Wednesday, October 19, 2011

Kwok & Rajkovich Addressing climate change in comfort standards

According to the Buildings Energy Data Book published by the U.S. Department of Energy, in 2006 the building sector consumed 38.9% of the total primary energy used in the United States. Of this energy, 34.8% is used by buildings for space heating, ventilation, and air conditioning. This energy often involves the combustion of fossil fuels, contributing to carbon dioxide emissions and climate change. Even if greenhouse gas concentrations are stabilized in the atmosphere, extreme climate events and sea level rise will continue for several centuries due to inertia of the atmosphere. Therefore, adaptation will be a necessary compliment to carbon dioxide mitigation efforts. This paper argues that both mitigation of greenhouse gases and adaptation to climate change should be added to our building codes and standards. Since space heating, ventilation, and air-conditioning utilize a large amount of energy in buildings, we should begin by redefining our thermal comfort standards and add strategies that mitigate carbon dioxide emissions and adapt to predicted climate variability.

This is very interesting. They mention the concept of a mesocomfort zone, between the low temp at which adaptive measures are taken and the 'optimum', allowing for flexibility.

Monday, October 17, 2011

Coley et al Changes in internal temperatures within the built environment as a response to a changing climate

Changes in internal temperatures within the built environment as a response to a changing climate
D Coley et al 2009 Building and Environment 45 (2010) 89–93

In August 2003, 14,800 heat-related deaths occurred in Paris [1] during what is considered the warmest summer since at least 1500 [2–5]. These deaths resulted not only from unusually high peak temperatures and a reduction in the diurnal temperature swing, but also from a failure of buildings to successfully modify the external environment. It has been estimated [6] that by the 2040s, a 2003-type summer is predicted to be average within Europe. Clearly this will have a great impact on morbidity and mortality and produce challenges for emergency services [7]. The effects of climate change on the internal environment are not well known and are the subject of much current research [8]. For building scientists and emergency planners, there is the need to know the general form of the relationship between increases in external temperature due to climate change and increases in internal temperatures. Here we show that the relationship is linear, and that differing architectures give rise to differing constants of proportionality. This is a surprising result as it had been assumed that, given the complexity of the heat flows within large structures, no simple relationship would exist and had not been found in previous work [9].We term these constants of proportionality climate change amplification coefficients. These coefficients fully describe the change in the internal environment of an architecture given a seasonal or annual change in external climate and can be used to judge the resilience to climate change of a particular structure. The estimation and use of these coefficients for new or existing buildings will allow: the design of more resilient buildings adapted to a changing climate, cost-benefit analysis of refurbishment options and the rational assembly of at-risk registers of vulnerable building occupants.

This paper shows that internal external temperatures of buildings are linearly proportional. Interesting (if simplistic) suggestion that if the gradient is greater than unity it could be considered non-resilient, in that is exacerbates the effect of climate change, and if it is less than unity it is resilient, in that it moderates the effect of climate change.

Roberts, S Effects of climate change on the built environment


Effects of climate change on the built environment Simon Roberts (ARUP) 2008
Energy Policy 36 (2008) 4552–4557

Abstract
New buildings will have to be designed to cope with the effects of climate change. These include
warmer weather in which keeping cool will be important, more extreme and wet weather, and
increased subsidence risk. Flood risk areas will increase, requiring measures for both resistance for
initial protection and resilience for rapid recovering.
At the same time, new buildings must use less fossil fuel in a low or zero-carbon world. Homes,
offices, schools and other buildings will need to maximise passive measures of more effective
insulation, improved airtightness and greater thermal mass. They will also need to make more use of
solar energy and other renewable inputs. New buildings will incorporate a range of new technologies toreduce their energy use, and to cut the energy needed to build them, including the embodied energy in the materials they contain.

This paper gives a good overview of how buildings (not just domestic) will be affected by climate change. Various adaptive techniques are discussed and their relative values. Predominantly looks at building design in a new –build context but many of the adaptive measures could be retrofitted.

Sets out the state of current science in the field – v useful

Friday, October 14, 2011

D P Jenkins et al Probabilistic climate projections with dynamic building simulation: Predicting overheating in dwellings

 Energy and Buildings 43 (2011) 1723–1731

This study, as part of the LowCarbon Futures project, proposes amethodology to incorporate probabilistic climate projections into dynamic building simulation analyses of overheating in dwellings. Using a large climate projection database, suitable building software and statistical techniques (focussing on principal component analysis), output is presented that demonstrates the future overheating risk of a building inthe formof a probability curve. Such output could be used by building engineers and architects to design a building to an acceptable future overheating risk level, i.e. providing evidence that the building, with specific adaptation measures to prevent overheating, should achieve thermal comfort for the majority of future climate projections. This methodology is overviewed and the use of the algorithm proposed in relation to existing building practices.While themethodology is being applied to a range of buildings and scenarios, this study concentrates on night-time overheating in UK dwellingswith simple and achievable adaptation measures investigated.

