The scope for improving building
standards
6.47. As we have already indicated, over 80 percent
of the energy consumed in domestic buildings is used for space
heating and hot water. This is therefore the area in which major
gains in energy efficiency can be made. Above all, there is enormous
potential to use passive design—that is, design which uses
inherent qualities of structure and materials to minimise the
need for mechanical heating or cooling.
6.48. Although there are examples of passive
design in this country, as well as of low or zero carbon technologies,
the only passive development we visited in the course of our inquiry
was at Lindås, near Gothenburg. The architect, Mr Hans
Eek, has been designing energy efficient housing since the 1970s,
though he admitted that many of his early projects had been over-complicated,
with an excessive reliance on mechanical devices. At Lindås,
in contrast, his analysis of the issues was fundamentally simple:
the key, he argued, was to make the house air-tight, and then
to control the flow of air into, out of, and around it. By applying
this principle, he has produced houses which, despite the Swedish
climate,[62] require
no heating. A more detailed description of Mr Eek's approach is
given in Box 2.
6.49. The challenges of passive design vary according
to location and climate. In Sweden the main focus is to bring
heat into the building; in marked contrast, Mr Eek recalled a
passive house in Arizona, where the challenge was to prevent over-heating.
Indeed, the architecture of many hot countries bears testimony
to the way in which builders throughout history have incorporated
elements of passive design.
6.50. The challenge in the United Kingdom falls
somewhere between these two extremes. Heat is lost from buildings,
as Mr Eek pointed out, through transmission (e.g. through walls),
through ventilation, and through water (e.g. sewage). We have
already drawn attention to Dr Wyatt's view, borne out by Mr Irving
(Q 201), that cavity wall insulation requirements in Part L are
approaching the point of diminishing returns, given the British
climate—in other words, there comes a point when, given
the difference between internal and external temperatures, energy
losses through walls cease to be significant. The key in most
parts of the United Kingdom is therefore to reduce ventilation
losses—not to add ever thicker insulation, but to improve
the air-tightness of the finished building. As Ms Sullivan pointed
out, in a typical new building "you can expect … one
or two air changes per hour"; in a high performance building,
you would aim for a figure "around one-tenth of that or less".
The impact upon the final heating requirement is huge. But in
order to achieve these results, one relies as much upon build
quality as good design—"you are basically predicting
by proper design and proper quality control what that variable
leakage factor is" (Q 154).
BOX 2
Lindås
A continuous layer of insulation, with no thermal
bridges, runs through the walls, roof, and under the floor, varying
in thickness between 30 and 50 centimetres; the windows are triple-glazed,
with krypton gas filling and a U value of 0.85 (compared to a
worst acceptable value, under the revised Part L, of 3.3). Overall,
the houses are four times as air-tight as the standard required
by Swedish building regulations. An internal ventilation system
ensures that air is circulated around the house—all incoming
air is warmed to near the ambient temperature by means of a heat
exchanger, which recovers around 85 percent of exit heat. The
houses are also laid out in such a way as to maximise solar heat:
large south-facing windows collect warmth in the winter, when
the sun is low, but balconies and overhanging roofs mean that
the windows are shaded in summer. North-facing windows, in contrast,
are small. The remainder of the heat is supplied by the occupants
themselves and their electrical appliances, whose total output
is calculated at around 0.5 kW on average. There is no separate
heating system.
6.51. If such improvements in design and build
quality are to be achieved, we believe that the construction industry
will have to embrace Modern Methods of Construction (MMC). These
remain controversial—the debacle of timber-framed houses
in the 1980s, when poor build quality contributed to serious problems
with mould and rot, and the inherent conservatism of the industry,
mean that MMC has yet to gain much of a foothold. Nevertheless,
the incorporation of prefabricated units, for instance wall units
which incorporate insulation and wiring, makes quality control
much easier. As Dr Wyatt said, "if everything is made
to factory tolerances rather than built on site, it is much more
likely it will pass air-tightness tests than something which is
fabricated from bricks, mortar and bits of timber on site"
(Q 537). We also note that MMC is familiar not just in northern
Europe, but in North America, and that there is no reason in principle
why techniques which have worked well and proved cost-effective
in those countries should not work equally well here.
6.52. Indeed, the cost of the Lindås development
was, according to Mr Eek, closely comparable to the cost of a
normal development built to Swedish standards—the additional
costs of insulation and the heat exchanger were offset by the
saving in not installing central heating. We have also been informed
of a private project to build a wholly passive house in the Isle
of Wight, using components imported from Canada, which, as a single
development cost some £880-930/m2 (excluding the
cost of piling the foundations). This compares with a target cost
for the ODPM's competition to build large numbers of new houses
for £60,000 or less of around £785/m2. Such
figures suggest that MMC, once it becomes more widely used, could
certainly be cost-effective in the United Kingdom.
6.53. One other benefit of MMC would be the increasing
use of wood rather than bricks and mortar. Wood, particularly
if it is locally sourced, offers a double benefit: trees draw
carbon from the atmosphere, which is then locked up in the building,
whose embodied energy thus contributes to a net reduction in atmospheric
carbon. In contrast, the production of bricks, mortar and cement
is highly carbon-intensive.
6.54. Nevertheless, there are also circumstances,
particularly in warmer parts of the country, or in larger buildings
such as offices, where cooling rather than heating is often the
priority, where the use of high thermal mass—for instance,
large volumes of exposed concrete—will offer greater "passive"
benefits. The effect of high thermal mass is to even out variations
in temperature, absorbing excess heat and releasing it at night,
so removing or at least mitigating the need for air conditioning.
While the production of concrete is itself energy intensive, the
gains over the life-cycle of a building are considerable—as
the British Cement Association commented, "the energy consumption
of a well-designed, high thermal mass building is typically about
half that associated with a modern, good practice air conditioned
office" (p 202). This point was confirmed in our discussion
with Professor Karl Gertis at the Fraunhofer Institute for Building
Physics near Munich.
6.55. The scope for improving the energy efficiency
of new buildings in the United Kingdom is clear. However, although
there have been individually impressive projects such as the BedZED
development in Sutton, many more such projects will be needed
before it is clear what approach yields the best results. Indeed,
the best approach may differ between the north and south of the
country.
6.56. Modern Methods of Construction have
proved to be a cost-effective way to achieve high levels of build
quality and energy efficiency in many parts of the world, particularly
in colder climates, and we support the Government's aim to introduce
them more widely in this country. However, in certain circumstances,
particularly in larger commercial or office buildings, or possibly
in warmer parts of the country, the cooling effects of high thermal
mass may yield better results in terms of overall energy use.
We urge the Government, particularly in its role as a major procurer
of new building, to show leadership in promoting innovation on
the part of a largely conservative industry.
46 
