in the Sun: Kings Cross

Housing and Overheating


Dealing with overheating in UK housing and apartment design is quickly working its way up the list of priorities. I still have difficulty believing that DCLG decided to ignore this in the Housing Standards Review, but they did. Despite the Climate Change Committee report on Climate Change Adaptation stating that :

Many homes, hospitals and care homes are already
at risk of overheating. By the 2040s, half of all summers are expected to be as hot, or
hotter, than in 2003 when tens of thousands of people across Europe died prematurely.
A standard or requirement is needed in order to ensure new homes are built to take
account of the health risks of overheating now and in the future. Cost-effective passive
cooling measures should be adopted rather than relying on air conditioning, which will
be expensive and exacerbate the urban heat island effect.

But meanwhile, other, more responsible organisations are ploughing on regardless. The TSB ran a project called Designing for a future Climate and the outputs are here, for anyone interested in the topic, this is essential reading.

The Zero Carbon Hub have just kicked off a project to look at overheating specifically, and will report back early next year.

But what are practitioners to do now? What is a responsible approach?

I propose the following four steps.

1. Don’t use SAP

2. Carry out simulations, and choose the criteria carefully

3. Don’t believe everything simulations tell you

4. People will adapt, make the buildings ready for adaptation

The Detail


Firstly, lets agree that SAP is an inappropriate tool for providing the answer. Overheating will occur in fairly specific circumstances, caused by a complex mixture of factors and may only occur for a specific set of hours in a particular apartment. For example west facing apartments are likely to overheat in the evenings while east facing apartments in the same building may not overheat or overheat at different times of the day,  and the strategy for dealing with the problem is likely to be different from the east side to the west side. Overheating is elevation specific, not plan specific. SAP is not sophisticated enough to tell us when overheating is likely to happen in time, and therefore is unable to point towards useful strategies for dealing with it. There are a number of other tools on the market capable of analysing the problem such as IES and TAS. These are designed for the purpose and are much more appropriate for this use.

Secondly, we should be carrying out simulations on a regular basis of current apartment schemes to assess whether they overheat using current weather as a minimum, and preferably also assessing them with 2050 and 2080 weather predictions.

The standards to use for testing should be adaptive standards such as EN 15251 or CIBSE TM52 for buildings occupied by able and healthy individuals who will adapt to external temperature and who can control their environment, or who can go for a walk in the shade or go to the swimming pool on hot days.

For buildings where the occupants are young or old both of who have difficulty regulating temperature, and who may not be free or able to move to colder places or unable to close shutters, we should use the more risk averse CIBSE Guide A which sets a temperature level that must not be exceeded for a set number of hours per day.

Thirdly, lets agree that simulations are useful and necessary, but again are only guides to likely scenarios and are not facts. Here is a good illustration of the problems caused by taking simulations at face value.

Whilst working on a recent project we were presented with some analysis of overheating carried out by a well known and respected firm of engineers. Among other sensible suggestions they recommended reducing the size of the windows by 50% to reduce the likelihood of overheating by about 1% for the 2050 high emissions scenario. So, to explain, the suggestion was to reduce the area of glazing by 50% because simulations suggested that this reduced the likelihood of temperature in the apartment exceeding an agreed limit by 1% of the time the apartment was likely to be occupied. 1% of the occupied time for an apartment is about 1% of a year, so lets say 3.5 days in total. To reduce discomfort in 2050 for a three day period, the suggestion was to reduce the quality of life for the remaining 18,250 days. We won’t succeed in adapting to climate change by building buildings that no-one likes or wants to live in.

Fourthly, I believe that we will adapt both our behaviour and our ability to deal with warmer climates. The rate of change is slow enough for many species to migrate ahead of changing climate, so why can’t human beings adapt their behaviour too. Wearing different clothes, travelling at different times, closing shutters before going to work, having a siesta are all cheap ways of adapting to warmer climates. All of this makes simulation difficult. A simulation will assume that people in 205o will be cooking using the same equipment that we are using today, and it will assume that the heat gains from cooking will contribute to overheating. It is likely that people will change their cooking habits in warmer summers to avoid cooking at a time of the day when it contributes to overheating, but a simulation run using one of the currently available tools isn’t able to model changes of behaviour and lifestyle over time.

