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BUILDING MORTALITY AND SUSTAINABILITY

KELVIN L WALLS

Building Code Consultants Ltd, P O Box 99-613, Newmarket, Auckland, New Zealand

ABSTRACT

Over the last few years the consciousness of the need to consider sustainability in our activities has reached new heights, as environmental ethics have been incorporated within most professionals’ codes of ethics, and sustainability is becoming important to many individuals. This increased awareness has taken place contemporaneously with a reduction in professional input towards the construction of buildings, along with a New Zealand Building Act which requires a specified intended life of buildings to be at least 50 years. This specified intended life could be seen as incompatible with the notion of sustainability, considering that many existing buildings in other countries are centuries old. On the face of it, there appear to be contradictions in this New Zealand Building Act arguably minimal specified intended life requirement of buildings, for which an attempt has been made in this paper to examine some of the competing issues in the present highly commercial world.

KEYWORDS

Building mortality; sustainability; construction supervision; building specified intended life; Building Act.

INTRODUCTION

The term sustainability may conjure up many different meanings to different people. It generally implies, however, that something should last for as long as possible so that it does not become prematurely obsolete. This should imply a positive impact on the mortality of a country’s building stock, so that buildings last longer before they have to be maintained and replaced. Since the actions of each individual affects the earth in some way, it must be kept in mind that building activities must not be considered in isolation. With in excess of 60,000 chemicals in common use and pollution paralleling technologic advances, increased pollution (that is anti-sustainable practices) is related to “the production and use of energy, the production and use of industrial chemicals …” (Plaa, 1998). The production of building materials is intrinsically linked with these processes. Reflecting on the UK building scene, Addleson (1977) stated that shortcomings in buildings owing to a proliferation of new materials and building techniques became prevalent in “the post-war period”. He questioned “the significance of the sixty-year economic life of buildings”, suggesting that they could be beyond their economic life before then. Furthermore, in the 1980s in New Zealand, there was the demise of the clerk of works and that of professional engineering input towards the supervision of buildings under construction. A further factor which could presently be having an additional negative affect on the mortality of buildings is the fact that under the Building Act 1991, the design life of most buildings in New Zealand is required to be only at least 50 years. These two factors tend to conflict with the notion of sustainability which is becoming a significant word in the lives of most people in developed countries.

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BUILDING CONSTRUCTION SUPERVISION

The Architects Journal (1977) featured a series of key ideas for the construction industry. Amongst them was the view that “Site supervision, and the checking of materials and workmanship for

compliance with the specification, must be improved. In view of the complexity of modern building

technology, specialist assistance may in many cases need to be called in.” Abbott (1977), in establishing priorities for improving the quality of the building process, included one of the three main elements as being, “Supervisory time spent on the assessment of quality of work during progress

or on completion, related to the standards required by the specification”. Bargh (1987) and Walls (1989) alluded to increasing commercialism in the building process leading to a deterioration of standards of buildings, owing also to a lack of supervision. As mentioned above, during the 1980s in New Zealand, there was the demise of the clerk of works as well as the increasing emergence of layperson-developers. From this time to the present day, many buildings have been constructed without any independent professional supervision. In a discussion on the earthquake about the Marmara Sea, Turkey on 17 August 1999, Sharpe et al (2000) stated that “monitoring of the

construction process by the local government engineers is very often non-existent”, and with buildings which are commonly up to 12 storeys high in Turkey, in excess of 70% may have been constructed illegally.

BUILDING MORTALITY

Building maintenance

Porteous (1992) found that dampness in buildings was the main catalyst for decay and building failure. Water is one of the most destructive forces endured by buildings. It needs to be eliminated by careful design, construction, and regular maintenance. Buildings generally represent the largest investment which most people make in their lives. Buildings are used as investments and as a hedge against inflation. To enhance the longevity of any building, it must be maintained regularly. Buildings must be designed and built to resist natural forces of degradation. From the time a building is completed, it is on the slow downward path of destruction, usually at an infinitesimal rate. But that rate will depend on how well it is cared for. It is prudent intervention of planned maintenance which gives building owners the optimum return on their investment. BRANZ reported that there was a national expenditure required of NZ$5.5 billion to bring the condition of New Zealand houses up to a moderate level. This represented a figure of about NZ$4000 per dwelling, while owners were then spending only about NZ$1500 per year (BRANZ, 1999). The national expenditure of house maintenance required is approximately equal to the annual turnover of the building industry in New Zealand, which is over NZ$5 billion (Building Industry Authority, 2000). Given that there are trade-offs needed when considering maintenance versus new construction, it is an important matter since the construction industry contributed NZ$2215 to New Zealand’s Gross Domestic Product (GDP) in 1989 (Porteous, 1992). This amounted to about 52% of that of the agricultural sector. The annual maintenance costs of a New Zealand dwelling are 1.0% of the costs to construct a new dwelling (Johnstone, 2000), but it appears that considerably less than this is actually being spent.

