Thermal Mass Explained

May 23rd, 2009
The potential of using a building’s thermal mass to reduce its ongoing heating and cooling energy requirements is being increasingly recognised. How to successfully realise this potential is often less understood but is explained in new technical guidance from The Concrete Centre.
Until recently, the use of thermal was often disregarded in favour of a largely services-based solution for the heating and cooling of buildings. However, the wish to reduce the on-going energy consumption of buildings both in terms of carbon dioxide emissions and energy bills has led to a re-evaluation of the contribution that thermal mass can help to achieve a more sustainable built-environment.
“Exploiting thermal mass so that it helps to reduce heating requirements in the winter and cooling requirements in the summer is not difficult. However, it does need to be considered at the outset of the design process when the building’s form, fabric and orientation requirements are being determined”, said Tom de Saulles, building physicist, at The Concrete Centre and author of the report ‘Thermal Mass Explained’. “Get it right and you can have significant energy savings and carbon savings over the life of a building with less need for expensive low carbon technologies”.
Thermal mass, in the most general sense, describes the ability of a material to store heat. For a construction material to provide a useful level of thermal mass it must have a high specific heat storage capacity, be of high density and have moderate thermal conductivity so that heat conduction is roughly in synchronisation with the daily heat flow in and out of the building.
Timber has a high heat capacity but a low thermal conductivity. This limits the useful heat absorption rate and so provides a low thermal mass. Steel also has a high heat storage capacity but it also has a very high rate of thermal conductivity which means that heat is absorbed and released too quickly for any meaningful thermal mass efficiency. Concrete and masonry, with their high heat capacity and density but moderate thermal conductivity offers a good balance. They steadily absorb heat and store it until the ambient temperature drops causing stored heat to migrate back to the surface from where it is released. Heat moves in a wave like motion alternatively being absorbed and released in response to the variations in day and night-time conditions.
“The absorption and release of heat enables buildings with thermal mass to respond naturally to changing weather conditions, helping to stabilise the internal temperature and provide a largely self-regulating environment”, explained de Saulles. “This action helps to prevent summer overheating and reduces the need for air conditioning. It can also reduce the need for heating during the winter by capturing and later releasing solar and internal heat gains”.
During warm weather, much of the heat gain in heavyweight buildings is absorbed by the thermal mass in the floors and walls thereby reducing the risk of overheating. This heat is then removed by allowing cool night-time air to ventilate the building. This daily heating and cooling of the thermal mass works relatively well in the UK as the air temperature at night is typically 10 degrees less than peak daytime temperatures during the summer.
“The benefits of thermal mass, which is well understood in warmer parts of Europe, will become increasingly recognised in the UK as climate change results in hotter summer temperatures”, said de Saulles. “As well as cooler internal temperatures, these benefits also include reduced heating bills in the winter as instead of purging the day-time heat gains with night-time air, the stored heat is allowed to radiate back into the building”.
For the winter, thermal mass works best when it is used as part of a passive solar design strategy (PSD). This approach seeks to maximise the benefit of solar gain in the winter, using thermal mass to absorb gains from south facing windows, as well as internal heat gains from electrical equipment, cooking and lighting. These gains are slowly released overnight as the temperature drops so helping to keep the building warm and reducing the need for supplementary heating. Applying simple passive solar design techniques can result in fuel savings of up to 10 per cent. This saving can increase to 30 per cent if more sophisticated passive solar techniques such as sunspaces are adopted.
“The need to design and build for higher levels of energy efficiency and to mitigate the effects of climate change means that the performance requirements of building materials continue to increase. Meeting these challenges requires a whole-building approach where the materials, structure and systems work in unison to maximise the building’s overall performance. The thermal mass of concrete provides a useful constituent of this whole building approach”, said de Saulles. “Efficient use of thermal mass used in conjunction with orientation, solar gain, ventilation and shading can do much to reduce the whole-life carbon footprint of buildings”.

http://www.concretecentre.com

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Invest in the future

May 23rd, 2009

Recently in an inauguration ceremony of “Crossrail” project of UK, Prime Minster Mr. Brown said the start of work was a  ” signal of faith in the future quoted a very beautiful saying “.  “If you don not invest in the future, you have no future. Today we are sending a message that our faith in the future is such that our faith in the the midst of a downturn, we are starting the biggest infrastructure projects in this country -…”

What we are looking that Our Government is investing a very little for its future. The shortage of electricity and its production in minus is the example of “invest in future” of the previous governments. This government is working to cover the shortfall in electricity but what we have quoted is a challenge for the future planning and policies.

A major drawback in planning is not to consult the engineers. The heads or secretaries or ministers of technical matters are non technical persons who have no knowledge of their departments or ministries. They are bureaucrats or have been appointed under political bribery.

