Thursday, February 19, 2015

New Housing - a Case Study from Louth

In Louth, Lincolnshire, there is a proposal for a new housing development, 149 dwellings on a greenfield site on the edge of the town.  Although initially opposed by both the Town and District councils the developer now has outline planning permission and has submitted detailed plans to the local authority, East Lindsey District Council (ELDC).  An overview is provided by Taylor Wimpy here and the planning documents are available here.

Of course all such developments are controversial, concreting over the English countryside, people have got to have somewhere to live, NIMBY, the town needs growth to survive, too much traffic, there will be a playground for the kids... and the rest.

But let's leave all that aside for now and, for the sake of discussion, accept that new houses will be built on this site and consider whether these are the right sort of houses.

Climate Change and Building Regulation

The 2008 Climate Change Act commits the UK to to reduce greenhouse gas emissions by at least 80% in 2050 from 1990 levels.  The Paris climate conference in December 2015 may well produce even stronger commitments. Such reductions will require, with legal force, that fossil carbon is no longer used to heat our homes.  How then, will the people in the new homes on this development be kept warm? 

Building Regulations only require that new houses comply with Code 3 of the Code for Sustainable Homes, with some local authorities insisting upon code 4 In December 2006, the UK Government promised that all new homes would be ‘zero carbon’ from 2016 but that promise is no longer likely to be fulfilled. East Lindsey District Council are not currently minded to require 'Code 6', which would make the homes close to 'zero carbon' and similar to the German Passivhaus standard.  

We have an emerging contradiction:  houses are about to be built which will soon become unusable without significant modifications if legally binding climate change legislation is to be complied with.

Our Proposals

To minimise greenhouse gas emissions and consequent climate change potential the development needs to be as low-carbon in both construction and use as possible.  The current proposals are for an essentially 20th century approach to building, using concrete block and brick walls mortared with Ordinary Portland Cement (OPC) on heavy concrete foundations.  Building orientation is not related to solar gain and no solar panels are integral to the construction. Heating is assumed to be by gas central heating with now provision for renewable energy sources planned.

Our proposals call for a low-carbon approach to construction.  All mortars should be lime based, using hydrated lime for most above ground situations and naturally hydraulic lime (NHL3.5) for footings, drains and other sub-surface and wet situations.  The buildings should be timber famed with straw-bale wall infilling.  The roofs should be predominantly south-facing single slopes covered with solar photo-voltaic and solar thermal panels integral with the construction. Window orientation should maximise solar gain.  These measures will eliminate almost all need for heating.

The remaining heat requirement can be met in a variety of ways and for security of supply it may be wise to consider more than one energy source.  Let us look at the possibilities.

Biomass boilers, either fuelled by pellets, woodchip or logs, are likely to deliver too much heat for one highly insulated house, but if supplying a larger building comprising more than one home, might be appropriate.  In the current proposal there is no provision for the siting of a plant room.

Ground-source heat pumps have also not been considered in the current plans. There is no provision of a collection area within the site but the purchase of the arable land to the north and east would allow an extensive array which could be linked either to individual properties on those sides of the estate or as part of a district heating scheme, perhaps in conjunction with a medium-scale biomass boiler to provide hot water for under-floor heating throughout the site.

Heat pumps require an electricity input, though with a large system an efficiency ration approaching 4 should be achievable.  If each house has installed solar pv capacity of 4kW, generating an average of 10kWhr/day there will be more than enough net surplus of electricity to supply household needs and drive heat pumps, averaged over the year.  In practice there will be a larger surplus in summer and a deficit in winter.  Wind power, which is larger in winter than summer, should therefore be part of the mix.  If the adjoining fields were included in the scheme there would be space for sufficient medium-scale wind turbines.  Alternatively, and to allay the fears of those who find proximity to turbines undesirable, a funding scheme could be initiated that supported investment in off-shore wind farms.  That part of the cost of the building that might otherwise be designated for heating could be invested in the wind industry on, say, the Dogger Bank.

Air source heat pumps are less efficient than ground source but have the advantage that they do not require a large area of land.  However they do also work best in conjunction with under-floor heating systems where lower temperatures than conventional radiators are appropriate.  There appears to be no provision for this in the current plans and retro-fitting would be expensive.

Whatever the mix of energy supply decided upon, the developer should demonstrate how the buildings are to be heated without the use of any fossil carbon for the lifetime of the building.

As climate change proceeds we should expect more extreme summer heat waves too.  Designing homes to mitigate heat stress is rarely considered by the short-sighted British housing industry.

Land use

The proposed development has a high density of housing allowing for only very small gardens.  We would prefer to see a lower density and larger gardens that could provide greater resilience for the community in an uncertain future when the ability to grow one's own food could be a significant advantage.  An alternative might be to incorporate the neighbouring land to the north and east, not only for ground-source heat gathering but also to provide allotment land for the residents. The loss of agricultural land would be more than compensated for by the increased productivity per unit are that labour-intensive allotment gardening has over industrial agriculture. Enough land to grow a significant proportion of household food would be a valuable contribution to the sustainability of the community.










1 Comments:

Blogger Biff Vernon said...

Here's an alternative approach from Cambridge:
http://www.cambridge-news.co.uk/Straw-bale-eco-village-planned-edge-Cambridge/story-26029293-detail/story.html

4:38 pm  

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