Fungal contamination (mould growth)

One of the most serious, and common, effects of dampness in buildings is the presence of fungi. This was found to be the case by Porteous (1992), as mentioned above. Extensive discussion on this relating to types of buildings, buildings’ uses, methods of construction, density of occupants, ventilation systems and state of repair, was given by Walls (1999a). Fungal contamination has been shown to play a much more important role in building contamination than what was first imagined (Walls, 1999b).

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Sealants vs Flashings

One of the main reasons for the ingress of water into plaster-clad buildings is the use of sealants over external wall openings. There is an increasing trend these days to use sealants on the exterior of buildings around door and window openings. However, many water ingress problems arise owing to this tendency to not use flashings. It is becoming a common and undesirable trend in New Zealand. A properly designed and installed flashing system will generally always be superior to sealants for preventing leakage around openings. This is mostly due to the fact that flashings are self-draining and they are more easily able to accommodate movement compared with sealants. Sealants should only be considered where the geometry is so complex as to make flashings impractical. In this case an appropriate sealant should be properly designed and carefully applied so that the appropriate durability requirements can be met.

Stucco

Stucco (plaster) exterior cladding is often the direct cause of dampness ingress in modern buildings. Over the last few years this type of cladding has become very popular in New Zealand. It is a good method of cladding, but extreme care needs to be taken with the details of construction. The majority of buildings clad with these types of products these days are poorly constructed in relation to this cladding, as most of them leak or are likely to leak in the near future. This is due to the fact that many shortcuts are being taken. It is essential to ensure that whatever approach or proprietary method of stucco application is used, the written instructions of the manufacturer are followed to the full. Many of the stucco problems relate to the following areas:

• A lack of construction joints to allow for controlled movement of the stucco.

• Roof parapets which are not constructed to shed rainwater and which are too ornate, allowing for too many crevices and areas where a good paint coating cannot be applied.

• Mixing more than one method so that crucial design features are overlooked.

• The lack of flashings over door and window openings (as mentioned above).

• The stucco extending down below ground level, instead of stopping above the ground.

Ventilation

The question of ventilation is best explained by first considering humidity and how it is generated within buildings. Humidity is the amount of water present in the air; or more specifically, the ratio of the mass of water vapour to the mass of dry air in any given volume of mixture. This factor controls the rate of evaporation of water, as fully saturated air cannot absorb any more water, resulting in zero evaporation. Relative humidity is the percentage saturation of the air. High air temperatures have the ability to hold more water than lower air temperatures. So if air at a given temperature is only partially saturated, any lowering of that temperature causes the air to become more saturated. When the air has cooled to a temperature which completely saturates it, this temperature is called the dew-point. If the air is cooled further than the dew-point temperature, the excess water will form as a mist or will deposit itself as dew or condensation on any convenient surface. This explains the phenomenon of condensation on windows. Most activities within buildings will contribute towards a buildup of moisture. It is moisture from any source within buildings which is attributable to much more rapid deterioration of buildings. The phenomenon of ventilation combined with condensation is one of those factors. To avoid an uncomfortable feeling of clamminess and the risk of mould growth and excess condensation, the relative humidity should be kept below about 70%. On the other hand, the relative humidity should

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also be kept above about 30% to avoid the discomfort of dry mucous membranes in the nose and throat, and allergies and asthma. In recent years with the widespread use of natural gas in many areas of New Zealand, the former problem has become more prevalent. This is because one of the by-products of combustion of natural gas is water. Having one or two open windows in a room will assist in reducing the problem whilst heating is being used. Such ventilation is also important for supplying fresh air, removing carbon dioxide and other toxic gases, and for removing odours. High moisture contents within buildings and the incidence of mould growth are intertwined. Mouldy interiors can be hazardous to the occupants, so the mould should always be removed from all surfaces of the interior of the building. Further measures should be taken so that there is no recurrence of excess moisture and mould growth.

