CIB TG 16, StlJlo;fUJble Conslrucl;oll, Tampa, Florida, USA, November &-9, 1994 .

ECO-HOUSE AN ENVIRONMENT, USER, CONTEXT FRIENDLY HOME

Jolm B. Storey School of Architecture, Victoria University of Wellington, PO Box 600, Wellington, New Zealand

Introduction

This paper analyses the stance taken towards sustainability by the 35 entries in the Eco-house design competition held recently in Wellington New Zealand. The principal objective of the study was to gain an insight into the level of understanding and competence displayed by the contestants, as an indicator of where future educational efforts need to be concentrated.

The Resource Management Act 1991 requires local authorities in New Zealand to address the issue of sustainable management. Wellington City Council (WCC) recognised that the question of how urban sustainability can be achieved is of fundamental importance. Therefore, in initiating an eco-house competition the Council was seeking to establish a base for investigating the development of sustainable urban housing, of a kind which was appropriate to existing conditions in Wellington. The site was selected and the competition brief carefully developed to support these intentions.

The competition site was located in an inner city suburb, called Newtown, with a broad cultural, etlmic and economic population mix. Houses in the immediate vicinity of the site are circa 1900 style, weatherboard, detached, bungalows. The site itself is flat, which is quite unusual in Wellington, and long and narrow with one of the narrow aspects facing north.

The brief, though simply stated, was highly challenging. The organisers, while encouraging environmentally sensitive design solutions, also required entrants to address issues implicit in the design of low-cost, community-owned, housing-for-rent. The competition was focused on the design of a house, with a1l that implies in the holistic architectural sense, rat her than on a structure to lodge teclmological equipment, however environmentally friendly. It had also to be a building of our time and one which employed readily available construction materials and techniques. In addition it had to be built within a cost limit ofNZ $120,000 (US $70,000), which is a similar price to a conventional house. Fundamentally, the competition was less concerned with innovation and more about generating a set of ideas, which could be understood by a wide section of the population and be used today without significant capital cost penalty. The reality of the total scenario was reinforced by the Council's commitment to build and subsequently after aperiod of exhibition, to tenant the property.

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Eco-House Competition Construction Analysis

Wall Structure

Most houses in New Zealand are built using a light timber frame of preservative treated Radiata Pine or untreated Douglas Fir, taken from sustainably managed, New Zealand plantations. Borax treatment is becoming more popular for low grade preservative treatment, but no satisfactory alternative has yet been found to Copper Chrome Arsenie (CCA), for Radiata Pine in ground contact situations.

Of the 35 competitors 25 specified a structure. Of these only 12 specified light timber frame throughout, although six of the remainder used timber framing in a hybrid combination with loadbearing walls. Loadbearing walls were the choice of a further six, a mixture of aerated and dense, reinforced concrete block and adobe/pise constructions. One competitor came up with an idea for a plywood portal frame which was to be bolted together for easy transport to site and later re-use.

Only one competitor specified Radiata Pine and even then with borax treatment. A further four competitors specified Douglas Fir but only as an alternative to Macrocarpa or Lawson's Cypress. The most specified timber species was Macrocarpa with Lawson's Cypress a close second. These timbers can be used without treatment and are regarded as coming from sustainable sourees; but they are normally only available ungraded and in relatively small quantities.

Single skin, 200mm wide, high density hollow blocks are the normal structural masonry material in New Zealand and these must be filled with mortar and reinforced with steel bars tied into the foundations to comply with the earthquake code. Similar reinforcement is needed with abobe/pise construction. Stone is normally bonded to a reinforced concrete core wall. All these constructions create a sort of Faraday Cage effect, which because of its localised disruption of the earth's magnetic field, is anathema to some environmental architects. Block, brick and stone are also regarded as high energy wall options. Adobe/pise construction is becoming increasingly popular in New Zealand but for the moment is essentially confined to rural locations.

Wall Cladding

The most common cladding material in use in New Zealand is paint finished, CCA treated Radiata Pine. Untreated, unfinished, Western Red Cedar is also popular mainly because of the lack of maintenance required. Both these materials have significant associated environmental problems. With Radiata Pine these are both its preservative treatment, and the paint finish which must be applied . Both alkyd and acrylic paint are used. Neither product is particularly environmentally friendly. The use of environmentally friendly paints is rare in New Zealand as they are more expensive and their durability in New Zealand's very high U.V. solar environment is not yet proven. Western Red Cedar used for siding usually comes virgin North American forest sources.

