Do modern homes overheat more than older ones?

Modern homes have a reputation for overheating more than old ones partly because they tend to be more airtight and partly because they are often more lightweight constructions that heat up quickly. However, overheating is not an inevitable consequence. For example features such as green roofs and external window shades can make a huge difference – but apparently ‘people are resistant to changes to the aesthetic of the homes and other buildings they occupy’ and these features ‘may be resisted by house buyers’ – so builders won’t build them [1]. Is it all our own fault then?

What do animals think of electricity pylons?

Britain's beauty spots are continually threatened by the prospect of strings of electricity pylons 'scarring a cherished landscape steeped in history'. The National Grid has agreed to spend £460 million on burying cables that would cross the Lake District National Park [1] - that is about £15 per household that we will pay through our electricity bills for just this one case. If this is a purely aesthetic consideration, I think it is rather expensive. However our national parks aren't just for our pleasure they are for wildlife and biodiversity too. So, what do the birds and the deer think of electricity pylons and wires crossing the landscape? We know they see these things in a different light - literally! Also they don't like places that are noisy. Perhaps 2017 is a good time to think about how we can make our technology more friendly from the point of view of the species with which we share our planet.

You may think these pylons ugly but what do animals think?

The Hempcrete Book - review

The Hempcrete Book: Designing and building with hemp-lime by William Stanwix and Alex Sparrow. Green Books.

Hempcrete is an alternative building material with excellent sustainability credentials. It can be used instead of masonry or SIPs to build walls and to insulate roof and floors. If you are thinking of an eco building project you should at least consider using hempcrete for the construction – and in that case you should definitely read this book. It is an easy and fascinating read with a huge amount of advice about what hempcrete is good for, how to use it and other important details such as how to deal with building control. (Most council building inspectors have little knowledge of it so you are usually better off employing an authorised inspector who does.)

The Eco-Home Design Guide, Christopher Day (review)

I have mixed feelings about this book - on the one hand it is comprehensive, easy to read, and is full of useful ideas and experiences. On the other hand it is somewhat overwhelming in its detail and spattered with opinions I don't agree with, particularly his rather excessive concerns about air quality.

More houses - less bricks and mortar

The fossil fuel lobby claims that we can't possibly reduce our fossil fuels consumption for the foreseeable future - but Carbon Tracker have ripped apart the assumptions on which these claims are based: over estimating population growth and economic growth, underestimating progress in energy efficiency and renewables rollout, and ignoring the potential for transformational change [1]. By that Carbon Tracker means breakthrough developments such as battery storage but there are lots of other possibilities for fundamental changes that could shred the business-as-usual scenarios. We can already see the beginnings of a transformational change in housebuilding, away from traditional bricks and mortar and towards timber frame and other construction types. The new styles can be built more quickly without sacrificing quality and their construction generates less carbon emissions. The rate of house building in the UK now is the lowest it has been since 1950 and it will be hard to build up again without more skilled workmen such as trained bricklayers [2] - except we only need more bricklayers if we want to build more brick homes.

Are our homes very high energy performance yet?

The government's decision to drop the zero carbon homes standard is a serious backward step but in my view energy efficiency is a more important target than carbon emissions as such. After all, the less energy we use the less we need to worry about where we get it from. Also, with our current electricity generation mix, a carbon target favours gas heating but in the longer term our electricity will become cleaner than gas. An energy efficiency target is at least neutral on which is the most appropriate fuel. Fortunately, our building regulations have an energy efficiency target as well as a carbon emissions target and it is not too bad - but it could be a lot better.

This chart shows fabric energy losses from a standard size semi-detached home with different constructions and regulations through recent history. It starts from a Victorian solid brick house and goes through to the present day: under current regulations and what can be achieved with the Passivhaus standard.

Improvements in fabric heat loss and ventilation loss in Watts/C for a semi detached home with the same size and shape but different constructions (details in the table at the end of this post). The heat loss is not directly related to heating bills because there are other important factors:  heat gains and hot water are discussed below; internal temperature - older homes are often  less well heated - and your actual bills depend on your heating system fuel and efficiency.  Data from [1][2][3][4]

Why are we building new homes based on carbon emission standards of yesterday?

The UK regulations for new buildings are based on predicted carbon emissions. On the face of it that sounds sensible, as it is carbon emissions that matter for mitigating climate change. However, the current carbon standards are based on historic data from power generation and in practice this is likely to change dramatically over the next few years. At the moment, generating 1 kWh of electricity produces 2.4 times as much carbon as 1 kWh of gas [1] but in three out of the four scenarios modelled by National Grid, (the ones that hit our 2020 renewable energy target) the intensity of electricity will be as good as or better than gas by 2025/2026 [2].

Why are we still designing buildings for yesterday’s climate?

Homes and buildings constructed today are very likely to be still in use 50 or even 100 years from now. (My home is 118 years old). So it would be sensible to design them to handle the climate that we can expect then, with warmer and drier summers and more frequent heat waves. However our current building regulations are more concerned with keeping us warm in winter than keeping us cool in sweltering summers. Plus the calculations they stipulate are based on historic weather patterns that are already out of date[1]. Between 1965 and 2006 the summertime daily mean temperature in the South East increased by 1.8°C and the daily maximum temperature increased by 2.0°C [2]. We can expect another couple of degrees on top of that at least.

External louvres on the top window and the overhang on the bottom window give shade that helps keep this home cool.
Picture from openecohomes.org