DURABILITY AND BUILDING ACT 1991 Section 39 of the New Zealand Building Act sets a requirement that all buildings are to have an intended life of at least 50 years, unless a shorter specified intended life is advised in the building consent application. The consent applies to its intended use. If it is subsequently intended to change its use pursuant to section 46, then under its new use the building is to have at least a 50-year specified intended life, unless some other shorter period of time is nominated. Does this sit well with society’s current expectations relating to sustainability? The proven ability of New Zealand houses to exceed a service life of 140 years seems to throw into serious question why such a relatively short specified intended life is allowed under the Building Act (Johnstone, 1999). From the author’s experience in the building industry, it has become apparent that this situation is leading to planned obsolescence, with many developers intent on meeting the minimum statutory requirements (or even less, if they can get away with it), for maximum profit, without considering any other adverse matters relating to environmental issues or other social issues. Moreover, under clause B2 - Durability, there are minimum specified intended lives of 15 years and 5 years for building elements which are more readily accessible than the main structural frame. For instance, this allows for claddings to have only a 15-year life requirement, a factor upon which many developers are relying, to the detriment of the environmental and social costs. However, Johnstone (undated) pointed out that timber weatherboards are replaced every 70 years and fibre cement planks are replaced every 50 years. The intended life of a building is associated with durability more than any other natural phenomenon, and it affects every aspect of a building. In the context of the New Zealand Building Code, durability is related to every technical clause. Despite the fact that durability has such a pervasive influence, “The building controls of many countries do not contain requirements equivalent

to B2 (the durability clause of the New Zealand Building Code), perhaps because durability has been

put in the “too hard” basket”. (Building Industry Authority, 2000). It appears that the present requirement in New Zealand for a life of at least 50 years was based on some Nordic countries. In Finland it “is normally considerably longer than 50 years”, in Sweden “it

is permissible for the service life of buildings to be assumed as 50 years, unless special circumstances

warrant some other assumption”, and in Denmark and other Nordic countries, there were no stated intended service lives (NKB, 1982). The Institution of Structural Engineers (1999) assumes in its discussions a life span of 60 years for buildings.

LIFE CYCLE COSTINGS

Energy requirements for new-build and replacement construction for a modal house are 255109 MJ (2.75 GJ/m2), and for annual maintenance it is 357 MJ (Johnstone, undated). This puts annual maintenance energy requirements at 0.14% of new-build construction. Several studies have been carried out relating the life cycle energy requirements of buildings from 3D CAD drawings (Johnstone, undated).

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A typical 50-year-old New Zealand dwelling can undergo rehabilitation including re-roofing, rewiring and upgrading of kitchen and bathroom for about 47.3% of the cost to construct a new dwelling (Rawlinsons, 1996). The rehabilitation cost for a 30-year-old dwelling would be up to about 32.5% of the cost to construct a new dwelling (Johnstone, 1997). Page et al (1995) found from a survey of 400 New Zealand dwellings that deferred maintenance averaged about NZ$3200 per dwelling. This represents almost three times the average annual maintenance costs. In order for society to start dealing realistically with sustainability, life cycle cost analyses of buildings need to be applied, which go beyond the monetary costs to the present owner. The most important concept here is to consider the amount of embodied energy in materials forming parts of buildings. This is discussed more fully further in the paper under “Greenhouse effect”. Other factors which need to be considered include the economical use of materials (especially considering energy embodiment), the ongoing energy consumption for heating, cooling and air conditioning, and the most simple design, possibly modular, to provide for the maximum number of uses over the life of the building.

SUSTAINABILITY The term sustainability usually implies in a general sense the wise use of resources. This can have many different meanings and interpretations. Not enough consideration is given to the energy embodied in existing buildings; instead, there is too much emphasis on new development of housing (Seip, 1979). Few buildings are ever demolished as a result of failure of their structural system. Johnstone (1994b) advised that “Departures of dwellings from a housing stock are the end result of

an economic process and the potential physical life of most dwellings is not realised”. It is proposed to cover only three main areas of concern in this discussion, namely complexity and nature of standards, over-emphasis on first cost and the greenhouse effect. However, there are several others which contribute to compromising the sustainability of buildings, as covered by Porteous (1992).