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Cladding was specified by only 20 cornpetitors. Surprisingly five of these selected compressed cement sheet, which is neither a low energy, nor a particularly environrnentally friendly material. This suggests a lack of awareness of some environrnental issues even arnongst the competition entrants. Most of the other specifiers employed timber in one way or another, with nine of these specifying environrnentally conscious cladding products. Untreated and unfinished Macrocarpa was the most preferred cladding being selected by 6 of the 20 specifiers. The most innovative wall cladding was a timber rainscreen cladding of recycled flooring .

Wall Insulation

Fibreglass batts 75mm in thickness are the normal wall insulation material utilised with light timber frames and give a U-value of 0.56 W/m 2 deg C. The minimum insulation standard to comply with the regulations is 0.66 W/m2 deg C, which can be achieved using 200mrn of dense reinforced concrete block.

Qu;te surprisingly only 5 of the 35 competitors specified an insulation value for the wall and only one of those significantly increased the amount of wall insulation. In that case the insulation became 150mrn to give a U-value of 0.26 W/m2 deg C. Only 17 competitors specified the insulation material and of these no less than 10 specified wool. One competitor deliberately rejected wool in favour of fibreglass because of an ilJ-informed concern about waterlogging of the wool.

Glazing

Only 4 out of 35 competitors specified the use of double glazing and only one, the winner, specified double glazing throughout. The fact that neither double glazing nor aluminium frarning without thermal breaks is an issue in New Zealand is perhaps mainly a commentary on the low energy cost and relatively mild winters enjoyed by many New Zealanders.

Wall Lining

PIasterboard is by far the most comrnon wall lining material and tends to be regarded as environrnentally neutral. Only 12 contestants specified wall linings and of those five specified pIaster board. Timber boarding was nominated by three specifiers. Even the cheapest boarding, untreated Radiata Pine, is very much more expensive than pIasterboard but if occasionally treated with linseed oil is very durable and requires little maintenance, unlike pIasterboard which requires frequent painting, normally with environmentally wlfriendly products. One of the competitors suggested re-used flooring as wall linings, which is certainly feasible if available in large enough quantJtles. Plywood was the choice of another three specifiers. One competitor suggested that fuH sheets should be used, screw fixed to frarning to facilitate subsequent re-use. Finishes were not weil specified and did not appear to have been an issue for most competitors.

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Ground Floor

The standard form of ground floor construction in New Zealand is a raised , piled, treated, Radiata Pine frame, finished in particle board. Reinforced concrete floor slabs are fairly comrnon on flat land.

A high proportion of competitors, 29, specified the ground floor construction. Of these 17 selected an on-grade reinforced concrete slab construction. This type of construction shows considerable energy savings over timber construction in use although it is composed of higher energy, non-renewable materials (Isaacs). A further four entrants specified a combination of a heat collecting slab near north facing windows with timber floors being specified elsewhere in their designs. Three competitors specified earth floors, the same nurnber who specified pure timber construction. Two of the reinforced concrete slabs were thickened in so me areas to provide extra mass for heat storage. Two floors were constructed as unreinforced mass concrete slabs bounded by reinforced ring beam footings so as to minimise the Faraday Cage effect described above. In this sort of construction it is comrnon to have some discontinuities in the reinforcement in the edge beams to prevent an electrical circuit being set up. One entrant specified bolt together precast concrete beams which could be taken apart and re-used .

First Floor Construction

The normal form of first floor framing in New Zealand is treated Radiata Pine or untreated Douglas Fir with particleboard flooring . The particleboard normally used has its chips bound together with formaldehyde, a proven irritant and a suspected carcinogen. A low formaldehyde board is available at slight extra cost but cannot be left exposed to the elements for a long period before deterioration commences.

Of the 24 designers which incorporated upper storeys into their designs, 15 specified the materials to be used. All were timber with the most specified timber being Macrocarpa (6), followed by Douglas Fir (4) and Lawson's Cypress (4). Only two people specified Radiata Pine and one of those required borax preservative treatment. One person specified eucalyptus but failed to nominate the species, which is vital when dealing with this timber. No one specified standard particleboard but two people cited low formaldehyde particleboard as an alternative to untreated timber.

Floor Finishes

A very wide range of floor finishes was specified. The only clear message that came through was an awareness that concrete siab heat storage areas should be exposed for solar energy collection or covered with heat absorbing materials like slate, clay tiles terrazzo, brick or screed. Most people in New Zealand would cover hard finishes with carpet especially in bedroom areas and often in Iiving spaces so there seems to be a degree of wishful thinking about so me of the specifications. The most popular timber flooring material was Eucalyptus Saligna (3) which is a good hard flooring material,

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sustainably produced in New Zealand, though available only in small quantities. The most interesting floor finishes came from the two runners-up . One consisted of a combination of ochre coloured concrete pIaster (sic) finish cut into flagstones, fired earth tiles and broken china mosaic applied by the occupier/artisan. The other was a polished, naturally pigmented concrete slab.