However we are pointing some future investments on which our government should consider seriously:

  1. More resources for Generation of Electricity and its supply, cutting off the leakage holes and collection of revenues;
  2. Improvement of Railway Infrastructure, new rail tracks, improvement of passenger coaches and reservation system;
  3. Improvement of level of Engineering Education and introducing new technologies;
  4. Health and Safety Legislation and Measures, respecting the life of a laborer,  in all sectors;
  5. Improvement in Transport and Logistics, standardizing the design of buses, trucks, trailers etc making the roads safe and easy for public;
  6. Improving the services level of Pakistan Engineering Council and introducing system of promotion in next grades with respect to experience, qualifications and knowledge of engineering developments .

These are the few examples on which we have mentioned but our readers can say more.

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Engineering Education in Pakistan

May 4th, 2009

Developing countries are facing many challenges in Engineering Education and one of the key issues is the question of curriculum adaptability to the growing needs in the concerned sector relevant to developmental process. For example the civil engineering curriculum equally revolves around structures and surveying.

During the last three decades, engineering and technical education in Pakistan has witnessed large growth. Setup of new engineering universities and other institutes of higher education have relatively good infrastructure with qualified teaching staff.

But there is need to focus in engineering education more on teaching the basics of technology (from textbooks). The subjects covered in universities are not up to that level which is studied in European Universities. It may be some institutes have the offer to its student knowledge pertinent to the needs of industry as a part of the curriculum but what has been examined in reference to developed countries institutes, some faculties of engineering are still to be modernized. For example some subjects like environment engineering, construction law and arbitration subjects are required to be introduced within their curriculum. Some faculties lack a clear vision regarding strategies needed to inform their students about the future technologies and demand of the industry. Thus, there is an urgent need for an important change in perspective and in the model used of for establishing new curricula.

In my opinion, universities in Pakistan should also offer courses based on e-learning formats using web-based tools and practicing engineers should take them “on a need basis” consideration the specific requirements for new knowledge and skills.

The engineers in all departments must have exams based on experience and skill minimum after 2-3 years and CPD points should be counted while promoting to higher posts. To be a member of Pakistan Engineering Council is not enough, engineers should prove themselves the engineers, not good clerks who only sign the bills and forward the files in government departments. The competency profile of engineers is changing dramatically in this age and it is essential to establish a close cooperation between faculties of engineering, industry and engineering council in order to participate in the formation of engineers.

The future engineering education must take the following into consideration while planning their courses and Pakistan Engineering Council should watch it in the scenario of other developed countries demand and environments:

  • Offer modular and flexible programs.
  • Redesign curricula and involve industry in the development of these new curricula.
  • Use of advanced lecture delivery tools such as projection systems, e-learning via intranet and internet.
  • Offer collaborative learning environment by tying up with leading foreign.

The engineering educational programs must prepare engineers capable to fulfil the demand of industry and standard of education and be fully aware of some important facts such as.

  • Understand that employers of engineers are multi-national companies with wide geographical spread and conduct business across international boundaries.
  • Engineers must deal with varied cultures, customs and languages and must be capable of working in global rather than local environments.
  • Engineering work must adhere to a variety of statutory and regulatory requirements.
  • Engineering designs need to address both local and international requirements, and in particular, environmental regulations.
  • Developed products must address a variety of customers and consumer preferences.

And new engineering curricula must address the following:

  • Clarify the impacts of technological change on societies.
  • Stress the need to make information technology part of engineering education.
  • Offer basic foundations of science and mathematics and offer opportunities for the inclusion of biology, energy and water technologies.
  • Offer opportunities for specialized knowledge without ignoring multi-disciplinary content of the curriculum.
  • Teach engineering students the real value of teamwork and stress the need for clear communication/soft skills including verbal, written and visual.
  • Teach engineering student basic elements of business, finance, management and quality.

In conclusion, developing countries should be committed to retaining high-level scientists, stimulating them, and providing funds and other support to encourage and maintain their productivity.

Abstracts from: http://www.arabrise.org

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Reducing C02 Emissions and the Potential for Fuel Poverty