Complexity and nature of standards

For quite some time, non-compliance with the appropriate requirements appears to have been a problem leading to a shortening of building longevity. Nelson (1977), in discussing causes of failure, stated:

One important conclusion we are forced to make from our analysis of failures, and indeed

from our continuing daily workload is that many happen because existing, authoritative

guidance, for example, in BS Codes and BRE Digests, is not followed. “It is a wonder that anything gets built at all”, was the view of Marsh (1978) in discussing the myriad of building regulations and the “incomprehensible” legal jargon involved. Porteous (1992) reported on the work of Tippett and Porteous (1980) where it was found that “it was possible for a mandatory

building code … to be modified on hearsay evidence to become so stringent that compliance became

demonstrably impossible”. Porteous (1992) asserted that code requirements often came about as a result of “theory and opinion” rather than on proof supported by research. It was suggested that this approach led to undue caution, increases in building costs, and an over-use of materials. Walls (1998) discussed general trends in complexity of New Zealand Standards, suggesting less understanding of the documents, more errors in the building process, and increasing non-compliance. Walls, Tonks and Aynsley (1998) expressed similar views in relation to wind design and light timber frame buildings. All of these factors which would tend to deviations from the “ideal” design of a building must result in a lack of sustainability.

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Over-emphasis on first cost

Normal commercialism, as it is today, has lowest cost as one of its underlying principles. That is normally based on the lowest first cost, as those most entrenched in this approach do not, or do not want to, understand that this could lead on later to further costs being incurred. Examples of this are many and varied, including using sealants over windows instead of flashings and choosing a cheap paint coating which does not prevent moisture ingress. However, perhaps the most subtle type of example is in the choice of designer for the building. Clients often choose designers based on the lowest quoted fee. However, a designer who has not had to compete for the design work with an undercut fee may well spend more time in preparing construction details which will better explain how the building is to be built. It is usual in cases like this for the extra fee to be small in relation to the cost savings in the construction process. The non-discerning building owner often sees only what is paid out in costs, not what has been saved through prudent design or in reducing the likelihood of disputes occurring in the construction process. The Building Industry Commission (1989) was replying to comments by BRANZ on durability. It observed the South African Bureau of Standards statement that a “modern high-rise office building in

an urban area is complex, costly and required to have a long life”. The Building Industry Commission (1989) contrasted this with the situation in New Zealand with the following observation:

This is not always true and the reality is that in NZ, owners will attempt to build as cheaply

as possible and in some instances, with no consideration of the expected length of life. This

depends entirely on the economic viability of the development with the standard of

construction and finish being determined only by the ability of the premises to attract tenants

at the rental return desired. - Building Industry Commission, 1989

Porteous (1992) has presented the over-emphasis on first cost as one of the main reasons for building failures, as it often relates to inferior or inappropriate materials.

Greenhouse effect

While the Greenhouse effect can be considered in several different ways, it is proposed here to limit it to one of the least understood aspects based on the conservation considerations of timber compared with steel framing. It is important to understand in the building process the environmental differences between different materials, such as the differences between using timber or steel framing in the construction or the refurbishment of buildings. Energy has been embodied in fossil fuels, such as coal, oil, and natural gas, for millions of years. In the very slow formation of such materials over millions of years, energy (carbon) was absorbed from the atmosphere. In considering a much shorter time cycle, trees and plants absorb carbon dioxide from the atmosphere, and through the process of photosynthesis, convert it to nourish the plant. As part of the process, they expel oxygen. When fossil fuels are burned to provide energy for industrial processes, there is a release of carbon which has been stored within the coal, oil, or natural gas for millions of years. When forests are felled to convert the wood to timber for use, this is in effect a use of a renewable resource, as the trees take only a relatively few years to mature (say, 20 years in the case of Radiata Pine in New Zealand), and the raw material is mostly left intact, with its embodied carbon. With a 20-year growth cycle, even if the tree is destroyed, there is a release of carbon into the atmosphere which has been embodied in the tree for only up to 20 years. Providing there is a replacement of much of what is used in terms of replanting, there is little or no net release of carbon to the atmosphere. Therein lies the problem of

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energy release contributing to the greenhouse effect. It is the substantial use of fossil fuels, whose energy has been embodied within the material for millions of years, which leads to the greatest build-up of greenhouse gases. Some further useful information relating to forestry operations is as follows:

New Zealand has cleared 90 per cent of its lowland forest - more than most countries - and

this has contributed enormous volumes of carbon dioxide to the atmosphere. We are now

adding approximately 26 million tonnes of carbon dioxide a year to that historic carbon

deficit by burning fossil fuels.