Our buildings need to be designed to accommodate shutters or blinds on the outside of buildings for those parts that are vulnerable to overheating. It may not be necessary to install them now, but it is likely to be necessary in the future, so design them in now. They are a familiar feature to anyone who has been to southern Europe and everyone understands how to use them immediately.

Thermal Bridging – what’s the value of a y-value

Thermal bridging of construction elements has become a very important part of the compliance of housing in the UK, but you would never know this if you worked for a contractor, developer or architect designing, planning or building the said housing. Despite this being an important factor since 2010, the level of knowledge and understanding in the industry is still very low.

For new readers, thermal bridging is expressed as a ‘y-value’ or amount of heat loss stemming from the aggregated thermal bridges in a design. The thermal bridges occur at every junction in the building, every wall-to-wall connection, wall-to ground connection, wall-to-roof connection, all jambs, cills and heads, and all balconies, projections or bays. Each junction has its own ‘psi-value’ and these are aggregated together to make a ‘y-value’. In order to assess the performance of the building, all the junctions have to be measured and a value assigned to them.

This calculation is carried out using specialised software that calculates the rate of heat movement, or heat flux, through the junction.

To summarise the regulations, there are three options for compliance under UK regulations regarding thermal bridging.

  • take a default value
  • use accredited details or other approved calculations
  • use calculated details where individual junctions are calculated by a SAP or other qualified assessor

The impact of this can be easily illustrated. If we take a typical mid floor apartment, where there is a simple envelope, and two large openings in the façade, one for a bedroom and one for a living room. Where all else is unchanged, the difference between the default value and a calculated value based on accredited details is 0.5% saving of the DER, but when the lintels are changed to a thermally broken type, the saving increases to 3%. If this is the impact on a single mid floor apartment with a very simple envelope, the impact will be greater in a detached dwelling with many more openings.

This demonstrates that changing the manufacturer for a single junction can change the overall performance by 3%. This is the type of change that contractors are used to making on the fly as they make purchasing decisions about the project. They are not used to being tied to a more detailed performance specification that makes such a difference to the compliance of their project.

This lack of knowledge was typified on a project recently where the main contractor substituted one timber frame manufacturer for another, without checking whether the new manufacturer could match the thermal bridging characteristics of the original. The SAP Assessor had used the psi-values of the original manufacturer in the design stage SAP. The replacement manufacturer not meet the specification and they could not supply any information on the thermal bridging of their product at all. They had never been asked for it on previous projects.

This baffles me. Timber frame construction is a naturally thermally efficient construction method, for a company to sell such a system without providing calculated thermal bridging information is to hamstring their own performance for the sake of a few thousand pounds.

The companies who are paying attention to the changes in the regulations are taking the steps to have their psi-values of their products tested in typical constructions and they are using that information to make sales to contractors earlier in the process than usual, bringing themselves into the design conversation at an early stage of the project. By doing so they are getting themselves and their products written into the performance specification for the project. Whether it is thermally broken lintels, high performance windows, better performing insulants, or aerated blockwork, there are a lot of products on the market now which rely on this focus on thermal bridging.

The concern I have is that there is a lot of evidence in the industry that site teams and purchasing teams are not picking up on this need to watch the performance of the envelope, and they are substituting products to save money without paying attention to the psi-values of the materials they are buying. To be fair to them , the design teams need to be more explicit in the information that is provided to them so that it is more obvious to them what products need to be installed to be compliant. It is not reasonable to expect buyers to read through a SAP calculation, so a schedule of psi-values needs to be provided to them with an explanation as to how they were derived and why.

In the long run this focus on the fabric of dwellings can only be a good thing, as this is the best place to find savings in energy that are likely to be sustained in the long term life of the building.