Conculsions
A methodology for using probabilistic climate projections with
dynamic building simulation has been developed and shown to
have potential as an alternative to multiple, and time-consuming,
iterations of building simulation software. Generating this surro-
gate procedure from an initial dynamic simulation means that the
detail required for an overheating analysis is maintained while
allowing the user to account for many other climate projections
for that specific building. The result is that, rather than relying
on single design climates to estimate future overheating, a broad
array of climate projections can be used to capture the uncertainty
inherent in all future climate projections. Incorporating this into
existing risk analysis practices within building design is proposed
as being a route for integrating complex climate descriptions into
real building projects.
The proposed regression approach was able to predict between
78 and 86% of hourly internal temperatures when compared to the
ESP-r simulation software, with the validation process covering a
large selection of hourly climate files and a range of adaptation sce-
narios. The regression equation was calibrated based on a range
of locations, emission scenarios and timelines. Converting these
hourly predictions into a general overheating metric (of number
of hours above a threshold) showed that regression and simulation
values agreed within an error of 5% across all identified climates.
While specific software and interfaces are not presented here, a
selection of possible outputs of any future overheating tool are sug-
gested as being suitable for demonstrating the effects of different
adaptation scenarios on a current building that, although providing
adequate levels of thermal comfort in a current climate, might be
at risk of overheating in the future due to climate warming.

This study shows that probabilistic climate projections  can be used to avoid running building simulation models many times. A broad array of climate proections can be used instead of a single design climate, allowing a better understanding of possible future climate effects

Thursday, October 13, 2011

Zero Carbon hub Compliance for New Homes

July 2010

In this report we present our findings and recommendations for the development of the carbon
compliance tool. This follows six months of effort by anexpert task group drawn from the wide range of industrysectors engaged with house building, including developers, designers, product manufacturers, consultants, professional bodies and academics.Carbon compliance is not the most approachable of subjects, but it is a key element in any strategy to deliverzero carbon homes. The compliance tool is the means by which we measure the carbon performance of new homes. Without an effective tool, we simply cannot tell whether a new home has been built in line with the zero
carbon standard.

The aim of the expert group was to identify the most appropriate compliance tool, standard assumptions and related regulations (collectively referred to as the carbon
compliance regime in this report) for the effective and efficient delivery of low energy/zero carbon new homes from 2016. The group acknowledged that the current compliance tool (SAP) is also used for other purposes, such as to produce EPCs for existing homes, and that other compliance tools (such as SBEM) are used for non- domestic buildings However , the group’s focus was on the most appropriate tool to guide effective decision making for the construction of new zero carbon homes.

Overheating - the need to effectively model overheating was highlighed as a key concern for future compliance.
"Overheating risk is a significant concern, with implications
for carbon emissions, health and consumer choice.
There is some anxiety that homes we are building today
may be at risk of overheating even in the current climate.
Given the prospect of significant warming, well within the
expected lifetime of homes, this risk will increase with
potentially serious consequences.
The assessment of overheating by SAP and other modelling
tools, including dynamic models which simulate change
during the day, shows little consistency. Further work is
urgently needed to understand and model overheating
effects, including how design features may help to mitigate
the risks. It is also necessary to confirm whether dynamic
modelling does indeed provide a more robust reflection of
reality, not just more comprehensive results.
The output from this work should be used to develop an
improved simplified overheating test. The test will
inevitably be used as a design tool (because compliance
defines the market) and it must therefore adequately reflect
the effects of both passive and active design features.
If an improved simplified test can be developed, SAP
should be retained as the carbon compliance tool. If
however an adequate simplified test cannot be found, a
dynamic modelling (or similar) approach will be required
to model overheating. This will beg the question
whether then other aspects, such as space heating
demand, should also be modelled in this way.
This work and subsequent decision is both urgent and
important. Whichever model is ultimately used, it should
be based on the projected future climate at a sub-
regional level including urban heat island effects.
Current regulations do not explicitly prevent homes
being built which are at risk of overheating. This needs
to change. Alternatively, regulations might simply assume
that active cooling is present and include the associated
carbon emissions within the compliance calculations if an
overheating risk is identified."