If we want less developed countries like Malaysia and Brazil to leave much of their forests

unlogged as carbon stores, we in New Zealand need to set the right example. We need to work

towards balancing all our carbon emissions by reabsorbtion in forests in the short term and

by transferring to non-fossil fuels in the long term.

Some of the forests could be commercial plantations which would mean jobs and economic

benefits for New Zealand …

- Maruia Society (1993) - now known as Ecologic Foundation.

From a building point of view, this concept of energy embodiment is significant. Comparing a light rough sawn timber joist with a similar strength light cold-rolled steel section, the steel section uses 19 times more process energy than the timber section. Similarly a reinforced concrete beam and a heavy steel I-beam had 5 and 6 times respectively the energy cost of a glue laminated timber beam with the same design strength (Honey & Buchanan, 1992). Widely varying amounts of energy are required in the production of building materials. Timber occurs “naturally”, and only requires simple processing. Steel is manufactured by energy-intensive processes. Owing to the vastly differing amounts of energy (carbon) release to the atmosphere in the use of different types of building materials, the use of timber where possible will always be the best material option from an environmental point of view.

CONCLUSIONS

The question of the ethics of so-called sustainability was raised by Buckeridge and Tapp (1999). They questioned society’s morals in emphasising the words rather than effectively dealing with the issues, and suggested that the road towards sustainability is even being thwarted. This feeling appears to be borne out from the preceding discussion and especially from the three more specific aspects discussed above under “Sustainability”. According to The Institution of Structural Engineers (1999), “Sustainable development is for all cultures, climates and geographical locations and for all

disciplines”. This is an interesting concept considering that most “developed” countries plundered their forests, sometimes, centuries ago, and when China, for instance, representing a quarter of the world’s population, is at the very early stages of its “modernisation” programme. Challenges like these are yet to be addressed by anyone (Walls, 2000). The sustainability of buildings is strongly linked with durability, a notion which is not even covered by building codes in many countries. The paper has discussed some of the areas where the path towards sustainability does in fact appear as being thwarted. “During the last 50 years, buildings in

general, and city buildings in particular, have become significantly less, not more, durable and much

more resource consumptive”. (Storey and Baird, 1998). Most of this derives from expedient practices motivated by short-term commercial (monetary) gains.

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Porteous (1992) advised that in New Zealand there is no nationwide system of investigating and recording events of building failure. This is likely to apply to all countries. It is unlikely also that any country has compiled a database of age-specific dwelling losses (Johnstone, 1994a). In order to practise sustainable living in a serious way, it is important that all the information tools available are implemented. Without those two knowledge databases in place on an ongoing basis, and without dealing with the issues covered in this paper, then it can only be said that society is paying lip service to the notion of sustainability.

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Johnstone, I M. Undated. “Energy and mass flow of housing: A Model and Example”’ Department of Property. The University of Auckland. New Zealand. Marsh, P. May 1978. “Why do Britain’s Builders bungle the job?” New Scientist. London. Maruia Society. July 1993. “Greenhouse Effect: Government Decides on Course of Action”. Bush Telegraph. Maruia Society. Nelson. New Zealand. Nelson, J. 28 Aug 1977. “The nature of common defects in building”. SAAT News. pp 7 - 8. New Zealand Government. 1992. “Building Act 1991”. NKB Report No 46E. August 1982. “Durability and Maintenance - A Review of Current Building Regulations”. (NKB stands for “Nordic Committee for Building Regulations”, covering Finland,

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Walls, Kelvin. 1999a. “Our Built Environment and the Likely Effects on People - A Case for a New Order of Engineering/Medical Professional Teamwork”. Australasian Environmental Engineering Conference. Auckland. New Zealand. Walls, Kelvin L. 1999b. “Microbiological Aerosols in Drainage Systems”. PhD thesis. The University of Auckland. New Zealand. Walls, Kelvin. 2000. Review of “Building for a sustainable future: Construction without depletion”. The Institution of Structural Engineers. 1999. London. England. For IPENZ “e.NZ Magazine”, Sept/Oct 2000.