March 26th, 2009
Thermal mass, particularly when used as part of a passive solar design strategy, is increasingly being used to reduce heating and air conditioning energy consumption and bills. Both benefits are of interest to housing associations wanting to build sustainable homes that reduce both their environmental impact and the potential for fuel poverty.
The ability of thermal mass to reduce overheating problems is increasingly recognised. Perhaps less appreciated is its ability to save heating energy when used in passive solar design (PSD). Consequently, it is possible for concrete, masonry and other heavyweight dwellings to exploit their inherent thermal mass on a year-round basis. During the summer, heat is absorbed on hot days, helping to cool the internal temperature and prevent overheating problems. The stored heat is then removed by night ventilation. During the winter, the thermal mass will absorb solar gains through south facing windows, and slowly releases the heat at night. This process is effectively the same as that which occurs on summer nights, the only difference being that during the winter the stored heat is beneficial, so windows and openings are kept shut to minimise heat loss. Shutters and blinds used to prevent overheating in the summer can also help minimise heat loss during the winter.
Useful levels of thermal mass are found in medium and heavyweight construction, which in practice is most easily provided by concrete in the form of blocks and precast or in-situ floors and panels.
The use of concrete often raises questions regarding its embodied CO2, which can be slightly higher than that associated with alternative materials, but in reality the difference is relatively small when compared to lightweight systems. And, when you evaluate this in whole-life terms, the operational CO2 savings provided by the heavyweight solution is actually much more significant over the long-term. This point can sometimes be overlooked in the drive to specify the greenest materials available, but should to some extent be redressed in the forthcoming revisions to Part L1 of the Building Regulations, which will take greater account of thermal mass in the Standard Assessment Procedure (SAP) calculation.
To establish the facts of embodied versus operational CO2, The Concrete Centre commissioned research to examine the embodied and operational CO2 emissions of a simple semidetached house built using a typical lightweight frame, with that of several heavyweight versions built using varying levels of thermal mass. The embodied CO2 for each option was calculated and thermal modelling was undertaken to see how each performed across the 21st century, taking account of the likely impacts of climate change. The results showed that a typical masonry house with a medium level of thermal mass, has around 4% more embodied CO2 than an equivalent lightweight frame construction, but that this could be offset in as little as 11 years due to the energy savings provided by its thermal mass. Increasing the mass through additional concrete elements, such as precast upper floors, resulted in a longer offset period, but ultimately led to the lowest whole life CO2 emissions of all the options, with a saving in CO2 over the 21st century approximately six times greater than the difference in its embodied CO2 when compared to the lightweight frame solution.
Due to the predicted increase in summer temperatures resulting from climate change, the lightweight home was found to need air-conditioning by 2021. This compared with 2041 for the medium-weight home and 2061 for the medium-heavy and heavyweight homes.
Thermal mass is of course only one of the steps needed to adapt homes to a warming climate. Effective ventilation and shading are also of great importance in all types of housing, particularly in the south of the UK where overheating is likely to be greatest. Traditionally, shading has not been a major feature of UK housing. However, this is likely to change, particularly if tougher overheating rules appear in the Building Regulations. There are many shading options, but the most effective at minimising solar gains are externally located, such as overhangs and louvered shutters. The latter has the advantage of also providing secure night time ventilation in the summer.
In addition to having a medium to high level of thermal mass the key design requirement for capturing solar gains during the winter is to locate a large proportion of the glazing on the south elevation, or within about 30° of south. This will allow the low winter sun to shine directly into the home, passing underneath any fixed external shading overhangs. There are no hard and fast rules for window size in passive solar design; the objective is to optimise solar gains during the winter without incurring summertime overheating problems. This typically leads to a glazed area that between approximately 20 and 40% of the façade area. Glazing on the north façade should be restricted to the minimum area needed for adequate daylighting, since over the course of a year this will have a net heat loss.
Incorporating these all design features can help to maximise a home’s year-round passive thermal performance thereby reducing both CO2 emissions and energy bills.

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Concrete as a leader of sustainable construction

March 26th, 2009

Jonathon Porritt, Founder Director of Forum for the Future, has applauded the concrete industry for its initiative and commitment to become a leader for sustainable construction.

Speaking at the launch of ‘The Concrete Industry Sustainability Performance Report’, Porritt commended the industry saying that: “I am genuinely impressed at the progress that has been made and the quality of the leadership shown. The industry is to be congratulated upon the journey that it is taking”.

Forum for the Future has been working with the concrete industry to develop and implement a sustainability strategy. The launch of the first industry-wide Performance Report marks a milestone for the concrete industry. It examines the challenges being faced and provides a statement of achievement. Importantly, the report provides industry data across 14 performance indicators against which the concrete sector has committed to be benchmarked against and to improve upon.

The performance indicators are wide ranging and include the implementation of environmental management systems, reduction of waste and carbon emissions, improved energy efficiency and the provision of locally sourced materials. In addition, there are commitments to enhance the environment and create sustainable communities. The report will be followed up on an annual basis so that ongoing sustainability improvements can be measured.

