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Ecohomes
From Building for a Future Spring 2004
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Green roof: You will get one credit for reducing peak runoff from the roof by 50%, but beware as the increased mass required to support the roof may mean three credits could be lost in the materials section. There may be ecological benefits depending on the type of roof used.
Timber from sustainable sources: Up to nine credits can be achieved if timber with suitable documentation is used, but only if it is certified by FSC or PEFC, or reused/ recycled timber.

Timber frame/ off-site construction: Timber frame tends to perform better than masonry with respect to the Green Guide to Housing and maximum credits can be achieved for all the relevant elements. However, masonry construction can also obtain maximum credits if the correct materials are used. Timber frame may perform less well for sound insulation unless measures are taken to significantly enhance the levels of sound insulation. Off-site construction is not in itself considered by EcoHomes – although there may be benefits in reduced transportation and waste generation, for example, it would be very hard to assess. Therefore, the materials used are assessed with the Green Guide in the normal way.

Rainwater recycling: A suitable rainwater butt or rainwater tank for external irrigation will get one credit. Alternatively, reusing rainwater for internal use (e.g. for flushing WCs and washing machines) may get one extra credit, but this depends on the dwelling (e.g. if you have three storeys or more, the rainwater will be spread rather thinly between each ‘bedspace’).

Greywater recycling: If you can reduce the overall water consumption to less than 30 m3/bedspace/year, five credits can be awarded, compared to a likely maximum of three credits with all other practical water conservation measures (e.g. low-flush WCs, spray taps, showers with flow regulators, best-practice white goods).
Improved daylighting: Three credits are available for daylighting and view of the sky, although beware that if more than 5% of the dwellings do not meet the criteria, credits will not be achieved (and the 5% must be due to existing site features rather than design).

Environment-friendly finishes e.g. paints with low VOCs: No credits are awardable for finishes. BRE proposes to introduce this into the next update – the main hindrance at the moment is the lack of labelling to enable benchmarks to be set.
Earth-sheltered dwellings: Credits may be achieved for good U-values, although these could also be achieved with conventional construction. There could be possible problems with materials, e.g. if a concrete roof is used, and no extra benefit can be awarded in terms of use of building footprint.

The EcoHomes myth exploded
As you might expect with a fledgling scheme, there is still some confusion about EcoHomes and its requirements, and as assessors we often hear of the same misconceptions from different sources. Naturally, it can lead to disappointment when credits are not achieved as expected. This section attempts to put right some of these misconceptions.

Minimising CO2 emissions due to space and/ or water heating is extremely critical in order to obtain a high rating: This is not necessarily the case. Although twenty-one credits (worth approximately 22%) are available for energy use, the majority of these are for discrete items: building envelope, drying space, white goods and external lighting. Ten credits are available for the CO2 emissions of the dwelling, but this includes energy use for lights and appliances which are the dominant factor in a new, well-insulated home. Two credits can typically be achieved with electric heating, four credits with gas heating, perhaps five with a condensing boiler or better insulation. Solar hot water heating is likely to gain one extra credit (about 1%). CHP is unlikely to gain more than a couple of credits more. A wood-burning stove may get eight credits in total but watch out for the NOx emissions. In fact, with six credits (approximately 6.5%) separating the best and worst homes with respect to CO2 emissions, the three more highly weighted credits for NOx emissions (also worth about 6.5% in total) are of major significance.

Low energy internal lighting is important: No. Specifying low energy lights throughout, although a worthwhile measure, will gain one additional credit at best. This does reflect the fact that Building Regulations requires dedicated fittings in the rooms with greatest lighting usage already.

Electrically heated dwellings cannot score well: This is partly true, as typically two credits will be lost for CO2 emissions (compared to gas) and, more significantly, three credits will be lost for NOx, worth about 8% altogether. But an electrically heated development with an advantageous site can still get a Good or Very Good rating without massive expenditure due to the spread of measures included in EcoHomes.
The location is important: Again, this is only partially true. Five credits (worth about 6%) are available for the location but these can be made up elsewhere. And, anyway, only the most rural locations will gain zero credits.

Timber frame performs better than masonry construction: There is no reason for this to be the case. Although timber frame performs better than some masonry constructions in the Green Guide to Housing Specification, ‘A’ ratings can be achieved for a masonry construction for all elements. In fact, it is actually easier with masonry construction to get credits for sustainable sources for timber, and sound insulation.
MDF is prohibited: No, in fact MDF can help you obtain points as it is a reused material. Previous versions of BREEAM have awarded credits for only using MDF which meets the appropriate British Standards (in order to limit the free formaldehyde content), but this has now been removed.

