Last week I finally got around to reviewing the new Approved Document Part L of the Building Regulations which, for those of you who I have completely lost already, deals with the Conservation of Fuel and Power in buildings. Part L (as I shall refer to it) has, for some time now, been the primary tool of the Government for reducing the carbon footprint of both our residential and non-residential building stock through the application of ever tougher performance standards for the thermal envelope of a new building, the efficiency of any heat source used to heat said building and, latterly, requirements for some energy efficient lighting installations.
The basic aim of Part L is to drive down the CO2 emissions of buildings on an ever steeper curve until, eventually, new housing will be carbon neutral. The latest version of Part L comes into force in October of this year and, according to some, is likely to add around 6% to the cost of the construction of a new dwelling. The cost implications for extensions and refurbishments is talked about less and will probably vary - needless to say it won't be cheaper to build after October '09!
Last week I also got to go to the first day of the first Test Match against Bangladesh at Lords.
Now, you may be forgiven for asking what the connection was between these two momentous events, let me explain.
On my way to Lords and facing an hour long commute to St Johns Wood, I grabbed a free copy of the Telegraph courtesy of a free voucher. Having caught the train at Harlow Town station I settled down and opened my paper to wile away the journey and, on page 3, was confronted by the headline "A summer of '76 every decade (Met Office predicts)", it's worth a read (although I would suggest you read the rest of the blog first before clicking on the link above)!
The long and short of the article is that the Met Office, whilst dropping their seasonal predictions (after all who can forget the summer of unbroken Bar-B-Ques we had last year) the Met Office continues to provide the Government with long range forecasts and is predicting that climate change will result in extreme droughts occurring ten times as often as they do now with their worst case scenarios indicating an increase of temperature of 4degC from current averages! All of this is being compared to the Summer of 1976 which (so I am told - being two at the time) was excruciatingly hot with temperatures reaching record highs of 36degC. These exceptionally hot conditions led to reservoirs and rivers drying up, water being rationed, people being rushed to hospital with heat exhaustion and forest fires breaking out left right and centre!
Now, we should take this with a pinch of salt, after all it is only a prediction and a long range one at that, but it does raise an interesting point. Eleanor Burke, Climate Extremes Scientist with the Met Office, states in the article that:
"Britain has to prepare for 1976-style droughts. This could include designing buildings to cope with heat......"
Approved Document Part L of the Building Regulations addresses the conservation of energy primarily through the use of insulation and air tightness to keep heat in but what happens when you want to keep temperatures low? The Approved Document does cover the control of Solar gain but, in my opinion, does not ensure that extreme air temperature levels outside the building do not affect the level of comfort inside the building.
One of the criticisms that can be leveled at Part L, is that it can promote a singular approach to energy efficiency (i.e. increasingly high levels of insulation) at the expense of other considerations, after all it was never originally designed to be a vehicle for driving down carbon emmissions! In doing so it fails to recognise the benefits that can be gained in providing a stable internal environment all year round.
As Architects, we often see buildings that have been constructed with a good level of insulation that have then needed air conditioning or other mechanical cooling devices to stop the occupants overheating in summer. This is particularly noticable in lightweight buildings.
We also see other examples, such as St Albans Cathedral (which I also visited this week - more about that in another post) where, through the limitations of building technology at the time, the building retains a stable internal temperature all year round due to it's massively thick masonry walls.
This use of thick masonry structures to regulate internal temperature is known as Thermal Massing. Thermal mass is a property that enables building materials to absorb, store, and later release significant amounts of heat. Buildings constructed to be thermally massive absorb energy (heat) slowly and hold it for much longer periods of time than lightweight buildings, which are designed to heat up quickly and rely on insulation to stop heat escaping.
This effect delays and reduces heat transfer through a thermal mass building component, leading to three significant benefits:
There are fewer spikes in the heating and cooling requirements, since mass slows the response time and moderates indoor temperature fluctuations.
A massive building uses less energy than a similar lightweight building due to the reduced heat transfer through the massive elements.
Thermal mass can shift energy demand to off-peak time periods when utility rates are lower.
The greatest advantage with thermally massive buildings, in the context of the Telegraph article, is that the effect is the same whether the heat source is internal (i.e. underfloor heating) or external (i.e. extreme external temperatures), the structure is slow to radiate heat.
If we are faced with the likihood of increasingly hot summers, it is not sufficient for Part L to simply look to make the heating of our houses and work spaces more effcient, it also needs to look to make the cooling of those same spaces equally as efficient and preferably passive.
Although the latest update to Part L is much welcomed, until it encompasses all aspects of achieving a comfortable environment for building occupiers, it will remain an ineffective way of addressing both the cause and effect of Climate Change!
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