To download the report, visit www.sustainableconcrete.org.uk

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Electricity Crisis in Pakistan

March 24th, 2009

It was claimed by politicians when the judiciary will be reinstated, all economic crisis will end in the country. Now after the reinstatement of Iftikhar Choudhry and other judges, we are looking any miracle which can end the load shedding. The TV media which was shouting over judiciary crisis now should shout over the load shedding and economic growth in the country. It should realize the politicians and beurocates that paying the bills to WAPDA by them as well as by their departments is the survival of the WAPDA. Paying bills by laymen or small shopkeepers cannot survive WAPDA untill those who thief the electricity. There are so many factors for the losses of WAPDA due or Karachi Electric Supply Company due to which new sources of generation have stppoed. In my opinion, following are the factors of load shedding:

1.  No new sources of generation as WAPDA have no sources.

2.  Politicians who use free electricity at their homes and industries and intervention in management of WAPDA.

3.  Free use of electricity in Sind and FATA or tribal areas.

4.  Leakage with support of WAPDA staff.

5.  Distrust by foreign investors over infrastructure of WAPDA and its mode of payment .

There may be other factors and you can mention here.

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THE CURRENT ECONOMIC CRISIS EXPLAINED, PAKISTANI STYLE!

March 22nd, 2009

Recently one of my friend Mr. Tariq from USA sent me a blog which has been published on an other website, represents the condition of Pakistan economy in a funny mode as well as of other developing countries. Engineers in any country are considered, the backbone of country’s economy and are consulted while at planning stage. This blog is published to consider and think about our country’s economy for planners and experts of economy.

Fajja is the proprietor of a Siri-Paya and Nehari Shop in Lahore . Sales are low and, in order to increase them, he comes up with a plan to allow his customers to eat now and pay later. He keeps track of the meals consumed on a ledger.

Word gets around and as a result increasing numbers of customers flock to Fajja’s shop. Fajja’s suppliers are delighted and are very willing to sell more and more raw materials for the meals he prepares. Fajja shows them his ledger of receivables and they extend him credit.

A young and dynamic customer service consultant at the local bank recognizes these customer debts as valuable future assets and gives Fajja a credit line and then increases Fajja’s borrowing limit.

Taking advantage of his customers’ freedom from immediate payment constraints, Fajja jacks up the prices of his Nehari and Siri-Paye. Customers don’t mind as they are not required to pay on the spot. Sales volume increases massively; Banks and suppliers lend more; Fajja opens more outlets. He sees no reason for undue concern since he has the debts of the customers=2 0as collateral.

At the bank’s corporate headquarters, expert bankers recognize Fajja’s customer loans as assets and transform these customer assets into BONDS. These negotiable instruments are given exotic names such as SIRIBOND, PAYABOND, MAGHAZBOND AND BONGBOND. These securities are then listed on the Stock Exchange and traded on markets worldwide. No one really understands what the names mean and how the securities are guaranteed but, nevertheless, as their prices continuously climb, the securities become top-selling items.

One day, although the prices are still climbing, a credit risk manager of the bank decides that the time has come to demand payment of one of the debts incurred by Fajja. Fajja in turn asks his clients to pay up. One by one they refuse; the clients cannot pay back the debts. Fajja refuses to serve them any more. The clients stop coming.

Fajja is really screwed now. He cannot fulfill his loan obligations and therefore claims bankruptcy. All Bonds drop in price by between 80 to 95%.

The suppliers of Fajja, having granted generous payment due dates and having invested in the securities are faced with similar problems. The meat supplier defaults on payment to the sheep and cattle supplier and claims bankruptcy. The atta supplier is taken over by a competitor; Fajja lays off the cook and staff. Bankruptcies soar, unemployment mushrooms.

The bank that lent the money in the first place is set to collapse. It is saved by the Government following dramatic round-the-clock consultations by leaders from the governing political parties with Fajja commuting back and forth in his Executive jet and Mercedes 500SEL, brokering the deal.

The funds required to save the economic collapse are obtained by a tax levied on the citizens, most of whom do not eat Nehari or Siri-paye.

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Construction Law in Pakistan

December 30th, 2008

I am not sure that in Pakistan, any university have the facility to teach the civil engineering students, Construction Law and Arbitration, subject which, I think is a fundamental for engineering students. The Civil Engineers should have the knowledge of the value of contract, its terms, clauses and terminology. When the contracts are awarded, what terms should be inserted and should be careful while inserting some clauses. The Arbitration clause is very important. If it is not well construed, the problems faced by either property during the contract may delay the project.

Similarly as I know , there are no typical contracts published by any body like in UK, where JCT Forms, NEC Contract document etc are published by IBA and ICE as a guide lines to landlords and contractors, an exemplary documents.

Can anyone comment on “Construction law and Arbitration” in Pakistan in these pages?

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Hello world!

December 27th, 2008

Welcome to World of “Forum of Pakistan Engineers” where you can write the issues and development related to Engineering sector in Pakistan.

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