Ground Floor Insulation

Some 14 competitors out of the 22 who specified total or partial concrete slab floors also specified insulation. Nine out of this fourteen were using the floor slab as a heat storage medium but only two specified edge insulation, which is the recommended construction practice in New Zealand. All except four specified polystyrene but did not define it as the closed cell type. Slab insulation is not common in New Zealand. It was disappointing to discover that even amongst this select cohort of designers there seems little understanding of the importance of edge insulating heat storage areas, of selecting the right insulant for the conditions or of its correct placement. Only one competitor seemed to have an understanding that beadboard absorbs water and that this reduces its insulating performance.

Roof Structure

Only seven competitors specified roof structure . The normal material would be treated Radiata or untreated Douglas Fir. No one specified Douglas Fir, the obvious sustainable choice, though three specified Macrocarpa or Lawson's Cypress.

Roof Finish

A very high proportion of New Zealand hornes are covered with corrugated steel. This is now normally provided prefinished with a plastisol paint finish and is known as Coloursteel. While this is durable and requires little maintenance the material has an inherently high embodied energy content. Twenty-five competitors specified the roof material and 14 specified Coloursteel. Three others specified ga1vanised steel which, though not quite as durable in New Zealand's saline atmospheric conditions, is regarded as more easily recyclable. Total or partial turf roofs were specified by five designers with a further three citing roof tiles. Two competitors specified Ondu1ine a bitumen impregnated, organic, fibre board. Manufactured in France this product is lightweight, low energy and much more environmentally friendly than steel. It has been used in small quantities on farm buildings in New Zealand for 40 years without obvious signs of deterioration and is becoming more popular for domestic buildings as an alternative to steel. Only two competitors specified shingles, one from Cedar, the other from Eucalyptus Saligna. Both of these timbers, if they are plantation grown and are of a suitable grade, would make durable, environmentally friendly roofs. There seems to be a clear vote for the familiar he re rather than a thinking through or perhaps an awareness of environmentaIly conscious options.

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Roof Insulation

Of the 16 competitors who specified roof insulation only 10 specified materials and wool was again the clear favourite, with seven competitors selecting it. Macerated recycled paper, which is rather easier to apply above ceiling level than in walls, attracted two competitors, with fibreglass being utilised by only one design team. Only five competitors specified an insulation value and only one designer significantly improved the insulation value of the roof beyond the New Zealand norm.

Passive Solar Construction

A great variety of passive solar collection devices were employed but many had significant design defects. In many cases, whiIe solar collection had been catered for, storage and distribution were poor or non existent. Virtually nobody designed to counter conductive heat loss at night, in winter, or during overcast conditions. Only one designer incorporated shutters, one other mentioned the employment of heavy, tight fitting insulating curtains and four others employed double glazing in association with either sunspace or trombe wall construction. Summertime overheating likewise was largely ignored; only two competitors incorporated solar shading devices, a further two mentioning the deployment of deciduous trees on the north side of the design, but without creating adequate space or noting the need for either mature planting or temporary alternative shading while the trees grew to a useful height.

Trombe walls were employed by seven competitors but were mostly small and were not always weil placed in relation to the solar path. Large north facing windows were, quite popular, with seven competitors specifically mentioning them, but only five of these had any associated storage and none mentioned distribution from the associated heated space. Similarly, while conservatory/sunspaces were incorporated into six designs, two of these were east facing and two others west facing, which is less than ideal. Thermal mass masonry was employed by five competitors, though in one ca se this was associated with south facing glazing! There was one interesting idea in this category; the dispersal around the building of masonry walls of different thicknesses with the intention of deriving different time lapses between collection and re-radiation to adjacent spaces. Although not fully worked out in terms of solar path and energy collection this idea would appear worthy of further work.

All in all the designs reflected only a limited knowledge of the principles and practice of passive solar design by the participants in the competition. It is fairly safe to assurne an even lower level of know\edge gene rally within the design professions.

Active Solar Energy Collection

Active solar water heating panels were specified by 15 competitors and were by far the most common 'eco-icon'. By contrast only four entrants specified photovoltaic electricity generators. Only one of these four designers mentioned the use of an invertor and battery storage system. One other scheme used the photovoltaic cells as

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a moveable shade over roof windows in summer. Two schemes deployed wind generators but one of these was a future 'add-on' option. In the winning design a wind turbine was linked to a heat pump to provide water heating. Excess power was used to heat the ground floor through aseparate water pipe circuit buried in the siab and passing through a heat exchanger. Mains back up was provided .