"SAP’s use of monthly averages fails to reflect the impact of
overheating. Extremes of temperature are important both for the
health and comfort of the occupants and for how they may adapt their
behaviour . An average temperature of 26° may not sound so bad, but
if it comprises 20 days at 21° and ten days at 36°, people’s health and
behaviour will certainly be affected, especially if the ten days fall
consecutively. In order to reflect this, a model is needed which maps
the impact of temperature peaks and does not rely on averages"

Wednesday, October 12, 2011

L Collins et al Climate change and future energy consumption in UK housing stock 2010

 Building Serv. Eng. Res. Technol. 31,1 (2010) pp. 75–90

This paper examines the likely effects on gas and electricity consumption and carbon emissions from heating and cooling systems in existing dwellings up to 2080, assuming a widespread uptake of cooling systems. This area of research is highly sensitive to the myriad of possible inputs and thus holds a wide range of predicted outcomes. However, general trends have been found, showing significant sensitivity to ventilation rate, U-values, occupant behaviour and location. Heating demand will still be dominant over cooling demand in UK dwellings by the 2080s, based on an UKCIP02 A1F1 weather scenario. A national worst case scenario for the 2050s, shows a 10 megatonne CO2 emissions saving on present levels largely due to a 20% reduction in gas consumption. Practical applications: The balance of heating and cooling demand causes more modest changes in CO2 than first anticipated. Despite first perceptions of future energy use in housing and climate change, heating appears to remain the major load rather than cooling, even into the 2080s. These predictions of future CO2 emissions will be useful to those in the building industry planning appropriate proportionate climate adaptation and climate mitigation measures. Also, the prediction of changes to future energy demands from the housing sector will be of interest to energy providers considering future demands for heating and cooling and may feed into larger bottom-up energy models.


Quotations:
Adaptation to future climates has to take
into account human factors such as attitudes
to acceptable lifestyle changes and public
awareness of climate change. The IPCC
have highlighted that occupant behaviour or
culture and consumer choice are major
determinants of energy use in buildings.

As existing properties will continue to repre-
sent a large proportion of UK housing stock
by 2050, efforts need to be focused on
improving existing stock as well as better
new build design. Despite testing a pessimistic
scenario with high cooling demands, the size of
the heating demand still far outweighs the
the effects of an increase in cooling load.Although
climate is predicted to warm up, UK
domestic property still has a significant heat-
ing load to bear. As climate change occurs,
winters will become milder and demand for
natural gas will reduce 20% by 2050. This is
due to climate change alone, without any
improvement in existing building stock. This
reverses the historic trend of increase, since the
1970s. Focus should be on reducing heating
load in existing homes, whilst not compromis-
ing building design for the emerging cooling
season. 

Relevance/Responses 
Methodology: A thermal simulation programme was used to theoretically test a range of dwelling types under different climatic conditions from the UKCIP02 scenarios. This was done to gain an
understanding of carbon emissions due to space conditioning at both individual dwelling and national level.

Adopts a business as usual case, with no adaptation/mitigation measures having been implemented, alos creates 'housing archetype' case studies which are then extrapolated to the entire housing stock.


Tuesday, October 11, 2011

C. Demanuele et al: Using localised weather files to assess overheating in naturally ventilated offices within London’s urban heat island 2011

http://bse.sagepub.com/content/early/2011/08/25/0143624411416064

Abstract:
Urban environments typically experience increased average air temperatures compared to surrounding rural areas – a phenomenon referred to as the Urban Heat Island (UHI). The impact of the UHI on comfort in naturally ventilated buildings is the main focus of this article. The overheating risk in urban buildings is likely to be exacerbated in the future as a result of the combined effect of the UHI and climate change.
In the design of such buildings in London, the usual current practice is to view the use of one generic weather file as being adequate to represent external temperatures. However, the work reported here demonstrates that there is a considerable difference between the overheating performance of a standard building at different sites within London. This implies, for example, that a building may wrongly pass or fail criteria used to demonstrate compliance with building regulations as a result of an inappropriate generic weather file being used. The work thus has important policy implications.
Practical application: The Greater London Authority has recently developed, with the Chartered Institute of Building Services Engineers, guidance for developers to address the risk of overheating in buildings via the provision of weather files for London relating to three zones. While such an initiative is welcomed, it may be that a weather file tailored to the building location would be preferable. Of course, this would add further complexity to the process and a view would have to be taken as the viability of such an approach. The work presented in this article, however, suggests that serious consideration should be given to the use of tailored weather data for regulatory purposes.