Greenfield sites will perform poorly and brownfield sites well: This is not true as EcoHomes does take into account the fact that a brownfield site can have a higher ecological value than a greenfield one. A greenfield site can get maximum marks if measures are taken to protect existing features and enhance the overall ecological value. With a brownfield site, unless a suitable ecological survey is undertaken, very few points will be scored if there is even one tree over 1m in height on the site (even if it is being retained!).

Impacts during the construction phase are important: No, they are not covered at all. However, the next update is very likely to include some aspects of the construction phase.

Eco-profiling
The Green Guide to Housing Specification (BRE 2000) awards ratings (‘A’, ‘B’, ‘C’) to construction types for each major element (e.g. external wall, roof), for a ‘typical’ residential dwelling. An example of a construction type for an external wall would be brickwork outer leaf, insulation, aerated blockwork inner leaf, plaster and paint – this is an ‘A’ rated construction type in fact. These ratings are based on a range of environmental issues such as climate change (reflecting embodied energy), freight transport, toxicity and resource use, based on the typical source and recycled content of the materials used in the UK, over a 60 year period (i.e. including any replacement during this period). An ‘A’ rating is the best with respect to environmental performance, and use of an ‘A’-rated construction type can enable credits to be achieved in EcoHomes.
Eco-profiling has a number of advantages, the main one being its user-friendliness. Anyone can quickly determine the environmental performance of a construction type with minimal knowledge of either construction methods or environmental issues.

Some manufacturers have had eco-profiling carried out on their individual products by BRE. This can be used to determine a bespoke rating for the product. This is a positive step as it enables manufacturers who allow BRE to scrutinise their manufacturing process with respect to sustainability to gain benefit under the EcoHomes scheme.

If an element is reused - e.g. as part of a refurbished building - it will automatically obtain an ‘A’ rating. However, if only a portion of an element is reused or recycled then it may not alter the rating as the impacts of the other materials used may still be high. Where construction types are not included in the Green Guide, BRE will review them individually as part of an EcoHomes assessment - the full specification of that element must be provided to enable an accurate calculation to be carried out. Some major construction types have been overlooked, e.g. beam and block ground floor with a screed finish. Very few ‘unusual’ construction types are included: if you are trying to assess your straw-bale house then you will struggle without BRE’s input.

The main disadvantage of the eco-profiling system is that, to create a universally applicable tool, assumptions have had to be made. A generic source is assumed for each material based on the typical case. Therefore, the actual impact of transportation of a material, e.g. whether it is locally sourced and manufactured or not, cannot be taken into account. Although it would be difficult to do this anyway, as all raw materials would need to be taken into account, and timber and aggregates are really the only materials where transport impacts are likely to be greater than manufacturing impacts. A typical recycled input is assumed, and the 60-year life cycle will not give full credit to very long-lived construction types.

The Green Guide to Housing Specification is a useful tool although the limitations of the methodology should be borne in mind.

Author: Michael Priaulx

Refs.
FaberMaunsell: www.fabermaunsell.com
FaberMaunsell EcoHomes team:
www.ecde.co.uk/breeam/breeam_ecohomes
BRE EcoHomes: www.bre.co.uk/ecohomes - download the EcoHomes Guidance document and Developer Sheets, and also obtain a list of licensed EcoHomes assessors.
EcoHomes: the Environmental Rating for Homes – S Rao, A Yates, D Brownhill and N Howard (BRE 2000). Available from Construction Research Communications (CRC) tel. 020 7505 6622.
Green Guide to Housing Specification – Jane Anderson & Nigel Howard (BRE 2000). Also available from CRC.
Sustainable Homes: www.sustainablehomes.co.uk - download a ‘Guide to EcoHomes’ and lots of other useful information on sustainable housing.
Housing Corporation: www.housingcorp.gov.uk/resources/sustain
English Partnerships: www.englishpartnerships.co.uk - search for ‘environmental standards’ to view minimum development requirements.
Brampton EcoHouse: www.brampton-ecohouse.org.uk
(see also BFF Vol.10 No.2)
Galliford Try Group: www.gallifordtry.co.uk
Stock Woolstencroft: www.stockwool.co.uk
Toynbee Housing Association: www.toynbeeha.co.uk