Recycling

The issue of recycling in constructional terms was poorly addressed. Less than half the competitors addressed the issue at all. Most of these were vague and many added ' if available ' or 'if possible' to their specification. Most ideas were very conventional, re-using floorboards or weatherboards as linings and sheathing and incorporating recycled windows andJor doors. Some re-use of brick was suggested for heat storage. Only three competitors took recycling seriously and only one of these incorporated recycled materials and designed for the recycling of the new materials incorporated . Another one of this trio came up with the bold and imaginative solution to move a displaced house, of about the same vintage as neighbouring properties, onto site and refurbished it using environmentally conscious design principles, which might be regarded as the ultimate in recycling. Moving houses is quite common and feasible in New Zealand . The third member of the triumverate suggested that floor and wall units be made from precast concrete bol ted in place for subsequent dismantiing, an interesting idea but probably not worth the trouble in relation to the possible future savings to be achieved.

Water Conservation

Water conservation was not a particular issue in New Zealand at the time of the competition, therefore it was gratifying to see so many of the contestants addressing this issue.

There were 8 schemes saving rainwater with half of these contemplating a garden end use with others using it for toilet flushing or the washing machine and 2 suggested it for whole house supply after filtering and purification. Greywater was apart of 5 schemes, collected from sources other than washing machines and used on gardens. Water from the washing machine is also usable, provided soap suds are used rather than detergents. It is doubtful whether greywater recycling would work in this context, as tenants might weil pour contaminants down sinks and could not be relied upon to avoid detergents in washing machines. Grey water filtering on site using plants would not be feasible because of the high water table. Black water recycling, which appeared in two schemes, is similarly meritorious; but like composting toilets, which appeared in !wo schemes, relies for its success on tenant servicing, and so is not practical in the circumstances of the competition. Surprisingly only two entrants mentioned water saving showerheads and taps which are simple and practical water conservation measures.

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Other Sustainable Construction Ideas

A whole host of other issues were raised either by small groups or individual contestants. These included minimising electro-pollution (4), use of high efficiency stoves (4), wind towers (2), low energy lighting (2), use of whole trees for varying purposes (I), windbreaks (2), natural ventilation (9), embodied energy (3), minimising waste (I), permaculture and food growing on site (4) and breathing wall design (I) . Ventilation, though mentioned in nine schemes was only properly worked out in four schemes. One entrant diagrammed an interesting wind tower and ground cooling ventilation system . Another competitor used tree cuttings to weave a curved "diagrid" pergola walkway structure over the public access adjacent to the site. Otherwise the ideas were notional and not worked out in sufficient detail to make them worthy of further comment.

ConcIusions

This competition was about creating an environmentally conscious architecture wh ich would be readily acceptable to the public and to building design professionals, using materials, technologies and techniques which are readily available in New Zealand today. At the same time it was concerned with demonstrating that being environmentally sensitive did not mean that the design would be contextually and culturally insensitive or that it would preclude architectural excellence. The sense of creating a paradigm for others to follow was a strong imperative in WCC thinking. Once built aild exhibited the winning design should provide a powerful demonstration of what is possible in addressing these issues. Just how successful it will be in shifting attitudes, particularly among entrenched members of the building industry, remains to be seen.

The brief ofthe competition discouraged the employment of experimental technologies in favour of using established ones more effectively, so it is perhaps not surprising that the most radical approaches came from foreign competitors who, knowing less of the context and conditions, were often less inhibited in their stance. The organie forms, use of adobe and pise construction, group housing with wind towers and light shafts which appeared in the their designs, added considerably to the richness of the fare.

Only a few designers addressed all aspects of the brief and generated aesthetically and spatially appealing architecture. This is the particular strength of the winning design by Anna Kemble-Welch and Martin Handley.

In construction terms it was perhaps no surprise that Radiata Pine was shunned by most competitors. The undesirability of the Copper Chrome Arsenic preservative treatment normally used is weil known to most environmentally conscious designers. Yet Pinus Radiata is New Zealand's principal sustainable resource and it is a fine timber fOT many construction purposes. Borax preservative treatment makes Radiata Pine suitable for framing and weatherboarding and is less environmentally undesirable

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than CCA treatment. Urgent research is needed however, to find an environmentally sound proteetion method for Radiata Pine. More surprising is the apparent lack of understanding amongst designers that Douglas Fir can be used untreated for framing . This timber is sustainable, readily available and is cost competitive with treated Radiata Pine, making it the obvious environmental choice for this purpose. Radiata Pine and Douglas Fir are the predominant plantation grown timbers in New ZeaJand with107,000 hectares ofthe former and 60,000 hectares ofthe later, as compared with about 800 hectares of Macrocarpa (Lambourne), the most specified timber in the competition. Demand for Macrocarpa already exceeds supply and this situation can only get worse unless designers use mainsource timbers to their maximum potential, consistent with environmental principles. None of the competitors proposed the use of tropical hardwoods, which used to be specified quite comrnonly for exterior decks in New Zealand . The New Zealand Institute of Architects has taken a hard line on this issue, urging its members not to specify tropical hardwoods (NZIA), and this seems to be having an effect.

It is clear that wool has become the preferred environmentally friendly insulation material. Concerns about fibreglass fibres as a possible carcinogenic source and the perception that it is a high energy product have led to its rejection by many environmentally conscious architects in New Zealand. Few competitors aimed to better the current, minimal regulatory insulation standards which was a disappointment. Energy efficiency is an issue in New Zealand and all the indicators are that both regulatory standards and energy costs will be reviewed upwards in the near future, and that this will be a continuing process. Incorporating substantially more insulation into a design therefore seems to be an obvious area for environmentally conscious designers to concentrate resources.

A similar attitude seemed to prevail amongst entrants with regard to the incorporation of double glazing. One possible explanation of the minimal use of double glazing is the high capitaI cost involved and the generally poor quality of double glazing units available in New Zealand, another that authoritative texts have tended to concentrate on payback rather than environmental quality arguments .

One message that does seem to have been heard by designers is the benefits of concrete slab construction on flat sites. It is recognised that in Wellington a concrete slab is significantly cheaper to build (Breuer 1988), inherently more energy efficient (Donn) and in association with carefully oriented windows a good energy collector (Breuer 1984). The benefits of slab edge and under slab insulation are apparently less weil recognised. Slab edge insulation is certainly currently economic and worthwhile. The case for underslab insulation is less clear cut.

Few competitors seemed to have been aware of the environmentally sustainable options for roof finishes. Bitumen impregnated, corrugated, organic fibre sheeting is available, durable, lightweight and economic, but is not much used, probably because it is not well known within the design community.

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One disappointing aspect of the competition was the way passive solar design was handled . Solar collection was reasonably weil addressed, but very few people appeared to think about other aspects such as conductive heat loss at night, in winter or on overcast days. Fewer still catered for summertime overheating. Even shading to allow entry of winter sun and exclude summer sun was only infrequently incorporated. This is rather curious as both university schools of architecture in New Zealand have run courses for many years in solar design and it is likely that a high proportion of entrants would have participated in these programmes.

Another disappointment was the apparent lack of consideration given to the use of recycled materials and components and the even less attention paid to designing to facilitate recycling of materials incorporated into the house. Current legislation, which does not favour re-use of materials, may have had something to do with this but perhaps, even within this special group of designers, the throw away mentality has not yet been displaced .

Another message that does not seem to have reached many designers is the profound effect simple changes can make to water and energy conservation. The incorporation of water saving showerheads, spray taps, and low energy lamps all pay handsome returns, but were rarely mentioned . Many designers seem to prefer the grand gesture. This was particularly the case with water conservation measures. Rain, grey and even black water conservation schemes appeared in quite a few designs. While meritorious in themselves it is unlikely that many tenants would be commited enough to make these schemes a success.

Overall its a rather patchy picture, but useful in that it indicates a number of knowledge gaps which it should now be possible to address.

References

Breuer, D.R., 1984: Design For The Sun, Energy Efficiency and Conservation Authority, Wellington, New Zealand.

Breuer, D.R., 1988: Report i 72: Technical-Economic Assessment and Market Potential For Reducing Energy in Residential Buildings, New Zealand Energy Research and Development Committee.

Donn, M. and Van der Werff, I., 1990: Design Guidelines - Passive Solar in New Zealand, Energy Efficiency and Conservation Authority, Wellington, New Zealand.

Isaacs, M. and Donn, M., 1994: Effect 0/ Thermal Mass on House Energy Use and internal Temperatures, Centre for Building Performance Research (CBPR), Wellington, New Zealand.

Lambourne, R., 1991: Architecture and Building, Environz OctINov 1991. NZIA Environmental Policy, 1992: New Zealand Institute of Architects (NZIA)

Wellington, New Zealand.

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